Photocathode R

1
Photocathode RD

• Saxet SBIR
• Greg and John visited SLAC May 16-18.
• The contactor was installed on May 17.
• The power outage took place during the initial
  pump-down. It could have been a disaster if it
  were a few days layer.
• The system was baked from May 26 to June 2.
  Vacuum is lt6?10-12 Torr on CCG.
• Installed a bulk GaAs sample for checking
  Cesiator and Mott channeltrons.
• Photocurrent after 1 hour Cesiation.
• Mott counting rates look OK.
• Polarization test next.

2
SIMS on IQE sample
New anodized/stripped Used anodized/stripped
heat-cleaned/Cs
anodized/stripped
3

• New photocathodes to be grown at SVT
• Strained-superlattice InAlGaAs-GaAs
• St. Petersburg structure
• 92 polarization observed at St. Petersburg, but
  not reproducible.
• Relaxed wells (GaAs) and strained barriers
  (InAlGaAs)
• Buffer layer is lattice-matched to substrate
• Wisconsin to pay for calibration (3K) and one
  wafer (4K), and Group EA to pay for two more
  wafers.
• The wafers are expected in a month.

4

• SBIR Phase I approved to develop
  strained-superlattice GaAs-InGaP
• 100 K (20 K to SLAC) over 6 9 months
• Strained Wells or Strained Barriers

Strained Wells
Strained Barriers
1) GaAs cap 2) In(0.35)Ga(0.65)P 3) GaAs
repeat 2) and 3) 4) In(0.35)Ga(0.65)P 2.5 um 5)
In(x)Ga(1-x)P x 0.48 -gt 0.35 6)
In(0.48)Ga(0.52)P 7) GaAs sub
1) GaAs cap 2) In(0.62)Ga(0.38)P 3) GaAs
repeat 2) and 3) 4) In(0.48)Ga(0.52)P 5) GaAs sub
Peter Chow, president of SVT, is coming to SLAC
tomorrow.