9 degree deflector plates at ISAC seem to be operated 5-10% below their theoretical settings
Most significantly seen in OLIS at IOS:XCB1A, but also routinely observed at other 9 degree deflectors. Most recently I ran the OLIS MWS with B1A (36 degree bender) at theory, but had to lower the XCB1A plates by around 13% to get beam to IOS:FC3. Some brief check of IOS:Q1-3 after showed they were not steering much suggesting beam was on axis through those quads.
I was curious and also checked a tune from OLIS SIS and found that XCB1A was ran 18% low in a tune in 210418_1123-ios-hebt1-db0.snap. So the 9 degree bender is ran low from either direction/polarity.
This behaviour is also observed at:
- ILT:XCB7
- ILE2:XCB11
- ILE2:XCB21
@baartman would be great if someone from beam physics could investigate this when someone has time. Is there a beam physics note on how the voltage of these deflectors is calculated?