Debuncher Cooling Limitations to Stacking Page: 2 of 12
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The effect of transverse cooling can be seen most directly by
looking at the D->A line SEM's. Changing the cooling time changes
the width on SEM806 and SEM807.
The D->A efficiency is measured by the ratio
A:FFTTOT/D:FFTTOT. Since the circumference of the two machines are
not the same this ratio should be 1.06 for 100% transmission.
A:FFTEFF is the ratio of beam within .2% dp/p in the
accumulator to the beam within .2% dp/p in the debuncher. Without
momentum cooling this would be a good measurement of the D->A
transfer efficiency for particles within the momentum aperture of
the accumulator, however, the debuncher measurement is made
before the beam has been cooled and the accumulator measurement is
made after cooling. A:FFTEFF can often exceed 150%, which simply
shows that momentum cooling is working.
By changing the trigger time for the FFT it is possible to
measure the amount of beam left behind by ARF1. A simple way of
doing this is to measure A:FFTTOT/D:FFTTOT with D:FFT1=1200000.
The overall efficiency of transporting beam from the injection
orbit to the core can be measured by plotting A:STCKRT/A:FFTTOT.
To convert this to an efficiency one needs to multiply by
10**6*120/(3600*19); which is the correction factor for 19
pulses/supercycle with a 120 second supercycle. This efficiency
includes the beam left on the injection orbit by ARF1, so for many
of plots below the ARF1 loss is added back in.
RESULTS
The measurements were taken with an accelerator timeline that
had 19 pulses per 120 second supercycle, resulting in 6 seconds
between pulses. Gating switches were used on the horizontal and
vertical cooling to limit their cooling time. The momentum cooling
and stack tail cooling were left on for the entire time.
Figure 1 shows the bunch rotation efficiency measured at
different times in the cycle. There is a very clear increase with
time, showing that momentum cooling is indeed working. It looks
like 2 seconds of momentum cooling at 800 watts is not enough to
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Halling, Mike. Debuncher Cooling Limitations to Stacking, report, August 13, 1991; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1014253/m1/2/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.