FD Virtual channels: gain ratio for a full camera at Los Leones

A.C. ROVERO, A. PICHEL, A. TAMASHIRO; P. BAULEO, J. BRACK, J. HARTON, R. KNAPIK, AND Y. PETROV

Otro; GAP note: Publicación interna del Observatorio Pierre Auger; 2007

The saturation of a PMT channel in the camera of a FD has been taken into account in the design of the electronics by adding low gain channels, the so called Virtual Channels. To recover a saturated signal at any given PMT the ratio of electronic gains of both channels has to be known. The tp_test does this measurement any time a relative calibration procedure is performed in the camera. Here we report a direct measurement of those ratios using the Cal-A setup and a mask on the camera of telescope 4 at Los Leones. This method has the advantage of being performed with light, but it is cumbersome since it requires a special mask to be placed on the camera, hence it is only useful as an infrequent test of the standard procedure, which is done automatically and remotely.