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2018  Proposal/BTR deadline: 2/1/18

Over the past decade electronic area detectors have brought entirely new capabilities and efficiencies to x-ray science and have had a revolutionary impact on biological studies. Prof. Sol Gruner’s group in the Cornell Physics Department is developing a new generation of large area electronic Pixel Array Detectors (PADs) for use at CHESS and other synchrotron sources. This integrating detector is capable of capturing full-frame images with microsecond exposures having accuracy better than 1%. The PAD consists of a silicon layer, which absorbs the x-rays, bump-bonded onto a CMOS electronics chip in which each pixel has its own processing, storage, and readout integrated electronics. A prototype PAD with on-chip storage for eight full-frame images has recently been tested, in collaboration with CHESS staff, as a "streak-camera" to capture x-ray data of fast, transient phenomena.

Prototype PAD
Prototype of 92 x 100 element PAD with each pixel of sizes 150 micron square with supporting components nearby.

The detector was first operated at the CHESS D1 beamline for microsecond time-resolved images of a rotating saw blade. Three radiographic strips of images taken with successive 5 millionths of a second exposure (a,b, & c) show excellent stop action performance.

In collaboration with a group led by Dr. Jin Wang at the Advanced Photon Source (at Argonne National Laboratory, outside Chicago) Gruner's group used the PAD to perform radiography of a fuel injector spray, similar to that which occurs in automobile engines. The first hundred microseconds of fuel injection are poorly understood, yet determine the efficiency of the fuel injection cycle. X-ray images of fuel injection were previously impeded by the lack of a detector which would image at the necessary microsecond rates. The groups succeeded in recording a radiograph movie of the injection process over the initial few milliseconds. Analysis of these movies hold the promise of leading to more efficient fuel injectors and automobile engines.