# MEMORANDUM 

**To:** Distribution

**From:** Gwyn Williams for George R. Neil

**Subject:** FEL Upgrade Project Weekly Brief -- October 15-19, 2007

**Date:** October 19, 2007

**Highlights:**

Admiral Landay signed the MOU contract extension that provides our base
funding.\
\
The gun test stand beamline is now complete and awaiting pump-down.\
\
The new regenerative amplifier for the GTS drive laser is working in Lab
6 and producing 60 ps IR pulses at 10 Hz with an energy of 1mJ. This
surpasses the design specifications, giving comfortable headroom.

We completed the upgrade to the safety system in user Lab 3, which means
that the upgrades to all user labs are now complete.

**Management:**

Jim Boyce attended the Industrial Physics Forum of the American
Institute of Physics (AIP) and, as JLab's representative, participated
in the Corporate Associates Advisory Committee (CAAC) of the AIP.  Both
meetings were held in conjunction with the annual American Vacuum
Society conference in Seattle, Washington.\
\
George Neil gave a presentation at the 13th International Workshop on RF
Superconductivity in Beijing.\
\
Gwyn Williams presented the FEL Annual Work Plan to JLab management.\
\
Michael Kelley presented a paper at the annual AVS meeting in Seattle
about surface studies to improve the performance of SRF accelerators,
such as the FEL driver.

**Injector:**

From Monday through Wednesday we hosted Philippe Piot, Daniel Mihalcea,
and Nikolai Vinogradov, from the Physics and Astrophysics Group,
Department of Physics, Northern Illinois Center for Accelerator &
Detector Development, Northern Illinois University, and Accelerator
Physics Center, Fermi National Accelerator Laboratory. We had a very
productive agenda and discussed possibilities for using the Gun Test
Stand for halo detector development as well as for starting a
collaboration on injector modeling.\
\
The vacuum group finished the installation of the GTS beam line, which
is ready to be leak check. We expect to start the beam line vacuum bake
early next week.  C. Hernandez-Garcia attended as thesis advisor to
Deepesh Kumar\'s M. Sc. oral defense at ODU, concluding one year
mentoring Deepesh on the thesis entitled: \"PARMELA-based simulations of
the Jefferson Lab Free Electron Laser Injector \". We continued
refurbishing the FEL gun.

**RF:**

RF -- All LCW lines in the RF system were checked for flow.  All small
orifices were opened with a 0.055 finger drill to ensure the acid flush
would work next week.  Several small lines were completely blocked for 2
klystrons and a heat sink with four 5 watt amplifiers.  Zone 4 has the
LCW by-passed to its circulators.  So it is ready for the acid flush. 
Zone 3 will be ready also by the end of today.

There are 48 LCW channels in parallel in the collector of the linac
klystrons.  The channels are 0.047" x 0.070".  If the flow through these
channels is restricted, hot spots in the collector develop and the
channel will soon be blocked completely.  If too many channels are
blocked, the klystron will have to be replaced.  The LCW flows in each
zone need to be closely monitored and acid flush the klystrons when the
flow starts to fall-off.

GTS HVPS -- When the SF6 system is finished, the HVPS is ready for
testing at high voltage (585 kV).  The Running/Conditioning Resistor is
ready for installation when the Gun Tank is installed.

**Instrumentation and Controls:**

This week we spent some time this week testing the Drive Laser Timing
and Synchronization system with the Antares Laser setup in Lab 6.  We
were successful in locking the Coherent RF and the repetition rate
timing signal\'s phases.  Once we were able to establish phase lock we
continued to add the required triggers with the proper delays.  We were
successful with the first couple of steps in these timing tests and then
found that the system was breaking down and going in and out of phase
lock as more triggers were added.  Currently we are testing these timing
signals and trying to maintain phase locked signals throughout the
timing system.  The first problem that we found and temporarily fixed
was the amplitude of the 37 MHz drive lacks the amplitude to effectively
trigger the timing system.  Currently we have several amplifiers in the
system to bring the signal to acceptable TTL trigger levels.  We are
currently looking into developing a high speed amplifier to properly
drive the 50 ohm timing circuit.

   We also managed this week to get the RS-485 communication established
between the IOC and the Varian Dual Ion Pumps.  Currently we have
successfully tested the digital I/O portions of the serial
communication.  We are currently assembling some required I/O jumpers to
enable to pumps HV.  Once we have the HV cables terminated or an
appropriate load to connect to the pumps we will test the analog
readback portions of the I/O.  First signs show that this system is
ready for operation and should be fully functional next week.

    This week we were successful in placing the FLog book onto the main
page of the Wiki through a PHP script.  This is just the first step in
the process so we began to debug this script in order to make the FLog
book more readable/user friendly.  This week we\'ve discovered some
issues with the fella account and how it affects the devlore server. 
The server appears to have a process using the incorrect password for
the fella, this causes the account to lock.  We are working to identify
the process in question and correct it.

   Efforts continued on the LPSS wiring in User Lab 5.  The master
control lines, mirror cassette, hutch interface and  status panel were
all completed this week.  We\'ve also managed to complete the required
safety modifications to User Lab 3.  Currently the safety committee is
reviewing this work.

   In order to have digital I/O easily and readily available for
applications a four port I/O panel was fabricated with four Burndy
connections for six 8-bit banks of digital I/O.  The IP-48 Digital IP
pack was installed in the carrier card in IOCFEL11 and the ribbon
conversion cabling to convert the 50-pin ribbon to a 64-pin schroff
connection was installed as well.  We\'ve begun testing the hardware and
the software for these 48 signals and currently have identified some
required modifications in software.  Once these modifications are
completed we will resume testing of this system.

   The GTS House Air Line Extension analysis and associated TOSP for
pressure and leak testing is nearing completion.  The final documents
are missing schematic diagrams (currently in George Biallas\'
possession) and calibration data from the operational checks of the
relief valves.  The operational checks of the pressure relief valves can
be completed as soon as the 200psi bottled gas regulator comes in.  The
threaded adapter that allows installation of the final relief valve has
been installed and is ready once the valve arrives.  The compressor
bleed line has been hooked up to the outlet line of the compressor for
the Gas Transfer system.  Two inch rubber hose has been installed
connecting the SF6 system to the bladder bag.  Two hose clamps were used
at each termination end to secure the connections.  The connections for
the GTS gas tank transducer have been established and tested.

   Other accomplishments this week included repairing a Mini ITX
computer by replacing the power supply board and some burnt wires. 
Check out of a new style camera lens and documenting the performance on
the Wiki for further reference.  Selecting the drive laser hutch hepa
filter and revising the hutch design to accept the filter.  Connecting
and debugging a new stepper motor and encoder required for the magnet
test stand linear stage test setup.

**Electron Beam Transport:**

***Improvements and Upgrades***

*Gun Test Stand (GTS*)

• In building the SF6 Gun Tank system, the JLab Shop completed final
machining of the o-ring surfaces on all the flanges on the two large
vessels (see protected surfaces in the 1^st^ photo). The shop is now
working on completing the tubular extension (see second photo).
Unfortunately, qualified welder, machinist and weld inspector are on
vacation next week. Pressure test will be the week of the 29^th^ of
October.

![](media/image1.jpeg){width="2.4902777777777776in"
height="1.4784722222222222in"}
![](media/image2.jpeg){width="1.6284722222222223in"
height="1.4895833333333333in"}
![](media/image3.jpeg){width="1.8541666666666667in" height="1.5in"}

• The tubing run for the House Air Line to the SF6 system is physically
complete. I reviewed the analysis and asked for the inclusion of some
additional items in the boundary of the system. Those need
documentation. In addition, the TOSP for the pressure test took some
time to write and iterate and now we need a regulator to match the
pressure of the test's relief valve for its calibration. A safe system
is in the details. The pressure test is now slated for early next week.

• In work on the GTS Beam Line, the Vacuum Group installed the complete
line and is about to start pumping. (See third photo)

• Matt Marchlik continues work on the hutch for the drive laser.

• Shukui Zhang, Carlos and I reached accord that the breadboards on the
new gun drive laser and cesiation optics can be most effective if they
are mounted vertically.

*SF Sextupole Magnet Testing*

• Magnet Test continued with the second magnet on the test stand where a
failed "x" drive motor prevented completing the measurement. Scheduled
crane safety training will prevent starting a third magnet until the
week after next.

**High Power Optics Risk Reduction**

Work resumed this week on the cw laser tester.  With Pavel Evtushenko\'s
assistance, the CCD camera used to determine the mode size on the
mirrors under test was calibrated.  We can now be certain that the
mirrors are subjected to high irradiances.  With the ability to scan the
mode across the optic, we can approximate larger mode area testing.  I
am now starting to calibrate the IR camera to collect thermographic data
that will later be converted to absorption values.

A teleconference was held with the team at Colo. State Univ. to discuss
results obtained at JLab earlier this month, and to plan our activities
for the next few weeks.

The documentation required for a proposal to the JTO was completed and
submitted.

**Optics**

With the high reflector cavity work complete we are now focusing on the
output coupler (OC) end of the machine. Unfortunately the vacuum furnace
needed to braze the OC mirrors has been down for two weeks. We
understand that the furnace was fixed yesterday but its usage schedule
has had to slide till today. We are now scheduled to begin brazing next
Wednesday with an anticipated completion on the following Wednesday. We
should be able to complete the OC installation on the first week of
November. The Cryo-Group has removed the "U-Tube" supply line from the
OC helium distribution can. We can now work on the OC vessel with the
conventional cooling setup. The modifications to the low power mirror
cassette were completed this week. We should receive those parts in two
weeks. We took advantage of the rearranging of the stored Helios
components to palletize four 440l/s ion pumps. If the weather permits,
they should be delivered today. We will check them out and install them
in the Labs next week. The stands to support the harmonic block filter
and hutch shutter has been assembled. These will be installed after the
ion pumps are in place.

**Lasers and Optical Diagnostics:**\
We preformed a successful laser certification for operating the
amplifier in lab 6. We are now focusing on the amplification experiment.
This is the most important part of the whole GTS drive laser. The test
shows great system performance, surpassing the designed specifications.
We are expecting to finish the remaining work soon.  The EPICS DLPC was
also tested and we found a few improvements are needed for stable
operation. We have been also working with GUN group and I&C group on
other projects related to the optical diagnostics for GTS.

**Terahertz:**

The 16 T superconducting magnet from Cryogenic, Ltd. was moved to the
FEL lobby this week.  We have made plans to setup the magnet and perform
the acceptance tests in mid November. 

In preparation for that, we have begun to work on the analysis of the
cryogenic/ODH, magnetic field, and electrical hazards.\
\
Also this week, we were notified of the publication of our manuscript
describing the THz beamline design in Nuclear Instruments and Methods
A.\
\
J. M. Klopf, A. Greer, J. Gubeli, G. R. Neil, M. Shinn, T. Siggins, D.
Waldman, G. P. Williams, A. Todd, V. Christina and O. Chubar, The
Jefferson Lab High Power THz User Facility, Nucl. Instrum. Methods A,
582, 114-116, (2007).

**Word version:** [FEL Upgrade Project Weekly Brief -- October 15-19,
2007](http://www.jlab.org/accel/fel/documentation/07weeklybriefs/upgradeweek07oct15-19.doc)