A gamma ray spectrometer with Compton suppression on the HL-2A tokamak

Area of Science:

• Nuclear Spectroscopy
• Plasma Physics
• Fusion Energy Research

Background:

• Accurate gamma ray spectroscopy is essential for diagnosing plasma behavior in fusion devices.
• Existing spectrometers often face challenges with Compton scattering, limiting spectral resolution and accuracy.
• Magnetic confinement fusion devices require specialized instrumentation for in-situ measurements.

Purpose of the Study:

• To develop and characterize a new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression for the HL-2A tokamak.
• To enable the acquisition of detailed gamma ray information in the 0.1-10 MeV range within a magnetic confinement fusion environment.
• To establish a benchmark for future gamma ray diagnostic systems in fusion research.

Main Methods:

• Designed an anti-Compton GRS featuring a high-purity germanium (HPGe) primary detector and bismuth germinate (BGO) scintillator secondary detectors.
• Implemented a digital data acquisition system with advanced software signal processing for anti-coincidence detection.
• Calibrated the spectrometer's energy response and efficiency using radioisotope sources and Monte Carlo simulations (MCNP).

Main Results:

• Achieved a Compton continuum suppression factor of 4.2.
• Demonstrated excellent energy resolution, with a Full Width at Half Maximum (FWHM) of 2.1 keV for the 1.332 MeV peak from ⁶⁰Co.
• Successfully performed gamma ray spectral measurements during HL-2A tokamak discharges under various operational conditions.

Conclusions:

• The developed anti-Compton GRS is the first of its kind for magnetic confinement fusion devices, offering significant improvements in spectral quality.
• The spectrometer's performance, including its high resolution and Compton suppression capabilities, meets the demands for fusion plasma diagnostics.
• The successful experimental validation paves the way for advanced plasma characterization using gamma ray spectroscopy in fusion research.