Trickle-Charge: a New Operational Mode for PEP-II Page: 2 of 3
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pulses. These diagnostics have been the primary tools
for the minimization of trickle injection related
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Figure 2. Top: BaBar background signal from HER
injection to 15ms. Bottom: PSD of that signal versus
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Figure 4. Top is a cesium iodide detector versus "mini-
train" bunch number. Below is EMC background.
JITTER SOURCE REDUCTION
In commissioning HER trickle-charge, the most severe
issue was high background injection pulses ("fliers").
Linking BaBar's signals into the PEPII control system,
we are then able to correlate incoming beam parameters
with such fliers.
The injected beam energy, phase (timing), transverse
position are measured and stabilized by feedbacks.
0 2 4 6 8 10 12 14 Nonetheless, jitter from faulty hardware or mis-set
Figure 3. Same as in figure 2, only after the energy of the
injected beam has been corrected.
Figure 2 shows the gated trigger rate against time after
injection and its FFT. The peak at 6 kHz indicates
synchrotron related losses caused by energy or phase
offset of the injected beam. In figure 3 this has been
corrected. These BaBar generated plots are continuously
updating at one Hz in the control room.
parameters is still possible.
Source intensity jitter, which can cause parameter
changes of the injected beam has been reduced by
progressive tuning, then hardware repair. In figure 5 the
beneficial effect of tuning and repair is clearly visible.
0 5 10 15 20 25 30 35
0 5 10 15 20 25 30 35
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In Gating the BaBar diagnostics from the EMC, from
added cesium iodide detectors, and other sources we can
correlate BaBar "On" system background with other
detectors in order to tune with BaBar "Off' if necessary.
In figure 4 a cesium iodide detector and EMC
background at injection are plotted against bunch
positioin in the mini-trains in the HER ring. Lower is
more background on these plots, so the ends of the mini-
trains cause somewhat more injection related
backgrounds than other buckets. Injection backgrounds in
the HER were seen early on to depend strongly on the
LER current indicating the significance of beam-beam
forces. It was also seen that injection rate and background
depend on the bunch being filled. This is presumably due
to some buckets only having a single parasitic crossing
rather than crossing on both sides of the interaction point.
This condition was rapidly addressed with a small change
in the horizontal tune.
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-0.1 bucket mod(72)
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Kozanecki, W.; Colocho, W. S.; Decker, F. -J.; Ecklund, S.; Fisher, A. S.; Iverson, R. H. et al. Trickle-Charge: a New Operational Mode for PEP-II, article, May 9, 2005; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc883371/m1/2/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.