Seminars Archive

PERCIVAL: a fast soft X-ray imager with high dynamic range

Abstract
P.E.R.C.I.V.A.L. (Pixelated Energy Resolving Cmos Imager Versatile And Large) is a soft-X-ray detector (250 eV – 1000eV) currently under development in collaborative effort between DESY, STFC, ELETTRA and Diamond light source. The project strives to fabricate a large (10cm x 10cm) pixellated detector featuring, a high dynamic range (1-10^4photons), a single photon (250 eV) noise floor, a spatial resolution of 25-30µm and moderate readout speed (up to 120 frames/s). The latter ensure compatibility with most of low-energy FEL sources (250 eV-1 keV) currently under development or in operation. PERCIVAL is based on a Monolithic Active pixel Sensor (MAPS), manufactured using a commercial CMOS technology. In order to assess the desired energy range back thinning and post-processing steps are mandatory. Each pixel of the sensor accommodates a multi gain amplifier to achieve and the target dynamic range as well as the necessary switching logic. A set of seven ADCs per column, which sums up to approx. 28000 ADCs per sensor ensures the readout speed of about 10 ms. Triggering, control and readout of the sensor relies on FPGA technology. Small size (4mm x 5.25mm) test prototypes not yet back thinned have been produced. At the time being these are thoroughly characterized utilizing front side illumination with visible light and soft x-rays (0.3-2 keV) with beam intensities ranging from 10^9 to 8*10^10 photons/sec. First small sized back-thinned sensors are expected at the end of 2013 while the final large size detector will be operational in 2015.