Cryocooler Systems for Improved GeD Gamma-ray Imaging and Spectroscopy

Placing germanium detectors (GeDs) in an MeV γ-ray Compton instrument on 100+day balloon and satellite platforms will enable unprecedented insight into nuclear line astrophysics, key multimessenger synergies, and new heliophysics applications. Compton telescopes with position-sensitive GeDs have excellent energy resolution, improved by two orders of magnitude compared to previous instruments, and are inherently sensitive to polarization. The Compton Spectrometer and Imager (COSI) 2016 balloon flight demonstrated the promise of this technology to realize key science goals.

We are developing the last critical technology components required for GeD operation on balloon and satellite platforms: cryocooler noise mitigation and associated thermal control system. We will describe our initial noise mitigation efforts, which improved the measured line width by ~4. Our versatile, low cost heat pipe design maintains the cryocooler’s required temperature range, while additional low risk measures will satisfy the lowest power output. We will also discuss our ongoing cryocooler noise characterization and mitigation efforts and our thermal design improvements. These developments will enable the promised improvements and thus science of COSI-X and of GRX, a SMEX mission for proposal in 2019.