To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report, March 24-March 28, 1997
Date: March 28, 1997
Management
IR Demo Project activities this week included replacement of the
HV stack assembly in the FEL gun and the placement of the first
equipment (including RF and DC power racks) in the second floor
of the FEL facilities.
Continuing our preliminary planning of the technology needed to
upgrade the IR Demo to the 10 kW range, we have surveyed options
for upgrading the injector cryounit to handle the required higher
currents. Several options are available for using or modifying
500 MHz cryounits that were designed for Cornell, DESY or KEK.
We are also exploring the available options for modelling electron
beam transport in high acceptance lattices.
Jefferson Laboratory hosted a workshop this week (March 26-27)
on "Contamination: its measurement and control in vacuum
systems". The attendees (85) came from the accelerator
and microelectronics communities and the supporting industries
that supply related vacuum and contamination control equipment.
The purpose of the workshop was to look for solutions to common
contamination problems that limit the performance of state-of-the
art microcircuits and accelerator structures. The workshop was
judged a success by the attendees. As a side benefit, we were
able to use the workshop to discuss the most recent results on
SRF cavity R&D with colleagues from the SRF groups at the
DESY, CERN, Saclay, and KEK laboratories.
We returned edits to Alan Todd at Northrop Grumman concerning
upgrades to Jefferson Lab's IRFEL for incorporation into the overall
Navy HEL Program Plan that Alan is developing.
Internal discussions started this week to preposition Accelerator
Division resources for commissioning the IRFEL beginning 1 October
1997.
C. Bohn presented a colloquium to the Applied Sciences Department
of the College of William and Mary entitled, "Phase Mixing
and Violent Relaxation in Intense Charged-Particle Beams".
The talk concerned the formulation and application of a theory
of beam dynamics in the presence of nonlinear space-charge forces,
such as will prevail in the IRFEL injector. William and Mary
expressed interest in putting together a joint proposal for possible
submission to the DOE's APT office, or elsewhere, to pursue various
questions about the basic physics that arise in the context of
the theory. Drafting of the proposal has begun.
Injector Test Stand
Regarding upgrading the photocathode gun:
Fabrication of the high-voltage stack was completed. Both the
stack and the coated cathode support tube were successfully installed
despite some annoying interferences due to machining inaccuracies.
As of Friday (28 Mar 97) the gun was under vacuum once again.
A cesium response was obtained on the gallium arsenide disk (which
underwent an atomic-hydrogen cleaning as an alternative for the
previous chemical-cleaning procedure). We stripped the beamline
of diagnostic hardware in preparation for the high-vacuum bake,
and we are working over the weekend preparing to start the bake
early next week.
Progress on the photocathode drive laser consisted of enhancements
to existing diagnostics. We anticipate receipt of a new-style
electro-optical modulator late next week.
Regarding other ITS activities:
One ceramic warm window was installed in the cryounit. Cool-down
is scheduled for Monday, 1 April, with cold testing to follow.
A test stand was developed to qualify ceramics prior to assembling
them into completed warm windows. Qualification of ceramics in
our present inventory will begin Monday, 1 Apr. 97. Window fabrication
will follow selection of qualified ceramics.
Assembly and alignment of the multislit transverse-emittance diagnostic
in the gun's experimental beamline was completed. It is located
in the cross with the existing 50 micron slit, thereby allowing
cross-calibration between the devices. We replaced the beam-viewer
vacuum windows with larger-diameter windows to allow more robust
camera placement and better field of view.
We also installed a computer in the Machine Control Center (MCC) with the capability to do video capture. This will allow acquisition of video signals during the May runs from the MCC.
Accelerator Systems
Regarding the beam-transport system:
Magnet Enterprises International, our contractor for the optical-chicane
dipole magnets, received their copper and began tooling design.
Everson Electric received their allotment of steel to start the
torch-cutting step.
Bids for the reverse-bend dipole magnets and the 180-degree dipoles
are due on Thursday, April 3.
The drawing-and-specification package for the injection-chicane
dipoles was signed off and went out for bid today (28 Mar 97).
We continued to deconvolve the magnet-measurement data on the
prototype trim quadrupole, and we also developed requirements
for bringing the drawing package for the sextupole magnets up
to production grade.
The design process is now underway for the corrector magnets needed
at 43 locations around the machine.
The girder for the Y-chamber connecting the energy-recovery dump
to the recirculation loop was signed off, and design started on
the remaining stands and brackets needed in the injection line.
Bids on previously signed-off stands needed for first light are
due today, and bids for back-leg girders are due next Wednesday.
Multipole measurements on 8 of the main quadrupoles were reviewed
and will be signed-off as qualified upon completion of measurements
for strength characterization. At the same time 4 more quads
arrived and 4 more of the total of 22 were shipped by the vendor.
Design continued on the vacuum chambers for the optical chicanes.
The design package of the vacuum chambers for the reverse bends
is being readied for detail design by Northrop Grumman. Specifications
for vacuum pumps was prepared in preparation for going to our
Procurement Department next week. Parts for the X-chamber connecting
the injection line to the recirculation loop are in fabrication.
Parts for the Y-chamber connecting the energy-recovery dump to
the recirculation loop were sent out for bid. Design of the 180-degree
vacuum chambers is nearing completion. A steam cleaner and portable
clean room were purchased as part of the equipment we will need
for installing the vacuum tubes per our cleanliness standards.
We worked to simplify requirements for the power supplies that
will drive the injection/extraction dipoles. This should increase
the probability for getting on-schedule delivery as well as lower
the price considerably. We may be able to place the order by
next Tuesday.
Regarding cryomodule fabrication:
Assembly of the first of four cryounits for the cryomodule is
on schedule; its cavity pair is scheduled to be inserted into
the helium vessel Monday, 1 April. The second cavity pair is
installed in the Vertical Test Assembly (VTA) and is to be tested
next week. The third cavity pair will be tested in the VTA following
completion of testing of the second pair. The fourth pair is
scheduled for assembly next week.
Alignment-tooling drawings for the cryomodule have been signed
off, and material is on order for fabrication.
Regarding electron-beam instrumentation and controls (I&C):
In addition to installing the personnel-safety-system box duct
and about 30 I&C racks in the FEL Facility, we procured the
balance of the charge-coupled-device cameras and lenses required
for FEL diagnostics. Design and documentation of the vacuum control
system is complete and awaiting review. Preparations continued
for the Personnel Safety System/Laser Safety System Review scheduled
for next week (1-2 Apr. 97).
FEL Systems
Wiggler
STI Optronics received the final magnets from Shin-Etsu. They
plan to measure them next week and assemble the wiggler by 4 Apr.
97. Final-certification measurements are scheduled for 28 Apr.
97 with delivery of the wiggler the following week. The layout
design for the wiggler's vacuum- chamber stand is complete. We
should have detailed drawings to check next week. The optical
bench for the wiggler and 90% of the other wiggler-support components
have been received. Assembly will begin next week.
Optics
As is summarized below under "Facility", most of the
optical transport pipe was hung in the accelerator enclosure of
the FEL Facility.
Several parts for the optical cavity assembly were not built properly,
and are being rebuilt. The Mach-Zehnder interferometer we are
considering for cavity-length monitoring was moved to the Test
Lab and set up with a 16 m round-trip path length. Even with
vibration from the HVAC, it appears to be stable enough to work
properly. Tests are slated to begin next week.
Operations/Commissioning
Possibilities for improving the rf-phase-reference system of the
photocathode drive laser were developed. The objective is to
reduce the laser's high root-mean-square phase error. The circuit
is observed to oscillate at around 800 Hz, corresponding to the
second pole in the system. Plans are, by 22 April 1997, to decide
on a set of experiments to try to solve the problem.
In addition, we began to organize the experimental plan for the
ITS during May. The "MUST" for this run is to measure
transverse and longitudinal emittances, as well as bunch length,
at bunch charges of 1 pC, 60 pC (corresponding to first light),
and 135 pC (corresponding to full power). In addition, a series
of photocathode-lifetime tests are planned, as well as possible
experiments at gun voltages exceeding 350 kV. Dates have been
set for 24 hour operation in the ITS.
Facility
Even monsoons on Wednesday didn't slow a week of rapid progress
on the building. Most contractor effort is now complete downstairs
with only touch-ups and punch-list items remaining. The principal
downstairs accomplishment this week was the installation of rails
around the injector and wiggler pits. Work by Jefferson Lab crews
included hanging the optical transfer line except for one spot
of interference with the sprinkler lines. It still remains to
complete the welding of the optical transfer line, and keep-out
zones were established for the optical transfer line. Welding
and leak-checking of the cryogenic transfer lines continued on
schedule. Progress upstairs was substantial with electrical and
plumbing installation continuing all over the Facility. By the
end of the week conduits and rough plumbing in the east end were
80% complete, and roof drains more than 50% complete for the whole
building. Studs were placed around the entire perimeter of the
second floor. Exterior wall panels covered the west end and were
proceeding down the south side of the building. HVAC duct was
hung, 90% complete. Interior stud bases were attached to the
concrete for 50% of the walls, and work commenced on interior
studding. Before the exterior studding was finished we took advantage
of the easy access to move equipment to the second floor by forklift.
We placed over 35 electrical racks upstairs including low-level
rf controls, trim magnet supplies, diagnostics racks, the high-power
rf amplifier, and a high-voltage rf power supply. Work commenced
on fitting the rf waveguides into the penetrations. We also set
two workbenches in the area and moved the WSMR optics into the
Navy lab for temporary storage. Modifications were made to the
placement of interior electrical transformers to provide better
access for maintenance, and a storage cage was ordered for tool
security. Phone-line installation was ordered.
An on-site review for the FEL Facility clean room is scheduled
for Wednesday, April 2. Design work for the ancillary components
of the high-voltage power supply is started.