The EBEX cryostat and supporting electronics.

Abstract

EBEX is a balloon-borne polarimeter designed to measure the B-mode polarization of the cosmic microwave background radiation. The instrument includes a 1.5 meter Gregorian-type telescope and a cryogenic receiver housing 1432 bolometric transition edge sensor detectors operating at 0.3◦ K. In this thesis I describe my work on the development and characterization of the EBEX cryogenic system and of several electronics sub-systems. I developed CANbus-based software to monitor temperatures inside the receiver and to control the operation of two sub-Kelvin adsorption refrigerators. I commissioned and tested an experiment-wide timing system that tags data from all subsystems with an accuracy that is a factor of 10 better than required. I constructed and tested two pressure vessels that store data on board. Data collected during the EBEX test flight in June 2009 show that all these subsystems performed according to predictions. The temperatures of the cryostat were stable. An analysis of the temperature data finds no scan synchronous signal in the cryostat temperatures. The timing system and pressure vessels operated as expected. A calibrator was installed inside the receiver to monitor detector responsivity variations. I analyzed the data from the test flight and show that in its current configuration the calibrator is inadequate.