LCLS Injector RF Gun: Design, Fabrication

1
LCLS Injector RF Gun Design, Fabrication
Tuning PlansD. H. Dowell, SLACInjector RF
Review November 3, 2004

• Injector Requirements
• Detail of Gun to Linac Region
• Load Lock, Gun Solenoid Description
• Some technical issues
• RF Gun Status (design procurement)
• Current fabrication procurement plans
• Schedule
• Gun tuning
• Cooling system (preliminary)
• Summary and Conclusions

2
LCLS Injector Performance Requirements
3
Gun to Linac Region
4
Load Lock Conceptual Design
5
S20 Alcove Floor Plan
S20 Alcove includes a Load Lock Room
for Installing Processing Cathodes in Load Lock
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Dual Feed RF Gun and Solenoid

• Dual Feed/Racetrack Design Corrects RF Fields to
  Second Order
• Solenoid Design Includes Both Dipole and
  Quadrupole Field Correctors

7
Gun Solenoid will have Dipole and Quadrupole
Correction Coils
Measurements of Gun Solenoid Multipole Fields

• Solenoid being designed with both
• dipole and quadrupole correcting coils

8
RF Gun Fabrication Acquisition (Near Term)

• April 2004 Released Request for Information to
  two vendors
• April 2004 Begin work on RF design for gun
• May 2004 Vendors respond with budgetary quotes
  and schedules for engineering and fabrication of
  load lock and RF gun.
• August 2004 Technical meetings with vendors at
  SLAC
• Now Finalize RF design
• Now Write Request for Proposal and send to
  vendors
• Recent Decision Load Lock prototype developed
  using SBIR with AES (Advanced Energy Systems)

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RF Gun Fabrication Acquisition Assumptions and
Plans

• Load Lock prototype developed using SBIR with AES
  (Advanced Energy Systems)
• Gun design should be compatible with future load
  lock
• SLAC does RF design for gun, provides design to
  vendor
• Vendor engineers gun including thermal analysis
  and design of cooling system
• Vendor cold tests, fabricates and re-tests gun
• Technical reviews at both SLAC and Vendor
  facility
• SLAC participates with Vendor in RF and thermal
  tests of the gun and cooling system
• Vendor may participate in high power RF
  commissioning of gun at SLAC
• Vendor Delivers
• Hardware/Software
• RF gun
• cooling system including plumbing hardware used
  to test gun cooling system
• computer control source code.
• Documentation
• All engineering drawings funded by this project
  especially those of gun and cooling system
• Written progress reports on contract progress
• Written reports of rf and thermal tests. Reports
  should include raw data acquired during tests.

10
LCLS Injector Schedule
Gun and L0-1 needed for installation October 2006
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Machining, Tuning Brazing the RF Gun

• Under-machine rf surfaces 0.010
• Clamp together and perform rf cold tests.
• Based on rf tests machine surfaces as required
• Re-do rf cold tests
• Iterate rf tests and machining until gun on
  resonance and balanced.
• Perform time-domain and frequency-domain
  measurements of 0- and pi-modes, bead drop,
  needle pull, etc.
• Braze gun
• Should a lower temperature braze be used to
  reduce softening of Cu?
• Use glidcop instead of Cu? (prefer Cu)
• Minimize number of brazes
• Assemble gun with dual feed waveguide
• Perform time-domain and frequency-domain
  measurements of 0- and pi-modes, bead drop,
  needle pull, etc.
• Install on solenoid. Align rf and magnetic
  centerlines

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Balancing the Dual RF Feeds

• Required tolerance between feeds (assume similar
  to L0-1 dual feed)
• Phase lt3 degree (s-band)
• Amplitude lt2
• Machine to fit
• Phase shift per length of waveguide
• 1deg-sband278microns
• Options for balancing feeds
• Deform (squeeze) a section of the waveguide
• Phase shift due to temperature is small
• For meter long waveguide section
  0.046deg-sband/deg-F

13
Dual Feed Using Standard Waveguide Components
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RF Gun Cooling System
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Summary and Conclusions

• Reviewed Load Lock (LL), gun and gun solenoid
  requirements and constraints
• Gun design compatible with future LL
• Gun solenoid designed as a single assembly for
  easy replacement with future gun
• S20 Alcove includes a Load Lock Room for cathode
  development
• Build prototype LL with SBIR with AES
• Present gun fabrication plan
• SLAC designs gun RF geometry
• Vendor does thermal mechanical engineering
• Vendor fabricates and cold tests gun
• Progress and technical reviews at SLAC and Vendor
  facility
• Vendor delivers gun, documentation
• Gun needed by Oct 2006 for installation
• Described machining, tuning brazing process
• Control of amplitude phase between the dual
  feeds
• Proposed cooling system for gun and dual feed
  waveguide