# MEMORANDUM 

**To:** Distribution

**From:** George R. Neil

**Subject:** FEL Upgrade Project Weekly Brief -- September 17-21, 2007

**Date:** September 21, 2007

**Highlights:**

The new high charge gun is under bake in the GTS.  It was ramping up to
250 C today and so far the level of water contamination is significantly
lower than we have seen in the past.  We also got our control computer
(IOC and VME crate) for the GTS running.   Both drive lasers were
certified for running, too.

 

**Management:**

George Neil gave a paper on FELs at a DE conference in Alexandria.

Gwyn Williams attended the Basic Energy Sciences meeting in Bethesda.
The Head of the Office of Science, Ray Orbach, announced a new charge to
the advisory committee to report by summer of 2008 on the
characteristics of a next generation light source that would address the
recently identified Scientific Grand Challenges.

Michelle Shinn, Steve Benson and George Neil attended the FEL TAWG at
Stanford to give a report on our high irradiance optics tests last
spring as well as the GTS status.

The entire staff attended a RadCon Training Session as part of a JLab
standown on handling of potentially contaminated components.

**Injector:**

***GTS***

The week was devoted to preparing the gun for vacuum bake cycle. On
Monday we discovered that the shield door inside the cathode ball got
loose from the actuator rood leaving the door half-way open. We had to
open one of the upstream flanges but the problem was solved and the
vacuum was recovered. On Tuesday we activated the NEG pumps with
excellent results, the vacuum chamber ion pumps where reading less than
1 micro-amp of current or about 1E-9 Torr prior to the bake. The RGA
shows water partial pressures below the 1E-7 Torr, the lowest we have
ever seen from an un-baked gun vacuum chamber. On Wednesday the gun was
prepared for baking and the oven panels installed. K. Jordan got us
bakeable connector for the NEG pumps which were installed for a partial
activation during the 150 C temperature ramp down. On Thursday morning
we started the ramp up to 150C in 8 hours. The pressure dropped one
order of magnitude overnight. This morning we started the final ramp up
to 250 Celsius. Typically the gun bakes takes about three weeks, but
based on the observed low pressure this bake might take less than 2
weeks.

The Safety Systems Group continued making progress installing the
Personal and Laser Safety Systems. The PSS laser interface chassis was
installed in the rack.

We started assembly of the PSS gun interface chassis. We also sent out
the PSS/User interface panel for fabrication and engraving. PLCs and
24VDC power supplies were panel mounted and installed in rack. The
electricians moved some AC conduit and installed signal conduit to the
PSS/User interface panel. There is general discussion about still
pending designs at scheduling meeting and more specific discussions
about laser hutch design and installation at LPSS meeting - still have
some unanswered issues.

GTS -- The HVPS for the GTS has been tested to 150 kV with no load and
to 5 mA with a short circuit load.  It needs the SF6 system to be
finished to test it for higher voltages.  The Conditioning Resistor (330
Mohm) has been made and assembled for the GTS.  The values of the
earlier Conditioning Resistors (3 -- 4 kM ohm) were out of our desired
range.  It is ready for final assembly into the GTS.

**RF:**

RF -- Received the repaired solenoid power supply for Quarter 3 and
changed a borrowed unit the borrowed unit.  We then discovered the
solenoid power supply for Quarter 4 had just failed.  It was changed it
out with the borrowed unit and sent out for repair.  A new spare power
supply is due from the vendor in October.  These power supplies have run
continuously for the life of the IR Demo machine and to date for the 10
kW Upgrade machine, nearly 10 years total.

Gun HVPS -- The Conditioning Resistor was removed to allow work on the
Gun.  It will be reassembled when the Gun is ready for it.

**Instrumentation and Controls:**

This week we continues our efforts in bringing online the IOC for the
GTS, IOCFEL11.  With support from the software and network groups we
were able to get the IOC up and running.  Currently the applications for
the RS-485 are installed along with the 64-Bit GPI/O card.  The GPI/O
card is being used to drive four timer cards which will make up the DLPC
and synchronization system for the GTS.  Currently two out of the four
timer cards are installed and configuration details are being worked out
to establish proper communication and control.  As part of the DLPC
system we\'ve successfully assembled several cable snakes for I/O. 
These snakes are currently being installed before the drive laser table
gets installed. Some time was also spent supporting Optics in completing
the Antares and Advanced Drive Laser certifications.  Wiring continued
on the SF6 control box.  With the front panel wired and installed we
were able to cycle the valves and are in the beginning stages of
commissioning the system.\
   We\'ve also taken the time to gather all of the VME I/O cards that
will be needed for the GTS.  Currently we have the cards to perform
RS-485 communication, ADC/DAC channels, BLM interface, Timer Cards,
Stepper Motor Control, and signal multiplexing.  Most of these cards
will be used for the Drive Laser controls and status readbacks.  Others
will be needed later in the project but we\'re gathering these at one
time to avoid the future headaches associated with this.\
   The Analog I/O distribution module has arrived from the board
manufacturer.  Currently a lite assembly is being completed by the
fabrication group.  Once this assembly is tested and verified three
fully populated pcbs will be added to the queue for assembly.  The
necessary parts to complete these assemblies were all ordered.  The bill
of materials for the HVPS Analog I/O configuration is slowly coming
together for this board.

**Electron Beam Transport:**

***Improvements and Upgrades***

*Gun Test Stand (GTS*)

• In building the SF6 Gun Tank system, the JLab Shop completed welding
the large flanges of the main vessel. The large nozzle hole will be cut
early next week.  The flange and the head of the Elongated Tank Head are
ready to weld.  Willy will weld the Outer Conductor Extension first
thing next week.  All the ASME grade fasteners were ordered.

• The SF6 Gas Transfer System piping continued with checkout of the
solenoid operated valves.  I am working on the documentation of the
extension of the compressed air and the nitrogen systems into the GTS
per our implementation of 10CFR851.  The air system will be extended to
the SF6 System next week.   

• The Assembly Group will install the stands for the beam line early
next week on overtime and the Vacuum Group can follow-on to mount all
their hardware.

• *We also plan to install the drive laser table (hanging from the
ceiling) during the gun bake next week on overtime.*

***SF Sextupole Magnet Testing***

• Magnet Test completed its first round of testing of the first
sextupole with the new power supply and controls.  They will now do
repeatability runs followed by use of the alignment group to
characterize the position of their probe in X and Y at magnetic center
with respect to nominal physical center.

**Optics/Transport:**

We have fully characterized the 930nm optics this week. We have two high
reflectors and two output couplers. One high reflector will get bonded
to a deformable assembly early next week. Both the output couplers will
go to Tom Elliott next week for brazing. One will be brazed into a
conventionally cooled mount and the other to a cryogenically cooled one.
A broad band high reflector mirror was rebounded this week. This optic
had previously failed to deform correctly. Tom is currently brazing six
optical dumps for us. Half are the 50kW variety need for the User Labs
and the other three are the 15kW type with 6 inch conflat flanges. The
later will be used to replace the iso flange ones attached to the
Optical Cavity Mirror Metrology System (OCMMS) crosses.

The Vacuum Group has completed installing the X-ray cross in the 4F
region of the machine. We will start the OCMMS realignment process early
week before the 4F region is pumped down. The upstream OCMMS has been
misaligned for some time and may require some disassembly before it can
be functional.

 

We have received the extruded aluminum hardware needed for User Labs
today. They will be used to support the harmonic block filter and hutch
shutters in Labs 3, 3a and 5. Drawings have been released to the Machine
shop to fabricate one prototype insertable mirror assembly. This
assembly will be first used in Lab 5 to direct the FEL into the PLD
(Pulsed Laser Deposition) apparatus. Delivery is not expected until the
first week of November. The linear stage needed to complete the mirror
cassette in Lab 3 was shipped to us this week. We hope to make the
necessary modifications and install it before we start the machine back
up. Work continues in converting the Turning Mirror Cassette (TMC)
drawing from Ideas to SolidWorks. This is necessary in order to design
the modification to the cooling chain attachment point. The current
design does not allow us to slide the cassette assembly out of the
vacuum vessel for installation and maintenance.

**Lasers and Optical Diagnostics:**\
We had a laser safety inspection by Lab's safety group early this week
and then finished certification of both advanced drive laser system in
drive laser enclosure and the Antares laser in Lab 6. Both lasers are
now operational. We have optimized the Antares laser to the
specifications required by the Gun Test Stand drive laser and are now
working towards the integration and systematic testing of the whole
system. An issue with the harmonic converter was found and being fixed.
We also spent time on the optical transport and getting required safety
shutters.

**Terahertz:**\
Work in the THz group this week was focused on continued progress toward
completion of the vacuum systems in the THz hutch.  It has been decided
to add gate valves to the beam ports on the sample chamber to allow for
faster pumpdowns after sample changes, and to limit the frequency that
the spectrometer and diamond window at F3 are subjected to the pump/vent
transients.

**Word version:** [FEL Upgrade Project Weekly Brief -- September 17-21,
2007](http://www.jlab.org/accel/fel/documentation/07weeklybriefs/upgradeweek07sep17-21.doc)