# MEMORANDUM 

**To:** Distribution

**From:** F. Dylla

**Subject:** FEL Upgrade Project Weekly Brief - June 6-10, 2005

**Date:** June 10, 2005

**Highlights:**

We spent two day this week on machine set-up for high power 2.8 micron
operation and devoted the latter half of the week to low-power,
broad-band operation (1.1-1.8 micron) operation for the second user run
for Harvard Mass General Hospital (MGH). This run was very successful
according to our Harvard collaborators. Data was gathered on the
differential heating of fat vs. non fat tissues at wavelengths that
correspond to C-H stretch overtones at 1.2 and 1.7 microns. The
broad-band mirror assembly allowed the entire resonant regions to be
scanned at 10 nm increments. Kudos were given to our Optics and I&C
teams who arranged for local control of the FEL and local viewing IR
videography of the exposed samples in User Lab 1. These feature greatly
facilitated the experiments.

After the MGH experiments were completed late on Friday afternoon, we
set up a follow-up series of spot size calibrations in the Dahlgren
set-up in User Lab 1 as requested by our Dahlgren colleagues who
collected valuable data early last month on IR sensor damage.

Next week, FEL operations will be devoted to high power operations at
2.8 microns.

By all accounts the workshop we co-hosted this week (June 7-8) on the
"Free Electron Laser Applications to Biology and Medicine" was
successful. The workshop attendance was limited to 60 attendees from the
7 sponsoring institutions and others who indicated interest. Four
program areas were identified as having high potential for FEL
applications: studies of phototherapies, UV photo-damage effects, high
brightness imaging from THz to UV, and laser based diagnostics. A
workshop summary and program plan is being written by topical chairs
nominated by the attendees.

Progress on the UV FEL system this week included a successful mid-course
design review on the UV cavity assemblies and the completion of the
first of the THz chicane dipoles (GW's) at the vendor.

**Management:**

We chaired and shared in the organization of this week's laser
bioscience workshop. As noted above, the workshop was successful and
generated quite a bit of favorable notice for the capabilities of the
FEL Upgrade.

Effort was devoted to contributing FEL project data into the Lab's
annual update of our overall staffing plan as we develop detailed budget
scenarios for FY06. We also contributed strategic planning documentation
for the lab's 5 year business plan as requested by DoE's Office of
Science.

**Operations:**

Monday was spent in recovering from the repairs to the buncher
RF system.  The repairs were quite effective in stabilizing the
buncher operation.  The injector was phased and we steered up the beam
in the wiggler.  We spent some time trying to suppress the dispersion in
the first arc.   After managing to suppress the dispersion pretty well
we realized that the procedure was flawed.  We will have to try
again next week.\
On Tuesday we set up the machine for lasing at 115 MeV in the 1.1 to 1.8
micron wavelength band.  The laser lased quite strongly even at 1.2
microns.  We spent some time on Wednesday calibrating the setup for MGH
and testing out single shot mode.  We also tried to use the new

88 MeV injector setup but were unable to get a good match to
the wiggler.  Since the performance was quite good with the
original injector setup we stuck with that one.  We had one problem with
an emitter turning on in zone 3.  The gradients were reallocated
to reduce the RF heat load in that zone.\
Thursday and Friday were dedicated to beam delivery for the MGH 
experiment studying the effects of light in the 1.1 to 1.8 micron  range
on lipid rich tissues.  The machine range quite stably and well.  We
could get over 4 J in a 100 msec pulse even at 1.2 microns.  Running
with short pulses and 1.25 mA we could get up to 170 W during a
macropulse delivered to user lab 1 using the broad-band mirror set.

**WBS 4 (Injector):**

More high voltage tests were performed this week on the flat electrode
coated with a thicker field emission suppression film. At 25 MV/m the
average field emission current is around 90 pA. The highest gradient in
the gun support tube electrode is 12.4 MV/m at 500 kV operation. More
conditioning and testing is planned for next week.\
\
A POISSON model of the new gun chamber shows that the gradient relaxes
slightly on the support tube near the ground ring. This relaxation is
beneficial and does not affect the gradient at the cathode.\
\
This week we started to work on drawings for the coil that will be used
for NEG coating the new gun chamber for the Injector Test Stand. The
tube segment polished earlier has been ultrasonic cleaned and sent to
the machine shop for welding the ring that supports the ball cathode.
Polishing of the second tube segment continued this week, the transition
from silicon carbide paper to diamond paste is just starting. Equipment
is being moved out of FEL lab 2 to our new lab in the ARC building as
part of the preparations of the labs for FEL users.\
\
With the help of Daniel Mihalcea and Court Bohn (Northern Illinois
University), Kevin Beard has begun to run large simulations in their
Linux cluster at FNAL both of the space charge effects in the FEL
injector (with PARMELA) and to estimate the beam breakup (BBU) current
thresholds for the FEL (with MATBBU) when the FEL03 cryomodule is
replaced with the "Renascence" cryomodule. Testing is under way and we
expect preliminary results next week.\
\
The new FEL injector configuration with a stronger solenoid setting (the
88 MeV configuration) was modeled this week in PARMELA. Preliminary
results show very good agreement between code predictions machine
behavior. Beam-based measurements are being planned for next week.

Gun HVPS - Operational in all respects.

**WBS 5 (SRF):**

The first cavity is going into the VTA this week for initial testing and
qualification. The second cavity is positioned in a test stand and will
follow next week.

Preliminary beam line bellows transition designs for the third harmonic
cavity have been forwarded from AES to JLAB for incorporation into the
injector unit layout.

AES has completed the purchase order for the titanium helium pressure
vessels; delivery is expected this fiscal year.

The requirement for HOM damping and power coupling has been identified
as an area needing further clarification. This will be discussed during
the coordination meeting.

A date for the technical coordination meeting between AES and JLab has
been set for 21 June 2005 at the JLAB site.

**WBS 6 (RF):**

RF - All systems are operational.  This week the Buncher\'s RF Control
Module was found to have corrupted calibration files and its
pre-klystron RF amplifier was found to have several loose internal cable
connections.  After making these corrections, the Buncher phase drift
errors are at 1 degree p-p over several days and the large 5 to 10
degree phase jumps are gone.

**WBS 8 (Instrumentation):**

In general, the week has been dominated by support of Ops for LOP-05-004
(MGH, Rox Anderson).  The I&C set up time for the experiment was much
quicker this go around due to the new A/V cart.  This provided us with a
much more centralized setup which cleaned up cabling and reduced trip
hazards.  The cart comes equipped with a video monitor, two quads, a
vcr, a computer interface, a microphone input, and a video chassis. All
of the cameras on the test equipment were connected to the system along
with the area monitor in lab 1. The experiment seems to be moving along
just fine.\
  Our efforts to build a rack mount PC to host the Acqiris AP201 card
have come to a halt due to a PCI incompatibility we have discovered
between the A2D card and the PC-motherboard. We are looking into
possible BIOS issues versus using another motherboard.   A 150 MHz
Bandpass filter evaluation board was designed this week.  The parts have
been ordered to fabricate the board and the quote for manufacturing of
the PCB has been received.  EECAD has completed all the documentation
for the project and it has all been signed off on.  Progress continues
on the 6kW polarity reversing switch.  Currently several layout ideas
are being examined to determine the best package design for the system. 
Parts continue to arrive for the beam viewer crate upgrade.  The back
plane design for the crate is nearing completion and will be turned into
EECAD at that time.  Pre commissioning of another stepper motor chassis
was done this week. Testing will begin once the move in to the new
trailer is complete.  Wiring and debugging of the 4 Channel Solenoid
Fail-safe Interlock prototype PCB has been completed.  During debugging,
it was found that the \"In_Limit_Status\" protection section of each
channel was erroneously checking the status of its corresponding \'in\'
limit in addition to the opposing three solenoids\'.  Corrections were
made so that each channel only checks the status of the remaining three
channels\' in limits.  All changes were documented and submitted to
EECAD.   Discussion has begun on the ceramic viewer in 3F12. After
installing Auto CAD 2005 on the computer in Area 51, we found the old
mechanical drawings made by Jessica Sheehan for the viewer. We know that
the problem is in alignment of the mirrors, but these drawings will be
used as a basis for the corrections that need to be made so that the
exact problem can be identified. Real work on it will not start until
the vault opens June 20th, where the plan of action will probably be to
disassemble it and begin a major overhaul in the alignment mechanics.
The final items in the DMA processing lab were completed early this
week. The area camera needed to be connected to its respective monitor
in the control room. We will align this camera again today and possibly,
if need be, put some locktite on some of the bolts/screws.\
  All of the parts for additional planned temperature monitoring crates
(using the Silicon Diodes) are on order and assembly of the boards
should begin early next week.  Three crates have been assembled and are
ready for the boards and testing.  The RTD portion of the design is
being reviewed and adjustments made to achieve the desired results.  
The new design of the magnet trim cards is progressing nicely.  The
prototype is complete and testing and fine tuning is in progress. 
Programming issues have been resolved and the next step is load tests
and temperature testing. Bids have been received from three vendors for
the production and population of all of the components involved.  Our
single-shot trigger archiver has worked well this week. The software
tool automates the task of chronicling the laser pulse parameters for
the users and allowing a time stamped and record of the entire
experiment to be printed out and handed to the user as a part of their
work here. This system will continue to evolve into a system performance
tool. Currently we have time stamp faults from the RF system and gather
the relevant EPICS information with the fault.\
  The process of moving into the trailers has taken full swing and
clearing out Lab 5 and Area 51 are well under way.  The two
transportainers have been reorganized and the majority of the parts in
area 51 have been split between them and the new trailer.  Other
non-essential items such as spare pcb\'s have been removed from lab 5
and placed in the trailer.  Additional parts for shelves have been
ordered, and the move in will continue today and into next week.

**WBS 9 (Beam Transport):**

***Sextupole (SF)***

• Fabrication continues and assembly and potting started at New England
Techni-Coil. All 66 coils are wound. The concept of ramp blocks at
transitions between layers of these two-in-hand wound coils was
successful at eliminating shorts. Machining/grinding of all core pieces
is complete. The first core was assembled and inspected, meeting
specification. The multiple, accurate "T" & Hexagon concept works to
create an accurate core from 12 parts that can be assembled around the
coil. Coil molds are complete and a first cycle of potting 3 to 6 per
day will start tomorrow. Ceramic tubes that act to isolate the LCW
circuit from the coil are starting to loom as a missing item. The vendor
we recommended has not come through. Jlab's Larry Munk is working the
issue. The stands Jlab supplied to mount the magnets on stands have a
small (.005 inch) interference problem that NETC will machine to a
custom fit. Also, some tapped holes for brackets in the core were
miss-specified and need to be re-done. NETC plans shipping all units the
week of July 4.

***Replacement Chicane Dipoles (GW)***

•  Fabrication continues and assembly of one unit is complete at New
England Techni-Coil. The first dipole assembly is good. The Purcell gap
glue-down of the second core meets specification -- this potentially
risky task, for a vendor doing it for the first-time, is not risky for
NETC. The sixth coil (of 8) is almost wound. A cycle of potting two
coils per week should start next week. Machining of the top and bottom
pole plates of the third dipole is 75% complete. Shipment of all units
is anticipated the Week of July 4.

***UV Line***

• The most important quality of the QX Quadrupoles of the UV Line is
that they meet 1 part in 1000 set ability and 1 part in 10,000
reproducibility specifications. Magnet Test made substantial progress
toward that goal this week. They spent the week investigating only
reproducibility, powering a typical QX using both the standard Bang-Bang
Hysteresis and Setting with Undershoot as well as the proposed Slow,
3-part Linear Ramp with Setting from the Particular Polarity Protocol.
They used all the available Power supplies: BOSS, Danfysik, Trim Card
with EPICS control as well as the new, Trim Card II, ("power end" only).
With all readings of field gradient integral from a rotating coil, they
also took readings of an accurate hall probe glued to the pole tip. They
found that the field, as measured by the hall probe, when corrected to
the current read by the transducer resolved at 1 part in 10,000 while
the rotating coil resolved field gradient integral at only 5 parts in
1000. Thus, they are taking the hall probe as the better instrument for
investigations. They find both the Bang-Bang and the Slow Ramp Protocols
are reproducible within 1 part in 10,000 using the BOSS and Trim Cards.\
\
They are now starting investigating set ability using the same cast of
resources. We learned from our FEL test that actual usage of quads
always involved iterating to a setting (while looking at a beam spot)
between forced, double hysteresis loops. This method produced different
fields (on a hall probe on a pole tip) in out test from those resulting
from just decreasing the current from the top of a positive hysteresis
loop. The set ability tests will compare new field maps generated by the
hall probe glued to a pole tip using the original top down method and
the map generated at settings after local hysteresis loops. They plan to
test this QX Quadrupole in the Magnet Test using the Epics Controlled
Trim Card Power Supply and then transfer the quad to the FEL Gallery.
There, the same trim card will run the magnet in one of the Trim Racks
and using the hall probe, verify the "between buildings" set ability and
reproducibility. This Gallery Test also allows us to address set ability
and reproducibility under scenarios where other trim cards are working
and cycling.\
\
This next item is "Huge". This week, Ken Baggett (on loan from the
Alignment Group) has finally been able to make an improvement to the
Test Stand that was on a wish list since the dawn of Magnet Test. Using
a piece of software from Christiana Grenoble, he obtained semiautomatic,
linked EPICS control of the available trim card power supply (in the
Injector Test Cave) and the functions of the rotating coil test stand.
This means we can test magnets with the same power supply system that
powers and controls them in CEBAF and FEL and put aside the cranky BOSS
supply. He predicts this semiautomatic ability will be fully functional
next week.

• The Region Assembly Drawing of the 6Fsub1 region of the UV Line was
signed off. Girder drawings for that region are still in preparation.
Regional Assembly of the 8Fsub4 (Last) is also in preparation but
because of its similarity to 6Fsub1, the stand alignment positions are
released to the Alignment Group so they can use them during the June
Down Period.

• The 8Fsub2 (GW Chicane) Sub Region Assembly Drawing and chamber drawn
by Advanced Energy Systems remains in signature while the stands are
signed off. Note that the Jlab Shop has started the chamber procurement.

***UV Wiggler Progress***

• No progress on the new Wiggler vacuum chamber.

***IR PM Wiggler Vacuum Chamber Progress***

• The raw tubing for the chamber was ordered.

**WBS 10 (Wiggler):**

STI Optronics is making good progress on the permanent magnet wiggler. 
The figures below show the finished frame before painting, the control
panel, and the motors and micrometers for the gap mechanism.  We ordered
the tubing for the vacuum chamber for this device this week.\
We have decided to hold the kickoff design review for the UV
wiggler next Friday via video-conference.  We can afford to do this
since most of the design details have already been worked out for the
infrared wiggler.

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**WBS 11 (Optics):**

***FEL mirrors:\
***This week we completed the debonding of the 1.6 micron OC, recheck of
it\'s figure, and clean up of the holder.  It goes back into the braze
furnace on Monday.  We were unable to get one of our 2\" holders to pass
leak check, after multiple braze attempts.  Our spare is ready to
receive the optic.  Our recently bonded HRs have low astigmatism when
undeformed, but are showing rapidly increasing astigmatism when
deformed, so we are looking at debonding them to determine what is
happening.  I suspect we have an adherence issue, which we can quickly
resolve.  We were informed by the vendor that one 1.6 micron HR will
ship today, while the other, and our 1.06 micron, 96% R OCs will ship
next week.  This is still sufficiently early to allow us to meet the
installation schedule for the last part of the month.

As mentioned in the Operations section, our broadband mirror set (hole
outcoupled) worked sufficiently well to obtain very good data. 

***Other activities:\
***   We are juggling a number of activities this week.  We supported
operations for the Mass. Gen team.  It appears that our beam quality
measurements will be observed by the Dahlgren team.  They may wish to do
a short set of calibrations as well.  We will be measuring the
near-field spot sizes two ways, with a knife edge test, and with a
scanning lens and our PyroCAM.  We did a brief set of measurements to
check out the latter technique earlier this week.  We also began the
move of some of the contents of UL 2, our \"home\" for some 5 years,
over to the new trailer.  This is freeing up room so we can start
building the hutch for the Dahlgren team.  We welcome Luke Osborne, a
student from the College of William and Mary, to the team for the
summer.  

***UV FEL\
***We received the LabView drivers for a fiber-based spectrograph. 
Initial checkout shows they give us the entire spectrum (4096 pts),
while we usually need only a small region.  So, we\'ll look at the
program to see if we can modify it appropriately, to all it to
be usefully accessed with our EPICS controls.  We had a mini-review of
the optical cavity.  It generated a list of comments, and two issues. 
The overall design is judged to be sound, and we are having the mirror
mounting internals for one assembly fabricated.  It should be complete
by July 1.

We removed the internal components of the mirror cassettes in User Labs
2 & 4.  They will be modified for better vacuum practice in general, and
for high average power (10 kW) operation in the case of the UL2 mirror
cassette.

**Terahertz Project:**

The hutch in lab 3 is ready for certification.  Specifications for the
vacuum chamber for the pump-probe measurements continue.  The THz
spectrometer is working again.