# MEMORANDUM 

**To:** Distribution

**From:** George Neil

**Subject:** FEL Upgrade Project Weekly Brief - August 29-Sept. 2, 2005

**Date:** Sept. 2, 2005

**Highlights:**

We commenced a month-long shut down for installation of the new STI
wiggler, srf cavity work, and installation of UV beamline components.
The EM wiggler has been removed and the new wiggler has been delivered
to the vault in preparation for installation.  UV magnet stands are
being installed and aligned while many components are being assembled,
cleaned and qualified (see individual reports below).   

**Management:**

The laboratory had a DOE Science Review over a three day period this
week to judge our performance in supporting DOE Nuclear Physics
scientific research goals.  The lab overall got exemplary marks and the
FEL program was specifically cited for contributions to the Nuclear
Physics Program including ERL research and accelerator
hardware development. 

We are incorporating latest \"lessons learned\" from a national DOE
laser safety review.  While we are in good shape in most areas there are
a few (notably housekeeping and equipment storage) that we could improve
on.  We expect a DOE audit of our facility and practices in the near
future. 

We hosted a group from Peking University who are interested in
continuing development of their srf injector for an ERL.  We held
discussions on collaboration on srf design and fabrication.

This week Gwyn Williams gave an invited talk at a special symposium at
the American Chemical Society\'s annual meeting in DC on our high power
THz facility.

The US Army Night Vision and Electronic Services Division, which is the
programmatic office of our THz programs, held a THz workshop outside
their headquarters of Fort Belvoir.  Gwyn Williams presented a talk on
our THz facility and on recent spectroscopic measurements, while Alan
Todd of Advanced Energy Systems presented a talk on the transportable
high power THz system that is part of the same contract.

**WBS 3.0 (Beam Physics) -- Dave Douglas**

Infused with relief spawned by the end of beam operations, we assaulted
various issues related to IR performance and UV installation.

1.  Extensive discussions on UV quad specifications reinforced the
    message that \"the spec is the spec is the spec\" and thereby
    verified than a perceived 0.4% field asymmetry (ultimately
    attributed to instrumentation issues) was \"out of spec\". The brawl
    on quad powering continues, flames fanned by the fascinating results
    from last week\'s trim system test (specially calibrated trim cards
    failed to allow magnets to make loop and knocked 3 other channels
    out when swapped).

> 2\. Review of difference orbit data taken during the final week of the
> run continues. Numerous problematic BPMs can be identified and are
> being checked. Quad excitations are apparently far enough from the set
> points that we are preparing SOLOMON 0.0: the \"Systematic On Line
> Optics Monitor, Optimizer, and Normalizer\" version 0.0, to crunch the
> data, as it has become apparent the available tools cannot reliably
> extract sensible beam matrix results from the data at hand. This
> information is critical for verifying BBU simulation models and to
> provide input for machine matching & beam loss control.
>
> 3\. We spend time in discussion with visitors from Peking University,
> which is planning to build an ERL driven FEL.

**WBS 4 (Injector) -- C. H.-Garcia:**

We started processing the first of three tube segments for the new gun
assembly with the field emission suppression coating in the W&M\'s
plasma chamber. The rotation system is working flawlessly and this tube
has been processed for 20 hours. Each segment will be processed for a
total of 48 hours to ensure coating uniformity and thickness.

The flange on the second tube segment is being polished in preparation
for plasma processing next week, as well as other mounts needed for this
purpose.

This week we also supported multislit and THz work.

PARMELA modeling of the 100 mA injector continued this week studying the
effect of the added drift space on the transverse emittance.

**WBS 5 (SRF)** **-- G. Neil:**

Testing and diagnostics continue on Renascence.

1.  An external rf feedthrough broke yesterday, creating a leak into
    insulating vacuum and making cavity 7 in operable. The module will
    be warmed up over the Labor Day weekend in order to replace the
    broken part early Tuesday, followed by recooldown.

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2.  A problem with pressure stabilization has been traced to an apparent
    bypass of the helium dam on the return side. This has the effect of
    creating an extremely narrow stable operating range for liquid
    level. Joe Preble\'s tentative assessment is that the range
    inadequate for operational use of the cryomodule. Options for repair
    are being evaluated.

3.  High power testing of began late yesterday with cavity 1. This
    cavity was found to be limited by a time-delayed quench \~ 8 MV/m
    CW, 9 MV/m with 50% pulsed duty cycle. Apparently, something is
    heating up outside of the cavity cells. Diagnosis will continue
    today and examination of cavities 3 & 5 for comparison will follow.

> Given these issues we are planning for rf processing of the Admiral in
> place in the FEL to restore some of the previously achieved gradient
> capability.

**WBS 8 (Instrumentation) --K. Jordan:**

Monday we took advantage of the vault being opened to remove all of the
I&C devices from the IR wiggler and surrounding area.  All of the cables
were placed in the cable tray above the wiggler so the cables can be
reconnected to the permanent magnet wiggler once installed.  The
permanent magnet wiggler control box from STI was unpacked so a support
structure could be designed and built.  A table that will fasten to the
board and the box has been designed and some finishing touches are being
completed today so the box can be mounted in place later today or early
next week.  A plan for how to route the control and power cables is in
place.

    Testing of the BPM electronics continues this week.  The second
channel has been calibrated successfully with no influence on the
adjacent channel.  Testing of the on board ADC is the next step for the
electronics.  Several control lines from the Coldfire were routed
incorrectly but they have been moved to the correct locations.  The
Coldfire communication will be tested at the same time.  The changes
have been documented so the schematics are now correct.  Plans to get
eight sets of the electronics ready for the new injector BPMs and
various other locations is in the works.  The parts have been checked to
ensure we have plenty of components for assembly, the few parts that are
needed have been ordered. The existing BPM system is being characterized
and will be finished early next week. We are proceeding with a detailed
design for the 4 pass multipass BPMs in the linac. The intent is to have
an operational multipass BPM system working when we come back up, we are
proceeding with the Acqiris AP201 2Gs/sec Peak-detection card as the
preliminary solution. This will be followed up with a cost estimate in
order to best evaluate the final solution.

    The Coldfire Processor/Power Card will be ready for production level
boards next week.  All of the design changes have been incorporated into
the schematic and are in the process of being changed.  The Coldfire
Simulation board design has been completed and a quote for the card
should go out today.  The Harmonic Blocking Filter Chassis is 95%
completed.  A mistake in the schematic for the Stepper Motor Driver
Chassis was found, resulting in some repairs to the spare stepper motor
chassis.  This chassis should function properly now and testing
will occur as soon as time permits.  The sextapole reversing switch
schematic is being checked over carefully so boards can be ordered for
these.

    The suspended ceiling/cleanroom was officially completed this week.
Tiles were installed in and the room is now fully complete and is in
use. The coating of new beamviewer targets began this week.  Eight new
targets have begun the coating process.  Four targets have the \"slow\"
coating and four have the \"fast\" coating.  A new Temperature Diode
crate has been bench tested and is ready to install in Zone 1 for
the 1/4 Cryomodule.

**WBS 9 (Beam Transport) G. Biallas:**

# *Sextupole (SF)*

•     At New England Techni-Coil they have four units at 90% assembled,
four at 70% and three at 30%. Shipping of the first batch may be next
week.

**Replacement Chicane Dipoles (GW)**

•     The second unit was set on the stand to start its measurements.

• Work continued at New England Techni-Coil on potting the last coil.
Rework of the mold again delayed potting the final coil with the mold
finally being closed today. Potting should start Tuesday.

# *UV Line*

• STI didn't qualify its method of measuring even though noise and
reproducibility are at the part in 10000 level. Their readings in the x
plane are consistently 40 Gauss higher than in the Y plane regardless of
magnet (They tested three) or turning the magnet by 90°. They are going
through every operation in their scanning sequence to find the source.
No solution yet. The hall probe system that slips into a fixture between
poles of every magnet repeats to the part in 2500 level.

• Meanwhile, quads are not tested and girder assembly remains on hold.
The window to start assembly starts September 6. It now looks like first
production-measured quads will not be here.

• Most of the stands are now received and most of those are now in the
enclosure.

• Regional Assembly of the 8Fsub4 is in back checking before signature.

• The Jlab Shop delivered three of the 5 chambers they have in
production.

• The downstream corner chamber with NEG Pumps is now in preliminary
production. The NEG Pump cartridge holder design is on hold until a
designer is available.

# *UV Wiggler Progress*

•     No progress on the new Wiggler vacuum chamber.

# *IR PM Wiggler Vacuum Chamber Progress*

•     The support structures for the OCMMs and chamber are in
fabrication. We received both tubes for the chamber. Fabrication can
start.

**WBS 10 (Wigglers) -- S. Benson:**

The EM wiggler was removed this week and the stands for the
new permanent magnet were laid out for installation next week.  
The detailed certification data was reviewed to see if there were
any problems.  The wiggler looks excellent and exceeds almost all
the specifications by a large margin.  The control panel was unpacked
and is being mounted in place for initial tests.  STI Optronics
is planning to come out the week of Sept. 19 to get the wiggler
working with no vacuum chamber installed.

**WBS 11 (Optics) -- M. Shinn:**

***FEL mirrors:\
***The newly made DMA created with a newer, 3\" deformer, had excellent
performance (astigmatism was 0.04 waves or less), with moderate (1 wave)
of deformation, but unacceptable amounts at the powers required to
achieve the correct radius of curvature.  Coma and spherical aberration
remained essentially constant.  We are considering adding the deformer
stiffening ring that George Biallas devised (and is on the 2.8 micron
DMA currently in the optical cavity). Meanwhile, we will have previously
coated optics refurbished with a shorter ROC, so when coated, they will
deform to about the correct value. 

***Other Activities***

IR FEL activity for the month has several primary tasks: 1) Remove the
OCMMS exterior hardware, so the EM wiggler could be removed 2)
Housekeeping duties in the labs, especially those where class IV lasers
3) Prepare to install low aberration, low loss optics in the optical
cavity.  4) Prepare for the 2nd generation OCMMS installation.  5)
Preparations to extend the OTS from its present terminus in UL1 to UL6. 
6) Bring the drive laser performance back to spec.  Item 1 was
completed; the other items are in various stages of completion.  The
test stand for the new delta ROC monitor (used for both the IR and UV
systems), is working nicely with the addition of sturdier mounts, next
week we\'ll look further into its performance.  The items required for
the new OCMMS crosses are in fabrication.  Catalog items for most of the
rest of the hardware are in Procurement. 

***UV FEL***

The final assembly drawings for the OC internals were signed this week. 
Alignment points were checked, to be transmitted to Survey and
Alignment.  In the process, I found that we (WBS 10 & 11) system owners
thought the wiggler was in the center of the optical cavity, when in
fact it is not.  This forces us to transmit new ROC values to the
vendor, and will cause a schedule slip.  We received the rest of the
Macor thermal isolation parts; the issue that led to the cracking of the
first one has been resolved.  We received management approval to
complete the tasks we defined to do the scaled down cavity, and are
proceeding with procurements.  The new pump cart nears completion.  We
bid a \"see you later\" to Michael Snyder, a contract mechanical
designer who has done the majority of the UV FEL optical drawings.  He
also did the design of OTS Lite.  His talents and drive will be sorely
missed, and we wish him the best.

**Terahertz - G. Williams:**

We continued working on the spectroscopy chamber designs and on
specifications for the cooled detector.  A further meeting took place
regarding safety of the existing bolometric detector cryogenic system.