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: http://www.intimal.edu.my/school/fas/UFLF/Papers/listofpapers.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