booster corrector measurement QA

Phil Schlabach1 May 2007

Proton Source Magnet Meeting

booster corrector measurement QA

• online QA– protect against bad measurements which are

not discovered until later– protect against bad magnets

• let’s assume for the moment there is an “offline” QA

– provide feedback during production measurements to

• “measurer”• “analyst”

measurement plan

• AC measurements with fixed coil array– excite each element individually with the

specified profile• other elements are connected to the PS, current

set to 0– excite all elements

booster corrector measurement QA

1. strength2. harmonics3. coupling• quality of the measurement

– 1, 2• quality of the magnet

– 1, 3

strength measurement

tolerances

compute a strength “error function”

=current_mon*TF_nom-measured_field

•apply tolerance band

harmonics

tolerances

1

1

1

1

max

max

)(

)(

0@

nN

mn refnx

nN

mn refny

RxAxB

RxBxB

y

monitor the field shape

•@y=0, By(x) probes Bn, Bx(x), An

•monitor min/max By(x), Bx(x), |x|<1.5”

•apply tolerance band

other

• centering, angles– see slides

• single vs. multi-element excitation– also slides

• should we monitor coil voltages, currents (or something)– coupling, regulation issues?

centering, angles

• so far, we have been looking at harmonics re-analyzed based the normal quadrupole center– this is difficult to do online as it links

information between “separate” measurements

– there are similar issues with the way we’ve done angles for certain cases

• this is better done offline

centering, angles (2)

• proposal: for online analysis leading to QA evaluation, analyze each measurement independently– centering, angle– monitor

• offsets• angles relative to expected angles• both should be small

• deviations will reveal both setup and/or coupling issues

centering, angles (3)• e.g.

– probe offset or rotated• will need some experience to know what to expect• mm for offset, few deg. for rotation?

– coupling• excitation of normal element skew

– shows up in the angle• excitation of (e.g.) sextupole dipole

– shows up in the centering offsets

• monitor in the same manner as strength error, field shape– plot x0, y0, , apply tolerances

• for any of this to be useful we will have to figure out how to deal with the field of the earth

single vs. multi-element excitation

• remarks so far deal with single element excitations

• multi-element excitations– one would have to choose an element for the

online analysis (e.g. analyze as “normal quad” by fiat)

– then try to devise a monitoring scheme– that’s as far as I’ve thought it out

list of variables

strength error strength-TFnom*I

field defect max/min of By(x), Bx(x) inteval of 1.5”

centering offsets field center for each element (except dipole)

angular offset field angle - nominal

post testing

• reanalysis, 2nd pass at magnet quality, and posting to repository

• trend analysis