Physics and Physicists

This is a fascinating and important advancement in the physics of light sources. It seems that it has been shown experimentally how one can get the short, intense light pulses that one gets from a FEL source, and combine it with the repetition that one gets from a synchrotron light source.

Now a Sino-German team has shown that a pattern of pulses can be generated in a synchrotron radiation source that combines the advantages of both systems. The synchrotron source delivers short, intense microbunches of electrons that produce radiation pulses having a laser-like character (as with FELs), but which can also follow each other closely in sequence (as with synchrotron light sources).

Another review of this work, from Nature where it was published, can be found here.

While this is an important step, it really is a proof-of-principle experiment, and it requires a bit more experimental work to show that this can be viable.

Although this paper represents a crucial step towards generating high-power, small-bandwidth light pulses in a particle accelerator, steady-state microbunching has not yet been demonstrated. Deng et al. have shown that, after one turn in the synchrotron, the microbunched beam can produce coherent radiation. The next challenge is to prove that this scheme can achieve such a feat over many turns. This will be difficult to accomplish experimentally for at least three reasons.

But if this can be demonstrated, a lot of things that are done at a FEL can be performed even more at an "ordinary" synchrotron light source, a facility that is a lot more plentiful.

An important point that I want to point out here is that, these are all "tools" that allow us to study things. Without these tools, we have no ability to experimentally detect, see, or measure things. It enables us to do things that we could not do before. So the advancement in science, technology, medicine, etc, depend on not only having these tools, but also the continual improvement of these tools. Advancement in science requires all of these things to occur to able to explore more difficult and complex ideas and scenarios.

This advancement in accelerator-based light source has nothing to do with high-energy physics. In fact, if you look at the type of applications that are being mentioned, there's nothing about particle physics at all!

.....on an accelerator that could extend the capabilities of these machines even further, potentially yielding applications in a next-generation chip-etching technology called extreme-ultraviolet lithography and an advanced imaging method known as angle-resolved photoemission spectroscopy.

So once again, this is my continuing attempt at trying to make people aware that "accelerators" do not automatically mean "particle collider" or "high energy physics". In fact, the majority of particle accelerators in this world are not involved in high energy physics experiments.

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Don Lincoln explains why the PIP-II upgrade at Fermilab will take the accelerator facility to the next level.

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The video actually explains a bit about how particle accelerator works, and the type of improvement that is being planned for.

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No, we're doing imaging ghosts here.

For the first time, ghost imaging using electrons have been accomplished.[1]

Optical ghost imaging using light has been previously accomplished.

Optical ghost imaging is a useful tool that can spatially resolve the characteristics of a sample using just a single-pixel detector – rather than the multipixel arrays found in digital cameras. The technique involves splitting a beam of light into a pair of correlated beams called the signal and reference beams. The signal beam strikes the sample before hitting the single-pixel detector. The reference beam goes directly to a conventional, multipixel detector. By measuring the correlation between the intensities of the beams as they hit their respective detectors, an image of the sample can be reconstructed using data from the multipixel detector, without directly imaging the sample itself.

In this new report, this technique has been accomplished using relativistic electrons. Their motivation for applying this technique using electrons is given in the text of the paper:

Potential benefits of applying ghost imaging methods to electron-based imaging systems include the possibility to minimize image acquisition time and to reduce the dose delivered to the sample and the resulting sample damage. In addition, electron ghost imaging can be useful for experimental methods (e.g. electron energy-loss spectroscopy, or cathodoluminescence) for which spatially resolved detectors either do not exist or severely increase the complexity of the setup. A special case is the growing field of time-resolved electron scattering where the use of multi-MeV, ultrashort relativistic electron sources for both imaging and diffraction has pushed temporal resolution to the ps and fs regimes. Employing structured illumination (i.e. ghost imaging) schemes on ultrashort electron beams offers the possibility to better manage the space charge effects in the electron column.

This is another opportunity for me to point out that this is a research work coming out of accelerator physics.

Zz.

[1] S. Li et al., Phys. Rev. Lett. 121, 114801 (2018). http://www.slac.stanford.edu/pubs/slacpubs/17250/slac-pub-17314.pdf

The upgrade to FACET facility at SLAC promises to improve the beam electron beam quality at the accelerator facility. One of the direct benefits of this upgrade is further advancement in the plasma wakefield accelerator technique. This technique has previously shown to be capable of producing very high accelerating gradient and thus, has the potential to produce accelerating structures that can accelerate charged particles to higher energies over shorter distances.

Now, when you read the press release that I linked above, make sure you are very clear on what it said. The FACET II facility is NOT a facility that operates using this "plasma wakefield" technique. It is a facility that produces an improved electron beam quality, both in energy and emittance, among other things. This electron beam (which is produced via conventional means) is THEN will be used in the study of this wakefield accelerator technique.

The project is an upgrade to the Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science user facility that operated from 2011 to 2016. FACET-II will produce beams of highly energetic electrons like its predecessor, but with even better quality. These beams will primarily be used to develop plasma acceleration techniques, which could lead to next-generation particle colliders that enhance our understanding of nature’s fundamental particles and forces and novel X-ray lasers that provide us with unparalleled views of ultrafast processes in the atomic world around us.

So read carefully the "sequence of events" here and not get too highly distracted by thinking that FACET II is a "novel X-ray laser, etc..." facility. It isn't. It is a facility, an important facility, to develop the machines that will give us more knowledge to make all these other capabilities.

Consider this as my public service to you to clarify a press release! :)

Zz.

This is the lesser known effort at CERN among the general public, and yet, it may have one of the most significant impacts coming out of this high-energy physics lab.

CLIC, or the Compact Linear Collider research project at CERN has been studying accelerator science for many years. This is one of a few prominent research centers on accelerator physics throughout the world. Both they and many other accelerator research centers are making advancements in accelerator science that have a direct benefit and application to the general public.

So my intention in highlighting this article is not simply for you to learn what the people at CLIC do. Some of the description may even be beyond your understanding. What you should focus on is all the applications that are already in use, or can be possible in the near future, on the advancements made in this area of physics/engineering. These applications are not just within physics/engineering.

Unfortunately, as I've stated a few times in this blog, funding for accelerator science is often tied to funding in high energy physics, and for the US, the funding profile in this sector has been abysmal. So while accelerator science is actually independent of HEP, its funding has gone downhill with HEP funding over the last few years, especially after the shutdown of the Tevatron at Fermilab.

Whether you support funding, or increase in funding, of this area of study is a different matter, but you should at least be aware and have the knowledge of what you are supporting or not supporting, and not simply make a decision based on ignorance of what it is and what it's implication can be.

Zz.

This is a neat animation video of the Fermilab Accelerator Complex as it is now, and all the various experiments and capabilities that it has.

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Of course, the "big ring", which was the Tevatron, is no longer running now, and thus, no high-energy particle collider experiments being conducted anymore.

Zz.

This is basically an inverse Compton scattering. The latest experiment that studies this has been getting a bit of a press, because of the sensationalistic claims of light "stopping" electrons in their tracks.

A review of the experiment, and the theory behind this, is sufficiently covered in APS Physics, and you do get free access to the actually paper itself in PRX. But after all the brouhaha, this is the conclusion we get:

The differing conclusions in these papers serve as a call to improve the quantum theory for radiation reaction. But it must be emphasized that the new data are too statistically weak to claim evidence of quantum radiation reaction, let alone to decide that one existing model is better than the others. Progress on both fronts will come from collecting more collision events and attaining a more stable electron bunch from laser-wakefield acceleration. Additional information could come from pursuing complementary experimental approaches to observing radiation reaction (for example, Ref. [7]), which may be possible with the next generation of high-intensity laser systems [8]. In the meantime, experiments like those from the Mangles and Zepf teams are ushering in a new era in which the interaction between matter and ultraintense laser light is being used to investigate fundamental phenomena, some of which have never before been studied in the lab.

I know that they need very high-energy electron beam, but the laser wakefield technique that they used seem to be providing a larger spread in energy than what they can resolve:

Both experiments obtained only a small number of such successful events, mainly because it was difficult to achieve a good spatiotemporal overlap between the laser pulse and the electron bunch, each of which has a duration of only a few tens of femtoseconds and is just a few micrometers in width. A further complication was that the average energy of the laser-wakefield-accelerated electrons fluctuated by an amount comparable to the energy loss from radiation reaction.

I suppose this is the first step in trying to sort this out, and I have no doubt that there will be an improvement in such an experiment soon.

Zz.

No, this is not some mumbo-jumbo New Age stuff.

While this technique has become more common, and there are already several places here in the US that are researching this, this is a nice article to introduce to you the current state-of-the-art in using charged particles in medicine, especially in treating and attacking cancer. It appears that the use of carbon ions is definitely catching up in popularity over the current use of protons.

When you read this article, pay attention to the fact that this is an outcome of our understanding of particle accelerators, that this is a particle accelerator applications, and that high-energy physics experimental facilities are often the ones that either initiated the project, or are hosting it. So next time someone asks you the practical applications of particle accelerators or particle physics, point to this.

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Here's a video from Don Lincoln on a physicist's view of proton radiation therapy in attacking a tumor.

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If you want a more detailed and technical information on proton therapy, you may access a more in-depth paper here. This, btw, is another example of the application of accelerator physics and elementary particle physics, in case you didn't know.

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The future of the next circular collider to follow up the LHC is currently on the table. The Future Circular Collider (FCC) is envisioned to be 80-100 km in circumference (as compared to 27 km for the LHC) and reaching energy as high as 100 TeV (as compared to 13 TeV for the LHC).

Now you may think that this is way too early to think about such a thing, especially when the LHC is still in its prime and probably will be operating for a very long time. But planning and building one of these things take decades. As stated at the end of the article, the LHC itself took about 30 years from its planning stage all the way to its first operation. So you can't simply decide to get one of these built and hope to have it ready in a couple of years. It is the ultimate in long-term planning. No instant gratification here.

In the meantime, the next big project in high-energy physics collider is a linear collider, some form of the International Linear Collider that has been tossed around for many years. China and Japan look to still be the most likely place where this will be built. I do not foresee the US being a leading candidate during the next 4 years for any of these big, international facilities requiring multinational effort.

Zz.

Here's a brief video on the superconducting radiofrequency (SRF) cavity for particle accelerators.

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I wouldn't call it "better particle accelerator" as in the video, because SRF cavity with Nb currently have a limit of 20-30 MV/m gradient, whereas normal conducting cavity can reach 100 MV/m or even higher at 1.3 GHz.

Still, these SRF cavities have properties that are "better" in other characteristics, especially in the Q-value. And in a number of applications, these cavities are the most efficient accelerating structures.

The technology for SRF is still evolving, especially in whether there is a need for superconducting photocathode sources for SRF guns. So there's a lot more to do in this field of study, both in terms of the physics, and in engineering.

Zz.

OK, before you send me hate mail and comments, I KNOW that I'm hard on this guy. He was probably trying to make a sincere and honest effort to explain something based on what he knew. And besides, this video is from 2009 and maybe he has understood a lot more since then.

But still, this video is online, and someone pointed this out to me. I get a lot of these kinds of "references" from folks online, especially with Wikipedia entries. And try as I might to ignore most of these things, they ARE out there, and some of these sources do have not only misleading information, but also outright wrong information.

This video, made presumably by a high-school science teacher, tries to explain what a particle accelerator is. Unfortunately, he described what a particle accelerator CAN do (i.e. use it in high energy physics colliders), but completely neglected the description of a "particle accelerator". This is a common error because most people associate particle accelerator with high energy physics, and think that they are one and the same.

They are not!

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As I've stated in an earlier post, more than 95% of particle accelerators on earth has NOTHING to do with high energy physics. One of these things might even be in your doctors office, to generate x-rays to look at your insides. So using high energy physics experiment to explain what a particle accelerator is is like using creme brulee to describe what a dessert is. Sure, it can be a dessert, but it is such a small, SMALL part of a dessert.

A particle accelerator is, to put it bluntly, a device to accelerate particles! Period. Once they are accelerated, the charge particles can then be used for whatever they are needed for.

Now, that may sounds trivial to you, but I can assure you that it isn't. Not only does one need to accelerate the charge particles to a set energy, but in some cases, the "quality" of the accelerated particles must be of a certain standard. Case in point is a quantity called "emittance". If these are electrons, and they are to be used to generate light in a free-electron laser, then the required emittance, especially the transverse emittance, can extremely low (in fact, the lower the better). This is where the study of beam physics is crucial (which is a part of accelerator physics).

The point I'm trying to make here is that the word "particle accelerator" is pretty generic and quite independent of "high energy physics" or "particle collider". Many accelerators don't even collide these particles as part of its operation (in fact, many do NOT want these particles to collide, such as in synchrotron radiation facilities).

What this teacher neglected to describe is HOW a particle accelerator works. The idea that there are these accelerating structures with a wide range of geometries, and they can have either static electric field, or oscillating electric field insides of these structures, that are responsible for accelerating these charged particles, be it electrons, protons, positrons, antiprotons, heavy nucleus, etc... And even for high energy physics experiments, they don't usually collide with a "fixed" target, as implied in the video. Both LEP, the Tevatron, the LHC, etc. all collide with beams moving in the opposite direction. The proposed International Linear Collider is a linear accelerator that will collide positrons and electrons moving toward each other in opposite direction.

So while the intention of this video is noble, unfortunately, the information content is suspect, and it missed its target completely. It does not really explain what a particle accelerator really is, merely what it can be used for. It also perpetuates the fallacy that particle accelerators are only for these exotic experiments, when they are definitely not.

Zz.

APS's Physics lists its highlight stories of 2015.

I need to point out something important that a casual reader might miss. The story on the 3D imaging of a virus may appear to be an advancement in biology or medical science. And it is, because this allows us to understand a virus better than before. However, it should be pointed out that this capability came into being because of advances in accelerator science. The imaging was done at SLAC's LCLS, which is a free-electron light source. This involves an advancement FIRST in accelerator science. Only after that are we able to create such a FEL that can produce light sources to do the imaging.

The point I'm trying to make here is that, if you value the field of biology and all the medical advances to help you live better, you should look at how these fields are able to accomplish such a thing. Just look at the National Institute of Health's funding projects, and see how many of them use instruments and facilities that all started out as something a physicist would use. Only later on were they adopted for use in other fields.

So without proper funding and support for the very basic research in physics, which in turn drives not only knowledge, but also the advancement in instrumentation and facilities, these new techniques and technology will not trickle down to the field of biology, chemistry, and medicine.

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I suppose I don't need to preach to the choir, but this is a nice, easy-to-read article if you ever encounter another person who is ignorant about how we have benefited from the study of nuclear physics.

A century is a long time in science, and things move quickly. It wasn’t long ago that we all had particle accelerators in our homes – the cathode ray tubes in our televisions. These have been superseded by LCD, LED and plasma displays, which are founded on our development of quantum technologies.

Perhaps the most prevalent application of particle accelerators today is in hospitals in the form of radiotherapy machines for the treatment of cancer.

In addition, Nuclear physics is the key to more or less all diagnostic imaging such as such X-ray, PET, CT, MRI, NMR, SPECT and other techniques that allow us to look inside the body without resorting to the knife.

If you’ve ever benefitted from one of these, thanks are due to many people, not least the nuclear physics pioneers who just wondered “what is this stuff?” and “what if…?”.

Certainly many aspects of nuclear physics overlaps with high-energy/particle physics, especially in the development of particle accelerators. But it is still worth noting that what started off as an area of study that had no obvious practical application has produced many indispensable necessities that are a part of our lives. This needs to be repeated many times for people who simply do not see the value of basic, fundamental research.

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Another example of where accelerators have wide-ranging applications outside of just high energy physics experiments.

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So let me point out this news article first before I go off on my rant. This article describes an important application of particle accelerators that has an important application in national security via the generation of high-energy photons. These photons can be used in a number of different ways for national security purposes.

The compact photon source, which is being developed by Berkeley Lab, Lawrence Livermore National Laboratory, and Idaho National Laboratory, is tunable, allowing users to produce MeV photons within very specific narrow ranges of energy, an improvement that will allow the fabrication of highly sensitive yet safe detection instruments to reach where ordinary passive handheld sensors cannot, and to identify nuclear material such as uranium-235 hidden behind thick shielding. "The ability to choose the photon energy is what would allow increased sensitivity and safety. Only the photons that produce the best signal and least noise would be delivered," explains project lead Cameron Geddes, a staff scientist at the Berkeley Lab Laser Accelerator (BELLA) Center.
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To make a tunable photon source that is also compact, Geddes and his team will use one of BELLA's laser plasma accelerators (LPAs) instead of a conventional accelerator to produce a high-intensity electron beam. By operating in a plasma, or ionized gas, LPAs can accelerate electrons 10,000 times "harder" or faster than a conventional accelerator. "That means we can achieve the energy that would take tens of meters in a conventional accelerator within a centimeter using our LPA technology," Geddes says.

I've mentioned about this type of advanced accelerator scheme a few times on here, so you can do a search to find out more.

Now, to my rant. I hate the title, first of all. It perpetuates the popular misunderstanding that accelerators means "high energy physics". Notice that the production of light source in this case has no connection to high energy physics field of study, and it isn't for such a purpose. The article did mention that this scheme is also being developed as a possible means to generate future high-energy electrons for particle colliders. That's fine, but this scheme is independent of such a purpose, and as can be seen, can be used as a light source for many different uses outside of high energy physics.

Unfortunately, the confusion is also perpetuated by the way funding for accelerator science is done within the DOE. Even though more accelerators in the US is used as light sources (synchrotron and FEL facilities) than they are for particle colliders, all the funding for accelerator science is still being handled by DOE's Office of Science High Energy Physics Division. DOE's Basic Energy Sciences, which funds synchrotron light sources and SLAC's LCLS, somehow would not consider funding advancement in accelerator science, even though they greatly benefit from this field. NSF, on the other hand, has started to separate out Accelerator Science funding from High Energy Physics funding, even though the separation so far hasn't been clean.

What this means is that, with the funding in HEP in the US taking a dive the past several years, funding in Accelerator Science suffered the same collateral damage, even though Accelerator Science is actually independent of HEP and has vital needs in many areas of physics.

Articles such as this should make it clear that this is not a high energy physics application, and not fall into the trap of associating accelerator science with HEP.

Zz.

Hey, if you have time to burn, why not build your own LEGO particle accelerator?

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Here's the synopsis accompanying the YouTube video:

This is a working particle accelerator built using LEGO bricks. I call it the LBC (Large Brick Collider). It can accelerate a LEGO soccer ball to just over 12.5 kilometers per hour. Watch the follow up video to see how it works: http://youtu.be/sjRPTDgjM0Q If you would like to see this potentially become an official LEGO set be sure to head over to LEGO Ideas and support the project! https://ideas.lego.com/projects/86253 You can find more information about how it works on my website at http://jkbrickworks.com/lego-particle...

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How would you like to own a 335-page book on the physics and engineering of electron photoinjectors? For free!

That is what you will get if you click on the link. If you are ever interested in electron accelerators, especially at the "birthing" end where the electrons are generated and given the initial acceleration, this is the review book to get. It explores not only the engineering aspect of the photoinjectors, but also the physics of photocathodes, and what makes a good photocathode for accelerator applications.

Highly recommended.

Zz.

This blog entry at Physics World presents an intriguing prospect at resurrecting high energy particle collider experiments in the US by reusing and re purposing the existing grounds in Texas that was meant for the failed Superconducting Supercollider facility.

However, a group of US physicists from Texas A&M University and Michigan State University is now proposing to wrestle back the energy frontier by constructing a huge accelerator in the US.

In a paper posted on the arXiv preprint server today, the researchers outline plans to use the partly constructed tunnel of the axed Superconducting Super Collider (SSC) just outside Dallas, Texas. Conceived in 1983, the SSC was to be the next big particle collider with a circumference of 87 km and a maximum collision energy of 40 TeV. But 10 years later the all-American project was cancelled, largely on grounds of cost, leaving a few buildings on the surface as well as tens of kilometres of tunnels deep underground.

Most of the cost of a new collider would be in excavating the tunnel, but the researchers claim that around 46% of the SSC tunnel has been already bored and some facilities built, such as the linear accelerator that feeds particles into the collider. This would then make it much cheaper than the CERN proposal.

If you continue reading the article, there are really seriously BIG proposals being mentioned here, up to a 270 km tunnel and 300 TeV machine!

I will admit that I am highly skeptical that the US will consider such a thing, at least, not under the current funding climate. I think they are a lot more organized at CERN, and with the wishy-washy political situation here in the US, having a center in Europe that is more "stable" is so much more preferred, especially considering that whatever this facility will be, it will involved a multi-national endeavor due to its expected astounding cost.

I'd love to be wrong with this one.

Zz.