STARGRASP Extras

We have been at the front lines of large mosaics, so we have developed quite a few tools to make life easier for the detector engineer who has to integrate a 500+ channel focal plane system.

Voltages are applied by the grasp_pon_ota.c tool. A custom tool should be written for each type of CCD that STARGRASP controls so that the tool can be responsible for enforcing safe voltage limits and power-up sequences for your particular flavor of device. The grasp_pon_ota.c tool does this as defined by MITLL for their type of OTA, specifically CCID58s.

We would like to create a graphical tool like "cestlavie" to tune voltages. This tool would do the work we do now with simple shell scripts (sometimes just typed from the command line) that edit the FITS header of your most recent set of FITS files and then re-run grasp_pon_ota. In this way, the grasp_pon_ota tool enforces that the new changed voltages are still within range relative to the other current settings.

We have used parameter search loops that work in this way, for instance, changing drain voltages to find the optimum setting. These scripts operate on the entire focal plane at once.

We have scripts which produce linearity plots for all cells of all devices in one image with lots of little graphs.

At the device level, we have a program which works like a stethoscope, providing audio tones proportional in frequency to the RMS noise in the overscan of a readout at a high rate. (2 outputs if you have stereo ... ooh.) This is useful for all sorts of tuning, including voltage changes, slight clocking pattern changes, and grounding changes.

A program called "slotmachine.c" can analyze a multi-dimensional (multi-sampled) STARGRASP FITS file and report the absolute best signal to noise possible by varying the weighting of the samples. This can lead to a better choice of a cestlavie timing pattern, especially if you are generating a relatively slow (>2usec) timing pattern.

We make extensive use of X-Rays (from Fe55) to measure gain and charge transfer efficiency. A tool called "otaslop" automatically reports all kinds of statistics for each cell in each OTA when you take an "XRAY" type exposure with STARGRASP. (Can demo this on GPC1, which has an internal XRAY source.)