I P F S
knowledge should be freely accessible to all
The Institute for Plasma Focus Studies was founded on 25 February 2008. The aim is to promote the understanding of plasma focus devices. The method used will be communication through the internet. The main instrument will be the plasma focus simulation package based on the Lee Model, the latest being the version RADPFV5.13.8. The inaugural exercise is an internet-based course on the use of this model code. This course “Plasma Focus Numerical Experiments” will commence on 14th April 2008 [Note: This document is dated 25 Feb 2008].
Rationale for and Introduction to the Institute:
From the mid-Eighties to mid-Nineties and on to the new Millennium a group of us assisted in the starting and strengthening of several laboratories on plasma focus studies, using a 3 kJ plasma focus the UNU/ICTP PFF, specially designed for this purpose. More than 20 Fellows were trained to build, use and maintain this plasma focus through intensive hands-on training programs sponsored by UNU, ICTP, UNESCO, TWAS and AAAPT. This plasma focus, though low-cost, has proved very useful in the education of plasma focus scientists. It is now actively operated in 7 countries and research on it has produced at last count in 1998, more than 22 PhD theses, 50 Masters theses and 200 peer reviewed research papers.
From the very beginning of the program it was realized that laboratory work should be complemented by computer simulation. A 2-phase model was developed in 1983. Over the years we have developed the model until its present form. It now includes thermodynamics data so the code can be operated in H2, D2, He, Ne, Ar, Xe. We have used the code to simulate a wide range of plasma focus devices from the sub-kJ PF400 (Chile) through the small 3kJ UNU/ICTP PFF (Network countries), the NX2 3kJ Hi Rep lithographic focus (Singapore), medium size tens of kJ DPF78 & Poseidon (Germany) to the MJ PF1000 (ICDMP Poland). An Iranian Group has modified the model, calling it the Lee Model, to simulate Filippov-type plasma focus.
We are now confident that the Lee Model in its latest coded version, RADPFV5.13.9a realistically simulates all Mathers-type plasma focus, from small to large, and produce reliable results for all the electrodynamic processes including axial and radial trajectories, total discharge currents and plasma currents, energy distributions; and also giving a good representation of the temperature waveform, SXR yields and neutron yields.
Although we can simulate any given machine, without any experimental input, our standard practice requires a measured total discharge current versus time waveform from the specific machine together of course with the bank parameters (capacitance, static inductance), tube parameters (cathode/anode radii, anode length) and operating parameters (voltage, pressure and fill gas). We then configure the code with these parameters; then use 4 model parameters (a mass swept-up factor and a plasma current factor for each of axial and radial phases) to fit the computed total discharge current trace to the experimental total discharge current trace. The process, carried out separately for axial and radial phases, usually ends with an excellent fit for both shape and absolute magnitudes.
The total discharge current, particularly the fraction of it flowing in the plasma, drives all the electrodynamic processes in the axial and radial phases; even the plasma heating and radiation are coupled into the equations of motion during the pinch phase. Conversely all these processes are reflected back through the plasma current to the total discharge current. The total discharge current carries in its profile and magnitudes the information about all the processes that go on in the plasma focus. Thus having fitted the computed Itotal trace with the measured Itotal trace, we then have the confidence that all the processes are realistically simulated; and the numerical results are a realistic representation of the actual properties of that particular plasma focus.
In the same spirit that was so remarkably demonstrated when we helped groups to initiate/strengthen their experimental research capabilities using the UNU/ICTP PFF, the Institute would strive to do the same for their computational research capabilities using the Lee Model RADPF code. In the last 3 months of 2007 we carried out numerical experiments using the code and found a new plasma focus pinch current limitation effect published in Applied Phys Letts (Jan 08). Another paper re-formulated neutron yield scaling laws from the numerical experiments and a third paper demonstrated the success of a new technique to deduce plasma focus pinch currents from a measured total current trace. These 3 papers have all been published and a fourth paper has just been accepted; all from those 3 months of numerical experiments. Details are available from the following link: Papers.htm
This is mentioned as proof that this code is a universal numerical laboratory that will complement any plasma focus laboratory; acting as a powerful research tool that goes beyond the normal experimental reach. The power of this tool is only limited by the researcher’s limit in imagination.
This tool is now available for anyone to download at:
The aim of the
Institute for Plasma Focus Studies
Adjunct Professor, Nanyang
Technological University, NIE,
25 February 2008