PI bins for the SIS

• PI bins are defined for the SIS to put all the CCDs on the same gain and to correct for gain changes, caused by radiation damage.

• The ftool SISPI runs on an event file and fills the PI value based on the PHA value, the chip, and the time. The default action is to set the PI as a 3.65 eV/channel gain.

• To extract PI spectra using XSELECT give the command set phaname pi and then carry on as usual.

• PI response matrices are available in the caldb. There are chip-to-chip differences in the response even when the gain is corrected. For some low count-rate sources it is probably safe to add together spectra across chips but watch out for systematic problems.

• SIS background files have been created with the PI columns filled and these can be found in caldb/data/asca/sis/bcf/bgd/94nov.