Minutes of the Orion Technical Meeting: Oct.
9, 2000
===============================================================
Location: Room 144D (Beige Room),
Admin. and Engin. Bldg., SLAC
Present:
Clay Corvin, Johnny Ng, Robert Noble, Dennis Palmer,
Robert Siemann, Dieter Walz
Minutes recorded by: Robert Noble
1. Meeting time:
Due to schedule conflicts, the time of
the Orion Technical
Meeting will be changed to one hour
earlier. Future meetings
will be on MONDAYS, 9 AM in the BEIGE
ROOM (Room 144D) in
the A&E Building (Bldg. 41) at SLAC.
2. Agenda Items Discussed:
- D. Palmer briefly reported on the
initial use of the
newly-received PC version of TRANSPORT (AccelSoft
PBO Lab
2.0, Gilespi Assoc.;
accelsoft@ghga.com). A trial design
of a transport line from the NLCTA
injector at the 50 MeV
point (after the chicane), through the
shielding wall
at a 20 degree angle, and into the proposed
Orion low-energy
experimental hall was performed with a
simplified input file.
A triplet of quads are placed on either
side of the wall
so only a hole accomodating a beampipe
with flange needs
to be bored. Improved calculations are
in progress using
more accurate beamline component
descriptions and input
beam parameters.
- In preparation for J. Rosenzweig's visit
to SLAC on Oct.
12 to discuss the Orion photoinjector
design, R. Noble
summarized the current design parameters for the proposed
S-band Photoinjector. The assumption is
that the Orion source
will be based on the well-known
BNL/SLAC/UCLA design of which
several units have been built. Although
an X-band photoinjector
would be a natural source for the 11.4
GHz NLCTA accelerator,
little experience exists in such a
source, and the risk to the
planned two-year Orion construction
schedule would be high.
Lower frequencies than S-band simply
make it increasingly
difficult to obtain a short enough bunch
for the X-band
accelerator. The suggestion was made
that the design bunch
length should be reduced from 10 psec to
2.5 psec to facilitate
this injection. The issue was raised
that simultaneously
obtaining a 1 nC bunch charge, 7.5E-7
m-rad normalized rms
emittance and 2.5 psec bunch length may
be too optimistic.
Although it has a low quantum
efficiency, a copper cathode
is the default choice due to its
long-life and robustness.
A consistent set of design parameters
that can likely be
achieved consistent with the perceived
user needs will be the
goal of the October 12 meeting. These
choices will impact the
parameters for the laser and rf
systems.
- A new scheme for the RF photoinjector
source placement at the
NLCTA front-end was discussed. Because
the present long-pulse,
electron gun at NLCTA will be needed for
some experiments
in the Orion program, runtime will be
shared between the
new RF gun and the NLCTA gun. Given the
limited overhead height
and limited aisle space, it was
suggested that only one source
be operating into the accelerator and
the other be stored
on its own support cart offline (for
repair or modification).
The sources would be interchangeable
with either one able to
be attached to the same front-end
beampipe flange. The two
sources and their carts can be located
on a narrow-gauge track
("The Orion Express") to
facilitate the interchange. D. Walz
will sketch out a rough design for this
concept.
- A new scheme for the extraction
beamlines needed at the high-
energy (300 MeV) end of NLCTA to send
beam to the Orion
high-energy hall was discussed. The
spectrometer magnet at the
end of the NLCTA beamline is presently
followed by two
beampipes terminating in the iron beam
absorber. For Orion,
it was suggested that two holes be bored
through the absorber
at these entry points. The
angled-beamline would be used for
normal beam extraction to the
high-energy hall. The straight-
ahead hole would be plugged with iron
but be removable if a
future experimental program required
this beam port. With the
straigh-ahead hole plugged, the beam
absorber with spectrometer
magnet locked off becomes a safety
device allowing personnel
to work in the high energy hall when the
low-energy part of
NLCTA and any rf systems are operating.
3. Added Notes:
Although not part of this meeting, it
should be noted that
later in the day a discussion was held
between R. Siemann,
R. Noble, D. Walz, Marc Ross and Chris
Adophsen regarding Orion
RF Gun placement and space issues at End
Station B where NLCTA
is located. The above-mentioned concept
for having inter-
changeable electron sources was agreed
to be a reasonable
working plan for the Orion Technical
Design Study. This
would always allow returning to the
original NLCTA source
arrangement. In addition, NLC cavity
testing will need
high-quality, single bunches
(anticipated for a few hours
per week), and the new Orion RF source
can easily provide
this service as part of its operating
schedule.
Regarding space at End Station B, the
floor area north of the
NLCTA enclosure will be partially
occupied for at least the
next three years by the racks, power
supplies, modulators
and klystrons for the so-called NLC
"8-Pack" rf-station test.
The Orion program has a need for a 20
foot by 40 foot area
in that neighborhood for the
Photoinjector's Laser Room as
well as a small triangular region next
to the NLCTA north wall
where the Low-Energy beamline connects
to the Orion Low Energy
Hall. Participants agreed to remain in
contact as the "8-Pack"
layout is drafted so potential space
conflicts can be resolved
early on. Also, coordination of the
utility (water and power)
modifications at End Station B needed
for the "8-Pack" test
and the Orion facility is needed in
order to avoid conflicts
and maximize the benefit of these
improvements to the Lab.
==================================================================