This week was a Mini-shutdown at the ATF and the NSLS Users Meeting.
Ilan Ben-Zvi.
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Magnetic Measurements
(Reported by George Rakowsky) |
VISA: The pulsed wire bench has been reassembled
on the smaller 12-ft granite table and measurements on Sections 1
and 2 have resumed. The new tabletops have come in from the shops.
They have been mounted on the base pedestals in Bldg. 726 and are
being surveyed and leveled. Robert Ruland’s interferomety rails
have arrived from SLAC.
HGHG: Tilt limit switch hardware has been fabricated
and is being installed on the Mini-undulator. In addition, limit switches
are being installed on the ends of the magnet arrays to open on contact
with the beampipe. Electronics modifications will be done next Tuesday.
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HGHG
Experiment (Reported by Adnan Doyuran) |
Yesterday the diving board has been installed, so I started aligning
the He-Ne laser. Today I got the beam to the FEL room. The doubling
crystal has been installed in front of the spectrometer. The crystal
has a large wedge so it is tricky to align. Next week we will use
the CO2 laser and try to generate 5 micron for the calibration of
the spectrometer. Also I did another test about the detector. We were
wondering how long this detector can operate after the cooling? I
cooled about 1:30pm Thursday and measured the signal from a 5 micron
diode. I got 63mV signal. I checked the signal frequently, lastly
at 7:10pm I still measured 63 mV. Next day (Friday) at 11:30 am the
signal was still 63 mV. I looked into the detector to check the liquid
nitrogen level. It was cold, but no more liquid left. At 1:30pm the
signal was gone totally. I cooled again and signal came back to 63
mV. I was surprised that after 22 hours signal was unchanged then
in 2 hours it was gone. I checked the noise at about 1mV both when
cold and warm.
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VISA
Experiment Progress (Reported by Roger Carr) |
Ben Poling and Roger Carr will arrive at BNL next Tuesday evening,
and work next Wednesday, Thursday, and Friday to re-assemble VISA,
with the newly machined pedestals and table tops. Marty Woodle informed
me today that the table tops are not done as of today (Thursday),
but he hoped that they would be done before Wednesday morning. He
will informally QC them. We have sent all the ion pumps, the trim
coil power supply buss, and all the small parts (washers, springs,
etc) to BNL in preparation for our work next week. We hope to get
the table tops mounted and aligned, and all the slides, bellows, etc
remounted, fitted to the vacuum chambers, and to align the chambers.
We have also designed and built a special jig for mounting the tungsten
carbide kinematic mounts, and we will install them into the undulator
modules.
If all goes well, the system will be ready for Robert Ruland and
his crew to start work on mounting and aligning the modules, starting
Monday, June 7. He expects that this work will take about 2 weeks.
The beamline reference laser was shipped from UCLA to SLAC this week,
where it will be checked out by Robert Ruland and crew.
During the period after undulator alignment, from June 21- July 6,
the system is available for installation and checkout of optical and
beam diagnostics, trim coils, vacuum systems, etc.
Any remaining design issues should be resolved by this time. If there
is to be any kind of readiness review, it can occur in this period.
Ben Poling and Roger Carr expect to return on July 6 to begin the
move to ATF, and we hope to complete this work by July 16. If all
goes well, Robert Ruland could begin the alignment in the ATF starting
on July 19. However, if the schedule slips, and the system is not
ready for him at this time, he will not be available again until September.
Therefore, it is important that any delays be dealt with at high priority.
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VISA Beam and Radiation
Probes (Reported by Erik Johnson) |
We have our first pop-in probe of the new design to look at. Also
this week
we received flippers that Alex ordered, the vacuum adapters, and
the vacuum
actuators for the pop-ins. Some issues need still to be resolved
for the
probe; the current mirror mount design was difficult (time consuming
and
therefore expensive) to make, so an alternate is being explored for
the
remaining probes. We also need to find out about how the mirror polishing
at UCLA is proceeding, and come up with an alternative way to get
them
polished if it proves to be more difficult that first anticipated.
The
attached file has a JPEG of the probe, one of the vacuum adapters,
and one
of the actuators.
May_28_VISA_probe
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COMPTON
Experiment Progress (Reported by Ping He and Shigeru
Kashiwagi) Calibration of the silicon diode |
We measured the number of generated electron hole pairs in the silicon
diode using a 670nm, 10ns laser pulses. The capacitance of silicon
diode was also measured using the special measurement system in Instrumentation
division.
>From the capacitance measurement, the capacitance of diode
is 329 pF at a
bias of 24V (220pF at biasVeV). Assume we use the silicon diode at
24V. The signal for 10^5 photons of 5 KeV (using 3.8 eV per electron-hole
pair) is estimated at 0.0671 V.
The thickness of our silicon detector is estimated using the size
(1" diameter) and capacitance of the silicon detector, taking
the dielectric constant of silicon as 11.9:
~ 157 microns for C = 329 pF
~ 235 microns for C = 220 pF
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STELLA
Experiment (Reported by Karl Kusche) |
1) In preparation for the next scheduled run, various issues from
the previous run were addressed. Included were camera iris and trim
coil response, and the installation/alignment of a temporary pop-in
inside of the ICA gas cell. This pop-in will allow us to better
visualize the beam transport through the cell while the last triplet
is oriented at 45 degrees. The results from the next run will help
us to decide the final rotation angle of the triplet which will
best compensate for the wiggler-induced skew.
2) The last portion of beamline #1 (between the cell and dipole)
was reconnected, pumped out, and leak-checked. The entire beamline
is now ready for the next run.
3) ICA optical system restoration & realignment continues in
preparation for ICA recommissioning during the month of June.
4) The NSLS Safety Approval Form for STELLA was submitted for renewal,
reflecting the recent changes in spectrometer shielding and internal
gas cell configuration.
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STELLA Beam Optics (Reported
by Ping He) |
We have got an improved beam-optics result based on last version
released May 14. The results are shown in the file at:
May_28_STELLA_Skew_optics
The results indicate that we have solved the problem of the skew
quadrupole component in the IFEL wiggler.
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Computer Control System
(Reported by Bob Malone) |
1) Program for YAG energy feedback has been written. Debugging
in progress.
2) New control system: 2/3 of network cabling have been installed.
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Technical Staff Tasks
(reported by Bill Cahill) |
Most of the week was spent trouble shooting the rf system, looking
for the jitter that has plagued the ATF for over one week. Marc Montemagno
found a deformed copper waveguide gasket on the reverse power terminator.
The unit was repaired and the system appears very stable and noise
levels have returned to acceptable levels. We recalibrated the time
constant of the klystron water system to reduce the temperature recovery
time. A power/sync chassis was built for the YAG camera system to
further reduce the heat load on the table. Four YAG flash lamps needed
replacement, two of which are done, the remaining will be changed
over the weekend. Drawings were submitted for new mirror mounts to
the NSLS Mechanical Group. Two mounts are currently being made, more
to follow. The YAG amplifier chiller was relocated to the air conditioned
"Z" line for improved temperature stabilization.
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CO2
Laser Status (Reported by Igor Pogorelsky) |
Optics installed to deliver the alignment and amplified CO2 laser
beams to the auto-correlator to measure the duration of the amplified
pulse. Alignment of the auto-correlator setup is verified.
Mechanical work that permits delivery of the CO2 laser beam between
the preamplifier, amplifier and experimental hall is completed. Installation
of beam enclosures for the transport line is in progress. Work on
eliminating gas leaks in the CO2 laser preamplifier and improving
vacuum in the terawatt amplifier is in progress.
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Beam Studies
(Reported by Vitaly Yakimenko) |
The slow phase feed back system has been tested and the results are
very satisfactory. The system uses the beam phase detector developed
by Xijie Wang around the strip-line beam position monitor HSL4 (downstream
of the linac). The results are shown in:
May_28__slow_phase_feedback
tm
One can see a correction of slow drift of up to 4 ps peak-to-peak
over half an hour to essentially a non-measurable drift. The fast
variations of about 1 ps are noise on the measurement system, not
in the beam. This jitter is averaged out by the program to extract
just the slow drift for correction.
Further testing is necessary to check for a correct behavior of the
code for large phase jumps and verify that the phase stability of
the detector does not introduce an error. This can be done by checking
the energy stability on the high energy slits.
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