MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report, September 22-26, 1997
Date: September 26, 1997
Management
The official milestone date for the completion of the IR Demo
construction project is next Tuesday (Sept. 30). This milestone
was defined as completion of the FEL User Facility with installed
FEL hardware ready for start of commissioning. On Oct. 2-3, representatives
from the Navy High Energy Laser Office and the DOE Site Office
will be reviewing the close-out of the construction project.
The FEL project team thanks all the Jefferson staff, contractors,
and collaborators who have helped us reach this important milestone.
Readers of this weekly report know that some installation activities
will remain after the Sept. 30 milestone, however, these tasks
have been staged to not impede start-up of commissioning activities.
Highlights for this week include the first commissioning activities:
the application of high voltage (420 kV) to the gun assembly.
Other highlights include completion of installation of the optical
chicane vacuum chambers; the first fit-up of a reverse-bend vacuum
chamber; and the delivery of HeNe laser light through the drive
laser optical transport system to gun cathode.
Monthly reports for the month of August for both the IR Demo project
and the Demo Commissioning and Upgrade project were completed
and distributed. A draft projection for the cost and schedule
performance for the last month of the Demo project (September
1997) was completed in preparation for next week's project close-out
review.
F. Dylla and a number of LPC collaborators attended this week's
workshop (Sept. 21-24) on "Atomic, Molecular and Optical
Physics" sponsored by the DOE-BES Program Office. In working
sessions on low field, high field, and surface phenomena, the
potential use was noted of 3rd and 4th generation light sources
(including specific mention of the Jefferson Lab FEL).
On Sept. 23, Jefferson Lab hosted the Virginia Technology Council,
which included discussions of continuing support of the FEL User
Facility and Applied Research Center in the Commonwealth's "Technology
Blueprint": being prepared by CIT and the Council.
Accelerator Systems
Regarding the beam-transport system:
Measurements continue on the Injection/Extraction dipoles. Integral
readings on the first DU unit were within the one part in ten
thousand specification over the good field region. The DU version
of these magnets is "all ends" and shaped like a wedge.
We have to refine our analysis techniques in order to create
legitimate characterizations. Field integral measurements will
continue over the weekend on the remainder of the available population
of four magnets as Everson reglues mu metal on two DU poles that
were sent back.
No more work was done on the magnetic model of the DV dipole and
the 10 MeV line that is adjacent to it due to competion with the
gun high voltage commissioning.
Everson shipped the four DX style reverse bends as well as the
trial assembly of the 180 degree dipole (after on site inspection
by Larry Turlington) while continuing gluing the mu metal and
brass on pole tips on the other style of reverse bends, the DQs.
Our plan to install the trial assembly 180 degree magnet as well
as two of the unmeasured DX dipoles and the pole tips from a DX
and a DQ onto their respective stands in the first arc may come
about next week. However, the permeability of the chamber welds
became a cause of some concern. The concern temporarily halted
welding on the 180 degree chambers. See below.
In the quadrupole and sextupole area, winding of coils and machining
cores for the eight Panofsky trim quads reached 65% complete status
at Magnet Enterprises International by week's end.
In the corrector area, manufacture of the coils for the phasing
dipoles (DGs) continued at MEI with forecast completion at the
end of next week. The manufacture of their mu metal cores was
started at Magnetic Shield Corp. with completion forecast for
24 October. Materials are on order and tooling in design at
Advance Magnet Lab (AML) for fabrication of coils for the reverse
bend correctors as well as the air core correctors with completions
forecast over the next two months. Two of the four sets of prototype
air core correctors needed for the injector line and injector
dump line were completed.
The bolted together chambers and the cross for the beam scraper
composing the beam tube for the first two reverse bends were placed
into position and are awaiting the magnets for a final assessment
before cleaning. Welding of ends onto bodies continues on the
remaining reverse bend chambers. However, magnetic measurements
on two chamber bodies from the arc chambers indicated a greater
effect from the weld bead than predicted by the original sample
chambers at the level of three parts per ten thousand. Welding
on the 180 degree chambers was temporarily halted, David Douglas
is constructing a better model to forecast the effect of the magnetic
anomaly and we are preparing to use non-magnetic Inconel rod on
the local portions of beam tubes to eliminate the problem if David's
analysis demands it.
Regarding RF systems:
The 500 kV High Voltage Power Supply and transmission line were
successfully high voltage tested to 420 kV this week. The PSS
interlocks for the buncher system are ready for testing. The
SOP was signed this week. The RF system for the buncher is about
90% complete. The installation of the 50 kW klystron systems
for the quarter cryomodule are about 90% complete. Both units
were operated and generated RF into waveguide shorts. The first
225 kW variable power supply was successfully high voltage tested
with a small load. The RF system for the linac is about 60 %
complete. Modified software was installed and partially tested
in the linac. The software changes for the Injector were implemented
and tested this week.
The gun high voltage power supply was successfully operated at 420 kV for gun conditioning. We had an early failure, due to arcing, of a transmission line center conductor support rod. To correct this, we made minor changes to the rod design and covered the new rods with "Raychem" to help the surface grading. The power supply is now very stable, at least up to the 420 kV level.
For these tests we ran a gas mixture of about 85% SF6 and
15%N2.
Due to a misunderstanding, last week's report incorrectly stated that the buncher cavity was powered with RF in the FEL Facility. Instead, the buncher's RF system was powered last week into shorts. We still need to install the buncher's water skid before running it. Plans are to power the cavity with RF early next week. We are not foreseeing undue difficulties because the cavity has already been successfully operated in the Injector Test Stand.
Regarding instrumentation and control systems:
This week's activities center around the operation of the dump
water skid. The instrumentation and control interlocks for all
of the fixed and insertable dumps are located in rack FL07B05,
in the control room. The interlocks for the skid are operational,
the chassis for the three fixed and three insertable dumps will
be worked on next week.
FEL Systems
Injector Reinstallation
All components for the drive laser transport are here with the
exception of a mirror which will arrive next week. The high voltage
power supply system is complete and being used to high voltage
process the gun. Final alignment was completed on all components
before the cryounit. Correctors were installed before the cryounit
as well. All air and water lines before the cryounit were hooked
up. A green He-Ne laser was installed to provide a local source
of green light for quantum efficiency checks as well as a source
for initial beamline checkout.
Wiggler
The wiggler vacuum chamber is leak tight and is being straightened.
It will be ready for assembly in its support next week. All
parts for the wiggler viewers are in house and the viewers are
being assembled.
Optics
Work continued this week on the drive laser optical system. All
mirror cans for the system are installed and all of the cans downstairs
are aligned to their surveyed positions. The relay telescope
has been reinstalled in its vacuum-tight enclosure. The piping
between the various mirror cans should be completed tomorrow (9/27).
A red He-Ne in the drive laser clean room transmitted by the
OTS enters the light box, but is not centered on the photocathode.
We plan to complete the alignment on Monday. A green He-Ne (Gre-He)
laser was installed on the light box stand and was aligned to
transmit a beam onto the photocathode. Once calibrated, this
setup provides a convenient check of the photocathode quantum
efficiency. The mirror cassette procurement continues, a large
number of vacuum components needed to make the bodies arrived
this week. The bids for the linear stages closed last week with
the award given to Aerotech. Receipt is expected in 8 weeks.
Procurement of insertable dump hardware began this week. We worked
with I&C and Software personnel to resolve minor problems
with the drive laser controls when the IOC was moved to FELSRV;
this happened fairly smoothly.
The cameras monitoring the FEL optical transport system mirrors
were assembled in their holders, installation will happen next
week. The optics for the relay telescope were also cleaned this
week, in preparation for the installation.
We hosted a visit on 9/23 by D. Denton and A. Ogloza from NAWC
China Lake. They, along with members of their group, have been
doing metrology on our cavity mirrors. They toured the facility,
and held meetings with the FEL optics group on plans for completing
metrology for our 5 and 3 micron mirrors, as well as getting cavity
mirrors for high power operation at 6 microns. We also sought
their advice on cavity optics for the R5 upgrade.
Commissioning/Operations
Procedures and test plans for starting up the photocathode gun,
rough setup of the injector, and setup of the 10 MeV injector
dump were polished and posted on the www at http://www.jlab.org/~legg/procedures/Injector_setup_proc.pdf.
The impact of off-normal performance of the injector and full
linac is under further consideration because the respective electron-beam
energies affect procedures for RF phasing and for setting up the
electron-beam transport system. In particular, performance of
the injection/extraction (DV) dipole magnets is sensitive to the
cryounit performance. We are pondering how to maximize the variability
of the beam-transport system for "5 mA, 42 MeV" performance
in view of uncertainties in the ultimate linac performance. There
is less, but not negligible, concern with "1.1 mA, 38 MeV"
first-light beam.
The major commissioning activity of the week has been preparing the gun for extracting electrons off the photocathode. The high-voltage system was completed and tested, including installation of the elbow leading from the stack to the gun. The first attempt to put voltage on the gun occurred Wednesday evening (24 Sep 97). It took only 10 minutes to reach 300 kV, but at that point a large arc occurred, frying one of the G10 supports for the inner conductor in the elbow. The support was replaced and a second attempt was made Thursday evening. That attempt was successful -- the gun reached 420 kV in just 3 hours of processing. Radiation outside the roll-up door to the truck ramp leading into the accelerator vault was measured during the test. This door is presently unshielded until installation activities are complete. Consequently, we are commandeering some portable shielding for the door, and we will subsequently install a boundary rope at the head of the truck ramp to warn of potential radiation. We are prepositioning Lab resources to help with radiation protection during the upcoming cryounit and cryomodule commissioning.