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.
- Shutter Parameters - G. Hurford (December 2001) Summary of the as-built parameters of the RHESSI shutters
- Plots of shutter transmission vs. energy (pdf) - G. Hurford (November 2001) (referenced in previous link)
- RHESSI Attenuator State Record - D. Smith (December 2002) Table showing the commanded changes in the attenuator state parameters for February 2002 to August 2004. Automatic changes in response to count rates (implemented in March 2002) are not listed here.
- Thick Shutter (Shutter A) Photos (first number is subcollimator (SC) number, second is version number)
- Thin Shutter (Shutter B) Photos (first number is subcollimator (SC) number, second is version number)