MAR345 Image Plate Detector

SSRL has several MAR 345 automatic image plate detectors. At present they are not installed permanently at any beamline but they can be used as a backup detector. The MAR 345 system consists of a scanning unit which holds the image plate and the equipment to read and erase the plate. The functions of the MAR base are supplied by the SSRL standard beamline system and data collection is controlled by the BLU-ICE system.

The x-ray detector is a circular image plate 345 mm in diameter. After an exposure is completed the plate is rotated and a scanning unit moves from the edge to the center of the plate and reads the data in a spiral format. As the scanning head moves towards the center the speed of the plate rotation increases to maintain a constant speed under the scanning head. This is why you will hear the scanner speeding up as it reads the plate. When the scanning is completed the scanning head is withdrawn and 3 strong lights are turned on to erase the plate. Erasing is necessary to remove any residual signal from the x-rays before the next exposure. The imaging plate can be permanently damaged by very strong radiation. Be very careful not to move the beamstop! Be sure to use the large beamstop when collecting very high resolution data.

For additional information see the MARresearch web pages.

The scanner can be used in 8 different modes, 4 different sizes of active area and 2 pixel sizes. The possible setting are given in the table below. The smaller plate diameter causes a lower resolution limit but the scanning and erasing are faster and the files are smaller. You should use the smallest plate diameter that will collect all your data in order to maximize the fraction of your beamtime that is used for collecting data. Unless your reflections are quite close together you should use the 150 micrometer pixel setting rather than the 100 micrometer setting. In the table the Total time is the readout (scanning) time plus the erasing time.