17 research outputs found
Current channel evolution in ideal Z pinch for general velocity profiles
Recent diagnostic advances in gas-puff Z pinches at the Weizmann Institute
for the first time allow the reconstruction of the current flow as a function
of time and radius. These experiments show an unexpected radially-outward
motion of the current channel, as the plasma moves radially-inward [C.
Stollberg, Ph.D thesis, Weizmann Institute, 2019]. In this paper, a mechanism
that could explain this current evolution is described. We examine the impact
of advection on the distribution of current in a cylindrically symmetric
plasma. In the case of metric compression, with |v_r| proportional to r, the
current enclosed between each plasma fluid element and the axis is conserved,
and so the current profile maintains its shape. We show that for more general
velocity profiles, this simple behavior quickly breaks down, allowing for
non-conservation of current in a compressing conductor, rapid redistribution of
the current density, and even for the formation of reverse currents. In
particular, a specific inward radial velocity profile is shown to result in
radially-outward motion of the current channel, recovering the surprising
current evolution discovered at the Weizmann Institute.Comment: 12 pages, 6 figure
Novel method for characterizing relativistic electron beams in a harsh laser-plasma environment
Particle pulses generated by laser-plasma interaction are characterized by ultrashort duration, high particle density, and sometimes a very strong accompanying electromagnetic pulse (EMP). Therefore, beam diagnostics different from those known from classical particle accelerators such as synchrotrons or linacs are required. Easy to use single-shot techniques are favored, which must be insensitive towards the EMP and associated stray light of all frequencies, taking into account the comparably low repetition rates and which, at the same time, allow for usage in very space-limited environments. Various measurement techniques are discussed here, and a space-saving method to determine several important properties of laser-generated electron bunches simultaneously is presented. The method is based on experimental results of electron-sensitive imaging plate stacks and combines these with Monte Carlo-type ray-tracing calculations, yielding a comprehensive picture of the properties of particle beams. The total charge, the energy spectrum, and the divergence can be derived simultaneously for a single bunch
High-resolution radial K alpha spectra obtained from a multi-keV electron distribution in solid-density titanium foils generated by relativistic laser-matter interaction
Commissioning and first results from the new 2 × 100 TW laser at the WIS
International audienceAt the Weizmann Institute of Science, a new high-power-laser laboratory has been established that is dedicated to the fundamental aspects of laser–matter interaction in the relativistic regime and aimed at developing compact laser-plasma accelerators for delivering high-brightness beams of electrons, ions, and x rays. The HIGGINS laser system delivers two independent 100 TW beams and an additional probe beam, and this paper describes its commissioning and presents the very first results for particle and radiation beam delivery