**MEMORANDUM**

**To:** Distribution

**From:** F. Dylla

**Subject:** FEL Upgrade Project Weekly Brief -- April 26-May 2, 2003

**Date:** May 2, 2003

**Highlights:**

We spent the afternoon and evening shifts this week performing the high
voltage conditioning of the photogun. As of press time we have
successfully completed conditioning of the gun to

420 kV, which provides our desired 20% head room in conditioning above
the nominal 350 kV operating voltage of the gun. We also continued
putting RF power to the acceleration system during the gun conditioning
activities. Next week we move on to bring the gun and injector on line
with electron beam.

**Management:**

On Thursday evening and Friday we met with two members of our Maritime
Technical Advisory Committee, Admiral Ted Parker and Dr. Alan Berman,
for review and counsel on the Lab's FEL program.

On Tuesday, participants in the joint NSWC, NRL JLab laser materials
lethality studies project met at JLab to discuss planned experiments
when the 10 kW FEL goes into operation.

We submitted on Monday "Work for Others" agreements to the DOE Site
Office for their review and approval for a joint project with AES on a
terahertz beamline for the FEL with funding provided by the US Army
Night Vision Lab, and for the next increment of lethality studies with
funding from the NSWC as noted above.

On Tuesday, S. Chattopadhyay and F. Dylla gave presentations to the SURA
Board of Trustees on accelerator light source developments at SURA's
spring SURA board meeting in Washington.

**WBS 4 (Injector):**

At the end of last week's gun conditioning activities, the gun was
conditioned to 300 kV by midnight on Friday night. Starting on Monday of
this week we spent 10-12 hr shifts on conditioning activities as we
brought the system up 420 kV. We encountered a half dozen field emission
sites that required a few hours of processing per site. In general the
conditioning went very smoothly and bored the operators as we
incremented the voltage by 1 kV steps to keep vacuum excursions in the
upper UHV range. Early next week we plan to do the in-situ heat clean
and cesiation to prepare the photoemitting surface on the GaAs cathode,
do the final alignment on the drive laser and fire up the gun.

**WBS 6 (RF):**

We put power on all the SRF acceleration systems for approximately 15
hrs this week for conditioning and controls adjustments. Both
cryomodules were operated at "drive highs". The injector cryounit
maximum gradient was pushed from 7 MV/m to 9 MV/m for each cavity as we
adjusted tuning and monitored window heating effects. This is 10-15%
below where we want to be so we will continue this activity next week.

**WBS 8 (Instrumentation):**

Completed interlocking the box supplies for the 1st Arc, DY Arc, and
Wiggler (on/ off and current out) to the MPS beam mode module. Checkout
and calibration is complete. Modifications to the current measurement
output board and the FSD/MPS status relay for the 5kW extraction power
supply has begun. MPS wiring for the 2nd Arc string has begun. The last
AC distribution chassis for the Danfysik power supplies has been
delivered and installed. Shunt modules for 4F06, 4F06A and 2F08 and the
1st Arc shunt chassis were pulled for repair and check out will continue
when re-installed. The vacuum signals have also been checked out through
EPICS and MPS. The MPS-Ops screen has been reviewed and the 1st set of
changes is underway.

Beam Loss Monitors (BLMs) - The exact positions of the BLM heads have
been determined and we are preparing to install the permanent support
structures for each channel. The BLM PMT signal monitoring cables are
all installed and can be connected to the analog monitoring system (AMS)
as needed.

The Dump Water Temperature/Pressure Monitoring Chassis\' for the 2G and
5F dumps are connected to the sensors in the vault and have been tested.
The Machine Protection System chain in each chassis is also functional.
The drawings for the chassis are being revised to reflect the new MPS
chain.

The new Charge/Dump Current Monitor Buffer Driver has been installed at
the 2G dump and tested satisfactorily. Cables for the Buffer Drivers for
the 1G and 5F dumps have been pulled and are terminated in the Control
Room rack. The EPICS readout has also been checked out.

The web-server PC \'laser.jlab.org\' is undergoing maintenance to keep
it up to date and secure

**WBS 9 (Transport):**

***Dipoles***

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

• The Large and Small Injection Chicane Dipole in the 5F region were
fully aligned.

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

• The data from measurements of the first GY at 210 MeV/c fields is
consistent with the

> 145 MeV/c data. The magnet looks good.

• Wang NMR reports that the potting of the second coil of the second GY
dipole was successful. No shorts -big sigh of relief. They are doing a
trial fit and brazing the fittings on the leads. Their plan is to ship
on Wednesday.

***Octupole (OT)***

• The order for the core machining is ready to be placed when funds are
available.

## Correctors

• The second (and last) coil of the special GA vertical corrector (the
last First Light punch list item) of the Optical Chicane was glued
together and will be ready to be installed with its bracket next week.

## Commissioning

• The vacuum group continued its vacuum quality assurance procedure for
chambers, completing the optical chicane and the first half of the
second arc.

• Dave Waldman performed tests of the helicoflex seals vs. o-rings for
the windows in the GY chamber. He sees a 1.5 mil deflection of the
rectangular flange with o-ring and no deflection with the helicoflex.

• Dave Waldman received the circular quartz window and the machined
rectangular flange covers with hole for the circular window that are the
work-around for the rectangular windows on the GY chamber that are late
from Ceramaseal. It is a robust solution to the problem that will be
ready for when the GY magnet is needed for recirculated beam.

**WBS 11 (Optics):**

Work on the e-beam beamline progressed to the point that we were able to
get a clear path back to the HR assembly. This allowed us to affirm that
the optical beam shields were doing a great job at eliminating beam
jitter due to air currents. The residual jitter was mostly attributed to
the optical bench supports. Since we had anticipated this, we began
adding plates that would stiffen the bench and saw a dramatic
improvement. In order to connect the optical cavity to the GX magnet
chamber, we purged the OC vacuum vessel with dry nitrogen; this also
gave us the opportunity to change out the ultraviewer mirror holder
clips and the viewport. We also added a spacer flange to the insertable
mirror (for the spontaneous output) that had been inadvertently left off
during assembly. At this writing the entire OC vacuum assembly was
pumped down sufficiently to get the ion pumps on. In preparation for the
cavity length determination efforts, the optical breadboard for the
in-vault diagnostics was anchored in place. The pyroelectric detector
for that diagnostic suite arrived this week, as did the upgraded
spectrometer. We received the molybdenum cooling rings the 4\" diameter
OC mirror mounts in (required for high power operations) and they will
be sent out for cleaning and plating. The water chiller for the optical
cavity was filled with water and checked out. We are fabricating the
breakout boxes for the piezos (and optical encoders). We continue to
work on the problem of noise and drift in the LVDT readbacks. We
received a fast shutter which we intend to use as a replacement of the
second EO cell. With it, we can chop the drive laser beam for periods as
short as 1 ms, and repetition frequencies as high as 200 Hz. This is a
more flexible arrangement (yet inexpensive) compared to our chopper. We
will retain our chopper scheme for those cases where short duration
periods are required.

#### Other activities

We assisted our users in User Lab 6 by loaning them our fast IR detector
and a preamplifier, as well as some vacuum hoses and connectors to vent
their He dewar. We hosted a meeting with staff from NSWC Dahlgren and
PMS 405.