User name J. Singh
Log entry time 05:29:54 on April18,2004
Entry number 118449
keyword=trouble getting to 100 microAwe moved to the carbon target and we are trying to run at 100 microA (no raster). every time the beam current gets above ~80 microA, it trips off. MCC has isolated the problem to some sort of "BLM trip in 1C0B." see ELOG 1207466. they said that the beam is not quite circular and therefore it might be clipping and spraying stuff all over the place. at high enough beam current this spray trips the BLM.
to fix this, they have to tweak the beam spotsize "knob". however, the "knob" that changes the spot size also affects the energy spread. therefore we all agreed to wait for the experts to come in tomorrow or monday and fix this problem. for now, we will just run at the highest current that gives stable beam, which is about 75 microA.
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