Friday, February 24, 2017

SRF Technology For Particle Accelerator

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

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.


Wednesday, February 22, 2017

Dark Energy - What Is It?

I've posted many articles on Dark Energy. But here's another one aimed at the general public that actually is quite instructive. It describes not only why we think there is dark energy, but also the puzzling phenomenon of the apparent "switching" between one regime to another.

Please take note that, while it seems that this idea has been floating around for a while, the study of Dark Energy is very much still in its infancy. The general public may find it hard to understand, but we really do need a lot more experimental observations on this, and that is easier said than done. Detection of this is not easy and requires years of design and work, and not to mention, funding!


Mildred Dresselhaus

An absolute giant in physics, and especially on condensed matter physics, Mildred Dresselhaus passed away recently at the age of 86.

Besides all of her accomplishments in physics, she was truly a trail-blazer for women in science, and in physics in particular with all of her "firsts". She, along with Vera Rubin and Deborah Jin, were the strongest candidates to break the drought of women winning the Nobel Prize in physics. Now we have lost all three.


Monday, February 20, 2017

Will SMASH Be A Smash?

Here comes a new extension to the Standard Model!

A new theoretical paper in PRL has extended the Standard Model of elementary particles to include new particles, and tries to mash different ideas and theories into this new standard model called SMASH - Standard Model Axion See-saw Higgs portal inflation (yeah, it's a mouthful).

SMASH adds six new particles to the seventeen fundamental particles of the standard model. The particles are three heavy right-handed neutrinos, a color triplet fermion, a particle called rho that both gives mass to the right-handed neutrinos and drives cosmic inflation together with the Higgs boson, and an axion, which is a promising dark matter candidate. With these six particles, SMASH does five things: produces the matter–antimatter imbalance in the Universe; creates the mysterious tiny masses of the known left-handed neutrinos; explains an unusual symmetry of the strong interaction that binds quarks in nuclei; accounts for the origin of dark matter; and explains inflation.

Of course, with ANY theoretical ideas, which often has long gestation period, a lot of patient waiting and testing will have to be done to verify many of its predictions. But this seems to create quite an excitement in revamping the Standard Model.


Friday, February 10, 2017

Politics And How It Affects US Physics Research

This is a very poignant article on how politics have impacted Physics research in the US for the past decade or so. Reading this can be very disheartening, so be forewarned!

The one impact that I had mentioned a few years ago is also mentioned here, and that had to do with not only the impact of budget cuts, but also the devastating impact of a budget cut AFTER several months of continuing resolution of the US budget.

I remember one year on December first, we had a faculty meeting where we heard funding levels would be up 10% across the board — a miraculous state of affairs after multiple years of flat-flat budgets (meaning no budgetary increases for cost of living adjustments — which ultimately means it’s a 3% cut). At our next faculty meeting on December fifteenth, we heard that it was going to be a flat-flat year — par for the course. On December nineteenth, we hear the news that there was a 30% cut in funding levels.

Now losing 30% of your budget is very bad in all circumstances, but you have to remember that the fiscal year begins on October first. The only thing you can do is fire people since all the funding is salaries and to do that legally takes about six weeks and with the holiday shutdown, that meant that this was a 50% cut in that year’s funding. There was some carry-forward and other budgetary manipulations, but 30% of the lab was lost, about three or four hundred if I recall. The lab tried to shield career scientists and engineers, but still many dozens were let go.

In a post from a few years ago, I showed the simple mathematics on why this effect is devastating for science research.

Unfortunately, I don't see this changing anytime soon. As the author of this article wrote, science in general does not have a "constituent". No politician pays a political price for not funding science, or wanting funding for science to be cut, unlike cutting funding for social programs, military, or other entitlements.

Regardless of who is in office or who is in control of the US Congress, it is business as usual.


Wednesday, February 08, 2017

Gamma-Ray Imaging At Fukushima Plant

I mentioned earlier of the muon tomography imaging that was done at the damaged reactor at Fukushima, and tried to highlight this as an example of an application that came out of high energy physics. This time a gamma-ray imaging spectroscopy was performed at the same location to pin-point contamination sites.

But as with the muon tomography case, I want to highlight an important fact that many people might miss.

To address these issues of existing methods and visualize the Cs contamination, we have developed and employed an Electron-Tracking Compton Camera (ETCC). ETCCs were originally developed to observe nuclear gammas from celestial objects in MeV astronomy, but have been applied in wider  fields, including medical imaging and environmental monitoring.

So now we have an example of a device that was first developed for astronomical observation, but has found applications elsewhere.

This is extremely important to keep in mind. Experimental physics often pushes the boundaries of technology. We need better detectors, more sensitive devices, better handling of huge amount of data very quickly, etc...etc. Hardware have to be developed to do all this, and the technology from these scientific experiments often trickle down other applications. Look at all of medical technology, which practically owes everything to physics.

This impact from physics must be repeated over and over again to the public, because a significant majority of them are ignorant of it. It is why I will continue to pick out application like this and highlight it in case it is missed.


Tuesday, February 07, 2017

Being Slowly Eaten For A Decade

This is the definition of the ultimate torture.

It appears that this black hole has been slowly feasting on this dead star for at least a decade. Ouch!

"We have witnessed a star's spectacular and prolonged demise," said Dacheng Lin, a research scientist at UNH's Space Science Center and the study's lead author. "Dozens of these so-called tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one."

The arXiv version of this paper can be found here.

Moral of the story: Never piss off a black hole!


Monday, February 06, 2017

Photons Steal Momentum From Sun's Surface?

We all know that photons carry momentum. But who knew that photons leaving the sun's surface actually may cause the varying rotation of the sun with its radius?

This new paper from PRL makes the confirmation that the sun's surface has a greater drag and a slower angular rotation than the deeper part of the sun. But not only that, it also proposes that this slowdown is due to the loss of momentum when photons are emitted from the plasma on the surface.
Kuhn and his colleagues also developed a model to explain their data. Photons are created in the Sun’s dense core, where the plasma behaves nearly like a solid. As they diffuse outward, they experience plasma that is less dense, faster flowing, and subject to turbulent convection. As the photons interact with the moving plasma, they exchange angular momentum with it. Inside the Sun, the photons scatter so frequently that they lose as much angular momentum as they gain. But in the photosphere, where photons escape the Sun, the plasma-photon momentum transfer results in a net loss of the plasma’s angular momentum, as photons radiate away. The effect on the plasma is a mild braking force, which slows its overall rotation. This braking is most effective at the outer edge of the Sun, where the plasma density is at its lowest.
Those photons! They can create havoc!


Thursday, February 02, 2017

The Emperor Has No Clothes

The impact of the Trump's executive order on the admission of citizens from the 7 countries continues to be felt and the topic of conversation in many college campuses, science labs, and conferences. But something triggered in my head when I read this Washington Post news article on how this ban would not have prevented the attacks in the US since Sept. 11. When I read this, I immediately remembered a similar scenario, and this is where I connect it to the theme of this blog.

Back in, oh, I forget exactly when, probably mid-2000s, there was a laser accident at a lab (I'm not gonna name names). I'm going to rely on my memory based on what I read as the official report on the accident, and from what I heard from a friend who happened to know the person involved.

To set up the scenario, most, if not the majority, of laser accident occurred when the laser is running and the safety mode is bypassed. The most frequent reason for doing this is that the laser is either being worked on, being repaired, being serviced, or the most common occurrence, it is being aligned. People who are authorized to do this are usually trained, and had to undergo safety classes to ensure that they know what they are doing.

What happened in this accident, from what I remember, is that this person, along with at least one other person, was doing a typical laser alignment. He was wearing a pair of safety glasses as required, which protected his eyes in case there were stray beam hitting his face. Unfortunately, while in the middle of doing this work (which was part of the standard operating procedure of the facility), he had an itch around his eyes. In a moment where instinct took over, before he had time to think about it, he reached inside his safety glasses with his hand to rub his eyes, causing the safety glasses to be lifted off his face. Unfortunately, without realizing it, a beam of the laserwas, at that time, pointing straight at him. It only happened probably less than a second, but it was enough that the laser hit his eyes and sufficient to cause damage.

I'm not going to go into detail of what happened immediately afterwards, because it isn't relevant to this story. So of course, after this incident is reported, the lab issued a lab-wide stand-down, and all operations of Class 2b laser and higher had to stop. We were told to evaluate our laser operations and safety procedure, and we had to get reauthorized before we can continue work. At the same time, all personnel that are involved in any laser work had to attend a safety seminar.

So I sat through this safety seminar where they described the accident, emphasize the need for us to work safely, re-enforce the requirements for safety procedure... etc...etc. But at the same time, in response to the accident, they produced a whole new set of policy and procedures for all laser facilities. We had to have yearly inspection, yearly authorization, and new documentation of our procedure and safety analysis. In other words, new set of administrative controls were introduced.

Of course, as you can guess, there were groans in the audience, because it meant that there would be more bureaucratic paperwork and administrative hoops that we had to go through. During the Q&A session, several people asked questions, and one could tell that a lot of people in the audience weren't too pleased by this. Finally, and this is where I came, in, I raised my hand, and asked something like this:

"So how would any of the new procedures that were introduced prevented this accident?"

Now, looking back on it afterwards, I would describe the audience reaction to my question as what I imagined would happen when someone finally yelled that the Emperor had no clothes. In this case, the Emperor truly had no clothes. It was an unfortunate accident, but no amount of training, regulation, safety briefing, paperwork, review, etc. would have prevented it, because that was something instinctual. The new administrative policy that was put in place didn't make any of us who work with these lasers any safer. I certainly didn't feel any safer than before. Yet, this was imposed upon us. It wasn't to make us any safer or to prevent any accident. It is simply to placate the higher-ups, the stakeholders, the policy makers, the regulators, the administrators, and finally and ultimately, the politicians (if they decided to look into this). They can say that they implemented this and that after the accident to make them look good. The rest of us who are actually doing the work get saddled with more paperwork and more hoops to jump through.

I'm certain that this isn't new, and that many people have gone through such similar situations where what is being done in the name of something really isn't effective and may miss the mark. Often times, we simply go along just to make the administration happy so that we can move on and continue with our work. But it still means that the Emperor has no clothes, and sometime, someone really needs to stand up and points out this ridiculousness.


Tuesday, January 31, 2017

Fermilab's Greatest Hits

Highlights from the first 50 years at the historic Fermi National Accelerator Laboratory.


Monday, January 30, 2017

Presidential Executive Order and US Conferences

With the two big conferences looming this year, the APS March and April Meetings, it will be interesting to hear how the recent presidential executive order banning entry by visitors from 7 predominantly-Muslim countries will have affect. Citizens from countries such as Iran already had a long and arduous process in gaining a visitor visa to come to the US, so much so that many won't even bother to try.

So now, with the entry ban, looks like this will have an impact on visiting scientists from these affected countries. Unfortunately, this will create an even bigger ramification, because international organizations will be less inclined to hold major conferences in the US where some of its members will not be allowed to attend. This should have both scientific and economic impacts.

So far, there has been no official word from the APS on this matter.


Friday, January 27, 2017

3 Things Everyone Should Know About Physics

This is an exceptionally good answer to the question: "What do physicists wish the average person knew about physics?" The answer was written by Inna Vishik, Assistant Professor of Physics at the University of California, Davis.
  • Physics makes predictive models about the natural world based on empirical observations (experiments), mathematics, and numerical simulations. These models are called ‘theories’, but this does not mean they are speculative; physics theories explain past behavior and predict future behavior. When a previously-validated theory fails to explain the behavior in a new physical system, it doesn’t mean the theory is suddenly ‘wrong’ altogether, it means that it is inapplicable in a certain regime. It is very exciting for physicists when these exceptions are found, and it is in these holes in our models that we propel our understanding of the physical world forward.
  • The domain of physics is vast. Some physicists study the existing universe around us. Some study the smallest constituent particles and forces of matter in this universe. Some manipulate clusters of atoms, and some manipulate light. Some study crystalline solids and the myriad properties they can have when quadrillions of atoms and electrons are arranged in slightly different ways. Others study biological systems. This is not a full list of the many subfields in physics, but what they all have in common is they combine classical (including continuum) mechanics, quantum mechanics, statistical mechanics, general relativity, and electricity and magnetism in various configurations to explain the physical and engineered world around us.
  • Research in physics and other fundamental sciences play three crucial roles in an advanced society; they cement our cultural legacy by exploring one aspect of the human condition (the universe we occupy), similar to the role of the arts; they educate a portion of the work force in solving difficult, open ended problems beyond the limits of prior human innovation; they provide the seeds for future technological developments, which is often realized decades in the future in an unpredictable manner (i.e. not amenable to quarterly earnings reports). At the time of their inception, electromagnetic waves (late 19th century), quantum mechanics (early 20th century) and lasers (mid 20th century) were viewed even by their progenitors as esoteric curiosities; now they permeate our life, technology, and medicine so deeply that no one would question their practical importance. In the modern physics research era, there are newer ideas that might have an equally important impact 50 years from now, but they will never be realized without continued investment in the public good known as fundamental science.


Metallic Hydrogen?

The big news so far this week is the publication on the possible (key word) creation of solid metallic hydrogen.

If this is true, then this is a significant discovery and confirmation of a prediction from many years ago. Understandably, with the press releases on this work, the popular media have been going ga-ga over this.

However, upon trolling all the various news reports, only the Independent so far has an update on the news story about doubts about this discovery.

This is taken from a news report published in Nature:

As with ANYTHING in Science, we have to give this a period of gestation before we all jump onto the bandwagon. It needs to be independently verified, and even the authors admit that this needs to be refined even more to produce a conclusive evidence of metallic hydrogen.