CCD Charge Transfer Efficiency test with the new DES Clock Board

The Dark Energy Camera will be comprised of 74 CCDs with high efficiency out to a wavelength of 1 micron. The CCDs will be read out by a Monsoon-based system consisting of three boards: Master Control, CCD Acquisition, and Clock boards. The charge transfer efficiency (CTE) is closely related to the clock waveforms provided by the Clock Board (CB). The CB has been redesigned to meet the stringent requirements of the Dark Energy Survey. The number of signals provided by the clock board has been extended from 32 (the number required for 2 CCDs) up to 135 signals (the number required for 9 CCDs). This modification is required to fit the electronics into the limited space available on the imager vessel. In addition, the drivers have been changed to provide more current. The first test result with the new clock board shows a clear improvement in the CTE response when reading out at the higher frequencies required for the guide CCDs.