Mapping of azimuthal B-fields in Z-pinch plasmas using Z-pinch-driven ion deflectometry

Abstract

B-field measurements are crucial for the study of high-temperature and high-energy-density plasmas. A successful diagnostic method, ion deflectometry (radiography), is commonly employed to measure MGauss magnetic fields in laser-produced plasmas. It is based on the detection of multi-MeV ions, which are deflected in B-fields and measure their path integral. Until now, protons accelerated via laser–target interactions from a point-like source have been utilized for the study of Z-pinch plasmas. In this paper, we present the results of the first Z-pinch-driven ion deflectometry experiments using MeV deuterium beams accelerated within a hybrid gas-puff Z-pinch plasma on the GIT-12 pulse power generator. In our experimental setup, an inserted fiducial deflectometry grid (D-grid) separates the imploding plasma into two regions of the deuteron source and the studied azimuthal B-fields. The D-grid is backlighted by accelerated ions, and its shadow imprinted into the deuteron beams demonstrates ion deflections. In contrast to the employment of the conventional point-like ion source, in our configuration, the ions are emitted from the extensive and divergent source inside the Z-pinch. Instead of having the point ion source, deflected ions are selected via a point projection by a pinhole camera before their detection. Radial distribution of path-integrated B-fields near the axis (within a 15 mm radius) is obtained by analysis of experimental images (deflectograms). Moreover, we present a 2D topological map of local azimuthal B-fields B(r,z) via numerical retrieval of the experimental deflectogram.

Self-driven ion deflectometry measurements using MeV fusion-driven protons and accelerated deuterons in the deuterated hybrid x-pinch on the MAIZE LTD generator

“…Our analysis [23] of the general principles of ion deflectometry in z-pinch B-fields and later the experimental measurements [9] have demonstrated that the ion beams fired axially into the z-pinch can investigate the specific distribution of the B-fields inside the z-pinch. To map the magnetic fields along the z-pinch axis, the electrodes must be permeable for passing ions from the ion source and to the ion detector.…”

“…The first self-sustained deflectometry measurements of the z-pinch B-fields not requiring intense laser pulses were performed in 2019 on 3 MA deuterium hybrid gas-puff z-pinch driven by the GIT-12 generator [9]. In these experiments, a rapid current disruption of the plasma neck in the z-pinch generated strong transient electric fields that accelerated hydrogen ion beams up to energies of tens of MeV [10].…”