I P F S
knowledge should be freely accessible to all
Institute for Plasma
Focus Studies
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:
http://www.intimal.edu.my/school/fas/UFLF/
The aim of the
Sing Lee
Institute for Plasma Focus Studies
Adjunct Professor, Nanyang
Technological University, NIE,
Adjunct Professor,
leesing@optusnet.com.au
25 February 2008