**MEMORANDUM**

**To:** Distribution

**From:** F. Dylla/gpw

**Subject:** FEL Upgrade Project Weekly Brief -- May 2-6, 2005

**Date:** May 6, 2005

**Highlights:**

We are pleased to report that FEL delivered light for its first user
tests since we commissioned the FEL Upgrade. This week we completed the
re-certification of User Lab 1 that will be used for a rather continuous
stream of users test over the next few months. The first user team was
led by Prof. Rox Anderson from Harvard Mass General Hospital who spent
the latter half of this week on experiments investigating differential
heating of fatty vs non fatty tissue in the near IR range. This proof of
principal worked beautifully to show that incident laser light at
wavelengths corresponding to overtones of C-H vibrations (at 1.2 and 1.8
microns) could be used to differentially heat fat tissue.\
\
The results of these initial experiments will be used to plan subsequent
measurements and analysis for the design of potential laser medical
treatments for skin disorders and fat removal. The experiment used
tunable IR light at power levels (20 watts cw and 100 watts pulsed) that
are unavailable with any other light source. For the entire two days of
this test the FEL operated on demand and without interruption using the
broad-band cavity.\
\
Next week we have a user tests planned by the Dahlgren group on IR
sensor damage effects followed by certification activities in the THz
lab.\
\
In other activities we had some success in identifying noise sources in
the FEL systems that will allow us to improve operations, and the optics
group made additional progress with their optical mounting techniques
and with the vendors that are completing the high power optics at 1 and
1.6 microns.

**Management:**

We had our monthly meeting on Monday with the WBS managers to summarize
the cost, schedule and technical progress for April for the UV FEL
project. A meeting was held with the project management staff on
Thursday to review the April and year-to-date cost-performance data for
the Navy IR FEL project.\
\
George Neil and Michelle Shinn attended this week's semiannual review of
JTO funded projects at JTO headquarters in Albuquerque. JTO is currently
funding projects on our advanced drive laser, optical damage
measurements and the test by the Dahlgren group that will begin next
week.\
\
Papers are being prepared for the Particle Accelerator Conference to be
held May 15-19, 2005, in Knoxville and the Navy FEL Workshop to be held
on May 23-25, 2005, at Northrop Grumman in Newport News.

**Operations:**

The first half of this week was spent refining the setup for 1.7 micron
operation with a hole coupler and certifying the laser safety systems
for the user run on Thursday and Friday.  We also did some more
detective work on sources of noise in the accelerator.  The latter half
of the week was dedicated to the Wellman lab user run in User Lab 1.\
On Monday we tried out a new match to the wiggler obtained on Friday. 
It lased a bit better than the configuration from last week but had a
low BBU threshold.  We then modified it to run higher current.  Finally
we did some studies of the gain and loss of the laser near 1.7 microns
and also at 2.8 microns, both with the hole coupler.  Calculations and
measurements show that the loss for 1.7 micron operation should exceed
20% if one is centered on the hole.  This is comparable to the gain and
so we run slightly off-center to reduce losses.  At 2.8 microns the
calculated losses are slightly less than the measured losses of 14%. 
This is low enough that we can lase centered on the output hole.  The
reason for the high losses at 1.7 microns is that we do not have a
working deformable mirror assembly (DMA) for the broadband cavity right
now.  Once we get a working DMA installed we can decrease the Rayleigh
range in the cavity, which will increase the gain and reduce the
losses.  This will allow much better lasing at shorter wavelengths.  We
spent quite a bit of time looking for noise in the system.  Two sources
came to light, one in the drive laser (pickup from the switching
supplies on the laser lamps) and one on the master oscillator. We are
looking at ways to reduce these noise sources.\
One Tuesday we used Nobuyuki Nishimori\'s new emittance script to
measure the Twiss parameters in the accelerator and improve the match to
the wiggler.  This produced a very nice match and the laser lased better
than it had to date.  We also commissioned the laser protection system
with the new hutches in User Lab 1.\
On Wednesday we finished all laser protection system certifications and
User Lab 1 was ready for operations.  The lab was prepared for the
experiment.\
Thursday and Friday were spent providing 1.6 to 1.8 micron light to User
Lab 1 for studies of the interaction of FEL light with pig skin.  The
laser lased well.  The main problems we had were with diagnostics and
running the laser close to threshold when low power was required.

**WBS 4 (Injector):**

The DC Photocathode gun is operational.\
\
Polishing started on the first of the three segments that will support
the ball cathode. Minor design work on the gun vacuum chamber continued
this week. Electrode mounts were cleaned for the College of William and
Mary as they continue to plasma-process several stainless steel samples
for field emission suppression film studies. The anode-electrode gap in
the high voltage test stand was set this week by Survey and Alignment.
Everything is ready for high voltage testing of the electrode coated
with the field emission suppression film two times thicker than
previously tested.\
\
A poster on the performance of the photocathode gun was prepared this
week for the upcoming PAC conference.\
\
The latest LANL PARMELA version has been installed and the 100 mA
injector deck is under testing. Simultaneously, the Superfish field maps
are being converted to the format of the FEL-CEBAF PARMELA version so
that we can eventually model the 100 mA injector in the two versions.

**WBS 5 (SRF):**

-   AES and the Navy have signed a contract authorizing funding for the
    SRF gun related tasks. This development will allow AES to move
    forward on engineering procurement of the remaining components for
    the 100 mA FEL injector unit.

-   AES has provided JLab with a CAD file containing the most recent
    version of the 100 mA cryounit, including the implementation of the
    third harmonic cavity and power coupler.

-   Cavity processing and testing is scheduled to resume next week when
    the seals, flanges and facilities are scheduled to become available.

-   Engineering tasks on the beampipe designs and layout drawings are
    progressing according to available resources.

**WBS 8 (Instrumentation):**

The primary focus of this week was preparation of the Harvard Mass.
General experiment in User Lab 1 and Ops support. We began with the
search to find the source of the FEL amplitude noise. At the time, we
suspected the HVPS ripple voltage was larger than spec. To confirm or
dispel this possibility, we routed the Gun HVPS monitoring cables to the
control room. We are still trying to determine the FEL noise source.\
    The problems we have had with the signal from the 1G dump have been
solved with a new configuration.  The 1G03 Dump measurement was changed
to reduce the noise within the system.  A new box was installed
downstairs at the dump where power is supplied remotely and the
capabilities to verify the calibration can be performed in the control
room without an access.  Other changes were made to the system including
additional filtering and various calibration points within the
electronics downstairs.  The Charge/Dump Current Monitor Chassis was
removed to include the power connections for the remote box and to clean
up the wiring to eliminate noise being generated within the chassis. Now
the focus on this system turns to matters of EPICS control. In
resurrecting the system, we reprogrammed the cards with a working but
less featured version of the firmware that the system used in the past.
The IR-Demo could run 10 us pulses and so our alignment mode had a
60Hz/10us feature. The 10 kW FEL has a turn-on time of more than 30 us,
so we are preparing a new version. We are also working to get the EPICS
interface back to full working order. This will also be fixed in the
next LPSS-AM card firmware version.  Special thanks to A. Grippo for
developing a whole new user interface for the Drive Laser Pulse
Controller Single-Shot Mode (DLPC-SS), that was produced overnight.
Additional LPSS hutch interlocks and their respective indicators were
installed and checked out. The control room and User Lab Status
Indicators were reinstated this week. Additional video requirements for
recording this experiment including various cameras that were needed for
looking at the experiment apparatus as well as video quads and
distribution amplifiers to put all of the video signals were setup in
the User Lab.  Several Microphones were setup for recording sound during
the experiment, inside and out of the user hutch. The necessary low and
high level LPSS certifications were completed and the experiment was
ready to be run.\
    Progress is being made on the new BPM Electronics.  A design to
incorporate the RF-DC Conversion circuitry onto the carrier board is in
progress.  Also incorporated into this design is the placement of the on
board Cold Fire Processor and all of the necessary components.  Part
orders have been placed for the BPM electronics including enclosures and
the processor connectors.  Connectors for the beam viewer chassis
upgrade have been ordered as well. Fabrication of a 60 Hz notch filter
box for the charge dump monitoring system is in progress.  Mechanical
and fabrication drawings for the 4 Channel Solenoid Fail-safe Interface
box have been signed off and delivered to EECAD.\
   Construction of the lab 3 terahertz hutch also continued this week.
The last wall pieces were picked up from Hampton Sheet Metal this week,
painted and installed. Once the doors are completed by Hampton Sheet
metal, the final panel can go up above the door.  Fabrication also
continued on the UV new sextuple magnet PS rack. Shelving for the first
rack was adjusted and is ready installation of the controllers.  The
EPICS read backs for the LPSS PLC upgrade are being sorted out. This
involves all the values used in the current LPSS system along with
incorporating the PLC status bits that can be used for debugging and
viewing the overall health of the system. This is the initial stages of
the data tables needed for the controller link aspect of the new PLC
system. Also working on our system for storing documentation on the PLC
memory as well as externally. A list of questions is being compiled for
our meeting with Doug Smith that is coming up.

**WBS 9 (Beam Transport):**

Sextupole (SF)

•   Fabrication is continuing at New England Techni-Coil. Hexagonal and
Tee parts continue through the final machining before grinding and pole
tip contouring. Coil winding has started again with shortened conductor
ramp pieces.

***Replacement Chicane Dipoles GW)***

•   Fabrication is continuing at New England Techni-Coil. They potted
the second coil. The fifth coil (out of 8) Is wound and being prepared
for pressing. They glued the first Purcell gap glue down and are
awaiting the epoxy cure. They are now anticipating shipping the first
magnet next week. The second core is about to be complete. All the parts
for the third and fourth cores are made except the 4 top and bottom
plates.

***UV Line***

• We have agreed on a current ramp protocol for testing the 26 QX
Quadrupoles so they that will match the capabilities of the Trim Card II
to enable us to set the quads to field levels at the one part in 1000
level.

• A third of seven electron beam transport sub-region's assembly
drawings was signed along with its girders. Two remaining regions being
designed by the Engineering Group are well on their way. They will try
to get the points to the Alignment group for next week's bolt-hole
location effort in the vault. The seventh is the wiggler zone, which
awaits the drawings of the wiggler jaw mechanism which is in the bid
evaluation process.

• Advanced Energy Systems has completed the drawings for the sixth (GW
Chicane) sub-region. We are generating the stand and cartridge points
for them. Drawings are checked and they are in the process of getting
them to us for signature.\
• We started ordering NEG Pumps and the valves. Bellows are next.\
***UV Wiggler Progress\
***• No progress on the new Wiggler vacuum chamber.

**WBS 10 (Wigglers):**

Discussions continued on the UV wiggler modifications.  We expect to be
able to request BAFO next week.

**WBS 11 (Optics):**

***FEL mirrors:***

We repeated the bonding procedure that gave such good results, and once
again got a low aberration bond.  We also tried a variant of this
procedure, applying pressure to the circumference of the mirror while
the epoxy cured.  This worked reasonably well on a figured, but uncoated
substrate (no power shift, 0.08 waves of astigmatism), but badly on a
3\" DMA (2.8 micron HR bonded to a deformer).  The astigmatism axes were
aligned with the water lines, similar to what we saw with a 2\"
deformer.  We are now checking our deformers by polishing the surface to
measure the figure and look for astigmatism.  During the JTO Annual
Program meeting (see below), I discussed our initial calorimetry results
(\~ 100 ppm) on our 1.06 micron HR with Al Ogloza (NAWC, China Lake). 
Based on information he provided, subsequent discussions with the vendor
for the 1.6 micron mirrors (who also coated the 1.06 micron mirrors) led
to my decision to switch the high index dielectric from hafnia to
tantala.  This does not affect the schedule, delivery is expected for
the 3rd week of May.

 ***Other activities:\
***   Work this week concentrated on setting up the laser calorimeter in
User Lab 6, where we will use it to qualify 1.06 micron coatings.  Work
continues on qualification measurements for the advanced drive laser. 
We completed the mechanical installation for the hutch in User Lab 1,
and provided operations support for the first user experiment (Mass.
General Hospital/Harvard Med.).  We also prepared for the next user
experiment, for Dahlgren NSWC. We assisted in noise measurements on the
drive laser and the FEL. 

I attended the final day of the JTO Annual Review and gave presentations
on both the advanced drive laser and laser damage research the JTO is
funding.

***UV FEL\
*** The design of the optical cavity internals continued to progress. 
Further discussions with the manufacturer of the He refrigerators
revealed that they can\'t deliver the heat transfer rate we require.  We
are pursuing discussions with other vendors.  Discussions on plasma
cleaning techniques continues. The strongback for the second assembly
was received, but went back to the Machine Shop.

**Terahertz:**

The spectrometer in lab 3 continues to function while work continued
this week on the hutch.  Activities involving the hiring of a postdoc
are still continuing.  We learned this week that the absolute THz power
meter was shipped.