Title
Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST
Date Issued
01 July 2021
Access level
open access
Resource Type
journal article
Author(s)
VanMeter P.
Barbui T.
Chellai O.
Wallace J.
Yamazaki H.
Kojima S.
Almagari A.F.
Hurst N.C.
Chapman B.E.
McCollam K.J.
Den Hartog D.J.
Sarff J.S.
Reusch L.M.
Pablant N.
Hill K.
Bitter M.
Ono M.
Stratton B.
Takase Y.
Luethi B.
Rissi M.
Donath T.
Hofer P.
Pilet N.
Princeton University
Publisher(s)
American Institute of Physics Inc.
Abstract
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.
Volume
92
Issue
7
Language
English
OCDE Knowledge area
Óptica Física de plasmas y fluídos
Scopus EID
2-s2.0-85109187890
PubMed ID
Source
Review of Scientific Instruments
ISSN of the container
00346748
Sponsor(s)
This work was supported by the U.S. DOE-OFES, under Contract No. DE-AC02-09CH11466, and LFDA’s 2015 DOE Early Career Award Research Program. The experiments were conducted at the Wisconsin Plasma Physics Laboratory (WiPPL), a research facility supported by the DOE-OFES, under Contract No. DESC0018266, with major facility instrumentation developed with the support from the NSF, under Award No. PHY 0923258. The MST Tokamak Thermal Quench Program is funded under DOE-OFES, Award No. DE-SC0020245.
Sources of information: Directorio de Producción Científica Scopus