Log entry time 00:45:38 on November 08, 2009

Entry number 298230

This entry is a followup to: 298187

Optics and dummy w/ hole targets are two line of foils targets. Optics target is above dummy. We suspect one of the dummy foil (upstream foil) is installed higher than the other. And it invaded into beam view optics target when raster is on and beam is at nominal BPM position.

As shown in plots below, beam is moved downward from nominal position until hitting bottom of carbon foils. It appears carbon foils are aligned reasonably parallel with beam, while the upstream dummy foil is much higher than the other one.

So, maybe we can avoid this invading dummy foil by set default optics target position lower on the ladder.

BTW, the invading dummy foil will be easy to cut out after a raster cut and VZ cut. So I would say it's also OK to do nothing

A copy of this log entry has been emailed to: xiaochao, jpchen

BPM Y = +2mm

BPM Y = 0 mm

BPM Y = -2 mm