The Cornell-SLAC pixel array detector at LCLS

Abstract

The Cornell-SLAC pixel array detector (CSpad) is a general-purpose integrating hybrid pixel x-ray camera developed for use at the Linear Coherent Light Source (LCLS) x-ray free electron laser at the SLAC National Accelerator Laboratory (SLAC). The detector has a full well capacity of about 2.Sk photons in low-gain mode and a SIN of about 6 in high-gain mode. Its 2.3M pixels are read out at 120 Hz. The detector comprises 32 500μm silicon sensors bump-bonded to 64 185×194-pixel ASICs. The pixel size is 110μm. The water-cooled detector quadrants can be radially moved in-situ to vary the beam aperture. SLAC has built, calibrated, and optimized three complete camera systems based on a sensor and ASIC designed by Cornell. The camera is read out by a DAQ system which provides extensive online monitoring and prompt analysis capabilities. We have also built a dozen smaller cameras in a portable form-factor for use in confined spaces and for ease of development, testing, and deployment. Through 2012 user experiments have taken almost a petabyte of data with these detectors in a variety of applications. We have extensively tested the detector at synchrotrons and with an x-ray tube, in addition to commissioning tests at the LCLS, investigating linearity, cross-talk, homogeneity, and radiation hardness. The SLAC detector group is deploying improved support infrastructure and an updated ASIC and electronics based on this experience. This paper describes the instrument, its calibration and performance, and presents preliminary results from the updated camera.