Wednesday, 21 December 2011

Dissipation and Ruin

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...

Friday, 16 December 2011

The demise of co-operation

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...

Tuesday, 13 December 2011

News of the Higgs

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.

Wednesday, 9 November 2011

Paul Dirac Talk at Surrey

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.

Tuesday, 18 October 2011

Approximation Theory

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.

Thursday, 13 October 2011


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.

Monday, 3 October 2011

Spot the difference

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:



Saturday, 1 October 2011

On the train through K-25

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...

Thursday, 16 June 2011

IoP lecture on Fukushima

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?

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!

Wednesday, 27 April 2011

Chernobyl on Radio 4

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.

Tuesday, 19 April 2011

Nuclear Physics in Japan

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.

Thursday, 10 March 2011

Dr Emma Suckling

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!

Saturday, 26 February 2011

STFC Advanced Fellow at Surrey :-)

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!

Wednesday, 9 February 2011

Talk on Friday

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.

Friday, 14 January 2011

Phil Elliot orbituary?

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".

Wednesday, 12 January 2011

First workshop of the year

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?

Thursday, 6 January 2011

Quantum Mechanics and The Archers

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.