Tuesday, 20 April 2010


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...

Sunday, 18 April 2010

In Edinburgh

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.

Wednesday, 14 April 2010

New element!

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.

Friday, 2 April 2010

The Antihypertriton

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 :-)