Contact: Tim Graber, +1 630.252.0462, graber@cars.uchicago.edu

The x-ray beam chopper at 15-ID-B was developed by Philip Coppens at SUNY Buffalo. A brass wheel with slots cut around its circumference is spun at frequencies of 5000 to 12000 rpm. At a given rotational speed, the opening time is determined by the width of the slot and the frequency is determined by the spacing between the slots. The laser is triggered using the leading edge of an optical pulse produced by the chopper with the LED/sensor device.