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An upgraded x-ray spectroscopy diagnostic on MST
D J Clayton1, A F Almagri, D R Burke
1Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. dclayton@pppl.gov
The Review of Scientific Instruments
|November 2, 2010
Summary
An upgraded X-ray spectroscopy diagnostic in MST measures fast electron distributions. This allows for the determination of effective charge (Zeff) and particle diffusion coefficients (D(r)), indicating improved plasma confinement.
Area of Science:
- Plasma physics
- Nuclear fusion diagnostics
- X-ray spectroscopy
Background:
- Understanding fast electron behavior is crucial for plasma confinement in fusion devices.
- Previous diagnostics had limitations in resolving fast electron distributions and associated plasma parameters.
- The Madison Symmetric Torus (MST) requires advanced diagnostics for studying plasma properties.
Purpose of the Study:
- To implement and utilize an upgraded X-ray spectroscopy system in the MST.
- To accurately measure the spatial distribution of fast electrons.
- To determine key plasma parameters: effective charge (Zeff) and particle diffusion coefficient (D(r)).
Main Methods:
- Employing a radial array of 12 Cadmium Zinc Telluride (CdZnTe) hard X-ray detectors (10-150 keV).
- Utilizing a new Silicon (Si) soft X-ray detector (2-10 keV).
- Digitizing detector pulses and fitting waveforms with Gaussians for high time and energy resolution.
- Using lead apertures and shielding, along with Beryllium (Be) vacuum windows and filters for optimal signal acquisition.
Main Results:
- The upgraded system successfully measured Bremsstrahlung spectra from both thermal and fast electrons.
- The diagnostic provided detailed radial profiles of fast electron distributions.
- Comparison with Fokker-Planck code (CQL3D) enabled deduction of Zeff and D(r).
Conclusions:
- The upgraded X-ray spectroscopy diagnostic is effective for characterizing fast electrons in MST.
- The measurements provide insights into reduced stochasticity and improved plasma confinement.
- This diagnostic advancement aids in the development of future fusion energy systems.
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