Alignment in IMS:SLIT0 to SLIT10A Section

by Pierre Bricault, July 2, 2004

This morning I noticed that the alignment between IMS:SLIT0 at the pre-separator focal point and IMS:SLIT10A was wrong. The beam position change[d] on IMS:HARP10 in the horizontal plane. We have to correct with IMS:YCB3 in order to reestablish the beam on axis. Furthermore, I notice[d] that [when] the beam is align[ed] horizontally in the section between the two magnets, it end[ed] up 3mm to the left on IMS:SLIT10A. The new position for the centre is 27.5mm instead of 30.5mm. I cannot explain why we have that now. The beam shift in the horizontal plane is not new. I suspect that we have a horizontal steering plate floating in this section that charge up and discharge. This will explain the slow variation and the sudden change of the beam position on the harp monitor in front of the mass separator.

Mike McDonald knows about it. There is nothing we can do unless we open the box to diagnose the problem. This is a two-week job. I will talk with Mike and maybe we will have to rebuild the entire beamline section with better access to the feedthroughs in order to remove this problem for good.

The operators have to be aware that if the intensity changes suddenly to check the steering [on] IMS:YCB3. IMS:YCB3 should be raised to 686 Volts if the CCB3 is 388V. This will correct the situation for a short period of time, and then it has to come down to the same value as CCB3.