Noisy Pixels

It is possible that with time some of the pixels of the detector start to produce an output not triggered by an income photon, i.e. to become ``noisy''. If the particular pixel countrate is too high relatively to the module countrate, then the on-board electronics switch it off. In ISGRI the noisy pixels can recover after being switched off for some time and disabled pixels are periodically reset to check their status. Data Structure ISGR-SWIT-STA with the list of noisy pixel switches in the ISGRI detector layer is produced during the pre-processing basing on the rise-time information and pixels light-curves transmitted, see Table 32.

Table 32: Content of ISGR-SWIT-STA Data Structure

Column Name	Description
ISGRI_Y	Y location in the ISGRI layer
ISGRI_Z	Z location in the ISGRI layer
OBT_DETECT	First time when the pixel can be declared as noisy
OBT_SWITCH	OBT when the pixel is switched off
NOIS_FLAG	Noisy flag

In PICsIT pixels cannot be recovered that easy. A PICsIT pixel will remain off once killed. Only if half of the detector (or so) will be off pixels will be attempted to turn on.The history of the disable pixels can be found in Data Structure PICS-FALT-STA, see Table 33.

Table 33: Content of PICS-FALT-STA Data Structure

Column Name	Description
PICSIT_Y	Y location in the PICsIT layer
PICSIT_Z	Z location in the PICsIT layer
OBT_DETECT	First Time when the pixel can be declared as noisy
OBT_FAULT	OBT when the pixel is switched off
FALT_FLAG	FLAG reflecting the changes of the pixel status. Possible values are ON-OFF and OFF-ON