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Comparison of SbKCs Recipes
ANL
From Anatoly Ronzhin
Oxygen Plasma
- Pressure of the oxygen: 0.3 torr
- Voltage to the glass: 20K
- Shape of the electrode: tip
- 1sec x 3 times
Sb
- Silk material: Pt-Mo
- Monitor the reflection light by the Photodiode
- Stop first deposition at 80% of maximum
- Oxigen plasma cleaning
- Second Sb deposition, stop at 50% of maximunm
K
- Outgas with small current (2A) during the baking time (1 / 1-1/2 hrs)
- Pressure ~7x10^6 Torr
- Monitor the photo current until the increasing trend stops
Cs
- Outgas with small current (2A) during the baking time
- Monitor the photo response current
- Stop baking the prototype after the increasing trend stops
- Cool down
IHEP (Beijing)
From Anatoly Ronzhin
Oxygen Plasma
- Pressure of the oxygen: 10-2 torr
- Voltage to the glass: 700V
- Shape of the electrode: planate
Sb
- Silk material: Ni
- Look at by eyes
K
- Outgas with the high frequency gun before baking
- Monitor the light current until the increasing trend stops
Cs
- Outgas with the high frequency gun before baking
- Monitor the light current until the increasing trend stops
- Continue baking the prototype at least 2 hours
IHEP (Protvino)
From Anatoly Ronzhin
Oxygen Plasma
- Total pressure: <10 to -5 torr always
- Voltage to the glass: few kV
- Shape of the electrode: tip
Sb
- Sb evaporated by RF inductor
- Monitor photocathode reflectivity
K
- Outgas by gettering, pressure <10 to -5 always
- Monitor current and dark photocurrent in 77 V/cm electric field
- IMPORTANT: photocurrent should pass through max (drop after max ~10%). Visual control: photocathode not activated if it has light yellow color. Repeat act.
Cs
- Monitor photocurrent and dark current. Photocathode (Pc) should have "metallic green" color in reflected light, "yellow red" indicated activation only by Cs.
- Run away excessive amount of K,Cs.
- Heat to 170 ℃
- Photocurrent (PC) should go up, dark current down
- Cool down to 50℃
- Repeat few times
- Stop when PC ~1.5 hight in cold wrt hot and PC in cold start drop by 10%
Breskin group
From thesis
Cleaning
- Initial pressure: <10-7 torr
- window cleaned with NaOH and distilled H2O, 10min rinse in acetone, 10 min in ultrasonic ethil alcohol bath, dried with N
- Alkali and pure (99.999%) Sb previously melted in 10-6 torr
- Shape of the electrode: 1000A Al film on circumference
- During baking, small current to Sb,K, Cs to outgas contaminants
Sb
- Evaporation at 25℃ or (150-160)℃, 15-30 sec
- Monitor with transmission of white light, stop when light 70% of initial value
K
- Bake at (195-200)℃
- Evaporate K to form K-Sb photocathode, done when photocurrent reaches maximum
- To remove excess K, heat at 240℃ for 10sec
- cool down to (195-200)℃ and photocurrent to 1/2 of maximum
Cs
- cool down to (175-180)℃
- Evaporate Cs and Sb alternatively, until photocurrent reaches peak
- Monitor current during cooling of photocathode, if it decreases evaporate small amount of Sb to stabilize
- Average and rms of QE: 30+/-9, 32+/-11, 22+/-8 at 254,312, 406nm wavelenght
- Surface composition (XPS): Cs 4.9+/-0.2%, K 35+/-2%, Sb 1.5+/-0.1%, O 43+/-2%, C 15.6+/-8%
