150 ns 2D detector project—initial design

Abstract

We report initial design work on a 2D pixel detector designed for doing submicrosecond time resolved protein crystallography or other X-ray diffraction studies. Because protein crystallography requires a resolution of between 512 × 512 to 1024 × 1024 pixels to be effective, the design is massively parallel, each pixel will have its individual electronics processing chain consisting of a Si pixel, amplifier, A/D converter and local memory buffer. The X-rays striking a pixel from each synchrotron flash are converted to charge carriers which are collected and amplified, digitized, and stored in a sequential 8K long buffer memory before the start of the next X-ray flash, 150 ns or more later. In the full size 106 pixel detector, the incoming data rate will be 6 Tbytes/s for “experiments” lasting up to 1 ms, during which time 6 Gbytes of data will be recorded. Following an experiment the data will be unloaded to permanent storage in 10–15 min at video rates to allow an initial visual inspection. Because data storage is synchronous to arrival of the X-ray flashes, the detector can also be used in strobed measurements and achieve time resolutions limited by the duration of the X-ray flashes themselves. In preliminary work we have demonstrated our ability to digitize the arrival of single X-rays in a one-pixel detector. We are now working to construct a demonstration 128-element linear array with the required data capture rate and density of electronic components.