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Title: Design of Faraday cup ion detectors built by thin film deposition

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Journal Article: Publisher's Accepted Manuscript
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Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 848; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-01-16 12:53:21; Journal ID: ISSN 0168-9002
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Citation Formats

Szalkowski, G. A., Darrow, D. S., and Cecil, F. E. Design of Faraday cup ion detectors built by thin film deposition. Netherlands: N. p., 2017. Web. doi:10.1016/j.nima.2016.12.007.
Szalkowski, G. A., Darrow, D. S., & Cecil, F. E. Design of Faraday cup ion detectors built by thin film deposition. Netherlands. doi:10.1016/j.nima.2016.12.007.
Szalkowski, G. A., Darrow, D. S., and Cecil, F. E. Wed . "Design of Faraday cup ion detectors built by thin film deposition". Netherlands. doi:10.1016/j.nima.2016.12.007.
title = {Design of Faraday cup ion detectors built by thin film deposition},
author = {Szalkowski, G. A. and Darrow, D. S. and Cecil, F. E.},
abstractNote = {},
doi = {10.1016/j.nima.2016.12.007},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = C,
volume = 848,
place = {Netherlands},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.nima.2016.12.007

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  • Multi-MeV beams of light ions have been produced using the 300 picosecond, kJ-class iodine laser, operating at the Prague Asterix Laser System facility in Prague. Real-time ion diagnostics have been performed by the use of various time-of-flight (TOF) detectors: ion collectors (ICs) with and without absorber thin films, new prototypes of single-crystal diamond and silicon carbide detectors, and an electrostatic ion mass spectrometer (IEA). In order to suppress the long photopeak induced by soft X-rays and to avoid the overlap with the signal from ultrafast particles, the ICs have been shielded with Al foil filters. The application of large-bandgap semiconductormore » detectors (>3 eV) ensured cutting of the plasma-emitted visible and soft-UV radiation and enhancing the sensitivity to the very fast proton/ion beams. Employing the IEA spectrometer, various ion species and charge states in the expanding laser-plasma have been determined. Processing of the experimental data based on the TOF technique, including estimation of the plasma fast proton maximum and peak energy, ion beam currents and total charge, total number of fast protons, as well as deconvolution processes, ion stopping power, and ion/photon transmission calculations for the different metallic filters used, are reported.« less
  • The loss of MeV alpha particles from JET plasmas has been measured with a set of thin foil Faraday cup detectors during third harmonic heating of helium neutral beam ions. Tail temperatures of {approx}2 MeV have been observed, with radial scrape off lengths of a few centimeters. Operational experience from this system indicates that such detectors are potentially feasible for future large tokamaks, but careful attention to screening rf and MHD induced noise is essential.
  • A thin foil Faraday cup array is being built to measure the loss of 3.5 MeV alpha particles and MeV ion cyclotron heating tail ions on Joint European Torus. It will consist of nine detectors spread over five different poloidal locations and three radial positions. They will measure the poloidal distribution and radial scrape off of the losses. The detectors will be comprised of four layers of thin (2.5 {mu}m) Ni foil, giving some resolution of the lost particle energy distribution as different ranges of energies will stop in different layers of the detector. One detector will utilize eight thinnermore » (1.0 {mu}m) foils to obtain a better-resolved energy distribution. These detectors will accept particles incident up to 45 deg. from the normal to the foils.« less
  • The design of a tapered stripline fast Faraday cup (TSFFC) to perform the impedance matching between the fast cup itself and the signal line (connector, cable, and amplifier) is reported here. The frequency response of the TSFFC as a high-pass filter is analyzed from a theoretical point of view and some solutions to achieve a broadband response are given.
  • The design and characterization of a Faraday cup utilizing modular components are presented. Design specifications were primarily tailored to satisfy the specific electron beam ([ital e]-beam) energy ([similar to]375 keV), rise time ([similar to]60 ns), and magnitude (30 A/cm[sup 2], peak) used in this work and permit convenient sampling of large [ital e]-beam areas up to 7 cm[times]7 cm. Characterization during evacuated conditions included [ital Z]-dependence measurements using beryllium, carbon, aluminum, and lead collector plates. Electron beam transmission measurements were made utilizing combinations of various metal screens and Kapton foils in both gas and evacuated conditions. Gas environments tested weremore » air, krypton, and a Kr/Ar mixture. An attacher gas, SF[sub 6], was also added inside the Faraday cup. Results reveal decreasing current densities with increasing gas stopping power and increasing electron propagation distance in a gas. Employing a carbon collector plate and a 25-[mu]m Kapton foil insulator, current densities measured through a 3.6-cm thick 760 Torr air slab are reduced [le]6% from the evacuated Kapton-free condition. Applying profile and full-aperture Faraday cup measurements, a consistent description of the [ital e]-beam is also presented.« less