From: H. F. Dylla (recorded by C. L. Bohn)
Date: January 10, 1997
Subject: IRFEL Injector Contingency Planning
A group of us (Bohn, Dylla, Neil, Krafft, Legg) met today to formulate
contingency plans for the IRFEL injector-development effort.
Continued slippage in the development of the photocathode gun,
coupled with our commitment to install the IRFEL in the FEL Facility
by 30 Sep 97, necessitates that we have sensible contingency plans.
Ideas that arose by way of brainstorming were the following:
1. Reduce scope/duration of 10 MeV experiments in the ITS
- add staff for 10 MeV ITS runs
- commission 10 MeV hardware with short ( 2 wk) run in ITS
2. Eliminate/descope 350 keV experiments
3. Do all 10 MeV work in the FEL Facility, not in ITS
4. Ask rf people to "optimize" injector reinstallation in FEL Facility
5. Build new gun and/or new rf system in FEL Facility in parallel
with ITS work
Idea #5 was eliminated quickly because we don't have the extra
money (0.5-1.0 M$).
To select from the remaining ideas, the group discussed and solidified
the ITS "mission priorities":
I. Ensure we can run the gun at suitable voltage ( 350 kV)
II. Establish confidence in space-charge modelling, e.g., the MacDonald algorithm -- this means knowing well what comes out of the gun as a function of the gun settings.
III. Ascertain problems with SRF/RF hardware.
Establish operability of electron-beam diagnostics: the SEE BPM,
the multislit transverse-emittance diagnostic, and the interferometric
Provide a fully commissioned, completely debugged high-current
(4 mA due to limited dc power supply), 10 MeV injector.
The group considered that we can accomplish the MUST and SHOULD
by way of the following activities: (1) running extensive experiments
at 250-300 kV, obtaining a good data base of transverse and longitudinal
beam properties while interactively running space-charge simulations
to correlate the results, (2) achieving stable operation at 350
kV, and (3) doing a short (2 wk) run at 10 MeV to commission the
SRF/RF and beam-diagnostic aspects of the injector, thereby identifying
any SRF/RF problems. Given that these are all accomplished, we
can delay complete debugging until after reinstallation in the
FEL Facility, a facet that also saves time by avoiding a duplicity
of 10 MeV commissioning activities, i.e., in both the ITS and
The net result of these considerations is recovery of schedule.
Most of the time needed for gun experiments can be done with
the existing gun, thereby accommodating "delays" associated
with the reconfiguration of the gun for higher-voltage operation.
After reconfiguring the gun and achieving stable operation at
350 kV, subsequent 10 MeV activities will require a total of 4-5
weeks, which is half the initially allocated time.
With this contingency plan, the FEL injector schedule reduces
to the following:
250-300 kV experiments Feb-Mar 97
350 kV gun reconfiguration/operation Apr 97
10 MeV operation complete by 1 Jun 97
Reinstall in FEL Facility Jun-Aug 97
Begin 10 MeV commissioning Sep 97
This schedule accommodates two important global concerns. It
employs Jefferson Lab manpower when it is available for the reinstallation
activity, namely during summer 1997. It also gives us a reasonable
chance to meet the Dec 97 first-light milestone.
Accelerator Division Department Heads
Accelerator Division Deputy Department Heads
FEL Department members