January FEL Monthly 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


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):

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.


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.

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.
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.


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.

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