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.