Blog of the Isotopes

In India

2012-02-12T17:17:00.001Z

I'm sitting in my rather grand suite at the guest house of IIT Roorkee, a rather prestigious science-based University in India. I'm here to teach a series of lectures at a postgraduate school for PhD students across India. I'm talking about the Hartree-Fock approximation, and I hope I've pitched the level right. Unlike the UK, where our nuclear physics summer schools have around 35 experimental students and 2 theoreticians, it's completely the other way round here. Oh well, they may find it all a bit easy. We'll find out tomorrow. I should remember that the UK has probably the most extreme ratio of nuclear experiment to theory anywhere in the world in its academic community. Still, my course will be rather practical theory, with details of how to really do the calculations in anger, rather than concentrating in derivations, so I think it will be interesting for the students.

This is my second time in India. I was here some years ago for a conference, and am happy to be back. There's so much to like about the place: The people, the culture, the food, the driving. Well, at least three of those things. Now I shall take a medicinal drink of quinine-laced tonic water (with some gin for good measure) and try to sleep through the jet lag. Good night!

The Elsevier Backlash

2012-01-30T10:02:00.002Z

For some time there has been disquiet in the academic community about the publishing model of many scholarly journals. The issue is basically that academic research work, often funded ultimately by the taxpayer, is given, for free, with a transfer of copyright, to a publisher who will send it out for unpaid peer review, and then publish it, charging libraries enormous sums for the privilege.

The argument goes, or at least went, that it is actually rather expensive to prepare, typeset, proof-read and print scientific articles in relatively small volumes. This is surely becoming year-on-year less and less the case. For some time, those writing the articles provide effectively camera-ready copy, and articles can be most conveniently distributed electronically.

The low-level antipathy towards some publishers seems to have become stronger recently particularly due to their support of some legislation in the US that will negatively impact researchers' ability to disseminate open-access versions of articles they write, as increasingly required by funding agencies. There is an informative blog post about it here, with many comments, and a pledge campaign not to publish in, or referee for Elsevier publications has started.

I am pro-open access. In some areas of physics, the ArXiv has become the standard means of producing final publications and academic debate. That hasn't happened in nuclear physics, but I'm more than happy to send my papers to e.g. APS or IoP journals. The most recent paper I sent off was to EPL in part because all nuclear and particle physics papers published there were open access, though I think that deal has ended.

There has been much discussion on the web about this issue, but I'd be interested to know what, in particular, the nuclear physics community thinks.

Overreaction over evacuation

2012-01-27T17:58:00.003Z

According to a story in today's Independent it was the spine-chilling fear of an abandoned Tokyo that persuaded the Prime Minister to scrap nuclear power in Japan. This came about because of a contingency plan to evacuate the city after the tsunami last year caused damage to the nuclear power plant in Fukushima.

It seems a bit of an over-reaction to base policy on worst-case scenario planning that never happened. Still, probably not the first time a policy-maker has done something I find difficult to understand.

I Melt the Glass with my Forehead

2012-01-16T20:24:00.005Z

I've spent some time this evening watching a documentary with the estimable title "I melt the glass with my forehead". It's about the (mostly) recent history of the route to moving to £9000 tuition fees for University education in England. I don't agree with all the commentators necessarily, but it seems pretty reasonable, and is quite damning of the process. It's slightly more equivocal about the outcome, but not a great deal.

I'm no fan of the new system. I found myself chiming with the quoted words of Lord Robbins, chair of an old review of higher education, who said that he thought education should be available to all who need it. I don't see higher education as a commodity, as if it were only a matter of getting training to get a higher salary, and that no other benefit to society as a whole were gained. Or as if there were a dividing line between A-level and a degree, after which education is selfish. This is the most insidious point in all the arguments that are ever made, I think. One commentator in the documentary said that Oxford could charge £25k fees, so students there were effectively being subsidised. I doubt that I would have gone there from my comprehensive school if the fees were like that. The market is not the only way to see the world. If you really believe that the point of education is to make the people that have it richer, then support progressive taxation. If you don't, stop using all that money from the poor hardworking families to support schools.

Stuff and Things

2012-01-16T13:51:00.001Z

Part of doing research involves telling other scientists about your research. A standard way of doing this is to write journal articles. There are many things to say about the process and practice of writing in journals, from which journals you publish in, and why, to open access models, to the efficacy of peer review. I'll try to get to those another time.

There are many journals out there, of varying quality and held in various levels of esteem by the science community, for reasons which are mostly reasonable, but probably sometimes spurious. Journals would, in general, like to get good scientists to send their papers to them, and most journals will do a bit of advertising to encourage submission of articles. I had a recent email from a journal which is quite young (on its second volume) and looking for people to submit articles. The journal is called "Advances in Internet of Things." They've emailed me a few times, and I've mostly ignored the email, except to think "what a strange name for a journal," to myself.

It turns out that the phrase "internet of things" is a phrase with a particular meaning, which at least makes the journal title sound less ungrammatical. What it actually means seems to be a little hard to find out. There is a .eu website carrying the name. It has a menu item entitled "what is the internet of things" but it doesn't give a straightforward answer. It seems to be a way of thinking of turning the relation between anything into either a real or virtual network. Maybe. I wouldn't be so surprised if the whole thing were just a piece of hoaxy performance art.

At the very least, I don't think I'll be submitting a paper to the journal.

Imposter Syndrome

2012-01-11T21:23:00.003Z

Ever felt like you're not really competent to do hard physics things? Like someone is soon going to find you out? It turns out to be a pretty common thing. I wonder if it's more common amongst physicists. Anyway, Peter Coles, who blogs under an anagrammatic version of his name as, umm, erect poles, I think, has a nice post about it here.

I have certainly felt this way. The fact that I don't so much these days is probably less a change in how I think of my own abilities, which probably never go up in time, but more a realisation that I am not so different to others.

Airtrack

2012-01-03T10:49:00.000Z

A tweet this morning reminded me about a new rail scheme which would have made travel to and from Heathrow much easier for lots of people - including me. Heathrow is pretty close to Guildford, and I and many of my colleagues fly from there for our research trips. The sad thing is, we all go there by road. Even the public transport route involves getting the rail-air coach link at Woking.

Heathrow is very poorly linked to the train network, and things only seem to get better slowly. The new station at Terminal 5 has helped a little, but it is still an airport that encourages road travel to get there. It looks like the new high speed line proposal from London to the Midlands and beyond has already considered and ruled out a stop at Heathrow. Too bad.

The Airtrack proposal would have linked Heathrow to nearby population centres (Reading, Woking, Guildford) with only a small amount of new track, but seems to have fallen foul of some people because it would involve more cars waiting at level crossings in posh parts of south-west London, and a reduction in car-parking spaces in Staines-on-Thames. The main part of new track would have been in a meadow, though the track would have hugged the M25, which already goes through it.

I think it's a shame the project is not going ahead. To a large extent for selfish reasons, but it seemed like such a good project. Oh well. Then there is also the matter of the fact that a train line runs right past the University here, then the major hospital, then the large research park, with nary a station in sight. Time someone took my light rail scheme seriously :-)

Still, it could be worse. At least there is a station within walking distance here. I can never understand, when I go to Edinburgh airport on my way to St Andrews, why I have to get a bus into the city, to get a train to Leuchars that passes along the perimeter of the airport...

Dissipation and Ruin

2011-12-21T11:41:00.001Z

It's the annual Department Christmas lunch today, from 12 noon 'til 2pm. Based on previous experience, I blocked out the afternoon in my calendar with an event entitled "Dissipation and ruin." However, I have since changed that to "Finish writing the Physics Annual Programme Review," which is probably a more sensible course of action. We'll see. There's always tomorrow...

The demise of co-operation

2011-12-16T09:13:00.000Z

I received an email from a friend and scientific collaborator of mine who works at the University of Frankfurt. By chance, he happens to live in the town, Friedberg, near Frankfurt, that was twinned with my home town of Bishop's Stortford.

He wondered if I had heard that Bishop's Stortford had unilaterally decided to break off its town-twinning arrangements with both Friedberg, and Villiers-sur-Marne, near Paris. I hadn't, and a quick bit of research reveals an article in the graun about it. According to my friend, it has caused quite a stir. Not so much that the Conservative council would countenance breaking away per se, but that they would do it unilaterally, sending a letter informing the other towns of the decision, without so much as a farewell party, looking back at the good times.

Frankly, I think it's embarrassing, but I'll carry on working with my colleague. Next time I visit him, perhaps I can take a trip to Friedberg and send some personal greetings from Bishop's Stortford. There's only so much I can personally do to help our continental neighbours think well of us...

News of the Higgs

2011-12-13T10:41:00.000Z

There will be a seminar in a few hours hosted at CERN to give the latest results in the search for the Higgs boson. I'm sure it will be interesting, but I'll be at my daughter's first ever Christmas play, which I'm sure I'll enjoy even more.

I'll take a look at the announcement afterwards, and try to write a sensible post about it (and why the Higgs is important to our understanding of nature), but to pre-empt anything too exciting being announced, the following text appears on the CERN home page as I write:

A seminar will be held today at CERN at which the ATLAS and CMS experiments will present the status of their searches for the Standard Model Higgs boson. These results will be based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the Higgs.

Paul Dirac Talk at Surrey

2011-11-09T12:04:00.001Z

Not being very good at saying "no" to things has its upsides. For example, I agreed to organise a series of evening lectures at the University of Surrey on behalf of the Institute of Physics South Central Branch. I've been doing this for a few years now, and it gives me an opportunity to invite people that I'd like to hear talk to give a lecture, suitable for the physics-interested general public.

Sometimes I invite people with little hope that they will really come, because they are too in-demand to consider a feeless (apart from a nice meal afterwards) gig with an audience of 100 to be a sensible use of time. I invited Andre Geim from Manchester, Nobel Laureate from 2010, to come this year, but unsurprisingly I got an automated response, which was very courteous, and gave instructions for how to contact him in different ways depending on the nature of the email, but pointing out that he is unable to accept most invitations to talk. Fair enough.

It was with a similar spirit more of hope than expectation that I invited Graham Farmelo to come to talk about Paul Dirac. Graham's book about Dirac, The Strangest Man, has been lauded widely, winning prizes along the way, and I figured our evening IoP talk might be too small a gig for him. I was delighted then, when he said yes.

He'll be here, at the University of Surrey, on 23rd November, talking from 7 to 8pm in the Griffiths Lecture Theatre in the Lecture Theatre Block (see campus map). Please feel free to come along. No booking is required, and the event is free. You can register interest, if you want, on the event's facebook page.

The nuclear physics link (since this is ostensibly a nuclear physics blog) is that, aside from laying down much of quantum physics, and its relativistic counterpart, which paved the way for the quantum field theories that underlie theoretical nuclear physics, he was the first to write the time-dependent Hartree-Fock equations, which are the basis of quite a bit of my research. It is not uncommon for me to cite the paper, from 1930, in which he laid down the theory.

Approximation Theory

2011-10-18T22:30:00.001+01:00

I spent three hours of this afternoon in a church hall in Guildford. I haven't found religion - far from it. I was there on purely secular matters, taking an exam for an Open University module on Approximation Theory. A few years ago I decided to start an MSc in Mathematics to learn more about various topics that I've never formally learned before. At the time, I approached my head of department to see if the University would part-fund, and he said no. Why couldn't someone like me with a PhD just pick a book to learn a new topic? A good question, but the answer is that without the rod of the assignment deadlines, I'd never in practice get round to learning the material.

So, today was the culmination of the year of learning all about different ways of approximating functions - polynomial approximations, splines, all that kind of stuff. As ever, I didn't revise perhaps quite as much as I should have (here I am learning about all the things my students understand very well), but it was okay. The exam was fair, especially after I asked the invigilators to turn the speakers off so that I stopped hearing them cut up paper with scissors next to the microphone (I have no idea what they were doing to bide the time). I'll find out the results in December, but I'm happy with how the course went, and there are even a few ways I might bring some of what I've learnt in to my research.

It's a shame the OU are putting up their fees so highly. It's not a good time to be a player in the HE market, but I can't see that their new fee regime will be good for them. Fortunately for me the existing MSc fees will be held for current students.

Bananas!

2011-10-13T18:00:00.000+01:00

There's a nice article on the BBC News website talking about the Banana Equivalent Dose as a measure of radiation. It's a kind of nice idea, since it's motivated by the desire to point out that everyday objects are radioactive. Bananas are more radioactive than most things since they are high in potassium, which has a radioactive primordial isotope, Potassium-40 (K-40). K-40 is also responsible for the last item in the table in the BBC article - sleeping with someone is equivalent to half a banana's worth of radiation dose, because your bed partner is partly made of potassium, as are you. Around 5000 radioactive potassium decays occur every second in a typical adult.

Spot the difference

2011-10-03T20:05:00.000+01:00

With due deference to Private Eye, and Peter Coles's Astronomy Look-a-likes, I must say that I have been struck (as pointed out by Kate Lancaster), by the similarity between neutron discoverer James Chadwick, and Old Vic artistic Director Kevin Spacey:

Spacey

Chadwick

On the train through K-25

2011-10-01T18:28:00.000+01:00

I'm in Oak Ridge, Tennessee. It's an important place in the history of nuclear physics, being built in the second world war for the Manhattan Project. One of the main jobs that Oak Ridge had was to separate the two main isotopes of Uranium that are found in Uranium ore, Uranium-235 and Uranium-238. U-235 is the one that is needed for nuclear reactors and bombs, but makes up a little under 1% of natural Uranium. For fission in either bombs or a reactor, a much higher concentration of U-235 is needed - the Little Boy bomb that was dropped on Hiroshima consisted of two lumps of enriched Uranium, which were pushed together by a chemical explosion in the bomb to create one lump exceeding critical mass. The average enrichment of those lumps of Uranium was around 80% U-235.

Three different enrichment techniques were developed at Oak Ridge: Gaseous diffusion, electromagnetic separation, and liquid diffusion, with gaseous diffusion taking place at the K-25 plant. The Uranium ore, which came from mines in the Belgian Congo, and bought by the US on the open market, was processed into Uranium Hexaflouride, which is is gaseous at about 55°C. The plant works by repeatedly allowing the gas (containing both isotopes of Uranium) to diffuse through a porous membrane, with the lighter U-235 finding it easier to do so, and so being more concentrated after diffusion. To get high concentrations, the process must be repeated many times, and a huge cascade of diffusing membranes was built, making the plant building enormous.

The picture on the right shows the main building. Each arm of the "U" is half a mile long, and it was reportedly the biggest building under a single roof at the time of completion.

The building is now part-way through being demolished, but today I took a train journey through the site, and saw some of what was left. The Secret City Scenic Excursion Train is a volunteer-run railway that does occasional trips over about a 7 mile distance and back, starting from the edge of the old K-25 plant, through the plant, and then on through some East Tennessee countryside, before getting to the junction with a freight line it's not allowed to use. It's been in existence for coming up for 10 years, so just young enough that it wasn't here when I lived in Oak Ridge, and I was glad I found out about it while I'm over visiting. It would be even better to have really got to look inside the K-25 plant while it was still operational. During decommissioning, the plan had been to preserve the top of the U-shaped building, but it turned out to be too corroded and contaminated to make it viable. A shame...

IoP lecture on Fukushima

2011-06-16T11:17:00.000+01:00

If I lived nearer Warrington, I'd definitely attend this talk by HM Chief Inspector Nuclear Installations, Dr Mike Weightman.

What's special about Thorium-229?

2011-06-16T10:48:00.000+01:00

As a UK academic, a combination of government and university policies push me towards publishing in particular journals, at least for a fraction of my research. One of the top journals that they (and indeed I) would like me to publish in is Physical Review Letters, as it is a highly respected and highly read journal. It publishes articles across all areas of physics, and with nuclear physics being only a part of all physics activity, and a somewhat small one at that, there are often no nuclear physics articles in an edition of the journal. This makes it somewhere that I don't always look for the latest nuclear physics research, but partly for the reasons stated above, I do look every now and then.

As I type this, there are indeed no articles on nuclear physics in the latest complete edition. If I look back to the last issue, then there are a couple of articles in the Nuclear Physics section. What interests me more from a nuclear physics point of view, though, is the article listed next - in the atomic physics section. The article is entitled "Wigner Crystals of ²²⁹Th for Optical Excitation of the Nuclear Isomer".

Thorium-229 (²²⁹Th) is a special isotope. Of all know nuclides, it has the lowest-lying excited state above the ground state, at only around 7eV. That's around 10,000 times less energy than it usually takes to make a nucleus excite into an excited state. It's comparable to the sort of energy an atom needs to excite an electron. The strange thing is that nuclei, being so much smaller than atoms usually require much shorter wavelengths - and hence higher energies - of light to cause excitations. What this means is that sooner or later we will be able to directly excite and control nuclei with light pulses in the same way that we can do with atoms. The scope for applications is immense, from UV lasers, to more accurate atomic clocks, to stable quantum computers. Nuclei are so much better isolated from their environment than atoms that devices relying on quantum effects are easier to make.

If the history of the development of fields that were at the cutting edge of smallness (e.g. as atomic physics once was) into practical applications is anything to go by, Thorium-229 will be the start of a technological leap in the forthcoming years. Watch that isotope!

Chernobyl on Radio 4

2011-04-27T14:41:00.000+01:00

Last night, there was a rather good program on Radio 4 about the legacy of the Chernobyl accident. As usual, the BBC makes an effort to provide a "balanced" view, even if it means putting mainstream views against outsider views on the same basis. This program, though, pits evidence-based view against non-evidence-based, and the program is definitely worth a listen. Well done BBC, this time. You can listen again here for the next 6 days.

Nuclear Physics in Japan

2011-04-19T03:48:00.003+01:00

I've been unreasonably quiet lately. Unreasonable for all sorts of reasons, but not least of which is that there has been, and is, a prominent news story related to nuclear physics issues that demands comment. I write, of course, of the damaged nuclear power plant in Fukushima Prefecture, Japan, which has released radioactive material into the environment following (non-nuclear) explosions at it, in turn caused by the power outage from the recent earthquake and tsunami.

In some ways, I feel a little unqualified to talk about it. My research expertise in theoretical nuclear physics reminds me of this tweet that I saw re-tweeted by @snim2. It says that "Asking a computer scientist to fix your computer is like asking a physicist to fix your car." In all honesty, I probably know a little more about nuclear reactors than a genuine layperson. Still, I will refer readers interested in detailed commentary on the Fukushima reactors to my colleagues, who have written sensibly on the matter in a series of articles and blogposts, including my own institution's Paddy Regan, my colleague on the Institute of Physics South Central Branch, Alby Reid and fellow nuclear researcher, at Oak Ridge National Lab, Kelly Chips.

I will only add to the Fukushima discussion reinforcement of something that has been said by many others, namely the irresponsible nature of much of the news reporting. A rather badly written article appeared a couple of days ago on the BBC News website, and has prompted me to comment. It's title marks it clearly as being about the nuclear power plant and ongoing problems there. The first paragraph, the second paragraph and the third are all about the nuclear power plant. The fourth paragraph states "Nearly 14,000 people died and another 14,000 are still unaccounted for." Now, the third paragraph does blame the earthquake and tsunami for the damage to the power plant, but one could easily read this statement as saying that the nuclear incident caused those deaths. I know it's not true, the journalist surely knows it's not true, and many readers will know it, but it comes across in a very misleading way. Very sloppy journalism, in my opinion. Mind you, the BBC News website is written in the style of a tabloid paper with the prose infantalised to single-sentence paragraphs that you could rather imagine reading one per page below a picture in a children's story book. I should know better than to go there for news.

Well, rant over. The real purpose of this post is to celebrate Japan's contribution to more basic nuclear physics research - i.e. the understanding of what atomic nuclei are and how they work, rather than nuclear applications. I do this, sitting at a desk in a research institute just outside Tokyo called RIKEN. RIKEN was founded in 1917 (initially as a private company) and has a long history of pioneering scientific research in many areas. If I stick to nuclear physics though, I can mention Yoshio Nishina, who made one of the first breakthroughs in quantum field theory, which has become part of the language of fundamental nuclear physics. The division of RIKEN which I'm visiting is called the Nishina centre in his honour. There is Sin-Itiro Tomonaga, who worked on nuclear physics in Nishina's group, and won his Nobel prize for work with Richard Feynman on Quantum Electrodynamics. Most prominent of all, though, as far as nuclear physics is concerned, is Hideki Yukawa.

Yukawa worked on the problem of nuclear forces. How is it that protons and neutrons can stick together to form a nucleus? It cannot be due to electric forces, as neutrons are neutral and protons positively charged. An electric force could only stick positive and negatively charged particles together. There must be some kind of independent nuclear force. Yukawa was the first to make a real breakthrough in to what it might be. He proposed that the nuclear force worked by the exchange of particles between the nucleons (collective term for protons and neutrons), and developed the theory to work out some of their properties, including a prediction for their mass (around 200 times heavier than an electron) and their charge (the same magnitude as the electron, but coming in both positive and negative charge versions). He predicted, too, that in sufficiently energetic reactions, a meson should be able to be freed from a nucleus. At the time (1934), no experimental facility would be able to create them, but Yukawa predicted that they should be observable in cosmic rays. As it turns out, most of the mesons from Yukawa's theory will decay in the atmosphere to a particle newly discovered in 1937, we now call a muon, but Yukawa's particles, by now christened mesons, were discovered in 1947. Yukawa won the Nobel prize in 1949 for his prediction and the meson-exchange view has been vindicated ever since, though we now know it to be a manifestation and approximation of an underlying theory, mesons themselves being composite particles, made of quarks.

Since Yukawa's time, Japan has remained prominent in nuclear physics research. I cannot risk lauding all of the activity going on today, since I will surely unintentially miss some world-class activity by a sin of omission, but I will deliberately mention, since I am here, that RIKEN hosts one of the leading nuclear physics experimental facilities: RIBF - the Radioactive Ion Beam Factory. It has been instrumental in recent years in the discover of new elements, and quite remarkably has added many new isotopes to our knowledge of the Universe. I mean that quite literally - knowledge of these isotopes is necessary to understand how heavy elements are created in stars.

I'm glad I made the trip to Japan. The ongoing aftershocks are a little disconcerting, but I understand the risks well enough to know that my radiation dose rate on the flight over (~5 µSv/h) is far higher than that here at RIKEN (~0.14 µSv/h). The average background in UK is about the same as here in RIKEN. I've no idea what it is in Guildford, though. Would be interesting to find out.

Dr Emma Suckling

2011-03-10T10:37:00.000Z

On Tuesday my PhD student, Emma Suckling, had her viva voce examination for her PhD. After a few years of hard work, she had the opportunity to defend her thesis to the examiners, and determine whether or not she would get her PhD. I had little doubt that she would succeed, since her thesis was really excellent, but it's always a bit nerve-wracking to undergo the examination process, both from the student and supervisor point of view. I'm pleased to say that she passed, with some minor corrections needed before final printing and binding, and she can now call herself Dr Suckling.

Her thesis was on the effects of an often-neglected part of the nuclear interaction in a particular model on things like nuclear fusion and the structure of superheavy nuclei. She had to combine some pretty tricky mathematics to derive the equations to implement and some pretty advanced parallel computing to implement them, along with a good understanding of the relevant nuclear physics - no mean feat.

Well done, Dr Suckling!

STFC Advanced Fellow at Surrey :-)

2011-02-26T20:56:00.000Z

This week brought the news that our current Marie Curie Fellow Arnau Rios has won an STFC Advanced Fellowship. Not only does that mean that he has been judged to be one of the best and most promising young researchers in the fields funded by STFC (particle, astro & nuclear physics and related fields), but also, that he will be with us at the University of Surrey for the next five years. Well done, Arnau!

Talk on Friday

2011-02-09T22:53:00.001Z

This Friday I'll be talking at the Farnham Geological Society on the use of isotopes in geological studies. See here for more details, and maybe see you there.

Phil Elliot orbituary?

2011-01-14T08:43:00.000Z

Phil Elliot, who died in 2008, was an important figure in the field of nuclear structure, showing how mathematical group theory could be used to explain the complexities of nuclear structure from a simple point of view. The protons and neutrons in nuclei are somewhat colloquially said to move in "orbits," so perhaps this is why the journal Nuclear Physics A has just published an "orbituary".

First workshop of the year

2011-01-12T17:43:00.000Z

I'm in Brighton attending the PRESPEC Workshop, aimed at discussing the sort of experiments my experimental colleagues will do at the GSI Facility in Germany. There have been all sorts of different topics discussed, from proton radioactivity (decay of a nucleus by emitting a proton), to isomeric states (long-lived excitations in a nucleus), to evolution of nuclear shapes as the number of neutrons or protons chances, to theoretical approaches to describe all these different things. Mine was a theoretical talk, covering the range of things that one can do with mean-field theories. I culminated with a movie that I think is pretty cool. It is of a simulation of a collision on two Uranium nuclei, which combine briefly, and the combined "compound" nucleus then splits into three. Such ternary fission is pretty exotic, and it would be good if the calculation turns out to be correct. I need to do a bit more work to come up with a predicted experimental signature. For now, I'd just like to be able to convert the movie into a much smaller file format, so that I could show it here. I'm sure the file size is not what it should be if it were efficiently encoded. Anyone know a way of reducing the size of an mpeg video file?

Quantum Mechanics and The Archers

2011-01-06T09:39:00.001Z

As I was lazily enjoying the Bank Holiday on Monday, my mobile phone rang. I answered it to find a researcher for the BBC's PM programme asking me if I was an Archers fan and if I knew anything about Quantum Mechanics. The answer was yes on both counts. In truth, the older I get and the more I study physics, the more I realise that I don't understand things, but I think there's no doubt that I'm an Archers fan.

For the show's 60th Anniversary edition on Sunday, they had a double-length episode, with a cliff-hanger in which we heard a long running cast member's scream as he fell from the roof of his stately home. What we didn't know for sure is whether or not he died. I didn't think about it at the time as I listened, but others apparently made the link between this situation and the Schroedinger's Cat thought experiment. The BBC picked this up and wanted to have me on PM to discuss it. So... I said yes, and walked the 30 seconds to the BBC studios that I conveniently live next to(!) and before I knew it, I was pre-recording an interview with Eddie Mair about the link between not knowing whether Nigel, the Archers character, was alive or dead, and not knowing whether a cat, locked in a box with a phial of poison which opens according to a random event, is alive or dead.

I thought I'd sound a bit nervous at the start of the interview, before I relaxed a bit, but listening to it when it went out (which I never much like doing!) it was actually okay. I think I gave a reasonable account of Schroedinger's Cat for a Radio 4 audience, and I got to talk to the great Eddie Mair.

Thanks to Jim Al-Khalili for forwarding my number to the BBC. They asked him (and according to Twitter, lots of others) before finally finding someone qualified to talk both about the Archers and Quantum Mechanics. That's one interesting Venn diagram.

If you want to listen, and you read this before the 10th of January, you can listen again on the BBC website. I'm about 40 minutes in.

Radiation and Reason

2010-11-17T16:01:00.002Z

Next Wednesday, Prof Wade Allison will be at the University of Surrey giving an evening Institute of Physics lecture based on his book "Radiation and Reason".

The talk is at 7pm in lecture theatre M, and is free to attend. Please turn up for a 7pm start, if you wish to come. I will summarise what he says here afterwards.

Here is a facebook event page for it, if you wish to register interest, but there's no obligation to.

Nuclei in Semiconductors

2010-11-03T12:23:00.000Z

Semiconductors are substances who electronic structure is such that they are neither good electrical conductors nor insulators, but whose conduction properties may be altered by various means, chemical and physical to produce materials which can do all sorts of amazing things. Things like transistors, and all the technology that comes from them, things like solar cells, things like cheap LED lighting, like lasers for BlueRay players - like a lot of the neat things that get developed by my colleagues in the Advanced Technology Institute here at the University of Surrey.

Usually, people interested in semiconductor materials are not terribly concerned with the nuclei that hold the electrons in place, except that the nuclei have to be the right element, say Silicon, in order to have the right number of electrons and so the right electron structure. It's not always the case, though. One cutting edge of semiconductor research involves using quantum "spins" to make quantum computers. Spin is a kind of quantum angular momentum - to do with things rotating - though in the quantum world things don't have to rotate to have angular momentum. In spin-based semiconductor research (or "spintronics"), one tries to manipulate the orientation of a spinning electron to store information, rather than by presence or absence of a charge. This is one of the promising ways of creating a quantum computer.

Once one starts to deal with electron spins, however, the nuclei can start becoming interested. Silicon is element number 14, with 14 protons in each nucleus, and 14 electrons around a neutral silicon atom. Silicon comes in three naturally occurring isotopes, though: Si-28 with 24 protons and 24 neutrons but also Si-29 and Si-30 with one and two extra neutrons respectively. Si-28 and Si-30 have no nuclear spin, so they don't interfere with spin-based quantum computers, but Si-29 (like all odd-numbered isotopes) has a non-zero nuclear spin, and their presence in naturally occurring silicon causes the quantum computer states to decay, or "decohere". The solution? Make isotopically-enriched silicon, without the natural Si-29. It turns out not to be that easy to either make a sample sufficiently isotopically pure, or even get rid of other contaminants, as a paper published last week, cited below, shows. Surprising sometimes where nuclear physics issues pop up.

Witzel, W., Carroll, M., Morello, A., Cywiński, L., & Das Sarma, S. (2010). Electron Spin Decoherence in Isotope-Enriched Silicon Physical Review Letters, 105 (18) DOI: 10.1103/PhysRevLett.105.187602

Nuclear archaeology

2010-09-30T15:59:00.000+01:00

Nuclear Physics can help in the world of archaelogy, helping to understand artefacts created long before humankind knew anything about atomic nuclei. I heard a story on Radio 4's Today programme yesterday about the discovery of the skeleton of a bronze age teenage boy near Stonehenge who came from the Mediterranean.

The story mentioned "geochemical" analysis, but the main interviewee mentioned nothing about the nuclei behind the story. What they really discovered was that the isotope ratios of both Oxygen and Strontium isotopes were more characteristic of someone growing up in a Mediterranean environment than a British one.

Heavy oxygen isotopes in water molecules tend to fall more readily as rain when a cloud is cooling, and when it gets colder and colder it tends to be more and more depleted in heavy oxygen. The ratio of Oxygen-18 to Oxygen-16 can be used therefore as a reasonable guide to temperature (and it is used, for example, in measuring the historical temperature of the earth by looking in ice cores from Greenland).

By looking at the oxygen isotope ratio in tooth enamel, which is grown during childhood, evidence of the climate one experienced while growing up can be found.

The other clue comes from the presence of Strontium. Strontium occurs all over the world in ores, but its occurrence, like with all elements varies across the world as a result of chance geological events. Strontium makes its way into the local food chain and then substitutes for calcium in bones, it being in the same chemical group of the periodic table. Looking at the strontium isotopes can then be correlated with where one grew up. This all adds up to the ability to determine where a boy from 1550 BC grew up!

More details can be found on the British Geological Survey's website.

NIF video

2010-08-24T20:23:00.000+01:00

To follow up the previous post about the NIF, I notice in a tweet from @lasers_llnl that they have a pretty cool-looking 3D movie of the facility online. Must make some 3D glasses...

The Conference Excursion

2010-08-17T19:12:00.001+01:00

I'm back from California now, and enjoyed the Nuclear Structure 2010 conference. I'll probably blog about more of the talks - I particularly enjoyed George Dracoulis' on Tantalum-180 - but not this evening. Instead, I want to talk about the conference excursion.

For those that don't have the pleasure of going to scientific conferences, let me explain the conference excursion. Not every conference has one, but often one afternoon of a week-long conference will involve taking a trip somewhere of interest near to the conference venue. It doesn't have to be somewhere of relevance to the conference topic. It could be a local place of historical interest, or something like that. The excursion is partly an excuse to socialise with the other people at the conference, which is an important part of the purpose of getting all the attendees together at a conference. Indeed physicists sometimes need help in socialising, and these events can lead to useful discussions and collaborations. Of course the excursions are also partly for fun.

The excursion at Nuclear Structure 2010 certainly counts as a physics excursion, and also a fun one. We went to NIF: the National Ignition Facility, based at Lawrence Livermore National Laboratory not too far from San Francisco. The facility is being built to make small pellets of Hydrogen-2 and Hydrogen-3 nuclei fuse together to give off energy, just as they might do in a future fusion reactor and just as they actually do in thermonuclear weapons.

The US has a stockpile of thermonuclear weapons (the phrase used to describe hydrogen bombs, which work by fusing hydrogen isotopes together as opposed to nuclear fission bombs used in anger in WW2), but it has agreed that it will no longer test them in either atmospheric or underground explosions. However, it would like to understand that they are being well-maintained and still functional - something that I suppose it not obvious when you have a rather hi-tech device which you have built and then left on the shelf for many years. The way around the test-ban is to build a kind of controlled thermonuclear bomb, and that is what the NIF is. They certainly make no secret that the driving purpose of the facility is weapon "stewardship" but given that the weapons already exist and will continue to do so, it seems that they have managed to build something that allows quite a bit of interesting basic physics research to take place, piggybacked onto the weapons programme.

To get to see the facility, alien attendees at the conference had to get security-checked months in advance, and thankfully I passed the tests (though I don't know what I was being tested for). So last Wednesday, I boarded a bus in Berkeley, showing my passport before I even got on, and we drove to the lab. We stopped at the security gate for a while, and were escorted to the badge office to get our temporary badges. The whole procedure was generally taking so long that I feared we would have an hour-long trip to the security office and a 10-minute tour of the facility. We were all enjoying joking about it, though, which I was also nervous wouldn't endear us to the facility people... but all was well.

The building in which NIF sits is a rather ugly warehouse-looking place, but inside it is impressively hi-tech. I've been to a few facilities (as a mere theoretical physicist, I don't actually see inside labs all that often) and I think it's fair to say that I've never seen one so sparkling, shiny, sophisticated and hi-tech. The fusion will take place by having a tiny capsule of H-2 and H-3 that you could hold in your fingertips, placed at the focus of a couple of hundred laser beams - the most powerful in the world, which will collapse the capsule causing compression and heating and then nuclear fusion. They haven't started fusion runs yet, but have fired the lasers at non-fusion pellets and everything looks good so far.

The current set up is such that the pellet is placed very carefully in a big spherical chamber into which the lasers are beamed. They will be able to make one explosion every four hours or so when it is all up and running. If they want to actually get fusion energy out of this, they said that they need a rate of 10 Hz - i.e. 10 explosions per second. That seems quite ambitions to me, but I expect that they will learn some important things about the hydrodynamics of fusing hydrogen plasma, which is really what is needed. Certainly the nuclear physics reactions are well enough understood.

After the tour, and I wish I could show you pictures but cameras were verboten, we were treated to cookies and a talk about the basic science that might come out - about matter at the extremes of density - and the promise that the majority of the experiments would be unclassified. Then it was time to head back to the bus, and back to Berkeley. Back from the borders of the sunny desert to the perennially cloudy Bay Area...

Superheavy in Berkeley

2010-08-11T00:59:00.001+01:00

I'm in Berkeley, California, attending the Nuclear Structure 2010 conference. There have been a few talks on superheavy elements (roughly those heavier than found on the earth, so heavier than Uranium). This is hardly any wonder since Berkeley is home of the Lawrence Berkeley National Laboratory, where superheavy element creation was pioneered.

Krzysztof Rykaczewski presented a talk about the recently-announed discovery of element 117. Like all superheavy nuclei, it is made by reacting together two lighter nuclei: In this case Calcium-48 (20 protons, 28 neutrons) and Berkelium-249 (97 protons, 152 neutrons). This is the most obvious choice, since Calcium-48 is the most neutron rich stable light nucleus that there is and then one needs to match with the right number of protons in the other nucleus to make the one you're interested in. The tough thing about this is that Berkelium has a half life of around 320 days and is itself a superheavy nucleus that has to first be made in a lab. They made it at Oak Ridge, Tennessee, where they placed (also superheavy, or at least transuranic) Americium (element 95, widely used in household smoke detectors) and Curium (element 96) samples in a nuclear reactor for 250 days, where they absorbed neutrons and underwent beta decay until heavier elements had been created, including the Berkelium, which was separated by chemical means.

They made a total of 22mg of Bk-249 which they then turned into a target which they shipped to Russia (which turns out to require quite a bit of paperwork) to the nuclear physics lab at Dubna. Here they installed the Berkelium target onto which the Ca-48 beam impinged. They had a total of 3g of Ca-48 to work with. It's not as rare as Berkelium, but it's pretty rare, and Russia have it all. They ran the experiment for several months, and in that time made a positive identification of the isotopes of Z=117 with N=176 and N=177. When there has been independent verification of the discovery, the group will be invited to name the new element.

As my Institute of Physics Branch colleague Alby notes, the same group are now in a position to name element 114.

The paper announcing the element, in Physical Review Letters, is available (to subscribers). Details below:

Oganessian, Y., Abdullin, F., Bailey, P., Benker, D., Bennett, M., Dmitriev, S., Ezold, J., Hamilton, J., Henderson, R., Itkis, M., Lobanov, Y., Mezentsev, A., Moody, K., Nelson, S., Polyakov, A., Porter, C., Ramayya, A., Riley, F., Roberto, J., Ryabinin, M., Rykaczewski, K., Sagaidak, R., Shaughnessy, D., Shirokovsky, I., Stoyer, M., Subbotin, V., Sudowe, R., Sukhov, A., Tsyganov, Y., Utyonkov, V., Voinov, A., Vostokin, G., & Wilk, P. (2010). Synthesis of a New Element with Atomic Number Z=117 Physical Review Letters, 104 (14) DOI: 10.1103/PhysRevLett.104.142502

229Th

2010-07-28T21:26:00.000+01:00

Thorium-229 is one of my favourite isotopes. With the lowest-energy first excited state of any known nucleus, it's the isotope of choice for interacting directly with things such as lasers, atoms and molecules, whose characteristic energies are much smaller than normal nuclear transition energies. One of the most promising practical uses of ²²⁹Th is in making a new time standard which is more accurate than existing atomic clocks. My friend and fellow blogger Rob Jackson has just published a paper on the chemical side of implanting ²²⁹Th in material for possible use in such a clock standard. He's blogged about it here.

IoP Schools Lectures

2010-06-12T20:09:00.002+01:00

I've been shortlisted as a possible Schools Lecturer for the Institute of Physics next year. My pitch is about applications of nuclear physics to medicine. Any clever ideas of how to present this to school kids would be most welcome. Please comment!

Understanding the triple-alpha process

2010-06-10T19:28:00.000+01:00

All nuclei heavier than lithium (atomic number 3) are made in stars. It's only pretty recently we've understood that and the confirmation that stars are giant nuclear reactors is one of the great stories of modern physics (which I will not tell here right now!) One of the stumbling blocks to realising that nuclear fusion happens in stars is that it seemed at first like there was no way helium nuclei could fuse to form anything, as they can't fuse with any single thing that's available in stars to make something stable.

The breakthrough was the realisation by Fred Hoyle that what must happen is that three helium nuclei must interact together to form carbon-12. This highly improbably process turns out to happen thanks to a resonance in carbon-12 just around the energy that is available when three helium nuclei meet inside stars. Without it, we would not be here. Some collaborators of mine have just published a really fantastic paper running simulations of this reaction and show how the alpha particles interact. It's available here and it takes the understanding of the process to a new microscopic level. Good work collaborators!

New isotopes

2010-06-10T16:45:00.001+01:00

I reported not long ago that there's a new element known to science. Some recent news should be just as exciting as that, but somehow hasn't made the same splash. The news is that 45 new isotopes have been discovered. Discovering a new element means finding a nucleus with a number of protons never before seen, whereas discovering a new isotope means discovering a nucleus where both the number of protons and neutrons in combination have never been seen. In either case, they are nuclei seen for the first time in experiment, and they push our boundaries of knowledge and test our understanding of how nuclei are made.

The press release from the Japanese lab does a good job of explaining their experiment (smashing two known nuclei together and seeing what fragments you end up with). It's pretty exciting: They're getting really close to the r-process path: The route through the table of isotopes that happens in supernovae and is responsible for making much of the matter heavier then iron.

I suppose it makes a recent paper of mine less exciting. We only discovered two new isotopes ;-)

Detecting irradiated food

2010-05-18T20:52:00.000+01:00

Quick Advert:

Tomorrow (Wednesday 19th May), a free public physics lecture is being given in Lecture Theatre M at the University of Surrey at 7pm. It's being given by Prof David Sanderson of SUERC - the Scottish Universities Environmental Research Centre, and it's about how to detect irradiated food, a technique which the SUERC group developed and is now a European standard.

I picked up a delivery today of some equipment that the speaker wants to use in the talk - and am intrigued!

No booking is required - just turn up to Lecture Theatre M for a 7pm start

What if everyone were a nucleus?

2010-05-09T00:53:00.004+01:00

In a series of tweets this evening Jim Al-Khalili pointed out that there has been a small disagreement between him in his Atom series and Michael Mosley in the Story of Science. They each illustrated the ratio of occupied space to empty space in atoms by saying that if all the empty space were taken out of the entire human population then we would occupy a volume the size of an apple (Jim's calculation) or a sugarcube (Michael's calculation).

In either case, the analogy makes clear that atoms have a whole lot of empty space, but in terms of volume, there's a fair bit of difference between a sugarcube (around 1 cm³) and an apple (around 200 cm³). So who is right?

The population of the world is around 7 billion. The average mass of people is usually taken to be around 70kg so the mass of the human population is 7×10⁹×70 kg = 490 000 000 000 kg. Let's call that 5×10¹¹ kg. Now, if all the space were taken out of all these atoms, we would essentially be left with an enormous nucleus (as Jim says, a pulsar). The density of nuclear matter (i.e. of the inside of an enormous nucleus) is 0.16 nucleons per cubic femtometer. A nucleon weighs 1.7×10^-27 kg.

So: The number of nucleons in total is 5×10¹¹ / 1.7×10^-27 = 3×10³⁸ nucleons, giving a volume of 3×10³⁸/0.16 = 2×10³⁹ fm³ = 2 cm³.

Looks like I agree with Michael, more or less... unless I've guessed the size of a sugarcube wrongly. I mean, I haven't seen a sugarcube for years.

Nuclear Physics and the Election

2010-05-05T17:56:00.001+01:00

I've not blogged at all about the forthcoming election. Nuclear physics is a pretty minor issue in the election, but not completely non-existent. The amount of overall science funding will be a factor in determining how much money will be spent on nuclear physics research, and the commitment to nuclear power (or otherwise) of the parties will be a factor in determining how much the UK is interested in keeping a knowledge base in nuclear science and engineering on a broader scale. These two facts are ironically approximately inversely correlated in the three main parties. I don't think I'd ever vote on a single issue alone, but there doesn't seem to be a completely obvious choice from a nuclear physics point of view. I think Martin Robbins' article in the Guardian sums things up pretty well, though, from an overall science perspective.

Edinburgh

2010-04-20T22:08:00.001+01:00

Well, to follow up the last post, I did go to the hat shop, and now have a nice grey trilby and a black bowler. I also did attend Jim Al-Khalili's talk, where he pointed out some of the sexy things about nuclear physics - the things that excite people - like the fact that looking up at the night sky means looking at nuclear reactions. He also said that no matter what you do in nuclear physics, you should be able to talk passionately and with enthusiasm about what you do.

I think that's right. You don't have to be creating new elements or looking at stellar nuclear reactions - if you're doing it, it should have a purpose that you should be able to enthuse people about. And of course, this goes for all scientists, generally. I wonder how many scientists would be able to do that to any member of the public. I like to think that I'm a little more practiced at it, but my recent encounter on I'm a scientist reminds me that it's not always so easy. Must make more effort to try - otherwise, why am I doing it?

In other conference news, I chaired a session earlier today featuring talks by current PhD students, and I am happy to report that they all gave decent talks and were clearly interested in what they are doing. Probably the best was the talk about laser spectroscopy, in which some pretty clever experiments were described which used atomic transitions to understand the properties of nuclei. Electrons in atoms get slightly affected by the fact that different nuclei have different sizes and shapes, and one can actually measure nuclei by looking at atomic (electron) transitions. A very nice talk by Frances Charlwood of Manchester showed how her group have been figuring out the size and shape changes in manganese isotopes, and showing how the sizes show distinctive changes when you reach the N=28 (28 neutrons) magic (extra-stable) number, yet the nuclear mass does not. It's a bit of a puzzle, and must be telling us something about nuclear structure - just trying to think what it is...

In Edinburgh

2010-04-18T21:33:00.001+01:00

I'm in Edinburgh for the annual Institute of Physics Nuclear Physics Conference. It's partly an excuse for everyone in the UK nuclear physics community to get together and chew the fat, to discuss latest research, to discuss funding issues and to drink wine. Or beer. I've mostly drunk beer so far. I made the excellent decision to book a seat on a train far in advance. In fact, three seats since my partner and daughter are here too. The train was completely packed, not helped by the lack of flights currently. I was impressed with how well my two-year-old coped with the long journey, though I have learnt that other passengers get somewhat irate when they see you use a nit-comb on your child in public, and tell you that you shouldn't be out spreading lice.

So, the conference has a fun-packed schedule of talks. I'm looking forward to Jim Al-Khalili's talk entitled Is Nuclear Physics Research Sexy? (presumably the answer is simply "yes") and a finding out what some of the students in groups around the country are up to in the parallel sessions. And everything else, of course. But I might find time during my stay to go to Fabhatrix, an excellent hat shop on Grassmarket. When I say might, I think I mean will.

Nuclear Power Quiz

2010-04-16T09:45:00.002+01:00

From CNN, a nuclear power quiz. I got 9 / 10 :-)

http://edition.cnn.com/2010/TECH/03/31/nuclear.power.quiz/index.html

New element!

2010-04-14T11:54:00.000+01:00

A paper, just published in Physical Review Letters, has announced the first observation of element 117. This element, which will only be named when confirmed by an independent experiment and ratified by IUPAC, has been observed in an collaborative experiment between groups in Russia and the USA. The experiment took an isotope of Calcium and an isotope of an already rather heavy synthetic nucleus Berkelium, and produced two different isotopes of element 117. These isotopes decayed by a combination of alpha decay and fission, with a chain of decays that left a trail from which element 117 could be deduced. The observation gives further evidence that there may be more long-lived elements in the region.

There is no element 117 on Earth, but it is possible that it is produced in supernovae. Better understanding of the superheavy elements created in the lab helps us understand element formation in the stars, as well as the way in which protons and neutrons interact to give stable nuclei.

The Antihypertriton

2010-04-02T00:00:00.003+01:00

So, part of the reason to write this blog is to talk about some of the interesting isotopes out there - some of the uses they get put to, some of the reasons why they're of interest to physicists, or astronomers, or geologists, or oncologists, or radiologists, or engineers, or ... well, you get the idea. So let's kick off with a specific nucleus.

Each isotope is defined by the number of protons and neutrons it contains. The number of protons tells you what element the nucleus is (1=Hydrogen, 2=Helium and so on. This number is also called the atomic number) and the number of neutrons specifies which isotope of that element you are dealing with. I thought I would write about nuclei with atomic numbers going up as high as around 120, and down as low as zero (and I thought that zero would be a neat trick, talking about neutron clusters with no protons present), but I was a little shortsighted in how low you can go in atomic number.

In an article just published in the journal Science, the STAR collaboration - a team of scientists from around the world working at the Relativistic Heavy Ion Collider (RHIC - think LHC but smashing heavy gold nuclei together rather than single protons) at Brookhaven Lab in New York State, USA - have reported observation of a really exotic nucleus with atomic number -1, so it has an antiproton instead of a proton, and with a particle that doesn't usual feature in nuclei called an antihyperon. This kind of "antinucleus" doesn't make up normal matter. Nature has provided us with a whole set of particles (protons, neutrons and so on) along with a complete mirror image set, known as antiparticles. Their behaviour seems to be pretty much the same as regular matter, yet most of what we see is made of regular matter, and it's not clear why. It's thought that the big bang created basically the same amount of matter and antimatter, but that some process led to matter being more dominant now. We can't go back and observe the big bang, but by colliding two heavy nuclei together, we can get a small scale version of the high density and energy that occurred just after the big bang, and see what happens. This occurrence of the antihypertriton seems to concur with the expectation that matter and antimatter behave exactly the same - but its nice to have experimental evidence that the big bang should have behaved that way, and it's pretty cool to be able to write about a nucleus so exotic that no-one has seen one on the Earth before.

The LHC may get all the press attention, but they haven't seen an antihypertriton yet :-)

Voted off

2010-03-25T15:21:00.000Z

Well, I got voted off of I'm A Scientist. Never mind! It was good fun trying to answer all the questions, and chatting to school kids about science. And hats.

This post serves to provide something for anyone who still didn't get a chance to ask me questions in the competition to ask me, now that I'm out. Please feel free to comment with questions!

Survived the first eviction

2010-03-24T12:25:00.001Z

Well, I survived the first eviction. Woo! I feel a bit bad for Sarah, though. What she does is really interesting, but I think computer science is a harder sell than disease-curing biosciences, or gee-whizzy space stuff. I hope she prompted some of the kids to think about things like computer science as proper science. She pointed them to Project Euler, too, and maybe some of the more keen ones will get started with the problems there. Which reminds me, I should try some more of them too. My solved problems page is looking a little weak.

Get me out of here?

2010-03-20T21:46:00.000Z

We're half way through I'm a Scientist Get Me Out of Here. From Monday, the students will start voting us off. Eek! Hopefully I won't be gone on the first day. They've just fixed the website so that you can see all the questions that we've been asked and what answers we've given. Mine are here. It's sort of a shame, but completely reasonable, that people not in the competition can't comment. Feel free to comment here though :-)

I'm A Scientist Get Me Out Of Here

2010-03-15T17:37:00.000Z

The two-week run of I'm A Scientist Get Me Out Of Here started today, and I've had quite a few questions from the kids taking part so far. Have a look at the lithium zone on their site to see what questions I, and the other scientists, have been asked. It's been pretty interesting to find out what sort of things the student are interested in. Everything from "was it really hard work to get where you are now?" to "do you harm animals in your work?" (quick answers: kinda and no)

The new alchemists

2010-03-02T23:33:00.003Z

One of the cool things doing nuclear physics is that it has realised the old alchemists' dream of turning lead into gold - or indeed any element into any other. While one of my colleagues has genuinely turned lead into gold, some of the most exciting work in nuclear physics comes from trying to make new elements.

The chemical elements start with element 1 - Hydrogen - with one proton in the nucleus, then on to element 2 - Helium - with two protons and so on. The heaviest element that you can dig out of the earth (in trace amounts) is Plutonium, with 94 protons. Beyond lead (element 82) all known nuclei are unstable against decay into lighter nuclei with characteristic lifetimes ranging from tiny fractions of a second to many trillions of years. As one gets, though, to heavier and heavier elements, the lifetimes get shorter and any nuclei heavier then plutonium that might have existed on the Earth have long decayed. This doesn't stop us trying to make new elements in the laboratory, though, to better understand the forces between neutrons and protons, and to try to understand what isotopes may have been made in nuclear reactions in stars.

These "superheavy" elements are made by colliding two lighter nuclei together and hoping that they fuse together. One then looks for the alpha particles that come from the decay and the resulting residual nucleus which one can hopefully identify as a known nucleus. Indirectly, by studying the decay chain, one gets a "genetic fingerprint" for the original superheavy nucleus. Recently, however, a group based at the GSI facility in Germany has actually measured a superheavy nucleus' mass directly, rather than by inferring it from the decay. By trapping it in a magnetic field and observing how fast it oscillates round the trap, one can determine its mass very accurately. Knowing the mass is important, as it is a measure of the stability of the nucleus. This helps us point to the possibility that there is a more stable region of superheavy nuclei inaccessible to experiment as yet, but containing nuclei long lived enough to make an appreciable amount of material from.

The work is published in Nature, and the IoP's Physics World blog has already reported it. It's perhaps not as earth-shattering, but before the Nature paper appeared, a PhD student of mine, and myself submitted a theoretical paper on the likely appearance of especially superheavy nuclei with very large numbers of neutrons. Fingers crossed the referees will return with positive comments!

I'm a scientist, get me out of here!

2010-02-25T16:15:00.000Z

I'm rather excited, as I've been picked for the next installment of "I'm a Scientist, Get Me Out of Here!"

I'll have to try to enthuse various groups of school kids about what I do, and in a better way than my competitors. Should be lots of fun, if a little daunting. Details of the competition are here. I'm up against a range of other scientists, doing lots of interesting sounding things. Now I have to think of all the reasons that nuclear physics is really interesting...

TTFN, BBFH

2010-02-21T23:41:00.002Z

Nuclear Physics is not an isolated subject, but influences, and is influenced by other areas of physics, other scientific subjects, and wider society. One of the strongest and closest scientific links is in astrophysics, since stars are nothing but giant nuclear reactors. This realisation - that all elements heavier than lithium were created in the stars - does not go back to the days when the chemical elements were identified as such, or when it was realised that the elements are made of atoms with tiny nuclei at the centre. They were both pre-requisites for astrophysicists to finally understand what powers stars, namely nuclear fusion. The bulk of the puzzle was not solved until the 1950s (and indeed the entire picture is still not known) when a seminal work by Burbidge, Burbidge, Fowler and Hoyle was published which laid bare most of the nuclear reactions that occur in stars, converting lighter elements to heavier, and responsible for all the heavy elements in our bodies ("we are all stardust.") Last month, one of the co-authors of the famous paper died. Though he wouldn't have called himself a nuclear physicist, he helped define the field.

Celebrity Nuclear Physicist

2010-02-14T16:58:00.001Z

Since this is a nuclear physics blog, I think it's definitely on-topic to mention that Jim Al-Khalili, theoretical nuclear physicist and colleague of mine at the University of Surrey, was the guest on Desert Island Discs this morning. If you missed it, you can still listen for the next twelve days. He talks a bit about his personal life, and a bit about science, but the most controversial thing he said was that no good music came from the 1980s. I've pointed out this basic error in his thinking before, so I don't know why he would repeat it on Radio 4 ;-)

Labour's ambitions

2010-02-01T10:33:00.002Z

A recent article in Policy Review by David Lammy makes uncomfortable reading for the future of Science funding in particular, and UK universities in general.

I don't think it's a misinterpretation of the article to conclude that the minister's position is that

Britain's position in the world is declining. The standard of its universities is linked to its position in the world. Its universities are currently disproportionately good and should be less good.
Expensive-to-run courses (specifically "medicine, engineering and the natural sciences") will be cut by many universities, because they need too much money to run, and no-one wants to fund them, including the government.
The ambition of most universities is too lofty - to be universal in what subjects they offer, and doing blue-skies research that does not directly attract private funding is not commensurate with the government ambition for UK universities.

I wish it were a misinterpretation, though.

Missing the "subcritical" point

2010-01-25T16:29:00.002Z

The Ion Report warned that further cuts in STFC's support for nuclear physics could make it "subcritical." According to a report in today's Research Day (needs a subscription) Lord Drayson said that this point was dismissed because international collaborations are independent of each other and "withdrawing from some does not adversely affect the others."

That is missing the point of what the Ion report said. Without the critical mass in size of UK community, we are not able to provide the broad student training, to run summer schools, the national conference, the vibrant MSc and specialist undergraduate programmes or the specialist training and advice to industry, to law, to journalists and the media. Without adequate funding, people are lost, and along with them the bright PhDs who go off to work in nuclear engineering and industry. Yes, the projects STFC have pulled out of will largely continue, albeit without some UK expertise, but the survival of the nuclear physics community in the UK, which is small by international standards, but packs quite a punch, risks falling apart, and with it, all the added value that it brings to our moderately ambitious country.

Doomsday update

2010-01-14T23:22:00.002Z

Sometimes, when people ask what I do and I tell them that I'm a nuclear physicist, they look a bit amazed and ask me if I make weapons. It's not terribly surprising since, of all the many uses that nuclear physics has been used to, weapons are the one that has made most impact on culture. Though there are lots of other interesting (and more positive uses) of nuclear physics, weapons will probably always be the most iconic one, and by association, I will have to get used to being vaguely associated with them.

I sort of feel that I came to nuclear physics too late to really be associated with weapons, and I sometimes forget what a powerful influence the threat of nuclear war and nuclear weapons had on the generation before mine. I even spent my first postdoc in Oak Ridge National Laboratory in Tennessee, which was built for the atom bomb project, and visited the museums... but I've never really felt too associated with weapons, though I find the history fascinating. One of the almost romantic hangovers from the cold war era is the Doomsday clock. It was set up by a group of nuclear scientists worried about the problems of the weapons that they created. It perpetually points at a time close to midnight to represent the danger the world is under from threats so serious (originally and particularly nuclear war) that it could spell "doomsday". The clock still exists, and today it was moved back one minute to be 6 minutes from midnight, reflecting an improvement in the global situation, as judged by the Bulletin of the Atomic Scientists. I guess that's good news... and the announcement, which mentions climate change in conjunction with nuclear proliferation, suggests that the era of nuclear war as the primary (perceived) threat to civilisation is over, and we have a new enemy.

Funding cuts - update

2010-01-07T23:21:00.000Z

So, as mentioned before Christmas, nuclear physicists were awaiting news of potential funding cuts that would come as a result of a shortage of money at the funding counil, STFC. We were worried that, of all the areas STFC fund, nuclear physics would face disproportionately higher cuts. We were right. I could have (perhaps should have) been blogging about this daily - it's too late to do a complete summary now, but my colleague Niels at Manchester has set up an excellent website summarising much of the information about the cuts and the response to it, and I suggest looking there for more comprehensive information.

This afternoon, I happened to look at a Twitter feed not long after STFC tweeted that their director of science programs had just had an op-ed published in New Scientist. It was something that deserved comment - and it's got it. Take a look (my comment is by user "drpdstevenson" since I logged in with my AIM credentials)

Dark Matter - Detected?

2009-12-18T10:14:00.000Z

Stealing a march on the LHC, it seems that groups looking for Dark Matter in a low-background experiment in a copper mine in the States may be about to announce the detection of dark matter. I noticed the story a day too late to put it in my particle physics course...

Interesting days ahead

2009-12-14T22:45:00.000Z

It can't have escaped many people's attention that there is a serious worldwide financial crisis going on. There have been innumerable reports in the news about forthcoming cuts, even before the recent pre-budget report.

It would be nice to try to place the financial responsibility of recovering from the crisis on the banking sector, which was largely responsible for the problems, but the time for that is long past. They have been bailed out and the City shown up as not the contributor to tax revenue it has liked to claim but a drain of historic proportions. This leaves the rest of the economy to figure out how to keep going. Whole countries are at peril of defaulting; Iceland a few months ago, and Greece in the news today.

Now it's the task of the rest of the UK economy to recover from the debts we've incurred. Science funding will take its part alongside everything else, as it must. I'm a nuclear physicist (hence the purpose of this blog) and nuclear physics will no-doubt be part of the cuts, of course. There is a fear in the nuclear physics community that (university) nuclear physics may be cut from the budget outright. A recent story in the Guardian quoting my colleague Jim Al-Khalili highlights some of the issues. You might well expect me, as a nuclear physicist, to say that funding in academic nuclear physics should be increased, rather than cut, because my job depends on it. In truth, my job doesn't - at least I hope the University of Surrey would give me support and a little time to make headway into other research areas - or if not, the skills that working in nuclear physics have given me would make me pretty employable. But the UK funding of Nuclear Physics is embarrassingly small by the standards of competitor countries, yet it was just judged in an independent review as high quality despite at a scale below OECD norms. It really is at such a low level that to cut it a bit is to essentially get rid of it. It may be that we can do without it, despite having plans to increase nuclear power to counter global warming. We can always buy the expertise in from elsewhere if we think that's right for the UK, but I can't really believe that cutting science that we'll then have to buy from outside can be cost-effective. I rather fear we'll find out pretty soon.

Expect announcements in the next few days.

NMR/Enema

2009-11-17T21:20:00.001Z

On Friday I went to a school in Slough to give my nuclear physics talk entitled "Field guide to the isotopes" which consists of a whistlestop tour of different isotopes, their uses and their significance in the realm of nuclear physics, in society, in medicine, in geology, in biology and ... just about every branch of science.

I used to worry about going into schools to talk, since I figured I'd be no good at dealing with naughty students (despite working at a University). I've long realised that it's not that hard - at least not as a guest speaker, so I wasn't too worried, and indeed it turned out fine. In fact, I found, as I always do, that the pupils were interested, they paid attention, and asked lots of interesting questions. One of these was related to a picture of the JET fusion reactor in Oxfordshire which showed it both in action (with a hot plasma of hydrogen isotopes) and out of action (to see the apparatus without all that hot plasma). One of the students asked, "how did they take the picture when it was switched on?" and I had to admit that I didn't really know. It's a good question: The temperature inside the reactor when it is on is exceedingly high and would destroy a camera. The answer I gave (with a caveat that it might be wrong) was that the plasma is contained in a magnetic field, which keeps it away from the walls, and a camera could be attached near the wall and away from the plasma. It's probably the right answer, but I don't know (if anyone does, please comment!). But that's one of the nice things about giving these talks - I get a combination of questions that make me think and comments that inform me of things I didn't know.

One of the best comments I have got when giving the talk was about the medical imaging technique which is these days known as MRI ("Magnetic Resonance Imaging") and used to be known as NMR ("Nuclear Magnetic Resonance"). I ask, as I usually do, if anyone in the audience knows the difference. Usually noone answers, and I explain that there is no difference, except that the word "nuclear" was removed to avoid worrying people that there was something nuclear about the technique. One time that I gave the talk, and told this story, someone came up to me at the end and said that actually the reason that they changed the name was because "NMR" sounds too much like "enema" and that people would get confused about what they were going in to hospital for. I told this story on Friday, and I thought that I got some glowering looks from the teachers. Oh well. It's a good story. I don't know if it's true though.

P.S. I'm glad that when this post is mirrored on facebook that people comment. I'd rather, though, that you'd do it on the original blog post so that everyone can see the comments and comment on the comments whether they are looking on facebook or not. Thanks!

Science and Politics

2009-11-03T23:13:00.000Z

So: the Home Secretary dismissed a scientific advisor for being a scientist and complaining that the Government deliberately ignored the advice of his panel. There's been a huge amount of rather interesting commentary about the link between science and government during the fall-out of the sacking of Prof David Nutt (which has the glorious Twitter hashtag of #NuttSack). It sort of surprises me and sort of doesn't that one arm of the people who run the country (the government) think that basing decisions on scientific evidence is a bad thing to do, and that another (the Daily Mail and its constituency) rants that it would be hell on earth to be governed by those that weigh up the balance of evidence and come to conclusions based on that evidence.

It's a real shame - and part and parcel of the two cultures that are as alive today as they were 50 years ago. It's a bit tiresome when the presenters of the Today program fail to challenge scientists like they do politicians because they don't have the ability or confidence to do so. It's a little annoying when Jeremy Paxman is impressed and surprised when contestants in University Challenge answer a basic science question but is scathing when a poor guess is made to a question in the arts. It's really annoying, though, when things that really matter - things like government policy - deliberately ignore the evidence.

Still, in other news, universities aren't going to be "ivory towers" anymore, with the intellectual and research freedom that goes with it. Instead they must concentrate on being drivers of the economy and respond to social need (which they already do alongside the "ivory tower" aspect). Research grants will be rated according to their financial payoff (as if it could be measured), not the science. Soon Universities can be a fully paid-up part of the service economy too, and we will no longer have to worry about troublesome disinterested scientists and their crazy evidence-based reasoning.

Lots of nuclear physics in the Guardian Science Podcast

2009-10-26T12:19:00.000Z

In the latest Science Weekly podcast from the Guardian there's a long interview with science writer Amir Aczel all about Uranium. Very interesting!

Sharing your bed with radiation

2009-10-22T17:53:00.000+01:00

So, last night I gave my "Field Guide to the Isotopes" talk at my home institution, the University of Surrey. It went, I think, pretty well, though the turn-out was on the low side for our evening lectures programme. I guess people must have been paying attention, as there were a few very pertinent questions along the way, and some interesting comments and questions at the end.

One of the comments was about the isotope potassium-40 (K-40). Potassium is an alkali metal, element number 19, which sits under sodium in the periodic table. It sits there because it has chemical properties similar to sodium, so it readily forms salts which are vital in the human body for the proper functioning of cells.

So, potassium is element number 19, which means that every nucleus of potassium has 19 protons in it but there are a few naturally-occurring isotopes which differ in the number of neutrons they have. The most common is K-39, next is K-41. They are both stable, but about 0.01% of potassium atoms has a K-40 nucleus at its centre. K-40 is radioactive (it will decay either to argon-40 or calcium-40), with a half life of around 1 billion years. Now, the earth is not so very much older than this (at around 4 billion years) so there is still some remaining K-40 that was created some time before 4 billion years ago to be found on the earth. Unlike the other main long-lived naturally-occurring radioactive isotopes (of Uranium and Thorium), Potassium is actually a biologically useful element, and so we all have some small amount of radioactive K-40 in us.

I expressed this in the talk by saying (and I don't take credit for it - it's been pointed out before) that if you sleep with someone else, you are getting an increased dose of radiation from their body by doing so - and vice versa. A questioner at the end was quite worried. Fortunately, humans have been sleeping with other humans for a long long time, and the doses are clearly not high enough to cause any trouble.

Still, all other things being equal, single people have a lower radiation dose!

First Post!

2009-10-18T22:39:00.000+01:00

Hello and welcome to my new blog about nuclear physics; Blog of the Isotopes. I've been occasionally writing a personal blog for many years, and often going off and talking about nuclear physics as part of my job as an academic nuclear physicist, also for many years, so it seemed like it was about time to join those two things up. So here we are: the blog of the isotopes - all about nuclear physics. The blog's name comes from the fact that nuclei - the tiny clusters made of protons and neutrons at the centre of each atom - come in different isotopes, just meaning a unique combination of a number of protons and neutrons in the same way that each chemical element differs from the others by having a different number of electrons in an atom.

Of course, it might be that blogs are on their way out and that I should be tweeting about nuclear physics instead, but maybe that will come too :-)

Anyway - a little about me: I work at the University of Surrey, which has the largest nuclear physics group in a UK university^#. I call myself a nuclear structure theorist, which means that I do calculations of the structural properties of nuclei (things like their size, shape, mass, and the ways in which they can vibrate) using our knowledge about the nuclear force - then I see how well these ideas about the nuclear force really agree with what my experimental colleagues observe and refine my theories based on that. No doubt I will be talking about this in future blog posts.

I plan to keep an eye out for topical nuclear physics news stories and talk about them from the point of view of a nuclear physics researcher, and also to share some of my interests in the wider field of nuclear physics beyond what I do research into... but I don't want to do it all in this first entry; so let me just justify the fact that I have chosen to start today by saying that I will be giving a public lecture at the University of Surrey this Wednesday (21st October) in Lecture Theatre M at 7pm on nuclear physics. The title of the talk is "Field Guide to the Isotopes," and it will be a little tour of some of the exciting things that nuclei are used for elsewhere in science and society from understanding climate change and other geological processes to medical diagnosis and treatment, to determining the ways that astronomical processes take place. If you wish to come, please just turn up in time for a 7pm start. Details are at http://bit.ly/GiBzV or leave a comment here.

more soon!

^# probably - it's slightly hard to count