APEX description, status and plans John Corlett for the APEX team Lawrence Berkeley National Laboratory 1

APEX APEX description, status and plans description, status and plans

John Corlett for the APEX teamJohn Corlett for the APEX team

Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory

1

Motivation

Tomorrow’s x-ray laser sources

~ microsecond

s ~ attoseconds to femtoseconds

Intense pulses at high rep rate≲millijoule

Coherent X-rays with high repetition rate, unprecedented average brightness, and ultrafast pulses

Approach

CW superconducting linac,laser heater, bunch compressor

High-brightness, high rep-rate gun and injector

Beam spreader

Array of independent FELs

X-ray beamlines and endstations

High average power electron beam distributed to an array of FELs from high rep-rate injector and CW SCRF linac

• Repetition rate 1 MHz

• Charge per bunch from ~10 pC to ~1 nC

• Emittance <10-6 mm-mrad (normalized)

• Electric field at the cathode ≥~10 MV/m (space charge emission limit)

• Beam energy at the gun exit ≥~500 keV (space charge control)

• Bunch length ~100 fs to ~10 ps for handling space charge effects, and for allowing different modes of operation

• Compatible with magnetic field control within the gun (emittance exchange and compensation)

• 10-11 Torr vacuum capability (cathode lifetime)

• Accommodates a variety of cathode materials

• High reliability for user operations

Injector design goals – APEX gun

Frequency 187 MHz

Operation mode CW

Gap voltage 750 kV

Field at the cathode 19 MV/m

Q0 30887

Shunt impedance 6.5 M

RF Power 90 kW

Stored energy 2.3 J

Peak surface field 24 MV/m

Peak wall power density 25 W/cm2

Accelerating gap 4 cm

Diameter/Length 70/35 cm

Operating pressure < 10-11 Torr

APEX gunVHF cavity operates in CW mode•Low power density on cavity walls•High conductance vacuum slots•High gradient at cathode

Injector design and beam dynamics – multiobjective genetic optimization

Gun

Bu

nch

er

Projected normalized emittance (m-rad, 100%)

RM

S b

un

ch l

eng

th (

m)

300 pC

APEX stages

Diagnostics systems in collaboration with Cornell

CLASSSEAccelerating cavities in

collaboration with ANL AWA

Phase I:Beam

characterization at gun energy

(750 keV)

Phase 0:Gun and

photocathode tests

• Planning for final installation in 2013

Phase-II:Beam characterization at 15–30 MeV

•6-D brightness measurements

Phase 0 scope:Phase 0 scope:• Demonstration of the RF performance at Demonstration of the RF performance at

full repetition rate.full repetition rate.• Vacuum performance demonstration.Vacuum performance demonstration.

• Dark current characterization.Dark current characterization.• High QE cathode physicsHigh QE cathode physics

(QE and lifetime measurements)(QE and lifetime measurements)

Under commissioningUnder commissioning

Phase I scope:Phase I scope:(Phase 0 + extended diagnostics)(Phase 0 + extended diagnostics)

• High QE cathode physicsHigh QE cathode physics(Intrinsic emittance measurements)(Intrinsic emittance measurements)

• Diagnostics systems tests.Diagnostics systems tests.• Low energy beam characterizationLow energy beam characterization

Planned operation in fall 2012Planned operation in fall 2012

Phase 0Phase 0

Phase IPhase I

8

APEX stages – 0, I

APEX Phase II layout

Phase II scope:Phase II scope:• Demonstration of the Demonstration of the

brightness performance at ~ 30 brightness performance at ~ 30 MeV at low repetition rate*MeV at low repetition rate*

(*Shielding limited)(*Shielding limited)

Planning forPlanning foroperation in late 2013operation in late 2013

9

APEX stages – II

Tuning mechanism principle testedTuning mechanism principle tested1.2 101.2 10-9-9 Torr achieved with 1 (out of 20) NEG pump and no bake Torr achieved with 1 (out of 20) NEG pump and no bake

Successful low power RF testSuccessful low power RF test

APEX DescriptionStatus & Plans

(J. Corlett)

10

Gun cold-test and installation

APEX gun: high-brightness MHz electron source• APEX cavity is successfully RF conditioned

APEX in the Beam Test Facility

APEX Activity and Plans

F. SannibaleYb fiber photocathode drive laser

• 1 MHz reprate Yb fiber laser• LLNL/UCB/LBNL collaboration

High QE

Good lifetime at10-9 mBar

Low transversemomentum

200 400 600 800 1000

100

200

300

400

500

600

700

800

900

1000 0

0.5

1

1.5

2

2.5

3

3.5x 10

4

Photocathode materials R&D

K2CsSb:6% QE at 532 nm 0.36 microns / mm rms n

>> 1 week lifetime

PEA Semiconductor: Alkali Antimonides CsKPEA Semiconductor: Alkali Antimonides CsK22Sb, Sb, (developed at LBNL)(developed at LBNL)

- <~ps pulse capability- <~ps pulse capability- reactive; requires ~ 10- reactive; requires ~ 10-10-10 Torr pressure Torr pressure- high QE > 1%- high QE > 1%- requires green/blue light (eg. 2- requires green/blue light (eg. 2ndnd harm. Nd:YVO4 = 532nm) harm. Nd:YVO4 = 532nm)- for nC, 1 MHz reprate, ~ 1 W of IR required - for nC, 1 MHz reprate, ~ 1 W of IR required

PEA Semiconductor: Cesium Telluride CsPEA Semiconductor: Cesium Telluride Cs22Te Te (In collaboration with INFN-LASA)(In collaboration with INFN-LASA)

- <~ps pulse capability- <~ps pulse capability- relatively robust and un-reactive (operates at ~ 10- relatively robust and un-reactive (operates at ~ 10-9-9 Torr) Torr) - successfully tested in NC RF and SRF guns- successfully tested in NC RF and SRF guns- high QE > 1%- high QE > 1%- photo-emits in the UV ~250 nm (3- photo-emits in the UV ~250 nm (3rdrd or 4 or 4thth harm. conversion from IR) harm. conversion from IR)- for 1 MHz reprate, 1 nC, ~ 10 W 1060nm required- for 1 MHz reprate, 1 nC, ~ 10 W 1060nm required

FLASHFLASH

INFN-LASAINFN-LASA


(J. Corlett)

Cathodes successfully developed at INFN/LASA and delivered to LBNLCathodes successfully developed at INFN/LASA and delivered to LBNL

Cathodes under development at LBNL (H. PadmoreCathodes under development at LBNL (H. Padmore’’s group)s group)Promising lifetime and intrinsic emittance results (Cornell and LBNL)Promising lifetime and intrinsic emittance results (Cornell and LBNL)

Transfer chamber to VHF gun in preparationTransfer chamber to VHF gun in preparation

Collaboration with BNL for diamond amplifier testingCollaboration with BNL for diamond amplifier testing

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Photocathodes

Modified version of the FLASH Modified version of the FLASH plug for reduced field emission. plug for reduced field emission.

Not tested yet!Not tested yet!

Status of the APEX Project

F. Sannibale

Flexibility for testing different photocathode materialsFlexibility for testing different photocathode materials

The APEX Projectat LBNL

(J. Corlett)

Adapted version of the Adapted version of the INFN/PITZ/DESYINFN/PITZ/DESYload-lock systemload-lock system

16

Cathode mount & vacuum load-lock

• Acceptance test completed at LBNL, fully operationalAcceptance test completed at LBNL, fully operational

• The 120 kW CW 187 MHz RF amplifier required to operate the VHF gun The 120 kW CW 187 MHz RF amplifier required to operate the VHF gun has been manufactured by ETM Electromatichas been manufactured by ETM Electromatic


(J. Corlett)


(J. Corlett)

17

VHF amplifier


(J. Corlett)


(J. Corlett)

Single RF sourceSingle RF source: 1.3 GHz, 25 MW pulsed at 10 Hz with 10 : 1.3 GHz, 25 MW pulsed at 10 Hz with 10 s pulses pulse

LINACLINAC: 3 accel. sections.: 3 accel. sections.AWA/ANL typeAWA/ANL type

Buncher cavityBuncher cavity::LBNL designLBNL design

Deflecting cavityDeflecting cavity:: Modified Cornell TypeModified Cornell Type

RF Distribution SystemRF Distribution System

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APEX phase-II RF distribution


(J. Corlett)


(J. Corlett)

The solenoid cure worked! The solenoid cure worked!

Minimal length, NTi coated and water cooled. Minimal length, NTi coated and water cooled.

Alternative approach Alternative approach

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Coaxial feed multipacting cure

At Dec. 15, 2011 integrated < 120 hours of conditioning.At Dec. 15, 2011 integrated < 120 hours of conditioning.December 15: CW mode at nominal power ran for 12,5 hours without faultsDecember 15: CW mode at nominal power ran for 12,5 hours without faults

Results reconfirmed the day after (> 24 hours no fault)Results reconfirmed the day after (> 24 hours no fault)Power stability ~2x10Power stability ~2x10-3-3


(J. Corlett)


(J. Corlett)

Gun RF conditioning started on November 7, 2011Gun RF conditioning started on November 7, 2011

PulsedPulsed

20

RF conditioning completed

Measurements performed in CW mode on a coaxial Faraday cup right Measurements performed in CW mode on a coaxial Faraday cup right downstream the beam pipe exitdownstream the beam pipe exit


(J. Corlett)

21

Dark current follows Fowler-Nordheim dependence on the E fieldDark current follows Fowler-Nordheim dependence on the E fieldAt the nominal field (19.5 MV/m) the present value is ~ 8 At the nominal field (19.5 MV/m) the present value is ~ 8 AA

Expected to decrease when the beamline is installed and vacuum bake Expected to decrease when the beamline is installed and vacuum bake completedcompleted

Dark current


(J. Corlett)

22

Measurements performed with a Dycor 2000 RGA systemMeasurements performed with a Dycor 2000 RGA system1 NEG pump out of 20 activated, 1 ion pump, 2 turbo pumps; no bake1 NEG pump out of 20 activated, 1 ion pump, 2 turbo pumps; no bake

H2 He O HO HO2N N2

O2 Ar CO2CC

Vacuum performance


(J. Corlett)

23

We have two We have two ““regimesregimes””: cold cavity in the first ~ 30 min where the copper is : cold cavity in the first ~ 30 min where the copper is going to temperature; warm when the copper temperature stabilizesgoing to temperature; warm when the copper temperature stabilizes

TS1

TS2

TC2

TC

Thermal effects on frequency

• The APEX injector is being commissioned• Designed for high-brightness electron beam at MHz repetition rate• VHF cavity• Flexibility in photocathode materials

• Progress:• VHF cavity is RF conditioned• Initial characterization of dark current and tuning• Cathodes under development

• Plans:• Photoemission experiments to start soon• Phases I and II add diagnostics, bunching, acceleration• Plan to complete construction and begin final beam

characterization in 2013

Summary – APEX R&D program

F. Sannibale, B. Bailey, K. Baptiste, J. Byrd, M. Chin, D. F. Sannibale, B. Bailey, K. Baptiste, J. Byrd, M. Chin, D. Colomb, J. Corlett, C. Cork, S. De Santis, S. Dimaggio, L. Colomb, J. Corlett, C. Cork, S. De Santis, S. Dimaggio, L.

Doolittle, J. Doyle, J. Feng, D. Filippetto, G. Huang, H. Huang, Doolittle, J. Doyle, J. Feng, D. Filippetto, G. Huang, H. Huang, T. Kramasz, S. Kwiatkowski, R. Lellinger, W. E. Norum, H. T. Kramasz, S. Kwiatkowski, R. Lellinger, W. E. Norum, H.

Padmore, C. Papadopoulos, G. Penn, C. Pogue, G. Portmann, Padmore, C. Papadopoulos, G. Penn, C. Pogue, G. Portmann, J. Qiang, D. Garcia Quintas, J. Staples, T. Vecchione, M. J. Qiang, D. Garcia Quintas, J. Staples, T. Vecchione, M.

Venturini, M. Vinco, W. Wan, R. Wells, M. Zolotorev, F. Zucca, Venturini, M. Vinco, W. Wan, R. Wells, M. Zolotorev, F. Zucca, ……

25

A team effort

Documents

APEX description, status and plans John Corlett for the APEX team Lawrence Berkeley National Laboratory 1