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.
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.
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.
