What Is A Plasma?

I love the Chicago's Museum of Science and Industry (MSI). In fact, I am a member and a donor to the museum. So let's get that out of the way first.

Secondly, I know how difficult it is to explain scientific concepts to the public. The need to use simple words and terminology, AND, make it accurate can be a daunting task.

Still, I can't help but be a bit disappointed by this sign that I saw at MSI this past week. Granted, this was in the gift store, but still, for an institution promoting science, this falls a bit short.

The sign accompanies one of those "plasma arc ball" thingy that they were selling:

Here's what the sign says:

A plasma is a gas that has been heated to extremely high temperatures. At these high temperatures, the atoms are moving so fast that they lose their electrons, creating ionized particles. The electrons and ionized particles jump from one place to another to try and get as far away from each other as possible, creating a "lightening" effect.

There are problems with this description.

1. A plasma need NOT be only a gas that has been heated to high temperatures. I can create a plasma by blasting gas atoms with energetic electrons. In fact, when you have an electrical discharge, that is essentially what happens. The gas has not been heated by any means. So there are other means of creating a plasma beyond just heating. So a plasma is NOT defined as ".... a gas that has been heated to high temperatures...."

2. At high temperatures, the atoms lose their electrons not because they are moving "so fast". They lose their electrons because when they move "so fast", they also collide harder against other atoms, and collide more frequently. This tend to give each atom the energy to knock off one or more electrons, thus causing it to be ionized. Atoms do not lose electrons simply because they are moving "so fast".

3. The description that "... The electrons and ionized particles jump from one place to another to try and get as far away from each other as possible, creating a "lightening" effect.... " is extremely puzzling and, frankly, irrelevant to the description of what a plasma is. In fact, if you think about it, when an atom is ionized, it has a net positive charge. An electron, having a negative charge, would tend to want to go back to the positively-charged ion. So why would they want to "... get as far way from each other as possible..."?

4. The last part is trying to describe the creation of an electric discharge or an arc. This is superfluous, and is not part of the definition of a plasma. An electric discharge is a form of a plasma, but a plasma is not JUST an electrical discharge.

So what is a plasma? If, say, someone at MSI who isn't a physicist needed to make this sign, and Googled it, he/she will see several definitions. I'll pick one (the bold is mine).

Plasma is the fourth state of matter. Many places teach that there are three states of matter; solid, liquid and gas, but there are actually four. The fourth is plasma. To put it very simply, a plasma is an ionized gas, a gas into which sufficient energy is provided to free electrons from atoms or molecules and to allow both species, ions and electrons, to coexist. The funny thing about that is, that as far as we know, plasmas are the most common state of matter in the universe. They are even common here on earth. A plasma is a gas that has been energized to the point that some of the electrons break free from, but travel with, their nucleus. Gases can become plasmas in several ways, but all include pumping the gas with energy. A spark in a gas will create a plasma. A hot gas passing through a big spark will turn the gas stream into a plasma that can be useful. Plasma torches like that are used in industry to cut metals. The biggest chunk of plasma you will see is that dear friend to all of us, the sun. The sun's enormous heat rips electrons off the hydrogen and helium molecules that make up the sun. Essentially, the sun, like most stars, is a great big ball of plasma.

The bold sentence, to me, is a sufficient definition of a plasma to be given to the general public. An ionized gas can be made up of equal parts of positive ions and electrons, unequal parts of positive ions and electrons, all ions, or all electrons, i.e. there are free charges floating around at a given time. This, to me, is a more accurate definition than what the MSI sign says.

I'm not sure how many of MSI guests paid attention to the sign or learned what a plasma is from that sign. But I hope those responsible for such signs pay closer attention to the accuracy of the info that they put out.

Zz.

Combining QM, SR, and HEP is "New"?

Often times, when science news is reported in the mass media, while the reporting might be somewhat accurate, the implications that it leaves behind, especially when read by someone not trained in that area, may lead to a horribly wrong idea. This might be the case here.

This news report is covering a paper out of the Princeton's Plasma Physics Lab (PPPL) on a new theoretical model to explain a plasma physics phenomenon. Nothing wrong there. However, I have a lot of issues with this part of the report very early on:

Researchers at the Princeton Plasma Physics Laboratory (PPPL) have developed a new way to explore some of the most extreme environments in the universe by combining three separate branches of physics: High energy physics (which describes charged particles traveling at or close to the speed of light), quantum mechanics (which describes the motion of subatomic particles), and Einstein’s theory of special relativity (which describes the propagation of matter and light at high speeds).

“People haven’t done this before,” Yuan Shi, a graduate student in the PPPL and lead author of a paper published July 29 in the journal Physical Review A, told Business Insider. “Nobody really wanted to cross the boundaries between the disciplines to see what other scientists are doing. The difficulty was mostly that there’s no communication between these fields.” 

Now, I'm sure that if you are a physics, or even a graduate student in physics, you can already spot something odd here. The existence of quantum field theory (QFT) is already evidence that Special Relativity (SR) has already been incorporated inside quantum mechanics (QM). And high energy physics (HEP) is a field that makes use of QFT!

But if you don't know that, then reading this news report will give you the impression that this isn't known till now, and that this is all new!

And the statement made that "People haven't done this before" with regards to crossing boundaries between disciplines in physics is blatantly false, especially with all the brouhaha surrounding the discovery of the Higgs within the the past couple of years. Anyone following the history of the Higgs field will have seen how the idea originated out of a condensed matter system, and how Phil Anderson, a condensed matter physicist and a Nobel laureate, was himself a strong candidate to be considered for the Nobel prize when the Higgs was finally discovered.

I know that press releases can sometime over-glorified the importance and significance of something. But there really is an important mission here to make sure that one is conveying a message that is clear and unambiguous to the audience that can easily be misled. What you mean may not be exactly what they understand!

Zz.

A Tour Of MIT's Plasma Physics And Fusion Center

If you haven't seen the inside of it, here is a quick tour of MIT's Plasma Physics and Fusion Center.

Zz.

Scientists Work on New Particle Accelerator

This news report describes the planned upgrade of the laser plasma wakefield accelerator at Berkeley Nat'l Lab.

Researchers at the Berkeley Lab plan to use microscopic waves to charge and accelerate some of the smallest particles in the universe.

The process will take place in the lab's "table-top" Berkeley Lab Laser Accelerator, a device that is planned to be built by fall 2009 and will replace the lab's current, smaller accelerator.

Not sure what the article meant as ".. some of the smallest particles in the universe.. " when they can just mention "electrons" and be done with, because that is accurately what the facility will accelerate.

The news report has some rather puzzling statements. For example:

A laser beam will then puncture the gas and cause a "wake" that will accelerate and charge the particle that follows the beam, said Paul Preuss, a member of the communications department for the lab.

The laser will cause the wake, yes, but it also "charge up" the following particle that is being accelerated? It will charge up the gas and turning it into a plasma, but the particles being accelerated, which are electrons, are already "charged"!

In this scheme, a high-powered pulsed laser passes through a cloud of neutral gas. The laser's electric field then ionizes the gas for a split second, creating a region of very high electric field gradient (what the news article kept referring to as creating "charge"). This high gradient is the accelerating gradient that will accelerate an electron bunch that trails after the laser pulse. I've highlighted this technique a while back.

This is such an amazing technique that can achieve quite high gradient. If it can be implemented, the energy ceiling for high energy physics experiments can be raised quite a bit without busting a budget. Too bad the reporting of the physics isn't that clear.

Zz.

Students Went Into Zero-G To Do Experiment

Well, this sounds like a lot of fun.

A number of students from New Jersey went into the "Weightless Wonder", a NASA plane that can make zero-g dives, to do their experiment on plasma dust clouds.

In 2008, the first Team DPX -- comprised only of students -- boarded a DC-9. This year, NASA invited Zwicker, who was one of the mentors for both DPX teams, to join the students. The 2009 team -- including several additional students -- took aboard a second dusty plasma experiment, as well as upgraded equipment and additional cameras.

That's almost as an exotic of a "location" to do one's experiment as going to the Antarctica. Still, I wish the news report tells us a little bit more of the nature of the experiment and what exactly is being observed.

Zz.

PPPL Gets A New Director

The Princeton Plasma Physics Lab will get a new Director. Princeton has announced that Stewart Prager from U. of Wisconsin-Madison (my alma mater) will be the new director of the DOE lab.

Prager, who also is the Dexter Professor of Physics at Wisconsin, will become the sixth director of the laboratory, which is funded by the DOE and managed by the University. His appointment as a professor of astrophysical sciences at Princeton is expected to be acted on in the fall.

Zz.

US National Compact Stellarator Experiment Cancelled

I suppose this is neither inevitable nor surprising. The National Compact Stellerator at Princeton Plasma Physics Laboratory has been shut down, mainly due to cost overruns and delays.

"In late 2006, it became clear that NCSX construction project would not be able to meet its approved baseline total project cost of $102M or its completion date of July 2009," said Under Secretary for Science Raymond Orbach in a statement. Since then the DOE, Princeton University, and Princeton Plasma Physics Laboratory (PPPL) have been reviewing their options for the project and PPPL. They concluded that "the budget increases, schedule delays and continuing uncertainties of the NCSX construction project necessitate its closure," said Orbach. The new proposed cost for NCSX was $170 million with an August 2013 start date, which would have put research at PPPL in peril said an April 2008 Office of Science report.

Zz.