Overview
The ePix100 is our main small-pixel energy- and position-reconstruction detector in psana1. It is a 500 um silicon sensor 50 um pixel hybrid charge-integrating single gain mode X-ray detector for low flux applications (up to 100 8 keV photons) above 2 keV. The pixel array is 704 rows by 768 columns.
What a detector person needs to know
The camera uses the standard epix run+daq trigger, R0, ACQ; CDS. The sensor is a single piece of silicon with 4 asics/module in a 2x2 arrangement. Since it's a single sensor there is no geometry associated with it. The bank structure of the ASIC is 8 banks below and 8 banks above the midline. The gain is about 0.06 keV/ADU and the noise is about foo (bar) after (before) common mode correction. Typical pedestal is ~4k ADU (check).
Electronics chain
The basic pixel design is shown here: ePix pixel design and timing
The basic functionality is as follows. Before the photons arrive (R0), the pixel switches its input node out of reset and samples the left over charge on to a capacitor via a CSA. When photons arrive, holes are collected from the reverse biased Si sensor by the CSA and after settling (ACQ) the presample is subtracted. The voltage is then passed down a column buffer to be digitized off-chip by a sigma-delta ADC per column. Note that a bank can in some rare cases, no longer seen, be out of sync with the ADC. See "ADC pipeline delay".
See paper here: https://doi.org/10.1063/1.4952880 - "ePix100 camera: Use and applications at LCLS". Note that Find It@Stanford gives easy access to papers: https://library.stanford.edu/search-services/google-scholar.
Other papers: https://iopscience-iop-org.stanford.idm.oclc.org/article/10.1088/1742-6596/493/1/012012/pdf
Quantum Efficiency
This should reflect 1 um of Al, about 1 um of dead silicon, and 25 um of polyimide.
Pixel layout
The pixel arrangement is described here: ePix100A 2x2 Tile Inter-IC Geometry.pdf
Note that the areas can be retrieved in psana via det.areas().
Weird stuff to be aware of
The gain correction formula is (raw-pedestal) * gain. The 10k and JF (in psana1, plus all detectors in psana2) divide by the gain (correction).