Polarized e Source Design and R

1
Polarized e- Source Design and RD10/24/05

• Laser Development
• Photocathode RD
• Proposed SBIRs
• Simulations

2
Laser Development

• Near term plan
• Use 76 MHz mode-locked TiSapphire (Mira 900) as
  pulse train source
• (oscillator and pump need to be relocated to new
  lab)
• Pulse train slicing with fast pulser/pockels
  cell combination
• Pulser 3 MHz burst mode ( 1-2 ms bursts at 5 Hz)
• Pockels cell Cleveland Crystal 3 crystal BBO
  cell
• (cost 20 K)
• Work will start upon completion of B006 roof and
  HVAC work (anticipated near the end of November)
• Laser Development is also subject of SBIR project
  

3
Photocathode RD

• SVT SBIR Phase I to investigate InGaP-GaAs
  strained superlattice
• First sample expected soon
• SAXET STTR Phase II to study bias effect on QE
  and polarization.
• Observe bias effect on QE, polarization next.
• InAlGaAs-GaAs strained superlattice
• Observe 84 peak polarization

4
Bias effect on QE
5
Proposed SBIRs(Submission deadline 12/02/05)

• Laser Development
• Discussions with KM Labs to submit SBIR phase I
  proposal to develop source laser that can be used
  with RF gun or DC gun based source
• KM Labs is a small laser company with expertise
  in TiSapphire oscillators and amplifiers
  (Boulder CO).
• Experienced with SBIR business (e.g. SPPS, LCLS)
• RF-Gun development
• Development of L-Band RF-Gun for a polarized
  source
• Small Business partner is SAXET (Greg Mullholan)
  expertise in vacuum work
• 1.6 cell L-band vs. HOM structure ? HOM
  preferable geometry for pumping
• RF testing with L-band RF test stand at Fermilab
  or SLACs ESB

6
RF-Gun structures and pumping requirements
Conductance and pressure differential at cathode
for various S-band gun designs with 2 assumed
outgassing rates for Cu.
1.6 cell / HOM
Details RF Guns for Generation of Polarized
Electron Beams J. E. Clendenin, A. Brachmann, D.
H. Dowell, E. L. Garwin, K. Ioakeimidi, R. E.
Kirby, T. Maruyama, C. Y. Prescott (SLAC), R.
Prepost (U. Wisconsin) Nanobeam 2005
7
Simulations

• Original work by A. Curtoni Jablonka TESLA
  2001-22(2)
• Study of the TESLA preaccelerator for the
  polarised electron beam, TESLA
• Extension of work for increased Gun HV (DC-gun)
• Started working on our own simulations using
  various beam simulation tools (E-gun, GPT, )

8
Simulations preliminary
What gun voltage do we need to simplify
pre-buncher ?
SLC polarized gun geometry 2 cm cathode
diameter 120 350 kV Include Space Charge
9
Gun HV vs. buncher frequency
To match bunch length in t/4 period of buncher
frequency