Testing of X-ray Active Pixel Sensors for Recording Data from STEM. JARED SCHWEDE (Yale University New Haven, CT 06520) PAVEL REHAK (Brookhaven National Laboratory, Upton, NY, 11973)

An X-ray Active Pixel Sensor (XAMPS) made for recording data from the Scanning Transmission Electron Microscope (STEM) is being tested. Previous tests using an electron beam of this 32x32 matrix of 180 micron silicon square pixels showed less than ideal behavior. It appeared that some of the columns were nonfunctional, indicating that some of the parallel electronics should be tested and perhaps replaced. A simple light source obstructed by a cover with a hole of diameter 1 mm created a beam that was demagnified to about the order of the pixels, much finer than the broad electron beam used previously, to make more refined tests of the sensors. An x-y table equipped with two stepper motors that could precisely determine the position of the light source was used to move the light beam on the sensor. Observations discovered a broken chip and faulty contacts. Replacement increased resolution and general performance, which had been poorer than in previous tests. Other components frequently broke before the installation of a cooling fan. Changes to the LabVIEW visualization program yielded satisfactory images. These tests of the XAMPS are one of many continuing tests of this sensor. This sensor is part of an ongoing project to increase STEM's available information.