Annealing

From RHESSI Wiki

Annealing is the process whereby the RHESSI detectors are heated to approximately 100 degrees Celsius in order to remove damage to the crystal structure of the germanium detectors. Radiation is main cause of damage to RHESSIs detectors. Radiation damage is a particular problem for RHESSI because its detectors are unshielded and due to its orbit which intersects with the South Atlantic Anomaly where high energy particles are enhanced due to a reduced geomagnetic field.

Annealing has occurred during the following time period(s).

• 2007 Nov 4 to 2007 Nov 27
• 2010 March 22(?) to 2010 March 27(?) (see the RHESSI Science Nugget RHESSI's_Anneal_Adventure)

Another annealing period will probably occur in the middle of solar maximum. This will be the last anneal before laboratory tests suggest that the detectors will become unsegmented (e.g. the detectors will lose the rear segments leading to a loss of sensitivity for gamma-ray observations).