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Beam offsets in the optimization 06/15/05

After talking with Dave, the epics scaler file was used to give the beamx and beamy positions (eg. IPM3H00A.XRAW was the BPM_A x position).

The average beamx and beamy over the run was calculated.

The final beam positions that were used in the lab frame (50126-50134) were
beamx = -0.10 cm
beamy = -0.01 cm

This agrees with Dave's Y offset for run 50130 (a run in the middle of the optics set) which was -0.012cm.
It also agrees with Dave's X offset for runs 51017-51610 (not an optics run, but similar bpm) which was -0.12cm.

However, the BPM offsets I calculate are:
beamx = BPM_x - 0.06cm (runs 50123-50135)
beamx = BPM_x -0.13cm (Dave's horizontal runs 51388 and 51610)
beamy = BPM_y+0.037cm (runs 50124 and 50130)

(BPM Beam X and Y position projected to the target) no offsets
(HMS Beam X and Y position) determined from hsxptar and hsytar and z_targ=0.23cm

50123
BPM -0.10333 0.0102733
HMS -0.166029 0.0489038
50124
BPM -0.107889 0.0094228
HMS -0.174724 0.0499618
50125
BPM -0.109164 0.0142014
50126
BPM -0.0311778 -0.0446308
50127
BPM -0.0277331 -0.0725982
50128
BPM -0.0316475 -0.070121
50129
BPM -0.0333127 -0.0706421
50130
BPM -0.0401325 -0.0468409
HMS -0.0919084 -0.0105913
50132
BPM -0.0148883 -0.0807896
50123
BPM -0.017562 -0.0823754
50134
BPM -0.0142467 -0.0808899
50135
BPM -0.0136236 -0.0771535
51388
BPM -0.0139095 -0.0816515
51610
BPM -0.09721 -0.0205395

Beam offsets in the optimization 06/08/05

The Carbon z=0 target position was assumed to be at z=0.23 cm in the lab frame. This agrees well with the surveyed position of 2.5 +- 0.5 cm and comes from Dave's result. Whith z_lab fixed, I then used Dave's method for calibrating the BPM's using the HMS, except that I did not need to use a number of HMS angles to determine the x position of the beam.

The equations I used to determine beamx and beamy in the lab frame using the HMS were:
(1) convert the mean hsxptar from rad to mrad
(2) xtar = <hsxptar>/(-1.73)    |in mm
(3) beamy = -xtar/10.0               |in cm
(4) HMS mispointing from survey at 18.0 deg was 0.01cm
(5) Add mispointing to mean hsytar, <hsytar> = <hsytar> + 0.01cm
(6) beamx = ztarg*tan(th_hms)-<hsytar>*sin(th_hms)*tan(th_hms)-<hsytar>*cos(th_hms)

This is the kumac used that does these calculations.

The BPM's were calibrated. The equations used to calculate the position at the target were:
(1) beamx = <bpma_x+327.15*(bpmb_x-bpma_x)/(327.15-231.46)>
(2) beamy = <bpma_y+327.15*(bpmb_y-bpma_y)/(327.15-231.46)>
(3) beamx = beamx - 0.130      |lab frame in cm
(4) beamy = -beamy+0.158     |lab frame in cm
The offsets in (3) and (4) were chosen to match the BPM with the HMS beam position at the target.

There were two problems...   My offsets are very different to Dave's offsets (-0.102cm and 0.031cm respectively for beamx and beamy)! This may be due to using the BPM's with and without offsets. Further, the beamy offset I calculated from run 51388 was different to the offset I calculated in run 50124.   I am not sure what caused this.

RESULTS

The beam offsets assigned to runs 50126-50135 were:
         beamx = -0.08    !Lab frame, in cm
         beamy = -0.02 !Lab frame, in cm

The results for individual runs are listed below.

Listed below is the x and y position of the beam in the lab frame respectively (in cm). In the lab frame, z points in the same direction as the beam, y is down and x points toward the HMS side of the hall. For runs 50123 and 50124, the HMS was used to determine determine the beam position following Dave's instructions and assuming that the target was at z=0.23cm.

50123 (Carbon z=0, beam alignment)
BPM -0.153175 0.048043
HMS -0.166029 0.0468848

50124 (Carbon z=0, beam alignment)
BPM -0.157777 0.048841
HMS -0.174724 0.0488383

50125 (Carbon z=0, beam alignment, HMS down)
BPM -0.160051 0.0838616

50126 (Carbon z=0, final beam position, HMS down)
BPM -0.08427 0.0953071

50127 (Carbon optics)
BPM -0.0852324 0.122422

50128 (Carbon optics)
BPM -0.0813713 0.124228

50129 (Carbon optics)
BPM -0.0874183 0.122591

50130 (Carbon z=0)
BPM -0.0976319 0.098506
HMS -0.0919084 -0.0105913

50132 (Al dummy)
BPM -0.0701107 0.132049

50133 (Al dummy)
BPM -0.0683091 0.130455

50134 (Al dummy)
BPM -0.0628837 0.134907

50135 (Al dummy)
BPM -0.0681908 0.134481