Friday, August 17, 2007

Accelerator Physics

I attended a meeting a while back where one of the topics was how to attract more talented students into the field of Accelerator Physics. There were several different ways that were proposed, including more money (of course), and getting the right faculty members in different colleges interested in the field of study and so, would channel students into it. Unfortunately, I had to leave early and didn't get the chance to say what I had in mind.

Accelerator Physics suffers from a serious "identity crisis". If I mention to you that I work in accelerator physics, what's the first thing that comes to your mind? I bet that you think about particle collider/high energy physics/particle physics/Fermilab/CERN/etc. Am I right? There's a good chance that I am. I've done many tours of our accelerator facility for students, general public (during our Open House last year), and even other scientists/physicists. The majority of them had that impression. People think that accelerator physics is synonymous with particle physics, which in retrospect, is highly understandable. High energy physics collider facilities have been given names such as "Fermi National ACCELERATOR Laboratory". Even nuclear physics collider facility has been called " Thomas Jefferson National ACCELERATOR Facility". So it is no wonder that the majority of people would associate the word "accelerator" with "particle collider/particle physics".

I have tried to correct this misconception earlier when I posted a blog entry titled "Particle Accelerator Are Not Just For Colliders". Still, I think people in this area of study do not realize the existence of this misconception, or they don't think it is prevalent enough. I certainly have never heard of this issue being addressed. So I would like to address it here. I'm hoping that my putting my thought on paper and writing it down, I can make a better case of it when I actually present this issue at our next meeting, if I have the opportunity.

The field of accelerator physics, to put it crudely, involves the study of the physics and engineering of various components that are related to particle accelerators. And rather than leave you with that esoteric definition, I will tell you what are some of these "components related to particle accelerators". They include:

(i) photocathodes that generate electrons to be accelerated in electron accelerators;

(ii) the study of RF fields in various geometry, configuration, waveguides, etc. that are the actual field responsible for the acceleration mechanism;

(iii) the study of the physics and engineering of those geometry itself, such as waveguides and accelerating structures

(iv) the study of beam dynamics, i.e. how does the electron beam propagate through the accelerator, what are its properties as it passes through various components, etc.

(v) the study on HOW to actually measure various beam parameters, i.e. the physics of the diagnostic techniques and equipment

(vi) plasma physics, since we are dealing with charged particles

(vii) computational physics of beam dynamics and RF fields. Many complex software packages are used (and often modified and adapted) to solve various uses. If one has an interest in computational physics, the field of accelerator physics has some of the most challenging and exciting opportunities to apply such skill.

(viii) high-powered lasers, especially those used to generate photoelectrons.

(ix) etc.

I've only scratched the surface. In fact, there are areas involved that you would not think to be associated with accelerator physics. I myself had to deal with issues of material science, since I'm involved in photocathode production (i.e. I make them). I also have to deal with the properties of dielectric material since we use that as a possible accelerating structure. We are also using a coating technique on some of our structures using atomic layer deposition (ALD) that is used in material science/condensed matter/chemistry. A good way to get a flavor on the type of subject s that are involved in being an accelerator physicists is by browsing the course material at a particle accelerator school that I also have mentioned earlier.

So yes, accelerator is a wide field involving many different aspects, as with any other field of study in physics. But what do we study these things for? To make better, more efficient accelerators that will provide the necessary charge particle beams to be used for whatever purposes. And what purposes can they be? The most obvious one would be for high energy physics/particle physics study, such as those at particle colliders. This is a no-brainer since we are often mistaken for that. But that's not just it. I have mentioned in that blog entry that a large portion of accelerator physicists work at various light source facilities such as synchrotron research centers. They work to maintain the accelerator that feeds electrons into the synchrotron ring, and they also study the dynamics of the electrons in the ring and see if there are any other improvements that can be made in terms of its "lifetime" , i.e. how long can a good quality electron beam can be maintained? Areas of study on free-electron lasers (FEL) are also in the realm of accelerator physics, because it involves the study of beam dynamics, accelerating structure, insertion devices, etc. We also have many accelerator physicists that work with medical accelerators in hospitals and clinics.

So where can you find accelerator physics-related papers? Almost everywhere. Both Science and Nature have published accelerator physics papers. In fact, Science even had devoted an issue that focused on the advancement in the next technique of particle acceleration. In Physical Review Letters, accelerator physics papers can be found in Plasma and Beam Physics section. The Physical Review also has a special journal devoted to accelerator physics called Physical Review Special Topics - Accelerator and Beams. Accelerator physics papers can also be found in journals such as Applied Physics Letters, Journal of Applied Physics, and Nuclear Instrumentation and Methods B. These are just some of the journals that publish accelerator physics papers. But beyond that, many more papers are published as conference or workshop proceedings. The Particle Accelerator Conference (PAC) is held every two years in North America, and there are the European and Asian version of this conference as well. There's also the Advanced Accelerator Concepts workshop, also held very 2 years. Then there are other numerous workshops and conferences such as LINAC, FEL, etc. Each one of them publish their own conference proceeding which is full of accelerator physics papers.

So while the field of accelerator physics suffers from an identity crisis, it still a very active field and has a significant impact on many aspect of physics, and even day-to-day lives. The field needs to clearly identify itself and what it does to attract more fresh blood. How to do that is a very good question.



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