ROTATING ANODE/AREA DETECTOR DATA COLLECTION ON AXES>300 Å AND NEW, RAPID CALIBRATION METHOD. James C. Phillips, Siemens Energy and Automation, Inc. Analytical Instrumentation, 6300 Enterprise Lane, Madison, WI 53719-1173

Crystallographers are investigating ever larger unit cells. HI-STAR with high resolution mode and Dual HI-STAR systems were designed to meet this challenge. The Siemens HI-STAR multiwire area detector has previously been calibrated with an Fe⁵⁵ radioactive source, as have the X100 and the X1000, earlier models. This procedure has taken several hours when the system is configured for large unit cells. However, the new calibration method, using amorphous Iron foil placed at the crystal position and generating fluorescence by irradiating it with CuK[[alpha]] radiation is much faster.For example, using a dual HI-STAR at 300/452 mm from the sample, on a rotating anode generator calibrations were done for both detectors simultaneously for flood field (15 minutes) and spatial ( 15 minutes). The 300 mm detector was in 1024x1024 pixel mode, the 452 mm detector was in 512x152 mode. An intensity comparison was made with a 2.92 year old 100uC Fe⁵⁵ source (reduced to 46% of original activity) for the dual detector configuration above. Foil count rates were 43 times stronger for the 300 mm, 46 times for the 452 mm. With calibration by this method data was collected on a crystal with a 346 Å axis and one 400 Å. The cell parameters and the statistics of the data integrated by SAINT clearly show the power of the dual HI-STAR system for these "front-line" experiments and that calibrations are accurate as well as convenient.