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Title: Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade

Abstract

A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPA and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. Additionally, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed onmore » SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.« less

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [1];  [1]
  1. Univ. of California, Irvine, CA (United States). Dept. of Physics and Astronomy
  2. Johns Hopkins Univ., Baltimore, MD (United States). Department of Physics and Astronomy
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1368180
Grant/Contract Number:
AC02-09CH11466; FG02-06ER54867; FG03-02ER54681
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 87; Journal Issue: 11; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Liu, D., Heidbrink, W. W., Tritz, K., Fredrickson, E. D., Hao, G. Z., and Zhu, Y. B.. Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade. United States: N. p., 2016. Web. doi:10.1063/1.4959798.
Liu, D., Heidbrink, W. W., Tritz, K., Fredrickson, E. D., Hao, G. Z., & Zhu, Y. B.. Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade. United States. doi:10.1063/1.4959798.
Liu, D., Heidbrink, W. W., Tritz, K., Fredrickson, E. D., Hao, G. Z., and Zhu, Y. B.. 2016. "Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade". United States. doi:10.1063/1.4959798. https://www.osti.gov/servlets/purl/1368180.
@article{osti_1368180,
title = {Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade},
author = {Liu, D. and Heidbrink, W. W. and Tritz, K. and Fredrickson, E. D. and Hao, G. Z. and Zhu, Y. B.},
abstractNote = {A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPA and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. Additionally, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed on SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.},
doi = {10.1063/1.4959798},
journal = {Review of Scientific Instruments},
number = 11,
volume = 87,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
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  • A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPAmore » and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. In addition, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed on SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.« less
  • A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (∼120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis neutral beams at major radii between 90 and 130 cm, 15 tangential sightlinesmore » that intersect new off-axis neutral beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any neutral beams is used to monitor passive signals produced by fast ions that charge exchange with background neutrals.« less
  • A solid state neutral particle analyzer array has been installed on the National Spherical Torus Experiment (NSTX). The array consists of four chords viewing through a common vacuum flange. The tangency radii of the viewing chords are 60, 90, 100, and 120 cm. They view across the three co-injection neutral beam lines [deuterium, 80 keV (typically) with tangency radii 48.7, 59.2, and 69.4 cm] on NSTX and detect co-going energetic ions. A silicon photodiode was calibrated by using a monoenergetic deuteron beam source. Deuterons with energy above 40 keV can be detected with the present setup. The degradation of themore » performance was also investigated. Lead shot and epoxy are used for neutron shielding to reduce handling any hazardous heavy metal. This method also enables us to make an arbitrary shape to be fit into the complex flight tube.« less
  • The solid state neutral particle analyzer (SSNPA) array on the national spherical torus experiment (NSTX) consists of four chords with tangency radii of 60, 90, 100, and 120 cm that view across the three coinjection neutral beam lines. Each chord utilizes a silicon photodiode that is coupled to fast digitizers to measure the energy distribution of charge exchange fast neutral particles (30-100 keV). By the end of the NSTX 2005 experimental campaign, the electromagnetic noise in the SSNPA was reduced by half and reasonable signals were obtained with good electromagnetic shielding, fast digitization of raw signals, software-based pulse height analysis,more » and pulse shape discrimination. Energy resolution of {approx}10 keV and time resolution of 2 ms have been achieved. Temporal evolutions of energetic neutral flux obtained with the SSNPA are in good agreement with those obtained with the E(parallel sign)B-type neutral particle analyzer. With these improvements, the SSNPA can be used to study magnetohydrodynamic instabilities and fast ion redistribution. Example data from plasma discharges are presented along with the noise reduction techniques and postshot pulse height analysis methods.« less