Presentation Title: Laboratory High Energy Density Physics
Daryl Landeg, Head of the Plasma Physics, Atomic Weapons Establishment (AWE), Aldermaston, UK

This Keynote Address attempts to describe how revolutionary developments in pulsed power and laser science over the past half century have led to ground breaking developments in laboratory high energy density physics. Necessarily taking the perspective from the speaker’s own laboratory, it describes periods when these developments have proceeded at an incredible rate and also tries to convey something of the culture needed for such accelerations. Looking to the future, the presentation will highlight some of the key facility developments already underway and anticipate some of the exciting research challenges and opportunities that await us in the coming decade.

This research was sponsored by the NNSA under DOE Cooperative Agreement DE-F03-02NA00057

Presentation Title: Twenty-five Years of Helical Flux Compression Generator Modeling leading to the current code CAGEN
Dr. Jay Chase, Consultant, Alameda, USA

Forty-five years ago the great James W. Shearer wrote a computer program called “Whale” that was a simple 1.5 D model of the operation of a coaxial generator. With it he was able to develop his intuition about these kinds of explosively energized electrical generators. Much later in time, I sought some guidance on how to model a helical FCG and took a lesson from the late Jim Shearer. I began to build the model code that much later became CAGEN.

It was clear then, and it is certainly clear to everyone today, there are three important time scales which guide the modeler: the time it takes light to cross the physical dimensions of the subject FCG; the time it takes the explosive charge to function, and this includes the time it takes for the resulting moving conductive metal parts to complete their job; and the characteristic time for the nonlinear diffusion of the magnetic field in all of the materials of the FCG. The last time scale is the most important. If it were not for the nonlinear processes involved in the distribution of the currents, the model would not be time dependant. That is, the model could be a simple sequence of stationary states, each one of which could be computed separately. It was the ability to compute/simulate the nonlinear diffusion that Jim Shearer had exploited in Whale. This nonlinear diffusion problem is discussed prominently in the many writings of the world renowned Heinz E. Knoepfel.

In this paper, I will talk about the relation of fully three-dimensional simulation to modeling. I will carry on to discuss the initial models in the early codes (the forerunners of CAGEN), their shortcomings and how each successive improvement in the models brought improvements in results. The early codes were only good to develop one’s intuition and to improve existing designs. With the recent addition of the Kiuttu Contact Resistance Model and the Kiuttu Proximity Model (both the creation of Gerald Kiuttu), CAGEN is finally able to produce results that are close to experimental measurement without the use of any adjustable parameters. Benchmark calculations will be compared to experiments on FCGs that range from the huge MK9 (C320) to the tiny LOBO, from FCGs with turns splitting to FCGs with single winding threads. There is certainly work yet to be accomplished.

Electrical breakdown in FCGs is a very important phenomenon. Single and multiple thread FCGs along with split turn designs have all shown examples of internal breakdown. The electric field structure responsible for these breakdowns is very complex and dynamic, perhaps requiring a three-dimensional approach to model properly. Flux trapping designs have the opportunity for electrostatic breakdown due to the large EMF generated in the secondary windings prior to connections being closed, allowing the commencement of current flow. For the vast majority of FCG designs, the possibility of one or more of these electrical breakdown thresholds is the limiting design parameter. Much more experimental knowledge is needed before adequate modeling for successful designs can be achieved. As new FCG designs are demanded by new applications, other new and critical challenges are to be expected.

Presentation Title: Megagauss Fields in Germany
Professor Michael von Ortenberg, Institute of Physics of the Humboldt University, Berlin, Germany

A review of high-magnetic-field activities in Germany with emphasis on megagauss research is given. The talk will cover the history of about forty years of generation and application of high magnetic fields in solid state physics in Germany beginning in the 1960s. Key experiments of the past and present aiming at the highest possible fields will be discussed and an extrapolation into the future projected to megagauss activities within the European Union.

Presentation Title: Towards 100T – European Activities in the Development of Non-Destructive Pulsed Magnets
Dr. Oliver Portugall, Laboratoire National des Champs Magnétiques Pulsés, Toulouse, France

Since the early 1990s several EU-funded consortia have been formed with the aim of developing large non-destructive user-magnets providing the highest fields possible. However, the first magnet actually used for scientific experiments was not commissioned until 2002: The ARMS-double-coil system provided >75T in 15mm bore, but failed two years later after less than 100 shots. As a consequence, the objectives of the most recent European collaboration (DeNUF) were adjusted in the sense that more emphasis was put on the development of magnets that can be operated reliably for a very long time and with little risk of failure-related secondary damage to scientific equipment. In addition it was found necessary to increase the magnets duty-cycle so as to make them more suitable for being operated in a user facility. The DeNUF development program was therefore centred around 5 essential points: the construction of several large prototype magnets, the design of rapid cooling coils with increased duty-cycle, the development of advanced FEA-software and a materials data base, the systematic study of coil ageing mechanisms and the development of coil monitoring tools to detect ageing effects and predict imminent failures. In our talk we will discuss the status quo of the DeNUF-initiative with frequent references to previous projects and the actual situation in different laboratories in and outside Europe.

In the paper we consider the sources of explosive pulsed power for obtaining and preliminary heating of a magnetized plasma in a MAGO system and high-power disk MCG for an EMIR complex, intended for soft x-ray radiation generation of 10-megajoule level.

Investigation results of helical generators for different purposes, and experimental results with electric-explosive and explosive current opening switches, are presented in the paper.

Presentation Title: High Power Microwaves - An Applications Perspective
Steve Bowater, High Power RF Faraday Partnership, Didcot, UK

The High Power RF Faraday Partnership was setup in 2001 with DTI support to integrate the UK's industrial and academic capability in microwave devices and systems. The Partnership covers all applications of microwave power including scientific and medical accelerators, defence systems, TV and radio broadcasting and industrial processing systems including plasmas. There are over 50 affiliated organisations covering component, sub-system and system suppliers, academic researchers and national laboratories.

The next generation of international scientific accelerators provide the opportunity for the UK to develop and sell state of the art RF systems. The functional requirements for these systems dictate higher power from smaller and cheaper devices. By fulfilling these requirements there is potential to transfer this knowledge into the defence and industrial processing markets. Interest in this technology from manufacturers and processors is increasing, roughly at the same rate as the price of energy, as the incorporation of microwaves into processing plant has been proven to reduce energy consumption by up to 95%.

By taking a multidisciplinary approach, the Partnership has generated a capability to design and
demonstrate commercially viable process plant designs. The time has come for high power
microwaves to contribute to sustainable production in the 21st Century.

This research was sponsored by the NNSA under DOE Cooperative Agreement DE-F03-02NA00057

Presentation Title: Configurations of quasi-force-free magnetic systems
Professor GA Shneerson, Saint-Petersburg State Polytechnical University

In the earlier published works devoted to the calculation and modeling of quasi-force-free magnets it was shown that the mechanical stresses in winding layers have the order of 0H02/(2N2), where H0 is the field intensity in the operational zone of the magnet, N is the number of equilibrated current layers. In the previous works the choice of the shape of the end part was limited to the case of the solenoid with the plane diamagnetic shield. In the present work the systems of the general form are studied presenting interest for the creation of non-destructible magnets with megagauss range field. The qualitative peculiarities of current distribution in the winding depth are investigated in the approximation of strictly force-free field. In the approximation of the winding of small thickness the various options of constructing the configurations satisfying the integral equilibrium conditions are examined. These conditions can be met by using separately and in various combinations of three methods: removing the excessive poloidal current, the choice of the special form of the winding boundary, and using extra loops with azimuthal current (shields). The procedure and examples of the choice of optimum current distribution in the real magnetic system consisting of discrete current layers are given

Very short exposure ‘flash’ radiography is the technique of choice for the study of the kinematics of explosive and ballistic events. Clear stop-motion pictures can be obtained of events that occur on sub-microsecond timescales, even when shrouded by smoke or debris. Careful circuit design enables the generation pulses of suitable duration and spectra to examine in detail many different types of phenomena.

Modern operational requirements and health and safety legislation demand that fuse and detonator systems for military items must function very reliably when commanded, possibly after many years in storage, but also have virtually zero probability of inadvertent ignition or detonation. Satisfying these disparate needs lies partly in the use of high voltage pulses of controlled shape to generate shock waves. This has enabled the progressive phasing out of the traditional, relatively unstable primary explosives, which could be activated by heat or friction.

A possible new application of pulsed power is the protection of vehicles or other structures from ballistic attack by the use of a double-skinned outer shield. This can pass a high current through the fast metal jets which issue from the warheads of rocket propelled grenades etc.

Much effort has gone into making electronic systems less susceptible to EMP (electromagnetic pulse) since the evolution of low current, low voltage semiconductors. But how might dangerous pulses and fields arise?