IR FEL Monthly Report for June 1997
Navy IR Demo Contract WBS Elements
WBS 1 Project Management
June 1997 was the twelfth full month for the IR Demo project funded
by the Navy.
Management
The IR FEL Demo project through the month of June 1997 has a total
of $6,816k (less SRF and building) of performance scheduled.
The work performed through the current period is $6,221k or 77%
complete versus 84% scheduled. The actual costs accrued through
June totals $7,053k. This results in a schedule variance of -$595k
and a negative cost variance of $832k.
Highlights of the month include the installation of the quarter
cryomodule in the FEL User Facility. The ITS work in the Test
Lab was completed.
The second meeting of SURA's Maritime Technical Advisory Committee
was held on June 9-10. The Committee reviewed the laboratory's
FEL development program, the Navy's interest in high energy lasers
and the potential linkage of these interests. Recent assessments
from ONR have significantly impacted the prospects for FY98 Navy
funding. Although, the ONR assessment was positive with respect
to the broad utility of the Jefferson Lab program for industry
and materials science, the Navy has declined near term support
for laser technology for more general defense applications because
of the current tight budgets and higher priority development programs.
MTAC has recommended that we focus all available FY97 Navy funding
and any potential FY98 funding (which will not be determined until
the end of the current Congressional deliberations) towards commissioning
and operating the baseline 1 kW demo and, as funds permit, initiate
the upgrade program to shorter wavelengths and higher powers.
At the request of Navy program office, revised proposals were
forwarded on June 16 for use of the $3.7M of FY97 DOD appropriations
planned for allocation to Jefferson Lab for July 1997-Sept. 1998
FEL activities.
The Navy Program Office reviewed the status of the ITS experiments
and the cryounit warm window development effort during a half
day review following the MTAC meeting. Criteria for declaring
completion of the ITS tests were agreed upon which allowed start
of the ITS cryounit move to the FEL Facility and the ITS gun move
on June 23. (See ITS report for details.)
A successful Laser Processing Workshop was held on June 25-26.
Approximately 50 attendees representing most of the LPC institutions
participated in the workshop. Accomplishments at the workshop
included initiation of a series of proposals to be developed over
the summer for initial R&D projects with the FEL and planning
by three of the working groups (polymers, metals and microfabrication)
for fit-up of the User Laboratory.
Solarex, a photovoltaic manufacturer, was visited by Jefferson
Lab, Old Dominion University and William and Mary on June 3.
Discussions are underway for collaborative university and joint
research using the FEL and the Applied Research Center.
On June 2, Senator Warner invited representatives of SURA, Jefferson
Lab, and SURA's Maritime Technical Advisory Committee (MTAC) for
a briefing on the status of the FEL project and outyear funding
prospects.
Jefferson Laboratory hosted a visit on June 18 from DOE Office
of Energy Research senior management for their review of the laboratory's
institutional plan. The visit included a status report on the
IR Demo project and a tour of the FEL Facility.
WBS 5.0 Instrumentation & Controls
Beam Instrumentation: The BPM electronics are being prepared
for installation. Most all of the required pieces are on site;
the RF cable assemblies have been procured and delivered, the
recycled 4-channel electronics have been identified and tested,
and all of the Switched Electrode Electronics (SEE) are ready
for installation. The bulk of the installation activities will
commence after the July shutdown of the CEBAF accelerator July
17. The M56 path length cavities have been delivered for frequency
checking prior to brazing. The drive electronics for these cavities
are ready for installation. The 13 back leg BPM's have been mounted
to the girders and are in the tunnel. The Happek interferometer
is still scheduled for testing at Vanderbilt in mid-July.
Safety Systems: The Oxygen Deficiency Hazard (ODH) system was
successfully commissioned and certified prior to the cool down
of the quarter cryomodule. The remainder of the Personnel Safety
(PSS) remains on schedule for completion on or before Aug. 15.
The Machine Protection System (MPS) design review was postponed
until after the July shutdown. Fabrication continues on MPS subsystems.
The access control and laser safety system was installed in the
drive laser clean room. The preliminary design is complete for
access control using smart cards for FEL and user access to labs,
high power optics control room, and for the drive laser.
Controls: The Injector Test Stand (ITS) server computer was moved
to the FEL building; this will be used to bring up the drive laser
controls and for RF re-commissioning of the quarter cryomodule.
The Uninterruptable Power Supplies (UPS) for the server computers
did not fit in the CEBAF standard racks; new racks were purchased
from Hewlett Packard. The new racks were delivered late June
and the UPS's were installed. The main servers will be installed
in July and be run for two to three weeks to demonstrate stability
of the new auto redundant configuration prior to full operation.
The three networks are up and operational. The Central Helium
Liquifier (CHL) has a separate direct fiber optic link for control
for the cryogenics systems, this along with the power from the
CHL should prevent any problem local to the FEL building from
crashing the CHL. The controls network hub was setup and installed,
all of the cabling is in place but not completely terminated.
This network will be used for running both the final redundant
servers and the temporary ITS servers along with all of the IOC's.
The CEBAF LAN cabling is also complete but not yet terminated.
A temporary hub has been installed for operation of this network.
This enabled the use of local PC's and printers in the building.
The software group continues to make progress, most of the sub-system
requirements and channel assignments have been turned over.
Vacuum Controls: The vacuum system control crates are being fabricated
on site at CEBAF. There are two crates to handle the entire machine,
these need to be in prior to the SRF commissioning of the quarter
and full cryomodule in August. The ion pump power supply control
cards are being fabricated on the outside, half of the required
PCB's have been shipped, these will be tested following the July
shutdown.
DC Power: The first shunt regulator has been installed in the
FEL. The box power supplies (salvaged from a CEBAF energy upgrade)
were removed from CEBAF, one will be used in the magnet test stand
for now and the other will be moved to the FEL in a couple weeks.
The trim cables (power supplies to junction box) were installed
but not yet terminated.
WBS 6 Cryogenic Distribution
Transfer lines finished, purified and ready to cooldown. Cooldown is scheduled to begin 7/7/97.
All necessary U-tubes and other support systems ready.
WBS 7 Beam Transport
The first optical chicane dipole magnet was successfully assembled.
Reverse bend and 180 degree cores continue in final machining
while the injection/extraction dipoles are almost-complete.
All injection/extraction dipole coils are complete, as are most
reverse bend coils. Tooling for the last and most complex dipole
coils (for the 180 degree dipoles coils) is being prepared for
winding in early July.
We signed-off and are bidding the Panofsky trim quad. Sextupole
cores and coils remain on track for a delivery on July 8.
In the corrector area, four styles are in design. Three styles
(four units of each required) are being made with mu metal cores.
A remaining style, a nested horizontal and vertical air core
coil set is being used for all 26 BPM and 2x4 chamber locations.
We will utilize this construction method for the remaining style
that will be a more uniform field replacement for the 5 positions
we had originally assigned to Haimson correctors.
In the vacuum system, substantial progress was made in setting
up the fabrication processes for welded chambers with three welders
being trained. More formalized welding and cleaning specifications
were signed and the X and Y chamber bodies were completed.
General design effort concentrated on the remaining arc stands
and the stands, vacuum pipes and shielding stands associated with
the dumps. Of the remaining two vacuum related components required,
the insertable dump was signed off and the three units placed
in fabrication while the design of the beam scraper started.
The shunts for adjusting magnet strengths in the dipoles strings
were completed and are being calibrated while the European vendor
making the two major power supplies that are not on hand (for
injection and extraction dipole strings) is projecting an early
September delivery if we authorize air freight.
Overall summary, dipole measurement, chamber welding and correctors
are on the critical path.
WBS 8 RF Systems
The high voltage power supply gas filled transmission line elbow was placed for fabrication. Promised delivery in 30 days.
The gun power supply high voltage multiplier stack was mounted
in the tank, and measurements taken to make modifications to the
P.S. support arm. The modifications were made, and we are preparing
to re-mount the multiplier stack in the tank.
Hipotronics has still not completed the acceptance test on the
klystron power supply. It now looks like possibly the second
week of July.
We made several operational tests of the magnetostrictive tuner.
We were able to easily lock the frequency in closed loop. The
system was very stable. We noted however that the tuning range
was very limited (a fraction of a bandwidth )
Hosted ALS group who are investigating the use of a 1.5 GHz cavity
for bunch lengthening in the ALS. Possibility of using CEBAF
or BNL cavity design with a CEBAF type RF system.
WBS 9.2 Injector Move
With the shutdown of the Injector test stand, good progress was
made in moving major components of the injector to the new building.
The crane rail was installed and tested. All stands located
after the cryounit were installed and aligned. The stands located
before the cryounit were all installed. The cryounit and gun were
moved into the injector pit. One 50 kW klystron and HPA, the
buncher klystron and HPA, and the low level racks were all transferred
to the klystron gallery. The clean room for the drive laser was
completed except for some punch list items and certification.
The laser safety system, the optical bench, the laser, its chiller,
and its control electronics were installed in the clean room.
The new mirror cans for the drive laser optical transport were
designed and in check by months end. All components for the high
voltage tank were ordered and progress was made towards installing
the high voltage power supply in the tank.
WBS 9.4 Wiggler
The wiggler girder assembly was completed and the girder was given
to alignment for fiducialization and alignment. The alignment
crew discovered some problems in the quadrupole girders which
were then modified. High quality tubing for the the wiggler vacuum
chamber was made and test welds of the tubing were made in an
effort to find the best way to weld the tubing. The supports
for the vacuum chamber were received.
WBS 9.6 Optics
It was an extremely busy and productive month for FEL Optics.
The optical cavity assembly parts went through the initial UHV
cleaning procedure fairly rapidly, then got stalled when concern
for particulate levels was raised. A procedure was ironed out
late in the month, and the parts are now being cleaned again.
We hope to have the cavities assembled in the building bythe
end of next month. The sapphire mirrors from Research Electro-Optics
(REO) and the calcium fluoride mirrors from Rocky Mountain Instruments
(RMI) were received. The RMI optics were sent for metrology tests,
and appear to have failed to meet the ROC spec. We have returned
them to RMI to verify these results, then we will determine a
course of action. The REO mirrors arrived too late in the month
to have results for this report period. The optical tables that
the cavity components are on were moved downstairs and onto their
supports. They are being aligned. We tested the indium braze
used to heat sink a calcium fluoride window (simulating one of
our cavity mirrors) to it's copper holder. This worked well with
uncoated substrates, but coated substrates cracked during cooldown.
We believe we can prevent this by cooling more slowly; this will
be tested next month. The Brewster window pickoffs (one plus
a spare) that are used for laser output monitoring were received
and passed inspection. They are being cleaned for vacuum service.
We have tested various cameras for electron beam diagnostics.
We determined the best pellicles to use for monitoring alignment
should be highly reflecting, as expected. The Mach-Zehnder interferometer
was mounted on the optical tables in the FEL building and measurements
indicate a relative change in separation between the two optical
tables of about +/- 60nm. The fundamental frequency of the oscillation
is ~28-29 Hz. While the amplitude of the vibration will not impact
performance, we are still interested in determining the cause,
and will investigate it.
The mirror can order was completely received and inspected. The
mirror can stands were received, but some were sent back to be
reworked. This was done, and we are ready to begin installing
mirror cans once the anchors are set. We received parts for the
optical collimator, such as the 3" molybdenum mirrors. Drawings
for the output Brewster windows that transition the beam to the
user labs were signed and released.
ITS drive laser
This marks the final report of drive laser operation in the ITS.
This month the drive laser was operated for over 280 hrs in support
of gun experiments. The power output was stable over this period,
with further increases in performance when the metal pump volute
was replaced with one made of PVC. The overall extinction ratio
of the EO modulators was deemed "very good' by the operators.
They also appreciated the ability to remotely control the DC
bias on the modulators. We have noted "ringing" of
the micropulse amplitude when long (e.g., 1 ms) macropulses are
created. We are working with the vendor to determine the nature
of this behavior and remedy it. The laser was shut down and moved
to the new Clean room on 30 June. We will begin operations as
soon as utilities are completed.
Injector, SRF, Facility, and Other
Activities Outside Navy IR Demo Contract
INJECTOR TEST STAND
Both the gun and cryounit were moved to the FEL Facility this
month after completion of extensive testing. Consequently, this
will be our last monthly report on the ITS.
Prior to moving the gun, we completed the planned measurements
of bunch length and longitudinal emittance, obtaining a complete
set of "good" data for 10, 60, and 135 pC bunch charges.
Although we still need to analyze the totality of the data carefully,
preliminary indications are that they agree very closely with
the predictions of simulations (PARMELA).
At high bunch charges, we detected scraping of the outer parts
of the beam on the light box at the exit of the gun, and we also
tended to see a relatively rapid degradation in the photocathode
lifetime. In view of these observations, we did an experiment
to measure the influence of dark current on photocathode lifetime.
Our goal was to try to eliminate this as a possible cause. The
net result is that there was no obvious dependence of the cathode
lifetime on whether the high voltage was on or off, nor on the
solenoid strength. This means that something other than the bad
effects of field emission or the simple presence of high voltage
on the cathode was shortening the photocathode lifetime. Whatever
was doing the damage was associated with electrons being emitted,
and the decay was likely determined by where these electrons went.
It is conceivable that things will be better in the FEL injector,
wherein the beam will go through the cryounit as opposed to directly
into a nearby dump, as long as there is no significant scraping
along the way.
Assuming identical performance of the gun after it is installed
in the FEL injector, we anticipate the photocathode lifetime is
sufficiently long to support all commissioning activities through
first light, but it is insufficient to support commissioning for
full-power performance. However, this assessment might prove
to be mitigated by a dearth of statistical results on photocathodes
and by removal of the dump that was located relatively near the
cathode in the gun experiments. We will learn more when we begin
turning on the injector, and we will naturally acquire more statistics.
Off line, as part of the nuclear-physics program, we will also
learn more about cathodes other than GaAs that may prove beneficial
in the FEL gun.
Prior to moving the injector cryounit to the FEL Facility, we
completed testing its waveguides with forward power limited to
10 kW. Test results verified that the ceramic warm windows will
support planned commissioning of the IRFEL all the way through
first light with head room available. We also did a first test
of the magnetostrictive tuners on the cryounit. These tuners are
designed for compensating the modest frequency shifts that will
result from electron-beam loading during turn-on of the injector,
which is a relatively slow process. The tuners have a bandwidth
of 0.3 kHz. We found that we could successfully drive and lock
them over their bandwidth, thereby validating their operability.
WBS 3 - CRYOMODULE
Warm Window
Work continues on three warm window efforts. The existing window
design is being supported with studies on ceramic performance.
The intermediate firing process has been eliminated as a source
for degradation of ceramic performance. Excessive ceramic heating
is a property of the initial material state and appropriate ceramics
have been identified and procured to support window fabrication.
Windows are in fabrication at this time. Additionally the Northrop
Grumman window design is nearing prototype completion. Final
flange parts are in fabrication at a local machine shop and are
scheduled for completion in early July. Fabrication will continue
with in house brazing of final components. The third design has
been progressing with finalized calculations for RF performance
and mechanical designs are progressing. Material has been ordered
for prototype flange components. Additionally e-beam weld parameters
have been developed to support potential flange design fabrication.
Cryomodule
The third cryounit has been delivered to the cryomodule assembly
area and is waiting for cryogenic piping and beam pipe installation.
The fourth cryounit is progressing with extremely good progress.
Schedule is continuing to be made up in the cryounit assembly
area. The cryomodule installation schedule for 4 August is still
being supported and should be accomplished.
WBS 2 -- BEAM PHYSICS
Follow-up studies with the simulation code PARMELA were started
to support an investigation of the source of scraping in the light
box of the photocathode gun (mentioned above in the "Injector
Test Stand" section). Thus far, identification of the source
of scraping remains inconclusive.
Simulations of the electron beam from the photocathode to the
wiggler proceeded. They were designed to include the last revision
of the gun in which the cathode-anode spacer is inserted, and
to integrate the ensuing electron-beam dynamics with the capabilities
of the diagnostic hardware that is being installed. Simulations
will continue toward determining sensitivities to machine settings
as they relate to bunch charge.
An initial test plan for coherent-synchrotron-radiation (CSR)
experiments was devised. Sustaining these experiments early in
the commissioning process should not be a problem, even at 135
pC/bunch, because they will be done in pulsed mode, i.e., at low
average current. If the software is available, we will try to
augment the measurements with phase-space tomography.
We made noteworthy progress on self-consistent N-body simulations
that include CSR. The simulations incorporate Gaussian macroparticles,
as opposed to point particles, to eliminate numerical noise.
The key ingredient is a correct calculation of the interaction
force between macroparticles, and we have developed what appears
to be an efficient algorithm for this calculation. To benchmark
the algorithm, we simulated the dynamics of the Gaussian rigid-line
charge using macroparticles and checked to see if the code replicated
our analytical steady-state wakefield, and it rapidly did so with
only 40 macroparticles. Having thereby established the validity
and efficiency of the algorithm in one dimension, we are moving
on to two dimensions. The force is correspondingly more complicated,
but the ingredients of the algorithm remain unchanged. Although
it remains to determine the speed and efficiency of the calculations
in two dimensions, the prognosis for having a self-consistent
simulation tool available in the next few months is good. Of
course, our intent is to use it to predict more accurately emittance
growth in the bends of the transport lattice of the IRFEL and
correlate the results with those of the planned experiments.
WBS 4 -- IRFEL COMMISSIONING/OPERATION
The principal focus of this month's commissioning-related activities
was on assimilating results of the experiments in the Injector
Test Stand and advising on the content of the ITS experimental
program. Key consequences of these activities are documented
above in the "Injector Test Stand" and "Beam Physics"
sections, to which we refer the reader.
There was considerable interplay between our lattice designer
and magnet engineers to assess the relative importance of various
manufacturing complications involving the mounting of mu-metal
sheets in the reverse-bend dipole magnets. The complications
were eventually resolved at the vendor, and so the dipole magnets
are being built per their original design.
A concerted effort is continuing toward establishing the design
of the weak-field corrector magnets to aid in commissioning.
We are planning to use mu-metal correctors in the eight high-aspect-ratio
positions in the recirculation arcs as well as for the four phasing
positions near the 180-degree bend magnets. However, this is
subject to verification that the mu-metal does not saturate in
the presence of fringe fields from the adjacent magnets. An experimental
technique was devised to measure cross-talk between sextupole,
trim quad, and mu-metal corrector magnets, and the experiments
are planned into the overall program in the Magnet Test Stand.
As regards the remainder of the corrector magnets, three-dimensional
magnet modeling is underway to establish their conceptual design.
At month's end, indications were that air-core correctors could
be designed to provide the desired 1% field flatness, and that
they would be relatively easy to fabricate.
We decided on the hardware for the magnetic-field-measurement
probes for the dipole magnets. The probes are off-the-shelf,
obtained from Rawson-Lush Instrument Co. They have very good
absolute measurement and good reproducibility. However, they
do present a challenge in that the probes are much larger than
a normal Hall probe, and mounting them in the tight magnets will
be difficult. We believe the difficulty is manageable.
At month's end, an effort was underway to ascertain whether the
tight alignment tolerances on the quadrupoles immediately preceding
the wiggler could be met by way of the conventional Jefferson
Lab alignment procedures. Specifically, residual twist, yaw,
and pitch in these magnets are potentially of concern. We are
modelling the effects of these possible alignment "errors"
on the beam leading to the wiggler to obtain a more refined specification
on alignment tolerances and/or a methodology for achieving them.
Facility
The building was effectively completed this month. While there
are a few touch up areas remaining (especially outside landscaping),
the building is complete in its functionality with only minor
exceptions such as the elevator. Even that is within a few days
of completion. The contractor will be on a punch list starting
in July. Specific work this month included the following:
Drywall work was completed everywhere. HVAC units were turned
on and balanced. The system is fully operational. Plumbing fixtures
were installed. Bathrooms are now functional but some touchup
remains. Tiling was completed in the labs, gallery, downstairs
and in the bathrooms. The cryogenic lines were hooked up to the
CHL and began circulating gaseous helium in preparation for LHe.
LCW and instrument air pipe welding on the walls continued. Safety
systems equipment made major progress in getting things ready
to go. ODH sensors are already activated in preparation for LHe
operation. RF staff moved ITS racks into the FEL building after
the ITS shut down. Hookup and checkout has begun. A large number
of workbenchs were placed in the building as were equipment cabinets
and electronics support equipment. The elevator installation was
completed except for a punch list. The optical tables for the
accelerator vault were placed on stands and initial survey performed.
They need a slight shift to bring them into position. Vibration
levels were measured and determined to be insignificant. The photo-injector
clean room was hooked up to electricity and HVAC. It was cleaned
and the optical table, electrical rack, and coherent laser installed.
It will soon be operational. The high voltage power supply installation
into its tank began.
All of these efforts successfully brought the building construction
effort to a point were the facility can support all activities
needed to get the FEL installed and operational. The major tasks
now shift to Jefferson Lab staff to bring the systems to completion
in the next three months. We are on track to do that. The closeout
negotiations with the contractor will begin shortly.
Upcoming Meetings and Reviews
International FEL Conference, Beijing, August 18-22, 1997
SURA Science and Technology Review, Sept. 16-17, 1997