Development and performance verification of a 3-D position-sensitive Compton camera for imaging MeV gamma rays.

Area of Science:

• High-energy astrophysics and detector development.
• Nuclear astrophysics and gamma-ray astronomy.

Background:

• The 1-10 MeV gamma-ray band is crucial for understanding nucleosynthesis, cosmic rays, and the interstellar medium.
• Observing this energy range is challenging due to low photon signals and high background noise.
• Detector technology for this band has seen limited advancement since the Compton Gamma Ray Observatory (CGRO) in 1991.

Purpose of the Study:

• To develop and test a prototype 3-D position-sensitive Compton camera (3D-PSCC) for MeV gamma-ray astronomy.
• To evaluate the performance of the 3D-PSCC using MeV gamma-ray beams.
• To design an optimized 3D-PSCC geometry for future small satellite missions.

Main Methods:

• Developed a prototype 3-D position-sensitive Compton camera (3D-PSCC).
• Conducted performance verification using a MeV gamma-ray beam from laser inverse Compton scattering at NewSUBARU.
• Measured angular resolution using the Angular Resolution Measure (ARM) at different energies and incident angles.

Main Results:

• Obtained sharp peak images of incident gamma rays at 0° and 20°.
• Achieved an angular resolution of 3.4° ± 0.1° (FWHM) at 1.7 MeV and 4.0° ± 0.5° (FWHM) at 3.9 MeV.
• Designed an optimized 3D-PSCC geometry for a 50-kg class small satellite with an SΩ of 11 cm²sr at 1 MeV.

Conclusions:

• The prototype 3D-PSCC demonstrates feasibility for MeV gamma-ray astronomy.
• The optimized design offers potential for observing bright gamma-ray sources with high efficiency and a large field of view.
• This advancement addresses the long-standing need for improved detectors in the challenging 1-10 MeV energy band.