# MEMORANDUM 

**To:** Distribution

**From:** George R. Neil

**Subject:** FEL Upgrade Project Weekly Brief -- September 24-28, 2007

**Date:** September 28, 2007

**Highlights:**

The gun finished its vacuum bake ahead of schedule with excellent
pressure readings. We can now move on to assembling the rest of the
beamline in the Gun Test Stand.  We were also able to hang the optical
table behind the gun.  Next week we should be able to begin assembling
the drive laser system.  The GTS Personnel Safety System passed its
design review so its installation can also continue.

**Management:**

We established approved Work Packages for the coming year for the
primary ONR effort and reviewed that with the outside support groups to
establish task priorities.  We also established baseline efforts for ERL
research activities and entered those into the system.

Ninety percent (90%) of the FY07 Personnel Appraisals were approved by
Human Resources so that activity is moving on schedule.

We provided Virginia with support packages for the budgetary requests
for the next biennium.

Gwyn Williams presented two papers on THz at the WIRMS conference in
Japan and Michelle Shinn presented at the Boulder Damage Conference as
well as participating in a program kickoff at CSU.

**Injector:**

***GTS***

The gun bake at 250C progressed better than anticipated leading us to
cool down to 150 C on Wednesday after observing that the pressure did
not drop more than 10% in 24 hours. Then on Thursday we ramped down to
room temperature and this morning the ion pump current is between 3 and
6 nano-amps. In the FEL gun during nominal operation we see about 3
nano-amps ion pump current.

The gun bake was complete in one week, a third of the time it usually
takes in the FEL gun. The ion pump current is already a few nano-amps
indicating that the vacuum level is at least as good as in the FEL gun.
We expect the vacuum to improve over the next few days as the chamber
keeps cooling down.\
\
The drive laser table was mounted to the GTS ceiling.

**Instrumentation and Controls:**

Activities this week again concentrated on the SF6 system.  The wiring
of the control switches was completed and  connected to the PLC
connection point.  Both transducers and limit switches on the gun tank
have been wired and terminated.\
Assembled and began sweating the 2\" copper tubing from the transfer
system to the HV tank. The actuated SF6 valves had to be troubleshot to
determine the location of missing

o-rings and replaced.  In support of the gun bake a UHV controller was
moved to the GTS to read the vacuum in the gun.  We are getting another
pair to run in the GTS permanently.\
To support the Drive Laser installation some time has been spent located
a second shutter of a different technology for the PSS.  Currently we
have a second shutter and some tests are ongoing to check lifetime
operation, specifically associated with thermal issues.  Now that we
have identified the second shutter style we will push forward with the
development of the shutter interface.\
In support of the GTS controls system we now have all four timer cards
configured and fully populated.  Quite a bit of time was spent to
develop the design for this wiring harness as there were several
problems that needed to be resolved before a timer card can be
controlled via the rear connection.   As part of the shake out process
we identified the proper PLD code and have a much better understanding
of the interface with the IOC and how all of the pieces work together. 
The software to control the four individual cards through the expert
screens have all been tested and verified to work properly.\
This week we received the partially assembled Analog I/O Distribution
Module from the fabrication group.  The channels that were assembled
were all tested and verified to work properly.  A simple test code was
written for the PLD and that was verified to be programmable and working
as expected.  We\'ve resubmitted the card to the fabrication group for
complete assembly.  The remaining parts that were ordered have all
arrived and have been turned over to the fabrication.

**Electron Beam Transport:**

***Improvements and Upgrades***

*Gun Test Stand (GTS*)

• In building the SF6 Gun Tank system, the JLab Shop completed welding
the inner welds of the large flange and head of the Elongated Tank
Head.  Machining of the hole for the nozzle port on the main vessel was
completed.  The nozzle flange and its skirt are being coped to the
saddle shape of the tank.  Arrangements are being made to pressure test
at Advex Co.

• The SF6 Gas Transfer System piping continued with the start of
extension of the piping to the tank to the outside air bag and bringing
in the airline from the wall location.

• The Assembly Group installed one of the stands for the beam line but
has postponed further work because to the short time of the bake. 
Instead of the beam line joining the bake on the gun we will have bake
it independently. Assembly will start up again next Monday when the bake
is cooled down ad the flange faces are cool and accessible.

• Installation of the drive laser table (hanging from the ceiling)
started up with installing and testing of the threaded rod hangers.

*SF Sextupole Magnet Testing*

• Magnet Test did repeatability tests on the first sextupole of this
series and worked with the alignment group to characterize the position
of their probe in X and Y at magnetic center with respect to nominal
physical center on this unit and on future units.  Ken Baggett reported
results to Dave Douglas.  The result was a nod from George Neil that
measurement of the remaining 7 magnets could commence. 

**High Power Optics Risk Reduction**

The last couple of weeks have been fruitful with off-site meetings and
seminars providing information relevant to our efforts.  The Optics
Collaboration we\'ve had for over a year (UNM & CSU) has been expanded
through funding by a Multidisciplinary Research Initiative grant.  This
grant funds staff at Stanford Univ. to do precision absorption
measurements like those done for the NSF-funded LIGO project.  It also
provides some funds to the FEL Div. for testing.  Last week I attended a
kick-off meeting with the co-PIs of the collaboration.  One of Carmen
Menoni\'s post-docs will visit our facility to do metrology and laser
experiments.  The annual Boulder Damage Symposium (the 39th) was held
this week.  As usual, there were a number of talks of interest to our
program.  I will put together a summary of the highlights.  I gave a
presentation entitled \"Operation of the Jefferson Lab Free-Electron
Laser at high irradiances\" at the Boulder Damage Symposium in the
Mini-Symposium session entitled \"Lifetime Issues for CW and Quasi CW
Lasers\".  A companion paper is being written.

**Optics**

We started an initial realignment of the Optical Cavity Mirror Metrology
System (OCMMS) this week. The downstream OCMMS needed realignment
because the X-Ray chamber was installed on one of the upper OCMMS
flanges. As it turns out the alignment was not to far off. The upstream
OCMMS has been unusable since its support was modified to accommodate
the wiggler thermal growth. While the cause of the input mirror
translation was not immediately obvious, the solution seems to be
relatively easy. A drawing for a modified 45-degree bracket was sent to
the machine shop. We expect the part on Tuesday. A final alignment will
need to be made once the region is pumped back down.

 

The drawings for the modifications to the Turning Mirror Cassette (TMC)
chain assembly was completed this week. The modifications consist of a
new end flange and a chain support bracket. The drawings were sent to
the machine shop. The parts are expected in two weeks.

 

A 930nm HR mirror was bonded to a deformable mirror assembly this week.
The broadband HR mirror that was bonded last week is currently being
tested. The OC mirrors were delayed a week and should go out for brazing
next week

 

We have finally received the linear staged need for the last lab
cassette. Some modifications will be need on the mirror holder assembly.
This new stage's dimensions are slightly different than our now
discontinued ones. Our goal is to make the necessary changes and have
the system installed by the end of the down.

 

**Lasers and Optical Diagnostics:**\
This week we fixed the problem with the crystal heater on the Antares
laser. We are now running the laser to test a few critical optical
components and devices that are important parts of the GTS drive laser
system. The laser amplifier has been received; the installation,
modification and certification of this laser are under way. The optical
table for the GTS laser was moved into the cave for installation. More
discussions were held to specify the technical requirement and time
schedule regarding the installation of optical transport.  We also
discussed and made decision on the selection of laser shutters require
by the laser personnel safety system. In order to improve the
temperature stability of advanced drive laser system, we have moved the
cooling system out of the clean room and the work on the protective
frame is near completion.

**Terahertz:**\
Work in the THz group this week was primarily dedicated to the
integration of the gate valves into the vacuum system in the THz lab.
Ideally, we prefer manual valves for the ease of integration, but the
valve position must be readable back to the LPSS system for both machine
and personnel safety interlocks, particularly once FEL beam is delivered
into the hutch.  We have been in contact this week with VAT to determine
which manual gate valves provide an electronic readback; we will be
ordering the proper type soon.

**Word version:** [FEL Upgrade Project Weekly Brief -- September 24-28,
2007](http://www.jlab.org/accel/fel/documentation/07weeklybriefs/upgradeweek07sep24-28.doc)