Leo Steinmetz Rose Hills
Testing TES Bolometers at 100 mK
Cosmic inflation is a theory that expands on the Big Bang model of the early universe to explain some confusing astrophysical observations. A major next step for physical cosmology is to find direct evidence of inflation. Theoretical cosmologists predict that inflation left patterns in the oldest light in the universe, the Cosmic Microwave Background (CMB), so the CMB measurement community is attempting to detect and characterize these patterns with a new generation of CMB telescopes such as LiteBIRD and CMB-S4.
In order to detect this pattern we need to develop extremely sensitive detectors. The satellite telescope LiteBIRD will use detectors called Transition Edge Sensor (TES) Bolometers, operating at a temperature of 100 mK, just 0.1 degrees above absolute zero. Over the next few years, we will be developing the detection electronics for LiteBIRD, and we’ll need to thoroughly test many prototypes. To that end, I’m working on a few different testing projects, including automated room-temperature wafer probing and probe card development. My main project is the completion and operation of a cryostat (a super-refrigerator) that will be able to cool prototype wafers to their operation temperature of 100 mK and characterize their response to light signals.