Simulation, design, and first test of a multi-energy soft x-ray (SXR) pinhole camera in the Madison Symmetric Torus (MST)

Abstract

A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid the study of particle and thermal-transport, as well as MHD stability physics. This novel imaging diagnostic technique combines the best features from both pulse-height-analysis and multi-foil methods employing a PILATUS3 x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. Further improvements implemented on the new cooled systems allow a maximum count rate of 10 MHz per pixel and sensitivity to the strong Al and Ar emission between 1.5 and 4 keV. The local x-ray emissivity will be measured in multiple energy ranges simultaneously, from which it is possible to infer 1D and 2D simultaneous profile measurements of core electron temperature and impurity density profiles with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. The expected time and space resolutions will be 2 ms and <1 cm, respectively.

Transforming X-ray detection with hybrid photon counting detectors

“…Specifically, from measurements of plasma X-ray emissivity at high spatial and spectral resolutions, the core electron temperature of the plasma and impurity density can be calculated accurately. Because of their high frame rates, adjustable thresholds and large uniform surface, HPC detectors are well suited to this application, and specific calibrations further improve analysis methods [43]. The achievable threshold energy resolution is of the order of 100 eV even at the lowest energies [44].…”

A versatile multi-energy soft x-ray diagnostic for Te measurements in the Madison Symmetric Torus

“…The ME-SXR detector is currently installed on MST such that it views nearly the entire poloidal cross-section of the plasma [8]. The PILATUS3 detector looks at the plasma through a small pinhole-like slit and a 25 µm beryllium filter which both holds the vacuum in the detector chamber and reduces the flux of low-energy x-rays, such as those from the H-and He-like Al excitation lines.…”

Plasma electron temperature measurement by foil soft-X-Ray spectrometer installed on TUMAN-3M and Globus-M2 tokamaks

“…In combination with other methods of studies, the X-ray diagnostics is quite useful for studying various processes in the tokamak plasma. For example, it allows to study internal MHD-oscillations of plasma and to determine location of the surfaces with a rational value of the stability margin [1,2], to evaluate losses of electrons by using the electron-cyclotron emission ECE [3] and escaping electrons [4], ELM-events [5,6], to monitor L−H-transitions [7] and many more [8][9][10][11][12][13][14][15][16]. Such devices are widely used in the tokamaks JET [17], MAST [8], DIII-D [18], Asdex-Upgrade [19], PDX [20], NSTX [21][22][23], EAST [5], MST [24], TCV [25,26], COMPASS [27,28].…”