TY - JOUR
T1 - Soft x-ray tangential imaging of the NSTX core plasma by means of an MPGD pinhole camera
AU - Pacella, D.
AU - Leigheb, M.
AU - Bellazzini, R.
AU - Brez, A.
AU - Finkenthal, M.
AU - Stutman, D.
AU - Kaita, R.
AU - Sabbagh, S. A.
PY - 2004/7
Y1 - 2004/7
N2 - A fast x-ray system based on a micro pattern gas detector has been used for the first time, to investigate emission from the plasma core of the National Spherical Tokamak experiment (NSTX), at the Princeton Plasma Physics Laboratory. The results presented in this work demonstrate the capability of such a device to measure with a time resolution of the order of 1 ms, the curvature and the elongation of the x-ray iso-emissivity contours, under various plasma conditions. Also, comparisons with the magnetic surface structure calculated by the EFIT code show good agreement between reconstructed flux surface and the soft x-ray (SXR) emissions for poloidal beta values up to 0.6. For greater values of beta, x-ray iso-emissivity contours become circular, while magnetic flux surface reconstructions yield elongation 1.5 < k < 2.2. The x-ray images have been acquired with a (statistical) signal to noise ratio (SNR) per pixel of about 30. Thanks to the direct and efficient x-ray conversion and its operation in a photon counting mode, this new diagnostic tool allows the routine investigation of the plasma core with a sampling rate of 1 kHz and extremely high SNR under all experimental conditions in NSTX.
AB - A fast x-ray system based on a micro pattern gas detector has been used for the first time, to investigate emission from the plasma core of the National Spherical Tokamak experiment (NSTX), at the Princeton Plasma Physics Laboratory. The results presented in this work demonstrate the capability of such a device to measure with a time resolution of the order of 1 ms, the curvature and the elongation of the x-ray iso-emissivity contours, under various plasma conditions. Also, comparisons with the magnetic surface structure calculated by the EFIT code show good agreement between reconstructed flux surface and the soft x-ray (SXR) emissions for poloidal beta values up to 0.6. For greater values of beta, x-ray iso-emissivity contours become circular, while magnetic flux surface reconstructions yield elongation 1.5 < k < 2.2. The x-ray images have been acquired with a (statistical) signal to noise ratio (SNR) per pixel of about 30. Thanks to the direct and efficient x-ray conversion and its operation in a photon counting mode, this new diagnostic tool allows the routine investigation of the plasma core with a sampling rate of 1 kHz and extremely high SNR under all experimental conditions in NSTX.
UR - http://www.scopus.com/inward/record.url?scp=3242659317&partnerID=8YFLogxK
U2 - 10.1088/0741-3335/46/7/007
DO - 10.1088/0741-3335/46/7/007
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AN - SCOPUS:3242659317
SN - 0741-3335
VL - 46
SP - 1075
EP - 1085
JO - Plasma Physics and Controlled Fusion
JF - Plasma Physics and Controlled Fusion
IS - 7
ER -