Brief overall description of the Task WP12.5 Photocathodes

Brief overall description of the Task WP12.5

Photocathodes

for the reporting period: 1.05.2013 – 30.04.2014

• Evaluate Pb photocathode deposition for improved performance of SRF guns

• Characterise and optimise performance of Diamond Amplifier Cathode solutions for SRF guns

• Material R&D for advanced photo cathodes for NC RF guns

Fields of interest:

SAPI commissioning and photocathodes characterisation STFC Pb photocathodes: deposition improvement, post-

deposition treatment, Q and QE measurements NCBJ, DESY, HZDR

DAC photocathodes HZDR, HZB

Actions and institutions:

WP12.5 Brief overall description

Numbe achievment Performer Deadline Product MS73 Commissioning of the SAPI for operation with metal photocathodes STFC M8 Publication report MS75 Investigation of quantum yield and energy spectrum of the electrons,

emitted from the metal photocathode surface in SAPI STFC M18 Intermediate scientific

report MS80 Demonstrated operation of improved deposition system, Pb layers

of 1 μm in thickness NCBJ M30 Report on sample

characterisation MS83 Manufacturing and commissioning of the photocathode transport system STFC M36 Technical design report MS85 Investigation of the brightness of different metal photocathodes in

a S-band NCRF gun STFC M42 Scientific report

Mile

ston

es

Number achievment Performer Deadline Product D12.4 Scientific report on photocathode R&D STFC M18 Report D12.8 Optimised procedure for microdorplets flattening with an UV laser NCBJ M36 Report D12.9 Pb/Nb plug photocathodes measurements and characterization. HZDR M42 Report D12.13 Results of DAC implementation in SRF guns. HZB M48 Report

Deliv

erab

les


Kick off Meeting Task 12.5 on RF Photocathodes at HZB on 12.07.2013


http://eucard2.web.cern.ch/content/work-packages

http://eucard2.web.cern.ch/content/work-packages

Q.E.th. Emittance(low E char.)

field emission &roughness

surface &layer

properties

gunperformancebeam param.

Preparation

Test stand at Swierk

QE vs λ with D –tube since March 14

since January 14 SEMGrazing-XRD

HV Cath. Arc Pb coating

HZDRSRF gun

access until March ´14 no test of „dangerous“ cathodes in the „new“ gun „old“ gun as a future tes bench?

QE in gun, RF properties, dark currentbeam parameters

HZDRprep. system

QE (260 nm)QE scan, QE(λ)laser cleaning?

HZB HoBiCaT& Gun

No access to HoBiCaT for further gun cavity testsGun 1 ready in autumn ´14, but very tight R&D schedule

HZBFE Testbench

Transverse. Therm. emittance

field emissionmapping for all cathodes

(

BESSY II(beamtime application)

Energy distribution with ARPES

In situ XPS, and other SR methodesall cathodes

DESYTest stands

SAFEM ?

Q vs EChechiaDark current

STFC QE at λ =const tUV transverseEnergy analysis GaAs, Metallic Photocath.

AFM for roughness only (in commissioning)

AES, XPS, multiprobe CLARA gun In developement

GaAs preparation facilityMetal photocath. PVD

WP12.5 Brief overall description Capabilities

• Work on Subtask 12.5.1 Pb photocathode deposition HZDR fabricated, polished and shiped four Nb plugs for Pb deposition to NCBJ Swierk. The plugs are deposited there with 2 µm Pb. Next step is laser cleaning (needs help of NCBJ)and quantum efficiency measurement at 252 nm in the photocathode preparation system at HZDR. (work for Delivery D12.9 in 3/2016)

• Work on Subtask 12.5.2 Diamond amplifier cathode development. Contact to BNL on requirements for integration in SRF gun.

• The goal of our task is to study next generation photocathodes delivering high brightness, high average current electron beams. We want to investigate wanted and unwanted beam properties and work on the integration of the photocathode into the SRF gun enviroment. Candidates for next generation cathodes include Diamond Amplifier Cathodes (DAC) and Diamond Field Emitte Arrays (DFEA).

Helmholtz Zentrum Dresden RossendorfWP12.5 Brief overall description


Field Emission Laboratory: Test dark current emission from substrates and cathode films under high electric DC fields

• Current measurement• Image of the emitters on

the view screen• Constant gap d=0.4 mm• Gradient can be changed

by controlling• bias voltage (Umax=10 kV)

Setup complete and under vacuum, first tests with diamond field emitter array cathodes (collaboration University Vanderbildt) and Mo substrates.

Next step is commissioning with 5 kV DC voltage, then increasing up to 10 kV voltage (at 0.4 mm gap 25 MV/m).

Helmholtz Zentrum Berlin

Status of the SRF-gun cavity with plug at DESY

0 10 20 30 40 50 601E+08

1E+10

TJNAF Test1, BCP DESY Test 1, EP DESY Test 2, EP

Ecathode [MV/m]

Qo

Gasket made of In wireGasket made of In foil

Deutsches Elektronen SynchrotronWP12.5 Brief overall description

see the further presentation

Further information will be provided by W Grabowski of NCBJ Swierk


AFM

LEED

X-ray Gun

Analyser

UHV Vacuum System

• A multi-chamber ultra-high vacuum system has been constructed and equipped with a number of surface analysis techniques.

• The commissioning of the SAPI system is a key milestone in this sub-task and has been reported as CERN-ACC-2014-0039

• Work is now progressing on the investigation of a series of alternative metal photocathode materials using the facilities at Daresbury.

Surface Analysis/Preparation Installation (SAPI)

Science & Technology Facilities Council, Cockroft Inst.

see the further presentation

WP12.5 Brief overall description Narodowe Centrum Badań Jądrowych, Świerk

UHV arc deposition devices Pb/Nb layers post- processing

IBIS rod plasma injector

Probe heater for vacuum annealling

Short arc device

Filtered UHV arc system

Surface analysis; photocathode tests

SEM laboratory

Photocathode diagnostic stand – under construction


Thank you for your attention !

Brief overall description of the Task WP12.5 Photocathodes

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