RHESSI Attenuators

The RHESSI attenuators (also called shutters) are two sets of aluminum disks that can be brought into the field of view of the detectors to prevent saturation during the largest flares. There is a thin set of disks that provide modest attenuation and a thicker set for the largest flares. Both have a small thin spot in the middle to allow at least some response down to the lowest energies. RHESSI operates in one of the following four attenuator states: 0=both attenuators out; 1=thin in, thick out; 2=thick in, thin out; 3=both in.  In practice, attenuator state 2 has not been used.

The attenuator state is part of the data stream, and can be retrieved in the RHESSI object software via the info parameters INTERVAL_ATTEN_STATE, SP_ATTEN_STATE, and IMAGE_ATTEN_STATE.