The Nature of Tin-100

Some large fraction of experimental work in nuclear physics concerns exploring the boundaries of what nuclei exist in nature and how they behave.  Nature allows nuclei - made of protons and neutrons - in certain combinations only.  Broadly speaking, the number of protons and neutrons should be similar, and not too large.  The conditions are set by the fact that protons like sticking to neutrons and vice versa, but not so much to each other, but as long as there are roughly equal amounts then it's okay, and that protons, being electrically positively charged, don't like to congregate together in large numbers.  This second effect means that when you start getting to the heavier elements (with >20 protons, say) then the proton to neutron ratio favours neutrons.

One of the most "exotic" nuclei with the same number of protons and neutrons yet observed in the laboratory is Tin-100, with 50 protons and 50 neutrons.  This is a particularly special case, since 50 is a so-called magic number in nuclei, which means that having 50 particles of one type is a particularly stable configuration.  The fact that it is heavy and does not have the excess of neutrons to balance the repulsive electric force means that it is nevertheless a bit on the unstable side.

Still, having these magic numbers makes it important to study, as the structure should be particularly clean and easy to understand from a theoretical point of view, which is why my colleagues have just published this article in Nature describing some of its properties.  Particularly they have looked at the beta-decay, which gives a measure of the structure of the nucleus as a proton decays into a neutron to turn it in to the neighbouring nucleus Indium-100. 

Good job Surrey colleagues, and I'm sure our REF coordinator will be pleased, too.

End of the year

It's that time of year when semester has just finished.  The undergraduate students have left, and we have had our first examination board meeting today, with the external coming along later in the week for a second meeting.  It's nice to see the results of the hard work of most of the students, and I'll look forward to the graduation ceremony next month, where I get to dress up in academic dress and see the students do the same as they are formally awarded their degrees.

So now I have three months ahead of me with little UG teaching-related activity.  Except that I'll be teaching a new course called "Advanced Computational Techniques" in October, so need to get that in to shape.  First stop, though, is conference in Bulgaria.  Hopefully my white linen suit from an online made-to-measure tailor will arrive in time...

C. S. Wu

Having noticed in my last post, somewhat after the fact, that it would have been the 90th birthday of Andrei Sakharov recently, I notice that my SEPNet colleague, Karen Masters, has just blogged about the 100th anniversary of the birth of another giant of nuclear physics, C S Wu.  Read her post here.

Sakharov Stories

When I was at secondary school, one of the biggest news stories was the ongoing changes happening in the Soviet bloc.  From perestroika and glasnost, then on to the demise of the Soviet Union and the rest of the communist countries in Eastern Europe.  It was through these stories that I learned the name of Andrei Sakharov for his role as a peace activist. I think I was vaguely aware at the time that he had a background in science, though I can't remember now if I knew he was a nuclear physicists.

Sakharov died while I was still at school, in 1989, in time to see most of the changes.  Now, in 2012, when 1989 is more than half my life ago, I am a nuclear physicist (though an inferior sort to Sakharov), and I note that the journal Physics-Uspekhi has published a series of articles commemorating Andrei Dmitrievich, on what would have been his 90th birthday, yesterday.  The all-round good guys and gals of the publishing arm of the Institute of Physics publish the english translation of Physics-Uspekhi, and being the generous sorts they are, they make all articles free to read for the first month after publication.  There are some nice biographical articles there, by old names from Russian physics, and they are worth a read.  There are some more technical ones, too, which are probably less suitable for a general audience...

Departmental Football Tournament

Yesterday was the annual Physics Department 5-a-side football tournament.  As ever, I took part in the lecturer team, the Hamiltonian Academics.  Not being a great footballer, and the sort who was always picked last at school, I never really excel, but usually enjoy taking part.  Today, my legs are a little sore.

I couldn't help thinking, while standing in goal, of Billy Casper at the beginning of the film Kes.  Fortunately, I got on a bit better that he did.  The scene has been put on YouTube, and is presented below for your delight

The Surrey Physics Blog

In case any of the readers of this blog are interested, I am a contributor to the blog of the Physics Department here at the University of Surrey.  I posted yesterday about finding the roots of cubic equations.

The end, and a re-start?

The big (and sad) news in the world of nuclear physics research is that the Holifield Radioactive Ion Beam Facility has ceased operation.  It's a shame, not because science facilities must run for ever, but that HRIBF really seemed in the prime of its life and was doing things that can't be done elsewhere.  As ever in such cases, though, science was not necessarily the highest priority when making the decision.  My (only?) colleague in the world of nuclear physics blogging, Miss Atomic Bomb, has written about it.  She works there.  My slightly tenuous link is that I used to work in its shadow, literally - in the (now demolished) theory building next door!

On the other hand, I flew to Germany today.  Usually when I fly, I pick up a free copy of the FT.  This is not so I can complete the look of an English businessman in a suit and bowler hat, but more because they print interesting news stories that are often not covered much elsewhere.  At £2.50 per issue, I tend not to ever buy it myself, but I enjoy reading it when I do, and more importantly it has what I consider a sufficiently challenging, yet sufficiently easy cryptic crossword to keep my occupied on the plane journey when I've finished reading the news.

Today, the FT carried a story on the expected future price of uranium mining stocks, which apparently have fallen to about half their pre-Fukushima value.  It is reported that Japan is going to restart some nuclear power stations following some stress-testing.  This is happy news for people with an interesting in uranium mining, I guess, and interesting to me as I didn't really see how Japan could do otherwise.

There were actually another couple of stories mentioning nuclear issues - about the talks regarding Iran's nuclear intentions and an editorial speculating about North Korea's.   Perhaps I should be reading the FT more often.  I do live a very short walk from a library at which I can read a free copy.

Anyway, while I have mentioned the FT crossword, I can tell you about the joke that I learned as a child, and obviously didn't understand at the time.  It goes, "What is pink and hard in the morning?"  The answer is "The Financial Times crossword."  I heard a friend of my parents tell it, and I re-told it as "What is pink and difficult in the morning?"  Much less funny.