MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report December 16-20, 1996
Date: December 20, 1996
Management
The first meeting of SURA's Marine Technical Advisory Committee
was held on Dec. 17-18. The committee was given presentations
on the status of the Navy's High Energy Laser Program, the Jefferson
Lab's 1 kW Demo and the MW FEL Workshop. An initial report from
the committee is expected next month.
A meeting was held on Dec. 19 with R. Marianelli (DOE-BB), and
D. Lehman (DOE Construction Project Office) to review the preliminary
agenda and list of potential reviewers for the Feb. 24-25 DOE-BES
review of the Jefferson Lab FEL program.
The top level design drawing for the IR FEL was frozen as of Dec.
20. All subsequent changes will be subject to a change control
process.
Injector Test Stand
Regarding upgrading the photocathode gun:
The College of William and Mary retested one of the electrodes
having the FM Technologies coating to assess its field-emission
characteristics after baking at 650 C. The test was successful
in that no field emission was seen. The new stalk was completed
and sent to FM Technologies for coating. Unfortunately, it had
just left our premises when the vendor called with the news that
their coating chamber could not accept the tube with its welded-on
flange. At week's end we are bringing back the tube and preparing
to remove the flange. Contractual arrangements for the coating
are still not finalized. The vendor is now estimating mid-to-late
January delivery of the coated stalk.
Concerning other ITS-related progress:
Installation activities remained on schedule except for the above
final assembly of gun. We upgraded the harp in the light box
with one of the new stainless steel frames to make it more structurally
resilient to baking. Work continues on upgrades to the photocathode
drive laser and its optical transport system.
Accelerator Systems
Today (Friday, 20 December) we froze the top-level machine drawing,
established a Lattice Review Committee, and formally instituted
a change-control process. The lattice is designed to provide
a high-brightness electron beam for lasing and high acceptance
for energy recovery in keeping with the goals of the IRFEL Program.
These goals are to generate first light (requiring nominally
38 MeV, 1.1 mA cw electron beam without energy recovery), followed
by high-power operation (requiring nominally 42 MeV, 5 mA cw electron
beam with energy recovery), and during commissioning, to investigate
effects of space charge and coherent synchrotron radiation on
the electron-beam dynamics. A second cryomodule can be added
to boost the beam energy to 75 MeV without affecting the design
or placement of the second recirculation arc. Details at the
subsystem level are generally fluid, i.e., not yet frozen, but
any changes at the subsystem level that affect the lattice are
now subject to review by the Lattice Review Committee.
Further tests of the prototype dipole magnet have shown that the
use of high-µ pole-surface material coupled with a Purcell
gap is sufficient to meet the specifications on the uniformity
of the transverse field profile. However, we have not yet closed
the dipole magnet review because we felt it important to consider
edge effects on the field and explore a geometry that will provide
a sharp cutoff. The magnet has been reconfigured for this, and
measurements of its edge fields are on the verge of beginning.
We project that, once this data is available, we can close the
review, and we anticipate doing so during the first week of January.
In the meantime, Northrop Grumman has completed the design of
the optical-chicane dipoles to the 99% level. Upon closing the
review, we will expedite their procurement.
Development of ceramic warm windows continues to be pursued vigorously.
We tested one window, but it failed at 50 kW, 50% duty cycle.
In preparation for manufacture of more windows, massive stainless-steel
flanges that are already in house have been inspected and cleaned.
They are ready for copper plating, and will be ready for final
assembly sometime today (Friday, 20 December). Testing of windows
should resume on 23 December. A detailed test schedule was developed
and implemented that leads to installation on the injector cryounit
of the best two qualified windows by 15 January 1997.
The higher-order-mode (HOM) stainless-steel subassemblies were
qualified, and final assembly started at the vendor. Braze tooling
for the HOM assemblies were designed and manufactured. We are
making additional glassy carbon tiles for HOM production.
Considerable progress ensued concerning the development of the
beam-position monitors (BPMs). Experiments with the prototype
stripline BPM indicated that the location of the troublesome 1455
MHz resonance could be adjusted by shortening the electrodes.
Doing so significantly enhances the ease and accuracy of calibration.
Thus, to affirm this finding, we decided to design and fabricate
a second prototype with shorter electrodes. This prototype is
projected to be available for testing by mid-January, after which
it will be available for commissioning with 10 MeV beam in the
Injector Test Stand. In addition, a schedule was drafted for
all of the families of BPMs needed for the IRFEL, and it was coordinated
with the beam- transport schedule. We could not close out the
BPM Review this week, so we set a date for the closeout meeting
at 9 January 1997.
The bunch-length monitor under development at the University of
Georgia is proceeding well. They are building two units, one
of which will be evaluated at 10 MeV in the Injector Test Stand.
The stepper-motor-controller printed circuit boards are complete,
and chassis construction is progressing. The University of Georgia
will also provide manpower to write the required software to enable
the measurement to be a single step operation. A graduate student
spent a few days with us this week as part of planning for these
tasks.
FEL Systems
Wiggler
We are still negotiating with Northrop-Grumman over the contract
for the vacuum chamber and vacuum chamber support. The detailed
drawings for the wiggler supports should be complete next week.
Optics
Meetings were held with the TJNAF Machine Shop to prioritize tasks
and assign responsibilities for fabricating parts for the optical
cavity. We are awaiting estimates from one more vendor for turning
mirrors for the optical transport before we begin placing orders.
Work is underway on detailing drawings for the optical transport
system, specifically the beam diagnostics pick-off.
Operations/Commissioning
A detailed draft of the goals and plans for the 350 keV experiment
was prepared. For the goals, we consider that we must: (1) achieve
"nominal" beam parameters for FEL operation, (2) achieve
stable operation at 350 kV, and (3) develop a procedure to reproduce
beam conditions using only diagnostics that will be in the FEL
injector. We also consider that we should: (1) attempt operation
at >350 kV, (2) perform beam-parameter studies to understand
the physics of the gun, and (3) make emittance measurements versus
solenoid settings. If done properly, the parametric studies would
satisfy all other goals except operation at voltages >350 kV.
Given that the "musts" are achieved, the breadth and
depth of our experimental program will ultimately be weighed against
schedule considerations.
Facility
We received a budgetary quote from Clean Air Technology for the
FEL Facility's clean room. This is the vendor we had used for
the ITS clean room. The quote is about 20% higher than for the
previous work, but this is not surprising considering the amount
of demand in the market today. Design of the high-voltage power
supply for the gun should be completed next week.
Preparations continued for the foundation of the services building
throughout the week. Above the facility filling was nearing completion
of the interfloor area. Most of the volume of fill had been placed
and nearly all of the penetrations had been set and prealigned.
The foundation work continued in the lobby/loading dock area.
The retaining wall was completed near the ramp door. Rebar was
placed in preparation for pouring the retaining wall near the
loading dock. Inside the facility the electricians began laying
in the conduit for the building power and lighting. Jefferson
lab personnel initiated the survey effort for the as built drawings.
The u-channel was begun to be hung on the wall for services piping.
Drawings of the cable trays were in signoff.