I am delighted to be involved with this small, but exciting meeting being held here in Dublin on the 6th and 7th of September. I published a number of papers in the 1990′s on pulsed plasmas, including a letter in Phys Rev Letters on efficient negative ions sources using modulated RF plasmas. The idea of using pulsed plasmas to select the electron energy distribution function (EEDF) is now used in Semiconductor plasma etching. Control of the EEDF is important in regulating negative ion flux, ion energy control and charging effects. The best way to control anything is to make the right measurements. Plasma diagnostics in pulsed plasma are challenging and we are bringing together an elite group of experts in the area of pulsed plasma diagnostics to share their experience and improve the quality of plasma measurement. The organizer is David Gahan and he has told me that due to a number of requests the early registration deadline for the PPDW has been extended until the 29th June. Please register now to reserve your place at the reduced rate as places are limited.
Please find the 2nd announcement for the Pulsed Plasma Diagnostic Workshop (PPDW) attached. Pulsed plasma discharges are used for a variety of applications in modern industry. Magnetron sputtering and HiPIMS discharges, used for depositing layers, generally use pulsed direct current (pDC) excitation of the target and/or substrate to generate the plasma and control the layer properties. Operating frequencies range from 100′s Hz to 100′s kHz, typically.
Recently, there has been a move towards pulsed radio-frequency (pRF) discharge operation by the etching community where the rf driving frequency is pulsed in the 10’s kHz range. In these devices (inductively coupled (ICP) reactors, for example) the source and/or bias frequency are pulsed independently or synchronously to provide better control over the ion energy and etch properties. There are many other examples and uses of pulsed plasmas in the wider community also.
The purpose of this workshop is to gather a team of leading experts from the various pulsed plasma fields to share their knowledge and expertise in the art of pulsed plasma diagnostics. This will provide a unique opportunity for plasma physicists from different fields to interact and learn about diagnostic techniques that may now be applicable to their own research. A stimulating workshop, along with some exciting social activities, will make this an event to remember. Please visit the link below for more information.
The International Thermonuclear Experimental Reactor (ITER) has finally been given the go ahead by French authorities.
The ITER organisation received a letter from the French Safety Authority, Agence de sûreté nucléaire (ASN), on 20 June 2012 which granted a license to build an experimental tokamak nuclear fusion reactor in the south of France.
The 13th International Conference on Plasma Surface Engineering will take place from 10 to 14 September 2012 in Garmisch-Partenkirchen, Germany. Plasma is an important tool for manufacturing high quality thin coatings. It is also an important component in the process of producing innovative new products and surfaces. For example, wet chemical and dry plasma treatments are used to synthesise functional materials, modify surface properties and produce engineered surfaces. The event will be an opportunity to learn more about the latest in research, development and industrial applications. Topics will range from fundamentals, to empirical studies, applications and industrial production.
I will not be going to Garmisch-Partenkirchen this year. My first time to miss this excellent conference in the last 10 years. The conference is held every two years and draws a strong interest from german industry as well a good international audience. If you are a plasma scientist or engineer with an interest in the applications of plasma then this is a conference not to miss. Let me know your thoughts on the PSE conference.
For further information, please visit: http://www.pse-conferences.net/pse2012.html
For further information on plasma measurement tools click here
A recent article by William Reville in the Irish Times throws cold water on the concept of fusion energy being a reality before 2100. Fusion energy is similar to Fission (on which nuclear reactors depend) in that both are based on Einsteins famous equation E=MC^2. Pronounced as E equals M C squared. E is the energy released and M is the mass destroyed and C is the speed of light. How is the mass destroyed? Well, nuclear particles will bind to each other using the strong nuclear force and will be repelled because of electrostatic forces. Therefore, an atom is a complex interplay of forces holding the atom together and other forces pushing it apart. There is an optimum size for an atom, not too big and not too small. So, taking two small atoms and adding them together to make a larger one makes a more stable atom and mass is destroyed to make energy. This is called Fusion Energy. Taking a heavy atom that is above the optimum, somewhere near iron, and splitting it into smaller atoms also results in less mass and energy being released.
Thermonuclear fusion in a reactor requires a gas to be very hot, this can be achieved by using a fission reaction to provide the high temperatures such as seen in the Hydrogen bomb. The atom bomb is a fission reaction which is easier to produce and this heats hydrogen to very high temperatures and causes the atoms of hydrogen to fuse to create helium. This is the basis of the H-bomb and it is a more powerful source of energy than fission. Trying to contain a thermonuclear reaction inside a vessel in a continuous reaction is the holy grail for fusion research and would create a relatively cheap and safe nuclear energy technology. It is just possible to make this work using a magnetic bottle to confine the gas. The magnetic bottle works because at very high temperatures all the electrons are knocked off the atoms to form a dense plasma. The atoms without electrons in a plasma are called ions and they are directed by the magnetic and so can avoid hitting the walls and melting the chamber.
The main alterative to magnetic confinement is inertial confinement, here the gas is heated so quickly that the gas does not have time to get to the wall and melt it. This is a non-equilibrium reaction so it can be called non-Thermonuclear fusion. Lasers can be used to heat and confine the materials and high energy beams can also be used.
Both Thermonuclear and Inertial Confinement have been shown to work and JET, the joint European thermonuclear reactor has produced many megawatts of fusion energy for several seconds. However, the next experiment, Iter is under construction and will take several decades to complete. There is a joke in fusion research that a reactor is 20 years away no matter when you start the clock.
Fusion energy still a pipe dream by William Reville.
I recently responded to a claim from Lawrenceville Plasma Physics that they were close to a commercial fusion reactor. I was annoyed that such claims were being made and even more concerned that such claims were not receiving a strong criticism from the scientific community. I read the paper published in the journal – Physics of Plasma by Lerner and his colleagues. The journal is a reputable peered reviewed publication. It was clear to me that the paper was not significant. Dense plasma focus devices are well understood and have been modelled in detail. The results quoted by Lerner did not show that the focus device which he has developed was significantly better than other devices and there was no evidence that a commercial fusion device was any closer.
I was dubious if the paper had achieved its claim of proving that fusion was the result of confined ions rather than beam ions hitting the pinch plasma (non-thermal fusion). This would indeed be a new result and would contravene the well-known and well accepted current theories that exist. The key point is that Lerner’s device still follows the scaling laws of other devices even if he proposes a different interpretation of results. The different interpretation does not increase the yield from his device nor does it bring him any closer to commercial fusion.
My conclusion was that Lerner had not built a novel device and had not proved or indeed disproved anything. He had replicated a standard focus device and the paper was not even wrong. I was contacted by Lerner and asked to explain my position. So I have prepared a short paper to refute Lerner’s claims and justify my conclusion and explain to those who might be interested the reality behind Lerner’s claims. I also want to make it clear that I have no vested interest other than seeking clarity and the truth and I respect Lerner’s right to do experiments and make claims based on his results.
To clarify the original claim I quote from the LPP web site
On March 23rd, 2012, we published in the journal Physics of Plasmas a report of the confinement of plasma with ion energy equivalent to 1.8 billion degrees C for a period of tens of nanoseconds using a dense plasma focus device. This achieved two out of three conditions—temperature and confinement time—needed not just for fusion energy, but for fusion energy using advanced, aneutronic fuels that have long been considered out of reach. We did all this with an innovative device costing less than one million dollars. If we are able to achieve the third condition, density, we could be on track to commercializing fusion within five years.
For background I will give a quick review of the concept of a dense plasma focus device. The key is that a high voltage is applied between an anode and a cathode. The electrodes have radii A and B, with A>B. A gap exists between A and B and an insulator shields part of the anode from the cathode. A plasma forms in the gap and is pushed along the anode by magnetic fields generated by the high discharge current. When the plasma reaches the end of the anode a pinch column forms where the anode had been and this has a very high density and temperatures. This focus is sometimes called a plasmoid. The ion energy is such that in a deuterium gas, a significant amount of neutrons are produced from fusion reactions.
It is generally accepted that the main mechanism producing the neutrons is a beam of fast deuteron ions interacting with the hot dense plasma of the focus pinch column. The origin of the fast ion beam is a diode action in a thin layer close to the anode with deviations from neutrality generating the necessary high voltages. This mechanism has been modelled in detail based on a expression for fusion yield given below;
Yb-t = calibration constant x ni Ipinch2 zp2(ln(b/rp))σ/Vmax0.5
where Ipinch is the current at the start of the slow compression phase, rp and zp are the pinch radius and pinch length at the end of the slow compression phase, Vmax is the maximum value attained by the inductively induced voltage, σ is the D-D fusion cross section (n branch)corresponding to the beam ion energy and ni is the pinch ion density. The D-D cross section σ is obtained by using beam energy equal to 3 times Vmax, to conform to experimental observations.
Data is available for the neutron yield Yn from a wide range of machines and can be used to calibrate the model and also to establish a clear empirical scaling law. It has been shown that the log of the neutron flux is linear with the log of the Ipeak.
The pinch current is higher for smaller diameters of anode, so a correction factor is required to convert Ipeak to Ipinch. In the case of LPP, I used 0.58 which is the factor measured for the NX2 device which is similar in anode dimensions to the LPP device.
Figure 1, shows a log-log plot of Neutron flux versus Ipinch, LPP best data point in red.
I have included the best result reported by Lerner, which is 1.1Ma and 1.5 1011 neutrons. It is clear from the paper that other shots at 1.1Ma had a lower yield. Figure 2, in Lerner’s paper shows three points at the highest ion energy ( highest Ipeak) and the spread is at least a factor of 3. So Lerner’s result fit exactly with all other Plasma Focus devices. What is different is that he drives a large current into a small radius anode, but the device scales just as expected. No new physics here I am afraid. I have to commend his team on making a solid job of measuring everything and proving that they have a standard plasma focus device, they could have got the calibration of some of the instrumentation wrong and then we might have had less clarity.
I would be interested to hear comments from you on whether you consider this an issue in science today and the role of the web in publishing “Facts” that might mislead.
For more information on the modeling of plasma focus devices and as a reference source for the data used here please see,
Neutron Scaling Laws from Numerical Experiments, S Lee & S H Saw, Journal of Fusion Energy, 2008.
The third in a series of a basic course in plasma physics, Basic Plasma Parameters explains the importance of the concepts of temperature, thermal speed and quasi-neutrality in plasma physics. The page is accompanied by a short video.
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 email@example.com
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.