I started this blog with the aim to promote topical stories in the area of plasma technology. I wanted to talk about things that interested me that I thought would interest a wider audience of scientist and engineers working in the area of plasma technology. In the last few months two new sources of news have started. The first is the recent release of the Plasma Post, an E-zine aimed at keeping people updated on what’s happening at The National Centre for Plasma Science & Technology(NCPST) and the Precision Cluster. The NCPST is based at Dublin City University(DCU) and the newsletter aims to relate stories on the progress of the latest research and provide a broad view of new innovations, applications and technologies being developed using plasmas. The E-Zine will also feature news from the NCPST’s industry partners. If you would like to contribute then contact them directly at firstname.lastname@example.org
The second is the Plasma News a blog edited by an MSc student studying Science and Media at DCU. The aim is to release a number of posts every week on the main stories in plasma technology. I am going to have to take a back seat on the news side, although I am really happy to let both sites use any material they like from my Blog.
I have to declare an interest in that I was one of the founders of the NCPST at DCU and I was also a founder of Impedans Ltd which is a partner in the Precision research center. I am also a keen supporter the The Plasma News as I think that there is a lack of good sources of stories in the plasma area.
I have said before that plasmas are often considered an art more than a science. This is true in industry where plasmas are developed to do many exotic things and then locked in copy exact mode to perform the same feat forever. It is why plasma measurement is usually referred to as plasma diagnostics rather than plasma measurement. It is also why there is no real market for plasma sensors. Imagine another industry using thermal ovens without thermometers. Am I the only person with this view? I would welcome your comments.
A friend of mine, Rita O’Donoghue from Galway, has written a poem about electrons, so I dedicate this to all the Plasma Fusion guys, especially those with magnetic pinch devices.
The Dance of the Electrons
He was one of the most dependable and stable of elements
the very foundation and workhorse of society
as any woman worth her physics will tell you
that he almost always avoided relationships
withstood all attempts to split, even with a bit of quark
Being a fermion he did not like being too close
Or share space; it excited his energy levels
so he almost always avoided other electrons
except of course
those in very powerful magnetic fields
who frequently associate with each other
and for a time the union maintained its charge
But as even the dogs in the streets know
when electrons in powerful magnetic fields
associate with one another and behave
like quantum fluid, inevitably they form
new types of particles.
One night, all hell broke loose
an electron charge, baring only a fraction,
acted as a bosom in a strong magnetic field
and finally made the connection:
He found himself like a like a storm at sea.
a force blown on every magnetic wind
where electrons of this or that quantum fluid
moved in and out between his eddies and waves
without ever being properly charged, until one day
a new phenomena was created, and changed him
and all he thought his, irrevocably.
I am publishing the second in a series of courses in Plasma Physics, A brief History of Plasma Physics. It is interesting that the term plasma was first used by Langmuir in 192o’s, less than a hundred years ago. The contribution made by plasma to our everyday life is now quite remarkable. Everything from Laptops to iPads owe there existence to plasma processes and plasma technology. The range of products that depend on plasma processes grows every year. I try to keep us all abreast of the more interesting. See for example a recent post on plasma in the home.
Find a short Video of the material in a Brief History of Plasma Physics on Youtube
I see that Lawrenceville Plasma Physics is back in the news again with the announcement of a collaboration between LPP and an Iranian research institution. The collaboration agreement is for scientific publications on aneutronic fusion, which some sources claim could be a possible route to cheap, safe, clean energy. This blog believes the claim is the result of an over active imagination of a science fiction writer. The US Government is taking this agreement seriously with claims that President Obama’s Council of Advisors on Science & Technology have been briefed on this agreement.
However, I believe that the efforts at LPP are more likely to be the flights of imagination of the lead researcher than any serious attempt at fusion. However, it is discomforting to see this nonsense elevated by this political manoeuvre by LPP. I can only hope it leads to the place being closed down.
Importance of Scientific Research
Scientific research is an important factor in the analysis of new technologies. It is important to have independent scientific data especially when we are talking about plasma technology. Plasmas are very complex and it is easy to make claims that are not based on true scientific fact. You can get a more detailed explaination of what a plasma is in the physics area, noting that it not in anyway linked to the biological plasma.
Examples of new plasma technologies
Examples of existing plasma technologies
We have all heard of the plasma TV, where small cells within the TV are exposed to an electric field. The gas in the cells break down to form a plasma. The light from the plasma, which is in the UV is used to excite a phosporous screen to give high quality pictures. Different types of phosphors create red, green and blue light to give the color. The plasma TV has excellent picture quality and color definition.
It is not so well known that in a smoke detector, a weak corona plasma is formed and electrical current flows via electrons across the smoke detector. Normally, with no smoke the plasma current is undisturbed and a stable current is reached; but when smoke enters the plasma region the electrons collide with the smoke particles. It is a little like elephants walking on a motorway, suddenly everything goes much slower. The plasma current drops and the smoke alarm is sounded. So plasmas can saves lives even in our house.
A recent new technology uses the same idea of electrons colliding with dust particles. It is called a ionic purifier. When the electrons collide with the dust they stick to the surface, this causes the dust clusters to become negatively charged. The ions also collide with the dust but the ions are much heavier and therefore much slower, so more electrons hit the dust than ions. In a purifier a weak plasma is formed and any dust particles present are charged up negatively. An electric field with a positive and negative side is set up and the dust is attracted to the positive side. The dust is then collected and removed from the air. This is very important as some people are allergic to dust and mites that float in the air.
The weak plasma also has some more useful effects. When the electrons are heated in the electric field they collide with gas atoms and molecules and knock off electrons, this is called ionisation or ionization to our American cousins. But not all electron collisions successfully knock off the electron from the atom, some collisions just shake the atom or molecule and cause the electrons to enter an excited state. These atoms or molecules with excited electrons are called radicals. Radicals can collide with other gas atoms or molecules and form short lived chemicals called metastable states. These metastable molecules or atoms are highly reactive because the electrons are excited and they will react with cells or other living organism, killing them. They do not travel far as they are short lived so the effect is localised but careful design is required to prevent a build up of radicals that might be harmful. Normally, the metastable states quickly decay into harmless air molecules. The weak plasma can excite oxygen and turn it into a sterilizing agent which is short lived. This cleans the air in the purifier of dangerous microbes that could harm your health.
Plasma are also formed in glass bulbs to produce light, usually in the form of UV and again a phospor is used to convert the UV light to visble light. These plasma bulbs are more efficient than incandesent bulbs. The main reason for this is that the incandesent bulb has a filament that is heated to several thousand degrees. When it is white hot we see the light. But we have to heat the filament so that creates a lot of heat energy and that is wasteful. With a plasma light we only heat the electrons and not the gas. As the electrons only make up a tiny mass compared to the mass of the filament then plasma lights are cheaper to run than filament. It is interesting that the father of plasma physics,Irving Langmuir, was also a developer of the incadesent bulb. So we see plasma are useful about the house even if plasma physicist like myself are not, and we have not got around to talk about all the things that are found in the house that are made by plasma. I think we will leave that for another day.
Principles of Plasma Diagnostics by Ian Hutchinson is now in its second edition. This book was first published in 1987 and the second edition was published in 2003. The first chapter is an introduction to particle distribution functions. An important concept in plasma diagnostics. Chapter two focuses on magnetic probes and issues around flux measurements in magnetically confined plasma. Chapter three is a comprehensive discussion on electrical probes. While the work is a little dated this is a solid chapter and one of my favorites books on probe diagnostics. It is good for someone starting out in plasma diagnostics. I would think that it stops short of a complete discussion on the latest techniques. Chapter 4 discusses optical diagnostics. This is a very comprehensive discussion of the more basic techniques and represents a good introduction to the new student of plasma diagnostics. The next two chapters focus on emissions from free and bound electrons. The final two chapters complete the optical diagnostics and a very comprehensive chapter on neutral particle measurements and fast ions. The second half of the book is more suitable to Fusion type studies than the industrial type non-equilibrium plasma but overall this is one of the best books available on plasma diagnostics.
If you are interested in further information and purchase details.
Naval Research Laboratory scientists have obtained a first-ever measured altitude profile of a dim extreme-ultraviolet terrestrial airglow emission that provides vital information needed to test and improve the accuracy of advanced techniques for remote sensing of the daytime ionosphere. They have obtained this altitude profile using scans from the Remote Atmospheric and Ionospheric Detection System (RAIDS) experiment. The results of the research are published in the Journal of Geophysical Research, 117, A01316, (2012).
This image shows a schematic representation of the dayside ionosphere remote sensing concept, using measurement of the scattered 83.4 nm emission to infer ionospheric densities. Measuring the 61.7 nm emission provides direct information on the intensity of the source region in the lower thermosphere that is currently only modeled for operational algorithms.
(Photo: U.S. Naval Research Laboratory)
RAIDS temperature measurements have already directly contributed to the Calibration/Validation of the operational (NRL-led) Special Sensor Ultraviolet Limb Imager (SSULI) sensors aboard the DoD Defense Meteorological Satellite Program satellites. This new result from RAIDS will lead to improved operational algorithms for characterizing the vertical structure and global morphology of the ionosphere, the weakly ionized plasma surrounding Earth that affects Navy applications such as high-frequency communication and over-the-horizon radar.
The RAIDS experiment, jointly built by NRL and The Aerospace Corporation, is a suite of eight optical sensors spanning ultraviolet to infrared wavelengths. Under the direction of the DoD Space Test Program, RAIDS and the companion NRL Hyperspectral Imager for Coastal Oceans (HICO) experiment were integrated and flown as the HICO-RAIDS Experiment Payload (HREP) on the International Space Station Japanese Experiment Module-Exposed Facility (JEM-EF). RAIDS exceeded its mission goals by collecting over 1 million scans of the terrestrial airglow between September 2009 and December 2010, and has continued to collect downward-looking spectra since early 2011. RAIDS is the latest in a significant line of NRL Space Science Division (SSD) sensors designed to advance methods and algorithms for remote sensing of the near-Earth space environment.
This graph, a 61.7 nm profile measured by RAIDS, is compared to the current model. Allowing for variations in absorption (Ïƒ) by O2 indicates that neutral composition used in the model may be in error by ~15%. Thus, the accuracy of algorithms used to infer ionospheric density can be improved by using the 61.7 nm emission directly.
(Photo: U.S. Naval Research Laboratory)
One high-priority science focus of RAIDS was the development of new ionospheric remote sensing techniques that use extreme-ultraviolet airglow features of O+ at 61.7 and 83.4 nm wavelengths. These naturally-occurring airglow emissions are particularly useful for this purpose in that strong absorption of these wavelengths in the lower atmosphere means that all the observed light comes from the upper atmosphere. The emissions are created initially when the Sun ionizes atomic oxygen in the region of 150-200 km, but the resulting 83.4 nm photons are scattered by O+ in the ionospheric region between 200-500 km. Ionospheric densities are inferred by modeling how this scattering process changes the measured 83.4 nm intensity. In effect, the ionosphere is like a thin fog whose characteristics are revealed via illumination by the 83.4 nm airglow from below. The 61.7 nm feature, which is not affected by scattering, provides the missing link to directly connect the intensity of the illuminating source in the lower atmosphere to the measured 83.4 nm profile, allowing the O+ density to be pinpointed.
NRL Space Science Division (SSD) researchers Dr. Andrew Stephan and Dr. Scott Budzien, along with retired SSD researcher Dr. J. Michael Picone (now at George Mason University) and colleagues at The Aerospace Corporation, analyzed RAIDS data for 29 Oct 2009 to provide the first independent test of the model that is currently used as part of this daytime ionospheric remote sensing method. The data show good agreement with the model, although subtle differences suggest changes on the order of 15% to the densities of specific neutral species are needed on this day to bring the two into agreement. These small differences confirm the notion that uncertainty in the density of the neutral atmosphere remains an important limitation to high-accuracy ionospheric specification. Results from this study will be used to refine this ionospheric remote sensing technique and remove these limitations to meet the growing need for understanding this important region of space.