Bunch Profiles in Rhic From Cni Polarimeter Target Scans. Page: 3 of 20
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ANL-HEP-TR-05-033
C-A/AP/206
Bunch Profiles in RHIC from CNI
Polarimeter Target Scans
H. Spinka
Argonne National Laboratory
13 May 2005
During the RHIC run-4 polarized proton operation, the intensity and polarization profiles were
measured by scanning the Coulomb-nuclear interference (CNI) polarimeter targets across the beam.
The scans reported here were all performed on flattop at beam momenta ~ 100 GeV/c, and all but one
was a vertical scan, since several of the vertical polarimeter targets had broken by the time of the
measurements. This note summarizes some analyses of these profiles. Wall current monitor data are
compared to these results for one beam and fill.
Transverse Intensity Profile Measurements
The raw data from the p + C CNI polarimeters (Ref. 1) included the summed counts passing cuts
from each of the six silicon-strip detectors in the relevant polarimeter (left, right, and 450 and 1350
to the vertical) for each bunch as a function of target position. The polarimeters were operated in the
scaler mode for these results, and the time of the measurements was also recorded. There were five
scans performed at flattop in run-4 - one each in the vertical direction for the yellow and blue beams
for fills 5236 and 5341. The fifth scan was in the horizontal direction for the blue beam in fill 5236.
For intensity profiles, the sum of counts from the six detectors was divided by the elapsed time.
The centroid and rms width of the profiles were computed for each bunch. Histograms of these
quantities for the yellow beam vertical scan in fill 5236 are shown in Fig. 1. The two scans in the blue
beam for fill 5236 are shown in Fig. 2, and the two vertical scans in fill 5341 are given in Fig. 3. From
these plots, it is clear that there is at least one bunch with considerably different properties in each scan.
There are several such bunches in the blue beam for both fills 5236 and 5341, while there seems to be
two classes of bunch widths in the yellow beam in fill 5341.
In each of the five scans, bunch # 21 (among 1 - 120, with the last ones being the abort gap, and
only the odd bunches "populated") has an anomalously large width. This bunch corresponds to the
one that is perturbed in order to measure the tune of the beam during acceleration in RHIC. Its profile
is usually much different from the other bunches; see Fig. 4.1
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Spinka, H. M. Bunch Profiles in Rhic From Cni Polarimeter Target Scans., report, June 3, 2005; United States. (https://digital.library.unt.edu/ark:/67531/metadc886188/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.