MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report, March 17-March 21, 1997
Date: March 21, 1997
Management
Members of the FEL team met with Alan Todd (Northrop Grumman)
on March 18 to review and brainstorm on Alan's strawman plan for
high power FELs for Navy SSD applications. Alan asked for specific
guidance on the near term Jefferson Lab plans for upgrading the
IR Demo to higher powers.
An overriding goal of the Jefferson Lab efforts is to plan and
implement an IR FEL upgrade design that maximizes the performance
of the CEBAF 1500 MHz hardware and minimizes the cost and schedule
envelope. The target is an approximately 10kW device that fits
the possible FY 97-98 Navy budget line.
We received the final report from DOE for the February 23-25 BES
review of the IR Demo project. The FY 98 field work proposal
was submitted to laboratory management for inclusion with the
Jefferson Laboratory submission to the DOE Oak Ridge Office.
Admiral Al Baciocco, Chairman of SURA's Maritime Technical Advisory
Committee visited Jefferson Lab on March 20 with the CEO of American
Superconductor Corporation. ASC may have an interest in laser
pulse deposition of high Tc materials for their superconducting
cable products.
We also hosted visits by Dr. Dave Shoemaker, deputy leader of
the MIT LIGO group and the two principles involved with the new
1.5 GeV synchrotron/FEL radiation source near Kobe, Japan.
Jefferson Lab will host an AVS sponsored workshop next week (March
26-27) on "Contamination Control and Measurement in Vacuum
Systems." The workshop will attempt to cross fertilize the
accelerator and microelectronics communities on common problems
in this area.
Injector Test Stand
We made three measurements of bunch length versus transverse position
at low charge per bunch. These measurements were in close agreement
with the laser autocorrelator signal, giving an indicated one-sigma
bunch length of 23 ps with the laser cavity optimized. We also
did a longitudinal emittance measurement at low charge per bunch,
thereby verifying the software and technique necessary for the
measurement. We also started to integrate lessons learned from
last week's remote run of the ITS from the Machine Control Center
(MCC) to enable routinely running from the MCC in the future with
operations support.
We discovered a curious hole in the electron beam following the
cathode life test last Friday. It is unknown whether this is
an artifact of the beamline, the laser optics, or the cathode.
Upon determining that the second high-voltage-bias supply for
the electro-optic modulators had failed, we returned it to the
vendor for repair. We also determined that the modulator's thermal
blooming problems were related to the indexing fluid used in their
manufacture. A dry design is being fabricated by the vendor and
will be shipped after it has been tested for the problem.
Regarding upgrading the photocathode gun:
Upon receiving the back-up ion-implanted ceramic from Lawrence
Berkeley Laboratory on Monday (17 Mar 97), we decided to use it
to replace the most severely misbrazed ceramic of the two we already
had on hand. We then successfully bent the kovar flanges to compensate
for the remaining gap that resulted from misbrazing in preparation
for welding the high-voltage-stack assembly. Welding proceeded
on Wednesday, and the assembly was verified to be leak-tight on
Thursday. Consequently, we began tearing down the gun on Thursday
to replace its ceramic stack with the new ion-implanted one, and
to replace its cathode support tube with the new one having a
field-emission-resistant coating. This effort is being expedited,
with work scheduled over this weekend.
Regarding other ITS activities:
We completed software development for remote control of the photocathode
gun's high-voltage power supply, including provisions for status
updates and current-limit and voltage-ramp-up controls. Remote
control of the power supply for the first electro-optical modulator
was likewise completed, as was the rf attenuator for this modulator.
One of the two "good" warm windows broke Sunday afternoon
(16 Mar 97) at 30 kW on the 50 kW klystron test stand, which is
now operational. This is one of the two windows that qualified
last week at 25 kW. The other is still intact. It's not yet
known why the one broke -- NASA's infrared monitoring system was
in use with the one that didn't break.
In view of the window breakage, we plan to proceed by qualifying
fully the surviving window to nominally 20-25 kW and install it
on the cryounit. Subsequently we will do all the planned experiments
per existing schedule using the one waveguide-window assembly.
Meantime, we will vigorously pursue warm windows to 50 kW by,
for example, getting consistent ceramics from vendors, further
klystron testing, etc. We are putting together a program to get
these windows at about 50% confidence by 1 June and at about 90%
confidence by August. If for some reason windows are unavailable
even then, it would take about 2 weeks to install and test them
on the cryounit once the unit is installed in the FEL Facility.
It is not a problem to have warm windows to support first light;
20 kW windows will be OK for 1.1 mA beam.
The diode temperature cards for the cryounit were installed in
the CAMAC crate. The readout software is to be loaded early next
week.
Accelerator Systems
Regarding the beam-transport system:
The photon optics of the machine in the optical-chicane region
were changed slightly to allow space for shielding in front of
the optical collimator. The shift does not affect clearance to
other features of the optical cavity or the design of the dipole
magnets.
Bidders received solicitations for the optical-chicane dipole
magnets. Design work continued on the remaining reverse-bend,
180-degree, and injection/extraction dipoles.
At the Magnet Test Stand, 304 stainless steel qualified as the
vacuum chamber material of choice after tests in the prototype
dipole. The prototype trim quadrupole magnet underwent detailed
magnetic measurements which will require extensive analysis over
the next few weeks. The prototype sextupole magnet went through
preliminary characterization with the conclusion that the basic
design is sound but we will need field clamps. The exact pole-tip
shape will need further work, but fabrication and even installation
can proceed.
The first article of the main quadrupoles arrived from the vendor.
It passed magnetic acceptance tests.
A very productive kick-off meeting was held regarding design of
the stands for magnetic elements downstream of the cryomodule.
Regarding the vacuum system, the differential pump station was
signed off, and design of the vacuum chambers in the remaining
first-light regions started. Substantial portions of the vacuum
hardware have been ordered.
Regarding the power supply system, the request for bid on the
two 100 A power supplies needed for the injection and extraction
chicanes was sent to the power supply vendor.
Regarding cryomodule fabrication:
We could not test the second cavity pair this week because the
Vertical Test Assembly (VTA) sprung two vacuum leaks and is being
repaired. However, we assembled the third cavity pair this week
and are anticipating putting both the second and third pairs through
acceptance tests on the VTA very soon, perhaps next week.
Regarding electron-beam instrumentation and controls:
An ever-increasing fraction of I&C activities is focused on
equipping the FEL Facility. For example, this week almost all
of the cable trays were hung in the accelerator bay, and the box
ducts for the Personnel Safety System are being installed. Installation
of AC power and panel assignments are proceeding in the Facility.
The location of the transformer had to be changed to avoid interferences;
the transformer will now hang from the ceiling.
The effort to assign channel locations for the many signals from
the machine continues, this week focusing on signals from the
beam-loss monitors.
FEL Systems
Injector Move
Vendor for clean room has received notification to proceed with
construction. HV tank on schedule for delivery at end of April.
Design of the ancillary to start next week.
Wiggler
Design work for wiggler vacuum chamber and support is on schedule
for detailed drawings to be delivered next week.
Optics
The 5 micron mirrors have cleared Procurement, delivery is expected
in mid-July. The metal mirrors that will be used in the optical
transport system also cleared Procurement. We expect a designer
sometime next week to replace the system designer who resigned
last week. During the interim there will be little progress in
the remaining design efforts.
Operations/Commissioning
The principal activity for the week in this area was an extensive
discussion concerning the Accelerator Readiness Review (ARR) process,
especially as regards its purpose and sequence. Operation of
the accelerator is envisioned not to be contingent on completing
the ARR process. Rather, the ARR process is intended to allow
routine and productive operation of the entire system, which means
we can commission without going through the entire ARR. The key
prerequisite in deciding how to implement the ARR is coming to
agreement with the regulatory parties (Navy and DOE site office)
about the relative importance to the ARR of EH&S issues vis-à-vis
technical issues. We started preparing a proposal concerning
ARR for the DOE site office. A www-based system will probably
be the vehicle for implementing and monitoring the ARR process.
Facility
Facility work continued at a rapid pace this week, only slightly
hampered by the rains. Downstairs the return leg stands were
grouted into position. The cryolines were positioned and welding
the pieces together began. Box duct for the safety system was
hung and the cable trays were essentially complete. Hangers for
the optical transport pipe were placed in the ceiling and the
optical transport line welding began. The contractor has received
the trench covers and pit rails and will set them early next week.
Upstairs roofing of the mechanical room was complete and decking
was 90% complete over the rest of the building. Plumbing is in
the process of being installed including roof drains. HVAC ducting
is being hung. Wall panels are commencing at the SW corner and
proceeding around the building. The wall studs have been placed
across the front except the injector area and is proceeding along
the back. Roof equipment was placed and plumbing and electrical
work continued in the lobby. Arrangements were made with the
contractor to begin putting electrical racks in the upstairs starting
April 4.