Attenuators

From RHESSI Wiki

RHESSI makes use of two attenuators (thick and thin) designed to cut down on photon flux in order to keep the detector dead time low. These have only two possible states, out or in. They are moved in and out through the use of shape memory alloy wires which contract when a large voltage is passed through them. These attenuators are also sometimes referred to as "shutters" or "filters".