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Site Details ATF Newsletters 
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2000 ATF NewslettersJan | Feb | March | April | May | June | July | Aug | Nov | Dec
STELLA Runs #00-03, 04, & 05 performed
this week. CTR signal reestablished,
but not as strong as previously seen (few 100mV this week versus 1 volt
a few weeks ago). We suspect
that, because of high sensitivity to electron beam quality and stability,
proper e-beam tuning & stability was not achieved.
Needed improvements have been identified, and will be instituted
before our next runs. Plans
to install the ICA cell and attempt staging experiments are still expected
for the end of February. Results
of these runs to be analyzed and reported next week.
We are currently preparing for the last run days before
the shutdown. We need to
determine what radiation was seen at the detector during the last run
(spontaneous?) As reported, we saw about 1.5nJ at period 200/pop-in 8 and
linear with charge. Plans are to use a polarizer- undulator radiation
horizontally polarized. Our large angular acceptance at the detector would
cause the spontaneous to be quite large. We will test a symmetric 125 winding horizontal steering
magnet. 125 windings can co-exist with BPMs.. The magnet power
supply glitches are being worked out. There is a decay in the output current
when run above 4 amps due to thermal effects. Better cooling of the supplies
is needed. BPM testing will continue. We need to be sure we can separate
the OTR from Spontaneous. and make sure we can see a reasonable and fairly
good resolution signal. Spontaneous is about 100x larger than OTR. This
means testing a filtration for the radiation including spectral as well
as polarizers and see what is best for our BPM design.
If time permits, propagate and look for signal. One way to reduce
the spontaneous is to decrease our angle of acceptance at the detector.
This along with increased lead shielding is currently being done. Aside from the snow and ice, and the temperature dropping
to 55 degrees inside the facility, business at the ATF was normal. Late
last Friday, we bled up the VISA faraday cup assembly and removed the
foil. The unit was re-pumped, leak tested and put back into service. The
fast detector experiment “CPOD” had requested a much needed diagnostic
screen for their alignment. Bob Harrington came to the rescue and prepared
a new phosphorus screen which was then installed. During their scheduled
run on Tuesday, they were able to observe the placement of the e-beam
in reference to their fiber wires with great accuracy. A lot was learned
from the phosphor. During the week, the remaining laser filter covers
were installed in the facility area. Igor Pogorelsky and Marcus Babzien have been searching for
a special laser iris with a calibrated aperture control to enhance the
operation of the CO2 . Their investigations have proved fruitless. Upon
explaining the problem and their frustrations to Bob Harrington, Bob asked
if they would let him solve their dilemma. Bob attacked the situation
with great enthusiasm. He found a polarizer mount calibrated in degrees
and with expert design and fabrication, came up with a device that can
be controlled and repeated with great accuracy. Igor installed the iris
device and it is working perfectly. Bob Harrington should be congratulated
on his innovation and expertise in solving a problem that has puzzled
many a laser expert for a long time. “Good job”. Marc continues to research the linac water servo system, calculating the needs of the facility and ordering parts for fabrication. And as always, the ATF technical staff continues to support the control room as duty operators on a daily basis.
Last Modified: December 3, 2007 |
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