Thursday, 30 June 2011

A great accelerator demo

I recently re-discovered this fantastic accelerator demonstration using a bowl and a ping-pong ball from Todd Johnson at Fermilab.



The thing I think is great about this demo is two-fold. First, the principle of acceleration is pretty straightforward; for a particle with a constant charge you need to have the right polarity (+/-) on the strips at the right time to make it accelerate. The second great thing to show is the analogy of the bowl as the magnetic field. This is especially relevant to the machines I work on, called FFAGs, as the magnetic field really does increase radially, so the particles spiral outwards just like in the bowl as they gain energy. But they don't spiral out *too* much, because the field gradient keeps them confined to a fairly tight circle, just like the curvature of the bowl does for the ping-pong balls.

I really want to make one to use in a new public lecture, so I contacted Todd about how he made it. I hope I can convince someone to help me, although I'm still a bit worried about the danger of using 15kV in a public demonstration.

In case you want to re-create it yourself, here is what he told me about it:

"The power supply I used is a surplus unit which provides about 15KV from a 12VDC input, intended to be used in an "air ionizer". Sadly these devices have disappeared from the market.  Several manufacturers make small DC/DC converters that look like they would do the job nicely, for example: http://www.ultravolt.com/products/348  These cost about $250 or so as I recall.

The clear "bowl" is actually a custom made part. I had found some serving bowls which worked well for the first couple of these I made but of course those also soon disappeared from the market.  The key feature is that there should be a central flat spot which then meets the curved side with no discontinuity. Any faint corner or step will trap the ball and prevent it from accelerating, due to friction between the two points of contact at different radii it will then have. My hemisphere was fabricated by a company that makes acrylic domes, and they were able to accommodate my request for a flat spot in the center. A regular hemisphere will also work, however the ball will need a  push to start it since with zero initial momentum it cannot travel from one set of electrodes to the other set (which would of necessity be uphill).

The ping pong ball is coated with a carbon-based conductive paint called "wire glue" which I found locally. I'm sure that coatings such as "Aquadag" would also work well. I gave the coating a protective layer of clear spray enamel (Krylon), which seems to make it extremely rugged and does not significantly affect the conductivity at the voltages involved.

Regarding the safety issue, it is not apparent from the video but there is an acrylic cover over the device which prevents onlookers from reaching in and contacting both sets of electrodes. The cover also improves the performance by allowing the air to begin to move along with the ball rather than remaining turbulent as it would if the top were open to the room."

Monday, 27 June 2011

Thoughts on a train

I was just thinking today that the machines I work with, particle accelerators, really sound too good to be true. My argument for this (in my head, on the train, to myself...) went something like this:

Imagine a tool that can see inside matter, right down to the level of atoms. This tool can not only see what types of atoms there are, but also where they are and what they're doing. Imagine how powerful that would be - being able to see proteins unfolding in real time, seeing how materials work from the inside, finding out all of nature's little secrets with ease. Then imagine that the same tool can be used to diagnose and treat diseases, like cancer for example. Not only that, but you can also use it to help in fields like security for scanning whole truckloads of cargo and in energy for driving new types of inherently safe nuclear reactors. Add to this the fact that you can use this tool to learn about the fundamental laws of nature, how the Universe evolved, answering some of the "big questions" of human-kind. But going beyond that, it can even create new matter that doesn't exist on Earth. (My head rambled on a bit more but I'll spare you the pain...)

You'd think "well, that's a pretty awesome tool..." and you'd be forgiven for thinking that it was, in fact, the ultimate scientific tool.

In my opinion, you'd be right.

Then I looked out the window as the train travelled from Wolverhampton towards Crewe, only 10 minutes behind schedule and thought: Imagine what we could do if we made this tool even better?

That's what I do. That is my research.

Wednesday, 22 June 2011

Is all publicity good publicity?

Over the past few weeks there have been two pretty misleading articles written about one of the projects I work on, called EMMA. 


The first article appeared in the Mail on Sunday, who at least can be credited with visiting the facility. But here is the problem: the article is still pretty inaccurate, one could say downright misleading in some cases. From reading it, I can only assume that it came out this way because of some miscommunication between the person giving the tour and the journalist.


EDIT (23/6/11): For the record, the facts in the Mail on Sunday article are pretty much solid. They could have been presented in a slightly less misleading way, clearly, or the other articles which I discuss below would not have gotten the facts so wrong. The article calls EMMA 'pocket-sized' and then says you can use a 'pocket-sized' accelerator to drive an ADSR thorium reactor. While it later states you need a 1 GeV proton accelerator, I believe this is the cause of confusion...


I thought that was it. But to my (and everyone else's) surprise, it then appears on the Fox news website. Now, not only does this new article mention nuclear *fusion* in a thorium reactor (it ought to be *fission*) but also implies how this 'pocket sized' particle accelerator called EMMA could not only "power" a thorium reactor but also one day be shrunk down to "luggage size".


This new article almost sent me into a fit of rage. I am used to the press getting facts slightly wrong, but this seems to be a case of someone not giving the facts correctly, or not giving them in such a way that the journalist could understand. I don't know who actually gave the information, so I'm not blaming anyone here... 


EDIT (22/6/11): OK this is getting ridiculous, I just found this one, which is so absolutely and completely wrong that I am now compelled to contact them. Oh, and another one talking about fusion (thanks to one my colleagues for sending these) - I've tweeted the author of that one, I hope he read the info below!
While I'm at it, here's some more who've taken the Daily Mail or Fox News' articles and perpetuated the problem:
PopSci.com
Propulsiontech (a blog I assume)
Sciencetechnologyupdates


But this incident has really made me question whether all publicity is good publicity. In my position as an early career researcher on the project, I can only see that this going to negatively impact me. 


If you claim you're going to save the world and cure cancer you've got a lot to live up to... so what happens when it turns out to be not *quite* as true as the news articles claim? 


Isn't it better to be cautious about what you claim you could do and then wow everyone with your amazing research? Certainly anyone on any funding board would see straight through these claims and wonder why they were being made in the first place. 


Worrying. Very worrying. I'd love to have some feedback of what you think of this situation. 


To clear up the issues that I have with both articles, here are the facts:

  • EMMA is the Electron Model for Many Applications and is the first non-scaling fixed-field alternating gradient (NS-FFAG) accelerator in the world.
  • It is a prototype machine based on the parameters required for accelerating muons for a neutrino factory, designed to accelerate relativistic particles extremely quickly.
  • It accelerates electrons from 10-20 MeV (this is quite a low energy, that's why EMMA is so small!)
  • A thorium ADSR would require a PROTON beam of 1 GeV, note that in this energy range protons are NOT ultra-relativistic, so the same acceleration mechanism (called serpentine acceleration) used in EMMA is not possible.
  • Accelerating protons to 1 GeV necessarily requires a LARGER machine, and sadly there is not getting around the laws of physics. A higher energy beam with heavier particles requires either much stronger magnets or a much larger bending radius than EMMA to go around in a circle.
  • That said, EMMA is a very compact machine. However research carried out in the last few years indicates that you couldn't use the same design as EMMA for a proton machine anyway, because of very strict tolerances on alignment errors and the difficulty of getting a beam in or out of such a densely packed & compact machine.
  • Because of this, the idea of a "suitcase sized" non-scaling FFAG is a complete lie. I have no idea where this originated.
  • The only "suitcase sized" accelerators possible would be based on radical new technology like a laser plasma wakefield accelerator. Maybe one day they will be possible, but certainly not with the technology discussed in these articles.
There you go. There are the facts. From the horse's mouth, as it were...