FEL Upgrade Monthly Report
December 2000


We made further progress with harmonic conversion of FEL light to green and deep UV light.  See the Operations section of this report for further details.  A draft version of the accelerator driver design (Version 1.1) was


A meeting was held with the DOE Contracting Officer and the ONR Contract Monitor, which led to the completion of a draft Memorandum of Agreement (MOA) and Statement of Work (SOW) for the FY 01 completion phase
contract for the FEL upgrade.  We sent out announcements and made preliminary plans for next month’s
Laser Processing Consortium/FEL User’s Workshop on Jan.18-19.

Project Cost Performance:

The project budget for the period June 1, 2000 to Sept. 30, 2001 is $9,029k. The project through the month of December has a total of $2,137k of performance scheduled (assuming the project started at the originally planned start
date of April 1, 2000).  The work performed through the end of December was $2,365k, which is 26% complete vs. 24% scheduled.  The actual cost accrued through December totals $2,469k.  This results in a schedule variance of +$228k and a cost variance of -$103k.

WBS 3 (Beam Physics):

A draft Revision 1.1 IR Upgrade machine design was completed and is undergoing performance evaluation studies. This revision uses "best knowledge" values for initial RF gradients (final energy of 145 MeV suspected) and consequently employs an enlarged injection condition (bx,y~10 m, ax,y=0) at 10 MeV (to compensate reduced focussing along the linac) and asymmetric reinjection conditions at full energy (for similar reasons). The machine is slightly wider and shorter and uses slightly different main dipole angles than the Rev 1.0 design. This allows both
additional space for correction packages in the end loops and allows future integration of additional FEL transport lines (such as the UV) through use of preexisting dipole designs. A proposal by W. Colson, NPGS, for accelerator physics and FEL studies was evaluated and was funded.

WBS 4 (Injector):

We completed field emission tests on titanium electrodes in the Field Emission Test system up to 20.83 MV/m. Emission at 20 MV/m on a 6mm gap was 84 nA.  The titanium has preformed better than stainless steel but
still not nearly as well as the nitrogen implanted stainless steel, which remains our choice for the gun electrode in the upgrade gun.

WBS 5 (SRF):

A current status report on the cavities for the new cryomodule: The second and third production cavities are completed,
The first cavity is currently being tuned.  Cavity 4,5 cells are pressed and are waiting to be trimmed before EB welding.  All flanges are machined.  All Beam tubes have had the nipples pulled for HOM tubes and are in chemistry for cleaning.  A copper seven cell has been setup to start HOM measurements and two HOM (copper) prototypes have been completed.  The first two Helium vessels have been received from the vendor and are under going QA.

WBS 6 (RF):

Zone 4 - Completed preliminary checkout of the HPA and its interlocks.  Software has been written to test the zone.  As soon as the LCW is restored to the FEL, RF testing will start.
 Zone 3 - The documentation is being updated as a result of the problems found in zone 4, so zone 3 should come together quickly once parts are available.

WBS 8 (I&C):

The Optical Beam Position Monitor (OBPM) has been installed in the End-of-line (EOL) FEL beam dump.  The viewer contract is in progress and the BPM contract was awarded.  Regarding trim magnet control the current
approach is to combine all iron core magnets into the existing trim racks (utilizing the on/off hysteresis loop capabilities) and look for a lower cost bipolar supply for the air core magnets.  This could result in cost savings of $200k (90 air core with <$1k/ch vs. trim rack cost of ~$3k/ch).  Commercial vendors are being consulted.

WBS 9 (Transport):

o We received budgetary estimates for our dipoles.
o  As a result of the magnetic modeling of the DW, we were able to assure ourselves that we could remove 20% of the
    iron in the return legs and top and bottom poles while getting no degradation of the quality of the central field.
    Some additional cooling calculations convinced us that the copper cross section of this and the 180 degree dipole
    should be increased.  These changes were reflected in the 3D drawing model and somewhat automatically flowed
    down to the details being prepared.  Additional GW dipole detailing continued.
o  We ordered for the copper for the GW Prototype.
o  In anticipation of DOE’s approval of the Engineering Services contract, we composed the interface document and
    collected its attachments so that DULY Engineering could productively start the design of the Injection and
    Extraction dipoles (GU &GV).  This document will serve as a model for giving the design of the Arc Bend (UV
    Modified GX) the Reverse Bend (GQ) and the 180 degree bend (GY) to the other contractor.
o During generation of the interface document above, it became evident that the requirements of the original IR Demo
   should be simplified for the upgrade.  These magnets could be cheaper.  New assumptions are:
    • These magnets would not be used to divert partially accelerated, straight-ahead beam to the extraction dump for
    •  The margin of 20% over field could be decreased to 10% (11 MeV)
    •  With the above assumptions, solid magnet wire with plate cooling was substituted in the GU and GV for the
         hollow copper conductor used in the IR Demo.
o  We received additional budgetary estimates for our dipoles and received cost saving construction method
o  Additional GW dipole detailing continued, concentrating on simplifying the bolting and alignment pin features as well
    as making the hoses larger and altering the magnet lead area in response to the thinner yoke material.
Quadrupoles QX (3.125" Quad)
Prototype Fabrication: Almost finished - the four quadrants were mechanically inspected and tolerances verified.
Interferences with the coil mounting were identified and corrected. Core and coils were assembled and the bore was verified to be in tolerance.  Plumbing and coil lead routing is almost complete. Magnet assembly was completed and measurements started.  Reproducibility of the pole tip field was measured with a hall probe and repeated to
+/-0.03%.  The gradient integral was measured with the existing 2" diameter rotating coil and found to meet the design spec.  Measurements will be made over the next few days on the 2" harmonic probe to get a feel for the field quality at the smaller radius.  Final field quality measurements, and the subsequent development of end chamfer modifications, will await the new 3" probe.
Budgetary Estimates:
Several conversations were held with Magnet Enterprises International (MEI) and hopefully they will present a quote shortly.  A lack of response from two other "new" coil vendors is taken as a lack of interest and will not be pursued.
o  Measurement Probe: Fabrication of the second analysis coil using 100-turn litz wire is progressing.  Fabrication of
    the 100-turn litz coil is progressing.  Drawings for the probe body have been signed off and a local shop has been given the job.
o  Comments on the modifications of the Differential Pumping stations to accommodate 3 inch tube were being
o  Dave Douglas notified us that the angles of the return lines in the Arcs are going to get smaller by about 5 degrees
    and that the pole face angles will change as he goes through his conversion of the lattice to an "Engineering" design.
   We are ready to morph the values of the design spread sheet and the available magnet packages to the new values.
o The Engineering Services Contract was signed by the two vendors and is in the DOE Office for approval.

WBS 10 (Wiggler):

Fabrication of the dispersion section is in progress.  A visit to the vendor is planned for the beginning of January.  The drawings for the wiggler viewers were signed off.  The 3D design of the wiggler vacuum chamber support was finalized.
The supplier of Group-3 Hall Probes (GMW) was contacted regarding information on planar Hall effect specifications.  D. Bullard attached the modified pole clamps to one of the wigglers.   Inspection of the gap showed a maximum spread of 0.0025" (spec 0.002".)  This shows that the design is acceptable.  Finished the design of the wiggler viewer optical transport assembly.  All the major design work is done for the wiggler vacuum chamber and diagnostics.  Detailing should be done soon.  This leaves the dispersion section supports, the wiggler cover and the measurement jigs as the only things left to design.

WBS 11 (Optics):

We received bids for the mirror test stand vacuum vessel and the work has been awarded to a local vendor.  Work proceeds at AES on the finite element analyses for the deformable mirror. The drawings for the internals of the mirror test stand are being reviewed.

The optics group had an internal review of the conceptual design of the optical cavity components that was quite useful, these comments are being written into the specifications documentation and being passed on to the ME group as input for our designers.  We also had a discussion on upgrades to the O-BPM system that will make them operate at wavelengths longer than 7 microns.  Two concepts were identified as being promising, and we are assembling hardware to try them.  Discussions were held with the two major vendors of laser interferometers (a diagnostic needed for the mirror test stand).  On the basis of these discussions we will begin the procurement of an instrument.


Beam was run for the Radiation Control group to verify radiation levels.  These measurements showed that the SRF cavities themselves were a source of neutron production. The RadCon group took data to determine whether radiation levels are sufficiently low to allow construction of the Helios addition without additional shielding.  Some FEL 3 micron
beam was also given to the Nanotube research group for a run.  We also ran the FEL for harmonic production studies.  We produced up to 26.6 W of average power at 524 nm using 100 W of IR light produced by third harmonic lasing. We then produced up to 2 W during a 230 microsecond macropulse by doubling the 524 nm to 262 nm.  The overall
efficiency was 5% from the IR to the UV.  The peak efficiency seen for doubling was 37% using a LBO crystal.  The mode quality of the IR was rather poor so the overall conversion efficiency can probably be increased. The micropulse length inferred from the spectrum was 0.5 psec for the IR.  It is noteworthy that we were able to produce the same level of 1 micron power as a month ago in about one hour of tuning.  More optimization is needed on the quadrupling however.  In addition, the fourth harmonic power is exquisitely sensitive to cavity length and cryomodule phasing which will complicate the delivery to users.

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