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.

Zz.

Just in case you don't know what's going on at SLAC's LCLS, and the upcoming upgrade to bring it to LCLS-II, here's a CNET article meant for the general public to tell what what they have been up to, and what they hope to accomplish with the upgrade.

Keep in mind that LCLS is a "light source", albeit it is a very unique, highly-intense x-ray light source. SLAC is also part of the DOE's US National Laboratories, which include Brookhaven, Fermilab, Berkeley, Argonne, Los Alamos, .... etc.

Zz.

CERN Courier has a rather informative article on the start-up of NSLS II and its capabilities. It certainly is the newest "from scratch" light source facility (rather than just an upgrade of an existing facility).

I hope they save some parts of the original NSLS and commemorate it with some sort of a marker. After more than 30 years of service, that facility certainly was worth every penny spent on it.

Zz.

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.

Have you been following this ridiculous debate about the color of this dress? People are going nuts all over different social media about what the color of this dress is based on the photo that has exploded all over the internet.

I'm calling it ridiculous because people are actually arguing with each other, disagreeing about what they see, and then found it rather odd that other people do not see the same thing as they do, as if this is highly unusual and unexpected. Does the fact that different people see colors differently not a well-known fact? Seriously?

I've already mentioned about the limition of the human eye, and why it is really not a very good light detector in many aspects. So already using your eyes to determine the color of this dress is already suspect. Not only that, but due to such uncertainty, one should be to stuborn about what one sees, as if what you are seeing must be the ONLY way to see it.

But how would science solve this? Easy. Devices such as a UV-VIS can easily be used to measure the spectrum of reflected light, and the intensity of those spectral peaks. It tells you unambiguously the wavelengths that are reflected off the source, and how much of it is reflected. So to solve this debate, cut pieces of the dress (corresponding to all the different colors on it), and stick it into one of these devices. Voila! You have killed the debate of the "color".

This is something that can be determined objectively, without any subjective opinion of "color", and without the use of a poor light detector such as one's eyes. So, if someone can tell me where I can get a piece of this fabric, I'll test it out!

Zz.

We had the 2005 International Year of Physics, and 2009 International Year of Astronomy. Now in 2015, UNESCO has declared that this will be the International Year of Light.

In case you missed it, the APS has made available a series of significant articles and papers related to this topic. Check them out.

Personally, as someone who has performed work at a synchrotron light source, and done studies using photoemission phenomenon, I can truly appreciate "light" beyond just what we normally do everyday.

Zz.

I mentioned of my final visit to the NSLS before its impending shutdown. I had to stop and chuckle at one of the UV beamlines during my casual tour around the place. There were cuddly plushes strategically placed along the beamlines, including Kermit and Miss Piggy in a rather amorous position (not that there's anything wrong with it).

And yes, I took a few photos.


I hope they remember to rescue these guys before the wrecking ball arrives.

Zz.

I had a chance recently to visit my old romping ground, the National Synchrotron Light Source (NSLS) at Brookhaven Lab. I spent 3 years there doing my postdoc work, and the facility is about to be shut down at the end of Sept. 2014 as the new facility, the NSLS II just right next door, will take over. The old lady is still running, but you can tell that she's old, decrepit, with lots of aches and pains, and about ready to retire. One can tell that this place is about ready to be shut down when even the vendors no longer refill the vending machines!

I was there on the day that Long Island, NY received 13 inches of rain within a 12 hour period, and walking in the next day, I saw leaks and a few water issues. Oh yeah, the old lady is definitely ready to go. The NSLS was such a workhorse during her glory years. To say that she was over-subscribed is an understatement. The place was packed with users on top of each other. The presence of two separate rings, one for the x-ray and the other for the UV/IR/low energy photons, made it quite unique and useful for many applications and studies.

Across the street from her is the new lady on the block, the NSLS II. She's huge when compared to the old lady, she's shiny and new, more powerful and sleeker. I look forward to visiting her when she's in operation, but I'll never forget the one I spent a lot of days and nights with. She gave me good data. How many dates have you been on where you can say that?

So long, NSLS!

Zz.

Another important science facility in the US is set to be shut down for good. The Synchrotron Radiation Center at the University of Wisconsin is set to close its doors for good on March 7.

After funding cuts from the National Science Foundation and the lab announced its preparations for closure, UW provided the lab with short-term funding as alternatives were sought. Bisognano said he has been looking for other sources for funding over the past several years, but with a shortfall of approximately 5ドル million, he has announced that the lab will be forced to close in March.
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“Over the past few years, we’ve developed an infrared beam that can measure the structure and the chemical identity of the target material at the same time,” Bisognano said in a statement. “This device is the best in the world, and that’s probably the saddest part about shutting this down.”

I believe if you also look at the incredible body of work out of the Campuzano's group at Argonne/UIC on ARPES measurement on high-Tc superconductors in the late 80's, 90's, and well into the early 2000's, you'll find that these were done at the SRC. This small facility, with barely a drop in the bucket in terms of funding costs, was a workhorse!

While many other countries, especially China, are racing to add scientific facilities within their countries, the US is tripping over itself to close one after another. At what point will the public and the politicians make this realization?

Zz.

In case you missed it from 2 weeks ago, this Nature article (Nature, v.505, p.604 (2014)) on X-ray FEL is similar to the article I highlighted earlier. The major difference here is that they are really highlighting the "trees", in this case, the XFEL facility and physics themselves.

In the foothills above Palo Alto, California, physicists have set up an extreme obstacle course for some of the world’s fastest electrons. First the particles are accelerated through a 3-kilometre vacuum pipe to almost the speed of light. Then they slam through a gauntlet of magnets that forces them into a violent zigzag. They respond with a blast of X-rays so fierce it could punch through steel.

But the scientists at the SLAC National Accelerator Laboratory have no interest in weaponry. Their machine, one of the world’s most powerful X-ray free-electron lasers (XFELs), is a tool for studying challenging forms of matter, whether compressed to the kind of pressures and temperatures found deep inside a star, or folded into the complex tangle of a protein molecule.

Again, this is possible due to advancement in accelerator physics, which is now a separate field of physics in itself. Only when the "instrument" is available can scientists from other fields use it to look deeper and in greater detail at many of the things they study.

Zz.

One of the most common misconception that I have to deal with is the idea that light can ONLY be created upon an atomic transition. You wouldn't believe how many people believe that this is the only way to create light. This shows a severe lack of understanding of classical E&M and Maxwell equations.

The one example that I typically use to counter such misconception is to tell people to figure out how synchrotron centers around the world create light, or EM radiation. In particular, many of these centers generate x-rays to be used for various purposes. These x-rays are generated via "charge acceleration", either by using the bending magnet, or using the insertion devices that essentially cause the electrons to "jiggle" up and down (or sideways) as if they are at the end of a spring. These cause the generation of EM radiation. No "atomic transition" is involved.

This video shows clearly how x-rays are produced at the Advanced Photon Source at Argonne National Lab.

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Zz.

A neat video that describes a program at Brookhaven Lab that allows high school teachers, and their students, the opportunity to make a proposal for an experiment.

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I wish they revealed the results of the experiment! That's the only part missing in here.

Zz.

We have news reports that the newly installed FEL system at Jefferson lab has broken its own record for laser power.

However, the news report may have a slight typo in describing the power that was reached:

Researchers at the Department of Energy's nuclear physics laboratory on Friday injected a record-breaking 500 kilovolts of power into the laser's accelerator. The previous limit set by Jefferson Lab researchers had been 320 kilowatts.

They may have meant 500 kilowatts of power. Kilovolts is potential difference, and it is also not kosher to compare kilovolts with kilowatts.

In any case, this is quite a significant increase! One would hope that the US Navy knows where to point one of these things if they ever build it on their ships.

BTW, in case people don't realize it, a free-electron laser (FEL) is an ACCELERATOR facility (i.e. it is not an optical/solid state light source). I'm simply highlighting another application/use of accelerator physics.

Zz.

{There was a pun in there.}

Here's a good video to introduce you to FLASH, the FEL facility at DESY.

[埋込みオブジェクト:http://www.youtube.com/v/555lKi37iws?fs=1&hl=en_US]

This, of course, is a counterpart to LCLS at SLAC. It looks like FEL facilities are popping up all over the place as the new "in-fashion" light source. This is almost like 20 years ago when synchrotron centers were the rage as light sources.

Zz.

This is a terrific program to allow teachers and students to work and see how science is done at major scientific facilities, in this case, the National Synchrotron Light Source (NSLS) at Brookhaven Lab. If you are a high physics school teacher, especially if you're in Long Island, this might be something you want to consider since this is such a wonderful opportunity to get a first hand look at how science is done at a major synchrotron facility.

[埋込みオブジェクト:http://www.youtube.com/v/3VMMjHeuvoE&hl=en_US&fs=1&]

Zz.

Congratulations to all the folks at SLAC's LCLS for completion of CD4 Milestone just today! Here's the official announcement.

Today at approximately 1PM, LCLS achieved its project completion (CD-4) milestone of delivering first photons to the Far Experimental Hall. This is a tremendous day for SLAC! I congratulate all of you who have worked so hard to make this happen. Above all, I want to congratulate and thank John Galayda for delivering this wonderful machine on time, on budget and with outstanding performance!

Persis

Well done, folks! This was one tough beast to construct, especially with such tight tolerances. It is an amazing accomplishment.

Zz.

All those theories that have the possible Lorentz violation will have to deal with a new lower and more stringent limit on light speed isotropy. A new study base on the Compton edge measurement at the ESRF has imposed a new limit on such isotropy.

Abstract: When the electrons stored in the ring of the European Synchrotron Radiation Facility (ESRF, Grenoble) scatter on a laser beam (Compton scattering in flight) the lower energy of the scattered electron spectra, the Compton Edge (CE), is given by the two body photon-electron relativistic kinematics and depends on the velocity of light. A precision measurement of the position of this CE as a function of the daily variations of the direction of the electron beam in an absolute reference frame provides a one-way test of Relativistic Kinematics and the isotropy of the velocity of light. The results of GRAAL-ESRF measurements improve the previously existing one-way limits, thus showing the efficiency of this method and the interest of further studies in this direction.

The new limit is Delta(c)/c of less than 1 e-14.

Zz.

I fully admit that I'm completely ignorant (and therefore, probably unable to appreciate it) of modern dance. So I certainly could have missed any kind of "message" and artistry from it. Still, maybe the Emperor really has no clothes!

[埋込みオブジェクト:http://www.youtube.com/v/CwW5gpJy1UE&hl=en_US&fs=1&]

This, I'm guessing, is some form of a kick-off celebration for the start of construction on the NSLS II at Brookhaven Lab. The info says that ".... members of the Center for Dance, Movement and Somatic Learning at Stony Brook University performed a special interpretive dance titled Time and Space for Celebration...." All I can say is that I'm glad I wasn't in the audience, because I will get a fit of the "church giggles" watching this. If you don't tell me the title of the dance or the occasion, I would have never guessed that this is an "interpretive" dance on "time and space for celebration". Besides, "time and space" is rather "generic", isn't it? One would think that for the NSLS II, which will be a synchrotron light source facility, one would want to have a subject closer to either light or electron storage ring/beam dynamics, etc, not "space and time". Either way, I don't get this at all.

Or maybe I'm just being extra bitchy this morning because I haven't had my coffee yet... :)

Zz.

It was a major undertaking and a total 'sex change' for SLAC going from a high energy physics facility to a "light source" facility with the LCLS. But it appears to be going smoothly and about to produce a lot of science.

Commissioning assisted by users is currently under way, with experiments taking place using the Atomic, Molecular and Optical (AMO) science instrument, the first of six instruments planned for the LCLS. In these first experiments, the researchers are using X-rays from the LCLS to gain an in-depth understanding of how the ultrabright beam interacts with matter.

And kids, please note that this is made possible by knowledge and advancement in accelerator physics, not high energy physics or particle collider. They are not the same thing.

Zz.

This is a nice, brief history of Cornell's synchrotron research lab and efforts, which has been at the forefront in not only synchrotron physics, but also the early efforts of experimental particle physics.

Still, what's wrong with this picture?

A synchrotron is a device that uses a magnetic field to accelerate particles (e.g. electrons) at faster and faster speeds by boosting their energies as they travel around the ring.

I guess they meant electromagnetic fields, since I'm sure we all know that magnetic fields can't accelerate charged particles.

Zz.