Highlights:
The Memorandum of Agreement (MOA) that allows us to complete the construction and installation of the FEL Upgrade was signed in January by DOE and ONR. This MOA will allow $4.5M of FY2001 DOD funds to be released to Jefferson Lab for the FEL program. We thank Eli Zimet, John Albertine and Wayne Skinner for their efforts and continuing support of the ONR/DOE collaboration which makes the FEL program possible.
We are also pleased to announce that the FEL program won a $400k grant from the DOD Joint Technology Office to study the effects of femtosecond, pulsed and cw laser irradiation on laser-materials interactions.
Our lattice designer (Dave Douglas) released Version 1.1 of the accelerator driver design to engineering in January. Congratulations to Dave for achieving this milestone.
Jan.18-19 we hosted the Laser Processing Consortium/FEL User's Workshop. Over 75 attendees from the LPC, present and potential FEL users attended the workshop. All seemed to enjoy the reports about FEL results to date and the progress on the upgrade projects.
During the first week of FEL operations for the Winter Run, we demonstrated second harmonic operation of an FEL. Operation of FELs on the even harmonics is considered forbidden by simple theory
Management:
We continued preparation of the cost and schedule documentation for the Phase 2 of the FEL upgrade project which we are planning to integrate with the Phase 1 cost performance data.
We were invited to give a presentation to the
Defense Science Board's panel on high energy lasers on Thursday (Jan. 25)
in Arlington. The talk presented a status report on the kW IR Demo,
the 10 kW Upgrade project, the user program and a brief discussion of the
technical issuers involved in scaling to higher powers. It appeared
to be well
received and we were asked to forward a written
summary of the talk to the committee.
We forwarded a draft statement of work to AFRL concerning the proposed FY 2001 effort for adding UV capability to the IR Demo upgrade.
We are pleased to announce that the DOE Jefferson Lab Site Office received the funding for the second phase of the FEL Upgrade project covering the period from Feb. 1, 2001 until Sept. 30, 2002.
WBS 3 (Beam Physics):
A POISSON model for the gun was resurrected and
is available for gun design modification studies. The pre-release
Revision 1.1 machine design was released to WBS 9 for layout and engineering.
This version nominally incorporates the near-concentric optical cavity,
resolves various interferences, allows additional space for compaction
management elements, supports injection/extraction line geometry providing
the desired beam quality, and uses parts that can be common with the UV
system. It is optimized
for the probable initial operating energy of
145 MeV.
Beam loss power limits for the FEL Upgrade were examined. Preliminary diagnostics, corrector system and configuration were passed to WBS 9-George Biallas. Work began on beamline layout and beam optics design for the Revision 1.1 UV bypass.
WBS 4 (Injector):
The use of the new reverse flow heater on the current wafer gave a uniform QE in the area that has consistently had good QE but lacked uniformity. The portion of the wafer with a low QE failed to recover to a higher level indicating more than a heater issue. The preliminary design for a cathode shield and internal cesiation scheme has been completed for the upgrade gun design. The rate monitor was received and installed in the system for mapping the focused cesiator. The system is being set up for bake out.
Reviewed the internal cesiation and shielding design and decided to keep looking at slightly different scenarios. Reviewed the new gun chamber concept which moves the solenoid closer to the anode and uses increased pumping through appendage pumps. We decided to move the concept forward into design. The second scheme for internal cesiation is ready for review.
Discussions are ongoing with Glassman concerning the need for an additional multiplier stack. R. Walker's circuit simulation did not indicate a significant change in the dissipation of the HV capacitors when the current load was changed from 5 to 10 ma. We are requesting their analysis of the problem in writing.
WBS 5 (SRF):
Jefferson Lab machine shop has completed additional tooling for cavity cell machining which will significantly increase cavity production rate. Helium Vessel vendor, PHPK, has detailed a modification to the helium vessel and will send samples of new welds. All other contracts are on schedule.
Waveguide tooling design has been completed by the vendor. Vendor proposal for modification to design has been reviewed and approved. Thermal shield procurement package has been completed and the purchase request signed.
End Can Technical Review Committee has selected a vendor and award notification is being prepared.
WBS 6 (RF):
The PO to build 16 RF Control Module by an outside vendor has been canceled and brought inside. Requisitions are in progress to procure all of the parts.
Operated all 8 klystrons at 11 kV in Zone 4. Checking 1 klystron for possible problem. RF Control Modules and Arc Detectors may be available in 2 weeks for RF tests.
Injector - Procurement was given the approval from the Technical Evaluation Team to use PSC, Inc to upgrade the Quarter's HVPS's. We are changing our specification to remove the 3 phase variac in favor of multiple taps on the power transformer and a soft on & off controller. This should reduce the cost and save space.
The 100 kW klystrons are on schedule for April delivery. Their HVPS upgrade is scheduled for the following year. We will test them with the present HVPS at reduced power levels.
WBS 8 (Instrumentation):
The major effort is upgrading the entire Laser
Safety System (LSS) to accept the use of an enclosed hutch. This
change will make all labs respond/certify/logic the same. By inserting
and turning a key in the local LSS box one can enable a (multiple) hutch.
Additionally six more monitors were added to the control room dedicated
to monitoring the user labs, this couples with "stop light" status lamps
allow an instant view of all user lab activities. On the individual
user lab doors stop lights were added to inform the user of
the following conditions: RED - NO Access, YELLOW
- Alignment Mode; Goggles Required, GREEN - Authorized users holding a
valid smart card may enter. The alignment mode was enhanced to give
the operator an option of running 60Hz, 10 microsecond macropulses, or
the standard 2 Hz, 250 microsecond macropulses. Both of these activities
were considerable more difficult to realize that the words to describe
them.
Additional video monitors were added in the control room for monitoring the user labs and mirror cans/ beam dumps. Work continues on the optical BPMs. There are four prototypes built for this upcoming run, these will be used with picomotors to create a lock on the optical transport system. The error signals will be used to drive each of the mirror cans to a zero offset. Parts continue to be purchased for the upgrade to the vacuum system. Good progress continues with the 3" BPMs and the 3" shielded beam viewers.
WBS 9 (Transport):
Dipoles
The task of designing the Injection and Extraction
dipoles (GU & GV) was awarded to DULY Research. The task of designing
the UV Modified GX, the Reverse Bend (GQ) and the 180 degree bend (GY)
was awarded to Advanced Energy Systems. Dave Douglas was able to
issue more solid specifications for all the magnets of the engineering
version of the lattice. We worked on making sure there is enough
gap in the magnets to
accept the thick vacuum chambers necessary to
span the wide good field width required by the electron beam as well as
have enough aperture to not vignette the expanding optical beam near the
mirrors.
o DULY’s magnetic analysis showed that the mu
metal pole is a magnetic short if carried to the edge of the return leg
and creates a smaller good field region. When the mu metal is placed
only inside the coils, the good field region expands significantly. We
will search for an optimum point somewhere within the coil bundle where
the good field region is maximized.
o Their analysis also shows that there is a natural
field gradient in the field at the plane perpendicular to the beam at the
center plane of the magnet. This means that the magnet is so narrow
and the gap so big that the end field drop-offs that begin within the magnet
gap are intersecting at the narrow end of the magnet. We discussed
closing the
gap enough at the narrow end of the magnet to
cancel the end effect.
o They suggested the use of permanent magnets
for this application which a simplistic analysis showed has excellent field
uniformity. This could be the basis of an additional task.
o George Biallas discussed designing the First
Reverse Bend, (GX), the Second Reverse Bend (GQ) and the 180 degree bend
(GY) with Advanced Energy Systems.
o The most significant issue with the design
of the 180 degree dipole is the insertion of the path length correctors
into the ends. As specified, at 35,000 G-cm, it is superposing a
1.75 KG dipole (for 20 cm length) on to the ends of a magnet that is 7.5
KG already. This implies adding to the local return leg and pole
tip iron thickness by almost 25%. Since this specified field is for
the worst case of a 180° phase advance at 210 MeV. We agreed
to clarify how the correctors would be used.
o Dave Douglas has formally issued the "cut iron"
engineering version of his beam transport layout to be drawn to check
for interference.
Optical Chicane Dipole (DW)
o We continued to detailing of this magnet with
a small correction to the 3D model to bring it up to the latest requirements
of David Douglas from the Version 1.1 of the lattice.
o We decided that the preliminary way to define
the path length corrector dipole for the GY dipole is to have it produce
a full wavelength of path length correction at 80 MeV, the low end of the
operating range of the magnets (High is 210 MeV). This way,
we will be
able to know where the real ideal path is at
low energy and will be able to move the dipoles to correct the path length
for the high energy cases if the correctors are not strong enough.
As designed, the correctors are robust and we may have to add 2 inches
to the pole pieces locally in order to accommodate their added field in
the iron path when the magnet is run at full field. The definition
of the path length corrector dipole for the GY dipole as providing full
wavelength of path length correction at 80 MeV was approved at the FEL
Upgrade Meeting (Jan. 22) subject to generation of a filled out change
request AES incorporated the GG correctors extra steel and the better way
of building the field
clamps into their drawings of the 180° Dipole
(DY). They are now starting to layout the coil's leads, incorporating
the 4-in-hand winding.
o We designed the coil for the path length corrector
and transmitted the sketches to AES to incorporate in the designs.
o AES did a number of layout sketches on the
180° dipole in order to start looking at its configuration.
o Robin Wines was able to optimize the position
of the edge of the silicone steel (high field replacement for the mu metal
we used for low field magnets. She found the flattest field was obtained
with an edge 1/3 into the coil bundle.
o We designed 4-in-hand method of winding the
coils for the 180° Dipole (DY) and went through it with AES.
o We checked the layout sketches on the 180°
dipole
o We defined the shape, conductor lengths and
return leg thickness of the first dipole of the Arcs, providing the outlet
of the beam to the UV machine.
Optical Chicane Dipole (DW)
o We reviewed the design of this prototype dipole
with the engineer and technician in Magnet Measurement to catch any potential
problems. We found a better way to build the field clams and incorporated
their suggestions in the details. The details are now ready for tolerance
analysis and checking.
o AES started their magnetic modeling of the
GY.
o We determined the shape and size of the First
Arc Bend (GX) with the provisions for UV extraction to transmit to AES
for their future layout.
Quadrupoles
3 inch bore magnets
We evaluate a simpler method of construction
for yokes that was suggested by a vender. When considering the entire
system with requirements for tooling balls for alignment, placement on
the magnet measurement stand and final attachment to the girders, we decided
that the simple method was not so simple after all and would cost the same.
We decided to stick with our present design.
QX (3.125" Quad) Magnets
Measurement Probe: The tube support was annealed
and sent back for final machining.
Trim Quad for the Arcs
Tom Hiatt, and Jeff Karn started forming the
concept of a real magnet from the specifications we received from Dave
Douglas.
Measurement Probe:
The 50 and 100 turn litz coils passed tests for
quality and continuity. The fiberglass plastic parts for the probe body
were cut by the vendor to rough shape and delivered back to us for annealing.
o Roughing of the coil support plate was completed
but an unacceptable bow was found in the material. A clamping fixture
was fabricated to flatten the plate and the clamped unit sent for annealing.
Sextupoles and Octupoles
With the advent of the firm specifications, Robin
Wines was able to start on forming the concept of both magnets using the
literature search a study she performed earlier. We will forgo making
a combined Corrector / Sextupole - Octupole in favor of the more conservative
and easily analyzed Sextupole – Corrector combination.
Path Length Correctors
Dave Douglas was able to give specifications
for the correctors that were just beyond the ends of the 180° bends
in the IR Demo. We envision combining them into the ends of the 180°
bends on the Upgrade, getting the return yoke for free, placing the field
in a more ideal position and freeing up space on the beam tube between
magnets for the Octupoles.
Vacuum
We ordered flanges for the shielded bellows,
the unshielded bellows, and
shield bellows for the vacuum chamber.
o We continued our discussion of beam chamber
dimensions in the arcs and
optical chicane. Since beam impedance has
become a heightened issue, we
are checking our intended chamber design with
the beam physicists.
General
The layout of the engineering version of the
lattice progressed with the addition of preliminary dipole icons and the
redefinition of the configuration of the change in the GX dipoles to switch
out the UV electron beam.
WBS 10 (Wiggler):
Assembly of the final configuration of the wigglers
started this month making up the water manifolds, their mounting brackets
and mounting the new pole tip clamps to achieve the required gap. Tom Hiatt
visited the manufacturer of the dispersion section coils just as they were
about to start winding coils. The steel for the magnet was rough
machined and
sent for annealing. PECO is just starting the
final machining on the magnet poles and has completed the magnet base.
All remaining drawings for the wiggler viewer optical transport and the
vacuum chamber are in check. The drawings for the dispersion section
support are signed off. The order for the wiggler beryllium viewers
is out for bid. Good
progress is being made on the assembly of the
water manifold of the optical klystron.
A rail design for Hall Probe measurements has been started. With buss bars, plumbing, and temperature switches completed, the wiggler was powered to 150 A (close to the max current.) The magnet was left energized for 7 hours for "burn in". Magnetic measurements were made using a hand-held hall probe and it was verified all coil turns were accounted for. It was observed that there is a 60 Gauss discrepancy between positive and negative field pole tip pairs. Steve Benson will explore the best cure for this DC bias field.
WBS 11 (Optics):
We received the final report for our contract
at AES on the deformable high reflecting mirror over the holiday, and have
been reviewing it. In particular, we have to perform a careful check
on all drawings before they can be approved for release. This has
been the major activity that occurred this week. In the meantime,
preliminary copies of the drawings have been sent out for bid. We
have received some of our optical quality standards, as well as more optical
components. With receipt and initial checkout of the deformable high
reflecting mirror design that came out of our contract at AES, we completed
the design of the internal components of the optical cavity mirror test
stand. Except for a few minor corrections, the prints are signed off and
will be going out for bid. We have started the design of the optical
cavity assemblies. So far, it is clear we can switch between three
wavelength ranges. At this time we are trying to make it an UHV
enclosure, so we can carry over the design to
the UV FEL. We installed other O-BPM optics on the upstream optical table,
to monitor the FEL position near the outcoupler, and near mirror can 2,
which is in the vault. We upgraded the optics at the end-of-line,
specifically a larger pickoff wedge was installed, and we changed the optics
for the
ModeMaster and O-BPM to more appropriate sizes.
We received 6 of New Focus' OEM single-channel picomotor controllers, the
very first released to the public. They will be integrated into a new chassis
for control of the mirrors associated with the O-BPM system. The vacuum
installation group swapped the LSS shutter with the "hole harp", an intracavity
aperture for mode control.
Operations/Commissioning:
We achieved second harmonic lasing. This is the first time any group has been able to do this with an optical beam. The interesting thing about this achievement is that a perfect FEL has zero gain on-axis at the second harmonic. Second harmonic lasing of 1.5W at 2.9 microns was achieved in this case by operating in the TM01 mode and taking advantage of finite wiggler length effects. Although of limited practical use, these tests serve to confirm our understanding of FEL physics.
Operations delivered beam for the nanotubes group,
for PLD experiments, for metal ablation studies, and for FEL optical mode
and beam quality characterization studies.