**MEMORANDUM**

**To:** Distribution

**From:** F. Dylla

**Subject:** FEL Upgrade Project Weekly Brief -- July 7-11, 2003

**Date:** July 11, 2003

**Highlights:**

We had a very productive week of installation/check out activities for
the completion\
of the high power (recirculated) configuration of the 10 kW Upgrade.  We
plan on starting\
hot check-out of various systems on second shift next week including rf
processing of the injector cryounit, with start-up of beam commissioning
activities slated for the following week\
(on or about July 21).  \
\
The following are highlights of this week\'s shut down activities:\
(1) We repaired the injector cryounit rf window that failed during last
week\'s rf bench test and successfully tested it to 75 kW input. At this
power level the window ceramic rose to a tolerable 100 C.  We took the
time to warm up the cryounit to ambient temperature, installed two rf
windows (both qualified at 75 kW), and began the cool down to 4k late
this morning. On Monday, the unit will be cooled to 2k and we will begin
rf processing during second shifts. (We thank the SRF team led by John
Hogan, the RF testing team led by Rick Nelson and the Cryo team led by
Dana Arenius for their extra efforts this week to meet the tight
schedule).\
(2) The string of 5 large dipole magnets in the second recirculation arc
was successfully powered last night.\
(3) The last vacuum components (viewer and BPM) for the recirculation
dump were completed this week and the dump line should go under vacuum
by tomorrow. Most of the shielding blocks were installed earlier in the
week. The last remaining blocks will go in Monday after the installation
of the iron plate shielding on Sunday and Monday.\
(4) After the last shielding material has been transported inside the
FEL ring we will install and align the last remaining vacuum pipe and
quad girders late on Monday to complete the high power configuration.\
(5) The I&C team has kept one step ahead of the check-out activities all
week (as usual).

**Management:**

Five papers that were prepared by JLab staff for presentation at the
July 29-31, 2003 Navy FEL Workshop (Laurel, MD) were reviewed and sent
to the Workshop office, with copies sent also to our ONR and PMS 405
program offices:\
\
G. Neil:  Status of the Jefferson Lab High Average Power FEL\
W. Funk:  SRF Accelerator Status\
D. Douglas: Beam Transport for MW Class FEL Drivers\
M. Shinn:  Overview of the Cryogenic Mirror Program at Jefferson Lab\
                Review of One Micron Optics Damage Thresholds

Michael Kelley presented a keynote plenary talk on the JLab FEL program
at Laser 2003 biennial joint meeting of laser societies in Munich during
the week of June 23.

**WBS 4 (Injector):**

The FEL Gun team met several times over the last two weeks to plan the
next 3-15 months\
of work starting with (1) testing of large area samples of the SiOx
field emission suppression coating, and testing of electropolished SS
and Nb samples for comparison; (2) assembly of a back-up electrode stack
for the 10 kW FEL for full voltage testing; (3) and discussions of the
gun assembly for testing in FY04 with the AES cryounit for 100 mA tests

Work continues on the refurbishing of the old photocathode gun. Several
jobs were submitted to the machine shop to modify the electrodes. This
week we started working on Nb field emission tests by submitting to the
machine shop the drawings for a 6-in test electrode.

Modifications to the support mounts for the field emission suppression
ion-implant system are in progress. A stainless steel tube is being
polished for further testing in that system.

The effect of space charge on the electron beam focusing by the
solenoids was studied this week using PARMELA. The results show that
some beam may have been lost in the second solenoid due to weak focusing
from the first solenoid as the charge was increased, as previously
observed

during the FEL injector setup operations. The beam size on the ceramic
viewer as a function of the first solenoid field strength was simulated
to calibrate the computer code against the actual solenoid, once the FEL
resumes beam operations.

**WBS 5 (SRF):**

SNS Module 6 is scheduled to vacate the clean room by next week
and assembly of the cavity string for the FEL 3 module should begin.  In
the intervening time some problems with the copper plating on
fundamental power coupler and welding issues with the stub tuner were
resolved.

**WBS 6 (RF):**

The water leak in the 2nd warm window for the FEL Quarter was fixed by
rebrazing the part. It was leak checked, hydro-tested, RF tested, leak
checked again, and then installed on the Quarter. The center of the
ceramic window reached about 103°C while the metal edge was about

130°C at 75 kW of forward RF power. The reflected power was about 2 kW
as the RF load was 50 ohms. The flange temperature rose about 11°C from
30°C with 2 gpm flowing in the cooling line.

The U-Tubes have been stabbed and the Quarter will be cooled to 4°K
today. It will then be cooled to 2°K on Monday. The waveguides are
connected and the remainder of the RF cables will connected Monday
morning.

The test set has been taken down and the waveguide, and various LCW flow
sensors have been reconnected.

C. Hovater is planning to do cavity and waveguide processing early next
week on the Quarter.

**WBS 8 (Instrumentation):**

Please see <http://laser.jlab.org/shutdown> for the latest update on the
I&C tasks needed for high power operations.

The wiring and initial testing of the HR RTD & Analog Chassis has been
completed.  The set-up of the front panel meters needs to take place. 
The fabrication as well as the wiring of the OC RTD & Analog Chassis has
begun.  The PCB layout for the HR & OC Analog Buffer board has been
completed by EECAD and a quote for manufacturing is in progress.  The
parts have been ordered for three boards.\
 

The S.E.E. BPM RF modules have been mounted for the 5F Region, cables
tested and are ready for functional testing.  Viewers 0F04, 4F003 and
3F12 have been re-installed and awaiting re-commissioning. Work
continues on installing the 1G dump, 5F01 and 5F03 viewer assemblies.   
Power and video cables were terminated and in the 2F, 5F and 4F region
for the SLM\'s.

The Drive Laser Pulse Controller (DLPC) upgrade/conversion is nearly
complete. The final revisions on the MPS card for the DLPC interface
have been made. All the arrangements for installing the system in the
clean room are being made. The old DLPC system will be converted over to
the new system over the course of next week. The Beam Current Monitor
(BCM) chassis is being modified to send out a Beam Envelope to the DLPC
as a part of the beam current/duty cycle confirmation - this confirms
that the actual beam current is consistent with the requested current
otherwise the shutter will close.

Work continues on the Happek interferometer for bunch length
measurement. A pair of frames were made to hold beam splitters as a drop
in replacement for the wire grids. The wire grids are needed because of
the long wavelengths used in the measurement but these are difficult to
use with a HeNe. All else is ready to complete the installation.

The 2nd Arc dipole string was successfully tested and current ramped to
200 Amps. These signal have been connected and checked out in the MPS.
AC power has been hooked up for the 2nd Arc string Dansfysik trim
supplies and tested successfully.  Effort continues on wiring the SF\'s
and QT\'s in this region.

There were two visitors from the University of Maryland here this week,
Ralph Fiorito and Anatoly Shkvarunets. Together we are going to explore
new types of electron beam diagnostics for the FEL and for future
machine. These efforts will start with a beam diagnostics table off to
the side of the 2G dump. This line can be run from \~90 MeV down to
perhaps as low as 10 MeV with out impacting and FEL operations. This
will prove to be a valuable test line for future diagnostics.

The video acquisition system for frame grabber has been designed and is
in the beginning stages of being implemented. Signal processing design
has also been established. This uses a PC with Linux as an operating
system running EPICS. The integration was confirmed by the use of
structured tests. The epics application will be implemented next week.
This uses a PC with Linux as an operating system running EPICS. The
system will replace the Datacube VME module.

The crystal quartz window evaluations continue with three trials of the
experiment done on 7/03/03. The results indicate that crystal quartz was
stronger than any the current literature suggests. The crystal quartz of
2.5mm thickness did not break at 250psi. It was decided, because of the
results, that thinner windows would be purchased to test. As soon as the
new windows come in, they will be characterized and tested.

**WBS 9 (Transport):**

## Dipoles

[Injector Dipoles (DU/DV)]{.underline}

• We measured the 5F GV and adjusted the field clamps to get the
appropriate integral gradient. We established the main currents and
saturation coil currents corresponding to 8.7, 8.2 and 9.7 MeV/c and
measured the integral at the center and edges of the good field region
for the three cases. The two GVs will be installed starting early on
Monday so when Alignment finishes with the two quad stands; they will be
able to align these two dipoles.

[Arc 180 Degree Dipoles (GY)]{.underline}

• The bottom yoke of the second GY had its Purcell gap shims
successfully glued on this week by the team of Don Bullard of the FEL
and Mike McCrea of the machine shop. They will now assemble the magnet.

***Multipoles:***

[Trim Quadrupole (QT) / Vertical Arc Corrector (GC)]{.underline}

• We measured the QT with its GC corrector at various corrector
settings. It should be ready early next week for installation. It should
bolt in place where it already had been aligned. Alignment should only
take a check.

***Octupole (OT)***

• We have placed the order for cores with New England Technicoil. We
will ship the steel to them early next week.

***Installation:***

• After the water was hooked up to the GY and the shunt was installed
across the GY, the power supply for the string of dipoles in the second
arc was run up by local control to 200 A (out of 230 A required for 210
MeV/c).

• The downstream pole of the 1st solenoid in the injector was cut in
half and removed from its trapped condition on the beam line. This
removal will allow access room to remove and install the spare special
Haimson correctors into the center of the solenoid. The installed
correctors had become "toast" during the last gun bake and the terminals
broke off while replacing the leads with non-magnetic leads. The new
split solenoid pole configuration (part due Tuesday) will be simpler.
The Haimsons don\'t have to be baked because they can easily be removed.

**WBS 11 (Optics):**

This week we vented the HR vacuum vessel in order to install the 4\" HR
deformable mirror (assembled over the holiday) and a new, more robust
connector for the LVDTs.  The LVDT work proceeded smoothly, but we ran
into problems installing the mirror, and chipped its edge when we
removed it.  The spare was assembled, but found to have a much shorter
ROC than before it was glued, behavior that had heretofore not been
observed.  Discussions with the vendor, along with literature research
suggested the cause was due to water adsorption in the coating. 
We annealed the optic at 70C (well-below the epoxy glass transition
temperature) in a nitrogen atmosphere to lengthen the ROC.  This worked,
lengthening the ROC to the long end of our control range.  However, this
morning we noted that the coating was delaminating, so our cooldown
cycle may have been too abrupt.  The vendor believes they can recoat the
optic within a week.  In the meantime, as a backup option, we will more
gently anneal the optic with the chipped edge and install that in the
unoccupied 4\" broadband position.

For the outcoupler (OC) mirrors, the high power (@ 10.6 microns) is in
the final stage of being ready for installation.  Assuming it passes
QC, installation will occur Monday or Tuesday, only \~ 48 hrs behind
schedule.

Our other subsystem work is on schedule.  The new EO cell replacement is
installed and undergoing commissioning.  The optical diagnostics bench
has been reconfigured with ZnSe optics.

We received the high power optical dump, which is nominally rated for 50
kW.

During this week we supported further RF warm window testing with our
thermometric imaging setup.  We also held a video teleconference meeting
with NSWC Dahlgren on facility modifications and equipment required for
future materials effects testing.