1999 ATF Newsletters
October 1 | October
8 | October 15 | October
22 | October 29
Greetings to all,
This week we got
a bit time to do a few beam measurements, the results are in an HTML
file. The measurements, done without significant compression, show
beam parameters that are close to what is required by VISA.
The HGHG Experiment
concentrated on getting the autocorrelator going for a pulse length
measurement.
STELLA has passed
beam through the new wiggler and the transmission is good.
Next week we will
host a VISA Collaboration meeting at BNL. The meeting will take place
at the NSLS Seminar Room. The tentative agenda is:
Monday,
November 1, Morning:
09:00
Overview of VISA status, A. Tremaine
10:00
Presentation of undulator status, magnetic measurements, alignment,
pre-installation, G. Rakowsky
11:00
Presentation of linac status, matching beam line, beam measurements TBD
12:00
Lunch
Afternoon
01:00
Presentation of status of undulator diagnostics, E. Johnson, A. Murokh
02:00
Status of optical diagnostics, and FEL measurements, J. Rosenzweig
03:00
Visit to ATF and magnetic measurement laboratory.
05:00
Executive committee meeting.
Tuesday,
November 2, Morning
09:00
Installation schedule, J. Skaritka
10:00
General group discussion
11:00
Executive Committee meeting
12:00
End of meeting
Ilan Ben-Zvi.
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STELLA
Experiment (REPORTED BY KARL KUSCHE) |
The new STI wiggler had
its first day of e-beam delivered through it this week.
Vitaly reports close to 100% transmission of ~0.5nC, with non-optimized
beam tune. There was no obvious
clipping or distortion of the transmitted beam.
The first week in November
will see two days of continued running to optimize the beam tune through
the wiggler. Coalignment
with the GPOP1 HeNe and spot size determination are expected.
Delivery of beam to the spectrometer will be possible after reinstallation
of the CTR diagnostic (0.25 mil Aluminum foil replaced) and pumpdown of
section #4.
During November &
December, it is planned to perform CO2 alignment and transmission optimization
with the goal of reestablishing bunching at the CTR diagnostic.
The ICA gas cell will probably not return to ATF before the new
year.
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VISA STATUS AND SCHEDULE
(REPORTED BY AARON TREMAINE):
Mirrors (for the diagnostic
pop-ins) received from Opticraft ended up being no good... not even for
the electron beam diagnostic. Currently, pop-ins made of silicon are being
machined and will be sent off for polishing.
Next week (Nov.1) we
will start mechanical testing of the pop-in diagnostics in the pre-assembly
area. Full assembly of the pop-ins will be done and will be tested on
the undulator sections not being measured by George (probably sections
3&4).
John is not here today
and results of the vacuum tests done this week
will be reported next week upon his return.
Agenda for VISA:
This is what the schedule
looks like for the next 3 weeks:
Nov.1 Test pop-in assemblies,
vacuum
VISA collaboration
meeting Nov.1&2
Nov.8 Robert and Brian to
trial alignment
Nov.15 Move to ATF
VISA MAGNETIC MEASUREMENTS
(REPORTED BY GEORGE RAKOWSKY):
We have completed measurements
on Sections 2 and 3, including at 90 degrees. We have set up Sections
1 and 2 on the bench and are beginning to align the magnetic axis. To
clear up the closure error issue, we have made arrangements with our CMM
inspector to remeasure Sections 2 and 3, as well as the wire finders.
(He has been tied up on another project the past couple of days.) Measurements
with calipers indicate the wire finder calibrations may be off by several
mils as well, thereby introducing systematic errors in all the fiducializations.
Using the caliper measurements, closure error is about half. Robert Ruland
is suggesting that perhaps the epoxy which bonds the tooling balls to
their studs has shrunk since the CMM calibration at SLAC.
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Beam Measurements(REPORTED
BY VITALY YAKIMENKO) |
Various measurements done
in the previous weeks provided good emittance / peak current results,
with the best being 1 mm-mrad at 125 amperes. This week we preformed a
few measurements at slightly higher peak currents, yet without attempting
a significant compression. Marcus Babzien provided various laser settings
and measurements. The results are peak currents over 150 amperes at emittance
bellow 2 mm-mrad. Some of the measurements results can be viewed in the
HTML file:
Beam_Study
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YAG Laser
(REPORTED BY MARCUS BABZIEN) |
There was laser maintenance
on Monday during which the amplitude instability from ground motion was
further studied. Inside the
room, walking around the table causes 3-5% percent fluctuations. Outside the room however, the fluctuations are much lower and
not measurable above background fluctuation of about 0.5%.
The system operated the
rest of the week for tomographgy and beam studies.
Today the effect of the the time slew correction for oblique incidence
on the cathode was tested. By
interchanging a mirror and grating, the charge vs. phase curves for three
small horizontally displaced beams could be compared with and without
correction. The curves taken
with the mirror (no correction) showed very close to the expected 6 ps
delay across 2 mm on the cathode.
A second check was to steer a single small beam across 2 mm on
the cathode, again producing 6 ps relative delay.
When the grating was used for correction, the delay was less than
1.5 ps, close to the measurement error.
The system required CW
realignment Wednesday because of poor amplitude stability, which was restored
to 2% rms at the cathode. The
system was last aligned more than three weeks ago.
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Technical
Operations (REPORTED BY BILL CAHILL) |
On the Monday maintenance
day, we anticipated finding a defective capacitor in the gun modulator.
It turned out to be a carbonized cable to the charging resistor on the
PFN. The cable was cleaned and the modulator is running well. The particulate
filter for the klystron water system was replaced. This filter was so
clogged, it was slowing down the flow. Periodic maintenance will have
to be increased to reduce this problem. The mother power supplies for
the Darlington transistor network were reconfigured for optimal output.
The lead shielding for the STELLA faraday cup was rebuilt and a radiation
fault test was performed. The electrical service for the FEL room was
completed. This will allow all components to be permanently installed
below the optic table. “finally”.
Mechanically speaking, we assisted the CPOD experiment with vacuum
expertise. The Plexiglas optical shield was installed on the ceiling between
the CO2 room and the STELLA table, the terawatt blow-off pipe was disassembled
for modification work. The plasma shutter for the CO2 pre-amplifier is
complete as is the machining of the stands for the CO2 amplifier breadboard
assembly. All in all, a very busy week.
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Last Modified: December 3, 2007
Please forward all questions about this site to:
Vitaly Yakimenko
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