A compact and portable gamma-ray spectrometer (GRASP) for inertial confinement fusion and basic science experiments

Area of Science:

• Nuclear Physics and Engineering
• High-Energy Physics Instrumentation

Background:

• Inertial confinement fusion (ICF) research requires precise diagnostics for gamma-ray spectra.
• Existing gamma-ray spectrometers can be bulky, limiting their deployment in facilities like OMEGA and the National Ignition Facility (NIF).
• Accurate spectral measurements are crucial for achieving high-energy gain in ICF and for fundamental physics research.

Purpose of the Study:

• To design a compact and portable gamma-ray spectrometer for ICF applications.
• To enable detailed diagnosis of gamma-ray spectra in the 3.7–17.9 MeV range.
• To facilitate fielding in diagnostic ports of major laser facilities.

Main Methods:

• The system utilizes a conversion foil for Compton scattering followed by four magnetic spectrometer arms.
• Halbach arrays of permanent magnets form the spectrometer magnets, optimized using COSY INFINITY simulations.
• Monte Carlo simulations were employed to optimize the conversion foil's performance.

Main Results:

• The designed spectrometer spans a broad gamma-ray energy bandwidth (∼3.7–17.9 MeV).
• With a 1.7 mm boron conversion foil, the system achieves an energy resolution of ∼15.8%–4.5% and efficiency of 5.4 × 10⁻⁷–3.7 × 10⁻⁷ e⁻/γ.
• Simulations indicate the design is effective for a simulated direct-drive gamma-ray spectrum, with potential for further optimization.

Conclusions:

• The developed compact gamma-ray spectrometer is suitable for deployment in ICF facilities.
• It offers valuable spectral measurement capabilities for advancing ICF energy gain.
• The instrument can support new measurement opportunities in basic science discovery.