What are the major differences between the undulator BL12-2 beamlines and other SSRL PX beamlines?
• Variable beam size : The other SSRL beamlines operate at a fixed focus, and the beam size is changed by opening or closing collimating slits upstream of the sample. On BL12-2, however, the beam can be focused from 200×200 microns to 20×50 microns. Important: Because the full beamline flux can be concentrated on a very small spot, it is important to avoid overexposing the samples. We strongly advice to use Web-Ice to calculate the data collection strategy, and to inspect the estimated dose before deciding on the exposure time and beam attenuation. In addition, it is possible to use a 6×15 micron beam by inserting a collimator in the beam. To use this feature, simple check check the ”microbeam” button in Blu-Ice. As a rule, the microbeam should only be used to study very small crystals; for crystals larger than 10-20 microns it will be usually more advantageous to use the ”normal” beam focused to match the crystal size. • High zoom on-axis camera: Besides the sample camera viewing
