PREPARED ON THE REQUEST OF UNESCO
The present situation of Plasma Physics research has raised the need of close collaboration between scientists worldwide and called for joint efforts. In many instances phenomena appear to be more complex than anticipated at first and consequently request detailed studies that are beyond the contribution local groups can make. This is already true in many fields for technologically developed nations and it is even more so for developing ones, whose human and economical resources are severely limited.
This need for collaboration was felt in particular in one area of plasma research, namely a class of dense magnetised plasmas. This has led after a succession of meetings, over a period of 30 months, of physicists from all parts of the world having extensive experience in the field, to the creation of an independent International Centre.
An argument has clearly to be put forward for the establishment of a new Centre. This lies in the mission of the Centre, which extends beyond the role of a traditional research institute. It is unique blend of fundamental research at the fore front of science, and basic training in research in experimental physics to developing countries, pursued on an open and equal right basis, in terms of position, contribution of ideas and exchange of knowledge, by a group of partners of different backgrounds and cultures. The scientific objectives of the Centre is not so much on the development of a single large apparatus to establish the validity of one scientific concept, but the co-ordinated co-operative study, under one roof, of a number of highly complex and transient non-linear phenomena requiring the use of many diagnostic techniques.
The concept of the proposed Centre rests upon three main ideas that are intertwined and of equal importance, and together they constitute the project.
From these initial statements it is clearly engrained in the concept of the Centre that many nations will contribute towards the establishment and maintenance of its operation. It is through the concept of shared costs and added value that the project will move ahead, involving as many interested nations as possible. The concentration of the best technical facilities in the proper atmosphere for joint collaboration of experts in the field will provide the proper conditions for addressing the main issues to be solved, taking advantage of cross-fertilisation of experience and knowledge. This venue may stimulate the synergism of different scientific cultures, nurtured by the continuous influx of ideas from scientists worldwide, and the exposure to new concepts through interaction. Simultaneously, the concentration of efforts and resources will offer high quality conditions for training of inexperienced personnel, who will have access to state of the art equipment and advanced knowledge and thus lay the foundations for the next generation.
After the present introduction the creation of the Centre are developed in Section 2. The main characteristics of the project with costs and expected time realisation are given in Section 3, as it has been elaborated within the frame of the Centre Project independently on the hosting country. This document is followed with a specific proposal of the Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland, chosen by the ICDMP Steering Committee at the end of 1997 as a site for the Centre
2.1. Training, Education and Scientist Exchange Programmes
One of the main goals of global significance for the Centre is to provide scientific growth of developing nations laboratories in the field of pulsed power technology and physics of dense magnetised plasmas. More specifically three programmes are considered.
The first is a training programme for a selected number of candidates on a range of fundamental theory and methods on dense magnetised plasmas based on a specific device, providing hands on experience in the use of modern sophisticated diagnostic equipment. For this purpose the plasma Focus is an excellent device due to its capability to produce hot and dense plasma conditions, despite its relatively simple set up and operation. At the end of the training programme, the trainees would take back to their home institutions a small plasma Focus device with which they have become fully acquainted, and confident to do research with. Once this phase is completed, scheduled visits could be arranged so that, former trainees can keep up their production and contribution to the field within an established programme.
The second programme is to provide Ph.D. students with thesis work. They will be able to receive education through projects at the forefront of the plasma Focus research with the most advanced and up to date diagnostic facilities available in the Centre. This implies a university association for each student so that the necessary conditions on supervision and basic lectures in the subject are fulfilled.
The third programme relates to the scientific exchange programme in which confirmed scientists from developing and developed nations will make extensive stays of 4 to 12 months in the Centre.
The general aim of these three programmers is to create a network of laboratories throughout the world working in close co-operation with the Centre, the facilities of which having the key role of reference installations. In this way the Centre will be able to accelerate the dissemination of knowledge and transfer of technology and it will benefit from the research of a much larger number of scientists for the investigation of fine scale phenomena which is a fundamental challenge in plasma physics as will be indicated in next section.
It is important to stress that they were worked out in the Asian African Association for Plasma Training (AAAPT) which has had a satisfactory experience of similar programmes for several years. Another point worth mentioning refers to the number and qualification of people present in the Centre. The ratios of trainees, Ph.D.s, visiting scientists, permanent and long-term personnel were established in relationship with the above mentioned experience. It has led in turn to chose the number of experiment housed by the Centre in accordance with the number of trainees, students and researchers.
2.2. Study Of Basic Phenomena in Dense Magnetised Plasmas
Dense magnetised plasmas have been one of earliest subjects of studies in the field of laboratory hot gases. It was proposed as a simple way to reach thermonuclear temperatures and fusion in a controlled manner for civilian applications. The schematic is straightforward: a column of current flows in an ionised gas; the lines of the magnetic field B created by the current are circles centered on the current axis and the current carrying gas is submitted to the Lorentz force orthogonal both to the axis and to B and directed toward the axis. The compression that follows can lead, assuming a number of simplifying hypotheses, both to high enough temperatures and density to create the fusion of a mixture of deuterium and tritium. As is well known these early hopes were not sustained by the experiments which show various types of instabilities so that a positive energy gain cannot be attained by this concept.
Instabilities, and notably microinstabilities, appear now as fundamental plasma physics studies and it is an important scientific objective to study them in one of the simplest schemes, namely the interaction of a straight column of electrical current with a gas.
Because this geometrical Z-pinch type arrangement (in which the current flows along the axis z of symmetry of the experiment) is met in other devices (wires, fibers,...) it is not entirely surprising that experimental similarities are observed. It is also possible that the generation of powerful beams observed in these experiments have comment features with the ones occurring in astrophysical media.
The scientific aim of the Centre is then to study challenging, fundamental physics with the farther goal - how remote future studies will-to direct and concentrate the forces which are present, and possibly to devise new schemes for fusion energy.
ii. Plasma Focus
The Plasma-Focus has been selected as the initial Dense Magnetised Plasma load for the 1 MJ facility for several reasons.
The plasma Focus pulsed power technology is less complicated, operating in the 10-100kV range of simple conventional capacitor bank designs, than more sophisticated megavolt power conditioning technologies to drive one ohm type loads to a few magaampers. For the Plasma-Focus this is accomplished through an electromagnetic process of converting the stored electrical energy over a time scale of several microseconds. At the final phase of this inductive energy storage a few megaampers of a cylindrical current sheath are collapsed radially at a rate of 5´ 107 cm.s-1 within a centimetre diameter. The system behaves as a built-in, constant current plasma inductive generator capable of coupling the megaampers current into a one ohm axial load with high efficiency.
A comparable state of the art pulsed power generator designed to produce a few megaamperes at the megavolt level would cost several million US dollars and would require a high and costly level of sophistication in operation and maintenance, beyond the budget envisioned for the International Centre for Dense Magnetised Plasmas. On the other hand, a Plasma-Focus system is more economical to maintain and operate, and costs 5 to 10 times less to construct.
Another important point is the total number of shots per year, which is two to three, orders of magnitude higher for plasma Focus machines.
iii. Extension of basic understanding
At present, the Plasma-Focus community has reported in the literature a wealth of phenomena. It is important to explain why in spite of the more than a thousand publications on the subject fundamental question are still unclear and why reference facilities at various energy levels are needed if a step forward in the understanding of the physics is to be made.
One essential reason is the dependence of the phenomena not only with the constructional specifications of a given device but also with its operational parameters. These are numerous and some of them as an insulator condition, impurities...are not very well known and consequently one cannot be certain that they are the same in two different installations. So that in spite of the fact that the general features of the discharge have been reproduced over and in all laboratories there is little progress in understanding the fine structure of the physics. To give but one example it is impossible at this stage to correlate the measurements of the ion beam structure with the same relative to the electron beam.
What is planned for the new Centre is to have experimental facilities that will act as reference standards to which the results obtained in the various co-operating laboratories will be compared in the frame of visiting scientist programme mentioned previously. The Centre will then develop a unique bank of data available to all. Theoreticians have expressed their interest in such a source that will allow them to formulate theories and compare them to the experiments.
An important aspect of the Centre is the development of diagnostic techniques and their proper calibration. Because the phenomena are complex they require a large variety of measurement methods. As they are short - lived and occur for some of them in small volumes time and space resolution is important. Progress has been done in past years notably for laser plasma studies but not applied to Plasma-Focus research to the same extent.
The operation of the Centre as a standard implies that particular attention be paid to the quality of craftsmanship. Mechanical parts in the plasma chamber, particularly the electrodes, have to be realised with great precision and retain their characteristics for many years. The design should also incorporate the features that have proved to be useful in giving degrees of freedom, integrate in a compatible way new advanced diagnostics and give the possibility of using new materials (sintered ceramics, alloys) and technologies. Sufficient time and financial means have to be given to the design and construction phases. There are a number of experts in the field that are able to contribute to this most important par of the project.
Even though the quality of research is the scientific motive of the new Centre one cannot escape the choice of the energy of the largest installation. This point was discussed carefully. Most experiments could be conducted at the 100kJ level as far as diagnostics are concerned. But there is an important issue in Plasma-Focus research: while proper operation of these experiments could be conducted from kilojoule stored energy to several hundreds, difficulties were encountered above 500kJ. It is important to deal with this problem and to find solutions. There has been satisfactory functioning with an injection valve that decouples two different phases of the discharge development and such a valve should probably solve the problems. However, the point has to be proven experimentally at the new Centre which means that the largest energy bank should be able to study the range from a few hundreds kilojoules to at least 1MJ. On the other hand the members felt that there was no real incentive to go to multi-megajoule experiments, which are more expensive and less flexible, without laving a specific application or purpose in sight. And in the case it would be felt in several years that such a large facility is needed it could be accommodated in the main room due to the vastly reduced size of present day capacitors. Besides the one megajoule facility there will be several smaller experimental devices, covering the whole energy and current ranges, as well as operating regimes used in conjunction with the Exchange programmes mentioned in the preceding section.
The methodology of operation in the Centre should be established. Great care should be given to the registration of data so that maximum information would be stored even the looks superfluous at the time of the experiment. It is indeed well known by experimenters that old data usually lack precisely the information one would like to have. The use of computers and of numerised data certainly can solve the problems as far as hard and software is concerned. But there is also a general attitude in which the Centre could play an innovative role by setting standards both in every one of the diagnostic methods and in the general operation of the experiment. To summarise this part one could say that facing the challenge of complex physics one has to resort to modes of collection of data which encompass more measurements with greater accuracy.
2.3. Applications and Technology Transfer
There are a large number of possible technological applications for the Plasma-Focus at different stages of development. They rely on some salient features of this experiment, such as its strong X-ray, ion, electron or neutron emissions, or its large changes of impedance. Among the most interesting ones we could mention ion beam implantation, gas laser pumping, pulsed ion and electron beam sources, pulsed neutron sources for biological and materials research and analysis, X-ray lithography and microscopy, and fast opening switches. In many cases the Plasma-Focus is seen as an alternative to other technologies. What is lacking is the possible development into an everyday working application. At this stage of development of possible applications, countries with large differences in technological capabilities are on a very similar footing. It is apparent that Centre as envisaged would provide an ideal environment to advance the state of development to achieve practical devices.
Apart from the development of new technology, there is a wide array of well proven technological developments, which would be used in the Centre on different experiments. High voltage technology, pulsed power, as well as vast array of diagnostics, such as X-ray detection, laser interferometry and other optical techniques, electrical and magnetic measurements, neutron and other fusion particle investigation methods. All these aspects would be used by scientists and trainees, resulting in a very efficient way of transfer of know-how from advanced to developing countries.
Although only a quick reference to Plasma-Focus applications has been made here, it is important to point out that other small plasma devices made available for research at the Centre have great potential for application. As an example one could mention the use of pulsed power technology to produce short-lived plasmas for high intensity pulsed UV radiation. Such sources can be used for food sterilisation, and would be of special significance for developing countries, where food conservation is an outstanding problem.
3. PROJECT DESCRIPTION
The first idea of a common Centre originated during discussions between H. Bruzzone and V.Gribkov in Buenos Aires in January 1990. Then through a Workshop in Zvenigorod, near Moscow an international Working Group was set up. The Working Group members worked together to write the main document defining the needs, values and requirements for such a Centre. The group was structured with open membership, which has been increasing permanently. At this time 17 countries are represented: Argentina, Chile, Czech Republic, Germany, France, Italy, India, Japan, Malaysia, Mexico, Poland, P.R. of China, Romania, Russia, Singapore, United Kingdom, United States.
During a present phase this document will be used to generate supporting interest and funding among many countries over the next two years to create such a Centre. Following the commitment and the construction phase, full operation would occur towards the end of 1998. During the past two years the Working Group members have had increased technical interchange in the areas of plasma Focus to establish the initial design criteria for the Centre. This activity will be intensified during the Centres realisation phase in the form of a Global Twinning Programme, COPERNICUS and others, for refining the detailed designs of the experimental hardware and diagnostics required for performing research at the Centre to the highest level of excellence.
The fully commissioned Centre is envisioned as a pair of buildings: one to house the largest experimental device with appropriate size and protection and the second to contain all other operational capabilities. This latter building consists of a top level with offices and conference rooms as well as an auditorium and library. The lower level contains facilities to support the training modules, various experimental devices, diagnostic equipment, and a machine shop.
3.1. Experimental facilities
The essential experimental equipment required to investigate the various aspects of the dense magnetised plasmas have initially been restricted to:
The staffing of the Centre required for performing both the scientific research, and the training, education and scientist exchange programme as described in section 2.1, consists of 14 scientists. This number has been arrived at with great care, in light of the requirements to perform multiple responsibilities with the 18 individuals-trainees, Ph.D. students, scientists participating in the training, education and exchange programme. Thus there will be in the Centre the following persons:
The Director will have the overall responsibility of the Centre and will be appointed by an Administrative Council. This Council will consist of members representing contributing countries and organisations and will have the responsibilities of maintaining the required funding for the Centre and assuring its proper utilisation. The membership to the Council will be limited to 20 individuals representing the twenty largest contributors to the annual budget. In order to maintain the truly international and independent nature of the Centre, no single contribution will exceed 20% of the annual operational cost.
The Director will receive guidance from a Scientific Advisory Committee, whose members are scientists in plasma physics. This Committee will consist of 9 members: the Director, four selected by the Administrative council and four by the Centres permanent and long term research scientists. This Committee will meet two or three times a year to evaluate the proposals and scientific programme of the Centre.
The Director, with the assistance of a Deputy Director, will oversee the scientific and operational activities of the Centre. Among the permanent scientists an individual will be the Operations Manager responsible for the proper operation of the facilities. Furthermore the staff will oversee the functional activities of the training, education and exchange programme.
The present proposal has the purpose of creating an independent Centre on an international scale, that would attract some of the worlds most experienced scientists working in the field of dense plasmas produced by large currents. However, it would also be a Centre with a mission, which would extend beyond the traditional research institute, as it would cross national boundaries, providing training in electrical pulsed power and plasma physics. As a clear-cut objective it should help to bridge the North-South divide. It could also be an important par of the growing solidarity between technologically advanced countries and those engaged in the process of industrialisation, because it would help the latter to develop their own research capacities and participate in the world research effort. Yet, international scientific co-operation cannot simply reduce to one way relations between those countries that provide scientific knowledge and those who benefit from it. It must be done as a scientific joint venture for mutual benefit. This will be possible with the present project, as research groups at developing countries are able to contribute to the field with the resources they afford.