An X-ray photon is absorbed by the detector, causing it to heat up. We measure this heat with a temperature-sensitive resistor (known as a thermistor). The absorber is partially isolated from the thermistor, so that the absorber temperature can stabilize before the thermistor temperature starts to rise. (Why is that necessary?)
The heatsink is kept at a constant temperature. Once the thermistor heats up to the temperature of the absorber, it begins to (more slowly) cool down to the temperature of the heatsink. After a few milliseconds the thermistor has returned to the heatsink temperature, and is ready to detect another X-ray photon.
Find out more about microcalorimeters
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This page written and maintained by Kevin R. Boyce (email:
Responsible NASA official: F. Scott Porter (email: Frederick.S.Porter@gsfc.nasa.gov)