CEBAF Guns July 1999 - Present
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CEBAF Guns July 1999 - Present. Cathode (GaAs). 4 days to load, bake, prepare new photocathode. Anode. Laser. -. e. -100 kV. Cs. (F.E.). NF. 3. (leaky). Present JLab “Vent/Bake” Polarized Electron Gun. New Load Lock Gun Assembled & Running Spring ‘06.

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CEBAF Guns July 1999 - Present

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Cebaf guns july 1999 present

CEBAF Guns July 1999 - Present


Cebaf guns july 1999 present

Cathode

(GaAs)

4 days to load, bake, prepare new photocathode

Anode

Laser

-

e

-100 kV

Cs

(F.E.)

NF

3

(leaky)

Present JLab “Vent/Bake” Polarized Electron Gun


Cebaf guns july 1999 present

New Load Lock Gun Assembled & Running Spring ‘06

Goal: 8 hours swap photocathode

Present: ~12 hours

Heat/activation chamber

x4

Small bake Load region

NEG-coated HV chamber

Suitcase


Cebaf guns july 1999 present

Experimental Setup

Faraday Cup

(450 C bake)

Laser

(1 W @ 532 nm)

& attenuators

High Voltage

(-100 kV)

NEG pipe

Activation

(Cs/NF3,

Mask=5 mm)

Solenoid

Centering

Spot Size

Adjustment

7 Precision

Ion Pump

Supplies

350 mm

1500 mm

Load lock port

(GaAs on puck)


Cebaf guns july 1999 present

Benchmarking the NEW Load Lock Gun (2006-2007)

  • CEBAF ~2500 C/year

  • LL Gun ~ 2500 C/week

    • No RF structure

    • Low-P wavelength

  • Demonstrated world best

  • GaAs lifetimes, & up to 10 mA

13 mA!


Cebaf guns july 1999 present

Future: High Current & High Polarization Programs

Qweak to test standard model >200 mA at 85% polarization

Proposed e-/ion collider facilities

JLab ELIC (>1 mA), BNL eRHIC (>50 mA)

Circulator <1 C/day

Linac >100 C/day

~20 C/day


Cebaf guns july 1999 present

Fiber-based Laser

Superlattice GaAs:

Layers of GaAs on GaAsP

chekc

100 nm

14 pairs

No strain relaxation

QE ~ 1%

Pol ~ 85%

@ 780 nm

Now: High Current & High Polarization

Ingredients: Good gun, good photocathode, powerful laser

NEW Load Lock Gun


Cebaf guns july 1999 present

Friday, Saturday & Sunday

  • Brief opportunity to use one of the fiber lasers, before installed into CEBAF on Monday:

  • Superlattice high-P material (85%)

  • Very good QE ~1% in New Gun

  • First running with 499 MHz RF

  • Qweak Demonstrated

  • 250 mA (2 days, 70 C)

  • Lifetime 250-1000 C

  • (translates > 1 week running/spot)

  • ELIC Circulator Ring Demonstrated

  • 1 mA (10 hr, 30 C)

  • Lifetime ~200 C


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