MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report Feb. 10-14, 1997
Date: February 14, 1997
Management
Draft presentations for DOE-BES Review on Feb. 24 were prepared
and reviewed by Jefferson Lab management. Briefing material for
the review was distributed to the external reviewers and observers.
As part of the preparations, preliminary estimates were prepared
for the IR Demo after the commissioning period. A draft Field
Work Proposal for FY98-99 support of the IR Demo User Facility
was forwarded to the DOE-BES Program Office for comments.
At this week's SPIE Conference on High Power Lasers in San Jose,
G. Neil presented a talk on modeling of the optics for the IR
Demo. M. Shinn gave a status paper on the IR Demo Project. Related
papers were given by J. Albertine, J. Cook, A. Todd, and M. Kelley.
On Friday, 7 Feb., C. Bohn presented a colloquium at the Naval
Postgraduate School entitled "Collective Effects in Electron
Beams for High-Power Free-Electron Lasers" and participated
in discussions of a tutorial nature on coherent synchrotron radiation
(CSR). The following Monday, 10 Feb., Bohn attended a meeting
at SLAC concerning research and development for the Linac Coherent
Light Source (LCLS), where he presented a talk entitled "Survey
of Jefferson Lab's IRFEL and Coherent-Synchrotron-Radiation Studies".
CSR experiments planned for the IRFEL are also of high interest
to the LCLS, as was highlighted in discussions at the meeting.
In view of the additional delay in producing a new ceramic stack
for the gun (mentioned below under "Injector Test Stand"),
we renewed consideration of a deferral of all 10 MeV experiments
to the FEL Facility. Were we to do this, we would be able to
do gun development through 1 Jun. 97, as well as thoroughly test
the injector's cryounit without beam, and then commission the
full injector with beam starting in Aug. 97. This would preserve
the milestone of installing all hardware in the Facility by 30
Sept. 97, and in fact would relieve some stress on the Laboratory's
labor resources in achieving this milestone. It also would enable
us to improve greatly our confidence in the photocathode gun.
The principal disadvantages of the deferral are delays in commissioning
and debugging some components of the injector hardware with beam,
though at present this is regarded as not being a particularly
troublesome concern. Deliberations on the matter are continuing.
The performance measurement reporting system for the project was
reviewed in preparation for the January monthly report. Using
the secondary peg points with dollar values below the previously
reported primary peg points ($100 K or more in value) significantly
improved the cost performance data for the project. A previously
reported negative cost variance was an artifact of taking credit
for only primary peg points.
Injector Test Stand
We turned on the gun, producing low power electron beam at 250
keV, and began commissioning the new experimental beamline. We
checked out the magnets, drive laser, diagnostics and rf systems,
and we also completed hardware checkout of the new diagnostics,
light-box harp, and aperture. Software checkout is in process.
Using both rf and beam-based measurements, we recalibrated the
harps after reinstallation, as well as the rf system for the kicker
cavity that enables measurement of longitudinal bunch properties.
Regarding upgrading the photocathode gun:
* Coated Cathode-Support Tube - We are expecting to receive the
coated tube from FM Technologies today (14 Feb.).
* Ion-Implanted Ceramics - After coating a ceramic via ion implantation
using half as many pulses as in the original test ceramic, Lawrence
Berkeley Laboratory tested its resistance and found that they
overshot the minimum resistance by a factor of ten. Consequently,
they are going to modify the rotisserie to enable continuous monitoring
of the second ceramic's resistance during implantation. They
also will use a new supply of platinum for this coating. In parallel,
they will apply a diamond scrub on the first ceramic to remove
the implantation and ready it for a second try. The net result
of these developments is another one-week schedule slip.
Preliminary review of the uniformity test readings on the test
ceramic yielded a moderately uniform grading along the length.
Regarding other ITS activities:
The upgrade of the ring-resonator test stand (for testing warm
ceramic windows) to improve its vacuum was completed. Today (14
Feb.) we are in process of commissioning it, and we have NASA
visitors on site to support us with diagnostics for infrared imaging
of the warm windows that will yield thermal profiles during testing.
Testing of two new warm windows in the refurbished test stand
is now in process in conjunction with commissioning of the test
stand. If commissioning the test stand goes well and the windows
successfully pass their acceptance tests, the schedule for testing
the injector's cryounit is as follows:
19-20 Feb. 97 Install warm windows
21 Feb. 97 Insert U-tubes for transferring liquid helium
24-27 Feb. 97 Cool-down
28 Feb. - 3 Mar. 97 Superconducting radiofrequency commissioning
6-7 Mar. 97 Radiofrequency commissioning
Accelerator Systems
Regarding the beam-transport system:
Measurements on the prototype dipole magnet were curtailed while
the technique of reliably bonding mu metal and brass to the pole
tips is being developed. By week's end the permanent bonding
to both pole tips was completed. Tests of the effect of the
welds in the beam pipe and the uniformity of the field integral
along the magnet width will now take place.
The geometry of the optical-chicane regions was finalized. It
allows for necessary positioning of the constituent dipole magnets
while allowing for sufficient radiation shielding in front of
the optical collimator.
Corrections to the preliminary prints of the optical-chicane dipole
were finalized. They include corrections for magnetic length,
use of mu metal for field uniformity, simplified stand-off-type
leads , increased width for accommodating end-field rolloff, and
instructions to match the manufacturing method. At week's end
our WBS manager (G. Biallas) was at Northrop Grumman reviewing
these changes with the designers in order to generate the finalized
prints for sign-off. The requisition and preliminary specifications
for these magnets are in Procurement's hands for review and generation
of the procurement documents. Designs of the reverse-bend dipoles
and the 180-degree dipoles continued at Northrop Grumman.
The first article of the focusing quadrupole magnets arrived from
the vendor. It looks good.
Magnet measurements were run on a modified prototype trim-quadrupole
magnet. Preliminary results from the probe rotated at the central
position meet specifications. Multipole results from the probe
moved to the extremes of the width have to be deconvolved to give
a result with respect to the magnet center before full approval
of the design can be given.
The design prints for the differential pump station and the girder
for the injection dipoles underwent checking. Several layouts
of the stands for magnetic elements downstream of the cryomodule
were generated. Designs for the back-leg girder were delayed
pending clarification of the cable harnesses.
An internal review of the IRFEL dumps was held on the on February
5. Several issues involving protection of dumps or the collimator
that are not designed to withstand the full beam intensity or
an odd beam distribution were identified and require further study.
Regarding cryomodule fabrication:
In addition to the warm-window activities mentioned above under
"Injector Test Stand", our WBS manager (J. Preble) visited
the vendor that is fabricating the shields for the cryomodule's
cryostat. Two of the four shields will be delivered on schedule.
The other two will be slightly delayed, but this will have no
impact on the completion date for the cryomodule. In addition,
assembly of the first cavity pair for the cryomodule was completed
this week. An internal review of the IRFEL cryomodule is scheduled
for 19 Feb. 97.
Regarding electron-beam diagnostics:
Twenty-two of the 52 slit arrays have been fabricated for the
multislit transverse-emittance diagnostic. The manufacturer was
concerned whether the machining tolerance they are achieving was
acceptable. After due consideration, we concluded that the fabrication
process is acceptable and asked the manufacturer to continue.
The vendor advises that all of the remaining arrays should be
complete by 28 Feb. 97.
Procurement of VME boards from Argonne National Laboratory for
the Machine Protection System (MPS) are on order. These boards
are the heart of the FEL's MPS system.
FEL Systems
Wiggler
On schedule for the projected delivery date.
Optics
The diagnostic spectrometer has arrived. The drawings for the
mirror can were signed off and forwarded to procurement. Multiple
crates of spare optics donated by the Navy arrived this week and
were inventoried.
Operations/Commissioning
Activities in this area were focused on considering the impact
of an alternative plan for injector development that defers all
10 MeV experiments to the FEL Facility. A brief synopsis of the
current thinking is presented above under "Management".
Facility
Final drawings of the FEL Facility's basement cable tray arrangement
and installation were signed and distributed.
The initial survey of the alignment network for the IRFEL was
completed. We are now in the process of orienting the alignment
network with respect to key reference points in the building.
Placement of the slab in the mechanical equipment room was completed
30 Jan. Placement of concrete for the loading-dock apron and
an equipment pad on the south side of the Facility was completed
last week. The structural steel for the lobby area at the entrance
has been erected. However, the contractor has been slow in erecting
structural steel for the remainder of the second floor due to
weather conditions and steel fabrication errors.
Clean room bids were technically reviewed. Recommendations will
be forwarded to procurement next week. A favorable bid was received
for the high voltage power supply enclosure for the injector power
supply for the IR injector.