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Site Details ATF Newsletters 
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1999 ATF NewslettersMarch | April | May | June | July | August | Sept | Oct | Nov | DecDecember 3 | December 10 | December 17
Greetings to all, A happy moment for George Rakowsky and his magnetic
measurements team. After a lot of work over a very long time, the VISA
magnet, the most advanced of its kind, is installed on the beam line.
George is a mainstay of the VISA collaboration. The extremely high-precision
measurements, innovation in solving intractable problems, strong participation
in meeting, knowing all there is to know about the system, all of these
were instrumental in getting us with some sanity to this point. George
will get the wiggler back, hopefully only when it is to be moved to the
DUV-FEL. Until then we will enjoy the benefit of a well measured and trimmed
wiggler. Thanks, George, Lorraine, Jeff and Mike! Steady, good progress continues on other experiments,
as can be seen below. Ilan Ben-Zvi.
1) Beamline
#1 spectrometer was reinstalled after allowing for HeNe line-of-sight
from GPOP1 mirror to end of Experimental Hall.
This permitted alignment of all BPM’s, direct inspection of the
dipole bellows, and confirmation of wiggler & spectrometer alignment
to the beam axis. 2) The
large-diameter spool piece upstream of triplet #2 was machined to allow
for the installation of an additional gate valve for vacuum isolation
of GPOP1 assembly. Thanks
go to John Skaritka for his invaluable assistance with this task. 3) Vitaly
performed electron beam tuning Thursday afternoon, achieving 100% transmission
of 0.5 nC (45.6 MeV) to the end of beamline #1. This was done with the new STI wiggler installed
(ICA gas cell still out). Radiation
survey cleared the new shielding configuration, which now allows for the
LOS mentioned in item 1. Three
OTR diagnostics need further work prior to the next run (Thursday, 12/6); a request has been submitted to the ATF. Plans for our next runs this month include HeNe &
CO2 alignment through the new wiggler, imaging of OTR at the new wiggler
pop-ins and GPOP4, and synchronization of laser and electron beams.
Confirmation of energy modulation (microbunching) will probably
carry into the new year. Progress
at STI: (Wayne Kimura) We finally got the VOx to image the CW CO2 laser
beam by using the VOx-on-mica sample.
It is interesting, the image is very easy to see with the naked
eye. However, it appears
to be best seen when the light is not too bright and also somewhat indirectly
illuminated. Using the VOx-on-mica
sample, Christian will try to obtain the smallest CO2 laser focus spot
size he can and then determine the best illumination configuration to
view the image with our macro-zoom camera.
He will then test the VOx chip.
Once we are satisfied that we can see the image well on the VOx
chip, we will then install the entire system inside the ICA gas cell and
send the CW CO2 laser beam into the cell.
We’ll use the axicon mirror to focus on the VOx chip and view the
image with a CCD camera using the new remotely-adjustable zoom lens that
was just ordered.
We nearly get to the point of measuring HGHG pulse
length yesterday before we run out of our running time. After about 5 week’s effort, Adnan was able to align
and test the autocorrelator with help from Marcus, Lou, and Sandra, so
we are ready to measure the pulse length. Because the laps of the 2 months, we need the last
two days to recover the HGHG running condition: 1)We synchronized CO2 to e-beam again on Tuesday.
2)Wednesday morning we recovered the energy modulation after fixed
several trim magnets power supply. 3) Wednesday
afternoon, we started to tune e-beam for SASE, but realized the quantum
efficiency was more than 5 times lower than October. Marcus changed the
YAG optics to increase the laser energy (this needs a trade off with profile
quality) to about 30 micro joules (October we used 5 micro Joules to obtain
1 mm-mrad 120 amp beam). With help from Vitaly, and this increased laser
energy, 20 minutes before the end of our run, we were able to obtain more
than 3 volts SASE output, indicating good beam quality, in spite of the
low QE efficiency. We did not have enough time to measure the beam emittance.
At this point we were very close to have HGHG and measure the pulse length,
but running time expired. In summary, we are ready to measure the HGHG pulse
length next week.
Ben came out last week and the vacuum chamber was
installed. This week Robert and the alignment
team are here and setting up the laser interferometer. The fiducialization
and measurement of the magnets has been completed and the undulator has
been set in the chamber and everything has been rough surveyed into place.
The pop-ins are being assembled and a combination undulator laser
alignment/ pop-in insertion will take place from Friday Dec. 3 to Mon.
Dec. 6. Results from the BPM test (X.J. reported a month
ago) makes us take a conservative approach with the pop-ins. YAG screens
will be used in half the BPMs and the other half will rely on transition
radiation. We will engineer the best possible set up using OTR while simultaneously
giving ourselves the best chances of guiding the beam through the undulator
using the YAG. The probability
of opening the chamber up again is high, and by that time a full understanding
of what needs to be done for OTR BPM implementation will be pursued. Week of Nov. 15-24 Ben
came out and the Vacuum chamber is in experimental hall Baked out system found and fixed leaks Nov. 29 Brendon is here and work on alignment installation
has started Nov. 30 Magnet fiducialization and characterization is
finished Dec. 1 Install magnets this evening in vacuum chamber Survey tonight the whole system at ATF Dec. 2 Set up optics for alignment system Assemble pop-in assemblies Propagate alignment laser through undulator Dec. 3-6 Begin alignment of system Use laser interferometer to align system Insert pop-ins (reiterations will be needed with alignment) The system is being run mid-day and we are setting
up in the morning and in the evening.
Well, the VISA magnet has finally been installed-on
schedule! Fiducialization of the VISA magnets was finished
Tuesday morning. Installation
into the vacuum vessel was completed late Wednesday night.
The vessel was buttoned up early Thursday morning. Meanwhile, optical
surveying and alignment was taking place. Robert Ruland and his team are
now aligning their interferometry system. They will be aligning the magnets
through the weekend.
VISA EXPERIMENT: DAC, ADC and relay contact cards for the VISA experiment
have arrived and been installed in the crate located in room C3.
Software servers for this new hardware are being finished and tested.
We are still waiting for a TTL input card to read the power supply
thermal interlock status. Kinetic
Systems has stated it should be shipped on Dec. 16th.
Work will begin next week on the operator displays needed for these
subsystems. CPOD EXPERIMENT: Controls and readbacks for the fast detector pop-in
monitor, associated lamp and video signal switching have been added to
the control system for beam line 2.
CPOD operators can access these control via their ATF account.
GENERAL FACILITY: 1) IMPORTANT
NOTICE TO ALL ATF CONTROL SYSTEM USERS Due to the recent attempts by hackers
to break into BNL computers, the main ATF control system no longer accepts
incoming requests from non-BNL machines for many services including telnet
and ftp. Only computers located
on the BNL LAN can access telnet and ftp.
Outgoing requests from the control system are not restricted. As such, outside users who collect/save data on the main control
system should ftp their data back to their home institution before* leaving ATF.
External access will be granted only in those circumstances with
a justifiable need and no alternative means of communication. 2) Problems
with analog readbacks from the 30 Amp Darlington power supply subsystem
have been traced to a faulty ADC card.
The card has been replaced with a spare unit and the defective
card returned for repair. 3) CAMAC
equipment located in room C3 has been relocated from the top of the laser
table to a new mini-rack underneath the table.
All cables from the experiment hall (particularly the new VISA
cabling) should be routed to this new location. NEW CONTROL SYSTEM: Work continues on development of the low level libraries
needed for porting the main system. The construction of the VISA stripline monitors has
been completed. All that
is needed is the power supplies which are on order. The cable tray array
for the VISA correction magnet power supplies has been installed.
Pedro has terminated quite a few cables but unfortunately ran out
of parts. The next phase should be the euro-crate power supply
system in the FEL room. The
CAMAC crate in the FEL “visa diagnostic room” room has been relocated
and cables rerouted for neater installation. A continuing effort will
be needed to further make ready the optic table, e.g., clean up old experimental
wiring and parts. The new Darlington power supply chiller has been installed
and is working very well. A de-ionizing filter should be added for future
protection. The CO2 interlock
system has been completed and certified. The HeNe shutter has been installed
and is operational. Marc continues to design and layout the I/Q modulator
RF system. The faraday cup shielding for the STELLA experiment has been
installed and a fault study performed.
The bucking coil was reinstalled in the rf gun clamshell and is
ready for testing. Bob Harrington has been assisting Igor on terawatt
activity, several components had to be remade due to confined space limitations
and trail and error installations. 1. ATF
schedule: To facility the HGHG experiment, no work should be scheduled
in the evening so HGHG can run late into night. Experiment hall will be
open in the morning for Wednesday and Thursday.
Monday of Dec.13 now is set for HGHG run, we are still waiting
for word from fast detect to see weather they can switch. VISA agreed
to give Friday (Dec. 17) to HGHG experiment. 2. YAG
Laser: Bob Harrington will work on the YAG laser shutter next Monday Morning.
Marcus expected new oscillator
arrives around Dec.20, Bob will help to prepare for
new oscillator installation in the week of Dec.27. 3. CO2
Laser: Bob will work on the CO project after the YAG shutter work. We
also discuss how to help CO2 by hiring a job shopper, and better coordinate
with NSLS help. 4. Fast
Detector experiment: They should install their detector next Wednesday
otherwise their running time will be not effectively used. Due to on-going
NSLS shutdown, no help for vacuum and survey, but they maybe work with
VISA group to get leak check. 5. VISA
experiment: Don Davis will help Mark next Thursday and Friday to finish
VISA actuator control box. George raised issue of possibility of radiation
damage on the VISA undulator if no collimator installed at the entrance
of the undulator. I believe this is not issue since we have destructive
8 BPM inside the undulator which
will produce much more X-ray and strayed e-beam than beam tail. We will
use low charge for initial beam transport studies. 6. STELLA
requested help on the POP in from Mark and Malone. Mark will finish the
low level I-Q modulator first, then help STELLA, and continue with VISA
work.
Last Modified: December 3, 2007 |
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