EDMS No. 888499

Photoinjector General +

Photocathodes

presented by Konrad Elsener (CERN-AB)

EDMS No. 888499

Acknowledgements (PHIN)

We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 “Structuring the European Research Area” programme (CARE, contract number RII3-CT-2003-506395).

EDMS No. 888499

Outline

Overview Photocathodes: Status + Outlook

(photocathode for CLEX) PHIN in CTF2 Summary

EDMS No. 888499

Overview

LASER

RF GUN

RF equip.

Photocathode

“Photoinjector”

bunched

electron

beam

Cs2Te

UV

…cf. next two talks…

G. McMonagle

(yesterday)

EDMS No. 888499

Photocathodes

cf. presentation by R. Losito, 17 Jan. 2007

HIGHLIGHT end of 2006:

Photocathode No. 166 produced (after > 3 years interruption)

Cs-Te cathode, co-evaporation,

Quantum Efficiency > 6%

very detailed description of No. 166: CTF3-Note-089

many thanks to Eric Chevallay

EDMS No. 888499

Photocathodes – No. 167

HIGHLIGHT 2007:

Photocathode No. 167 produced 29 November

(Cs-Te cathode, co-evaporation)

Quantum Efficiency Lifetime

measured during 1000 hours

EDMS No. 888499

0

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200

time [h]

Qua

ntum

Eff

icie

ncy

[%]

data taken in DC-gun, 80 kV (-> 8 MV/m)

29 Nov. 2007 Xmas break 9 Jan. 2008

CTF3 specs

(drive beam)

Photocathodes - No. 167

EDMS No. 888499

manipulator

DC- gun

preparation

chamber

transport

carrier

~ 1.4 m

Photocathodes – No. 167

EDMS No. 888499

basic unit: Cu “plug”

on the “arm” inside

the transport carrier:

up to 4 plugs

Photocathodes - No. 167

EDMS No. 888499

Photocathodes

Process Control and Reproducibility (A. Barbiero and E. Chevallay)

- cleanliness / UHV vacuum

EDMS No. 888499

H2

CO

N2

N

CH4

O

H2O

...

a long period of improvements, pumping, leak testing, baking-out, leak testing,

repair, pumping, baking out, ...

vacuum before cathode preparation: < 3x10-11 mbar

residual gas analysis in preparation chamber (29 Nov. 2007)

Photocathodes - vacuum

EDMS No. 888499

Photocathodes – film thickness

Process Control and Reproducibility (A. Barbiero and E. Chevallay)

- cleanliness / UHV vacuum

- film thickness monitoring (Te, not Cs)

-> new stylus profilometer, calibrated

EDMS No. 888499

Photocathodes - film thickness

Te films on

quartz substrate

new Stylus Profilometer

EDMS No. 888499

Photocathodes – film thickness

cross-check of Stylus Profiler using a calibrated sample* (Rank Taylor Hobson)with 3 grooves, 24 nm each

solid lines: =24 nm

dashed line: =26 nm

Result:

Profilometer intrinsic error < 2 nm

* sample on loan from CERN-TS/MME (W. Vollenberg)

0.5 mm

EDMS No. 888499

Photocathodes – transfer arm

Process Control and Reproducibility (A. Barbiero and E. Chevallay)

- cleanliness / UHV vacuum

- film thickness monitoring

-> stylus profilometer, calibrated

- possibility of cathode chemical analysis (X-ray Photoel. Spectr.)

-> new, smaller transfer arm (for 1 plug)

(collaboration with team of M. Taborelli / TS-MME)

EDMS No. 888499

Photocathodes – transfer arm

(attached to preparation chamber) (courtesy A. Barbiero)

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Photocathodes – plug surfaces

Process Control and Reproducibility (A. Barbiero and E. Chevallay)

- cleanliness / UHV vacuum

- film thickness monitoring

-> stylus profilometer, calibrated

- possibility of cathode chemical analysis (XPS)

-> new transfer arm

- reproducible “plug” surface

-> test programme on surface preparation + analysis

(work in progress - No. 166 and No. 167 are very different)

EDMS No. 888499

photocathode for CLEX

Preparation chamber for CLEX

(ex-CTF2 Probe-Beam)

Cs + Te sources (no co-evaporation);

1 quartz thickness monitor (DN 100 flange)

manipulator arm

(position for “plug”)pumping

port

EDMS No. 888499

“CTF2” (south)

photoemission

laboratory

“CTF2”

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“CTF2” - status

EDMS No. 888499

Acknowledgments

Nathalie Lebas: expert help with the laser

Arnaud Brielmann: expert help with controls

and interlocks

(for equipment safety)

EDMS No. 888499

Summary + Outlook

Photoemission Laboratory:

ready for production of cathodes Cs-Te cathode No. 167: ready for PHIN work in progress to improve reproducibility near future: CLEX cathode

continue contributions to PHIN in “CTF2”

EDMS No. 888499

spare slides

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spare slides

8 Nov. 2007

EDMS No. 888499

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PHIN overview

RF Network

Laser Beam Line0.37mJ / mPulse

2332 mPulses

Electron Beam2.33 nc / mPulses

Transportcarrier

3 GHz RF gunE = 85 MV/mU = 5.6 MeV

I = 3.5 ACs2

Te

cath

QE

= 3

%

Photocathodepreparation

chamber

Under the responsibility ofCLF-RAL

Under the responsibility ofLAL - Orsay

Under the responsibility ofCERN

Under RAL responsabilitywith CERN collaboration

Total efficiencyIROUT UVcath = 3.6 %

KLYSTRON3 GHz - 30 MW

Freq. X 4 l =

262 nm

Power Amplifier : DPSSL3-pass x 5

200 ms ; Ptrain = 15 kWl = 1047 nm ; 10.3 mJ / mPulse

Pulse width 10 psRep. Rate 5 - 50 Hz

Master oscillatorl = 1047 nm f = 1.5 GHzP > 0.2 W

W/mPulse > 0.13 nJ

Pulse shaping and stabilization

Phase coding

3 GHz RF source

Pre-amplifierl = 1047 nmPCW = 10 W

W/mPulse = 6.7 nJ

1.5 GHz

3 GHz

High Q Laser

First Amplifier : DPSSL3-pass x 300

400 ms ; Ptrain = 3 kW

2 mJ / mPulse

Pulse width 10 psRep. Rate 5 - 50 Hz

High Q Laser

Phase coding+ amplification