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Photoinjector for the ILC test facility at FermilabPhotoinjector for the ILC test facility at Fermilab

Sergei NagaitsevFermilab

May 24, 2007

S. Nagaitsev 2

f Fermilab NML plansFermilab NML plans

Fermilab is constructing the NML facility at the existing building (called New Muon Lab) for the ILC tests and generic accelerator research

The NML is being constructed to address primarily the ILC S2 R&D list However, our plans go beyond S2. We would like to

include elements of S4 R&D tasks (crab-cavities), diagnostics development, personnel training, and accelerator R&D.

The NML facility is staged (1 CM, 2 CMs etc); when complete, it would include 1 (or 2) rf units running ILC-like beam at 5 Hz.

1 rf unit with beam requires building an extension tunnel and a new cryo-plant

The progress is resource limited

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f NML inside (now)NML inside (now)

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f Outline of our plansOutline of our plans

Cryomodule delivery 1st (Type 3+) cryomodule is planned to be delivered

in fall, 2007 2nd (Type 3+) CM – summer 2008 3rd (ILC Type 4) CM – Mid FY09 Replace all three CMs with ILC Type 4+ in FY2010

The NML facility will start as a Cryomodule Test Stand in FY07-08

FY08: add beam; start civil construction of the building extension

Convert to an ILC RF Unit beam test facility in FY11

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f NML Schedule (Phase-1)NML Schedule (Phase-1)

Phase - 1 (FY07 thru early FY08) Prepare Facility for Testing of Capture Cavity II (CCII)

and 1st Cryomodule (CM1) without Beam• Building Infrastructure (AC Power, Water, Air,

Mechanical)• Electrical Infrastructure (Racks, Trays, Cables)• Build Cave to Test these Devices (~ 3/4 of Full Cave)• RF Systems (3MW for CM and 300kW for CCII)• Cryogenic System (1st Refrigerator, Feed Can, Feed

Cap, End Cap, Distribution)• Control Room• LLRF, Controls, Safety Systems, Instrumentation (non-

beam) Move CCII from Meson Detector Building (MDB) to

NML• Cool-down and Power Testing

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f Phase 1: 1st CM (end of CY07)Phase 1: 1st CM (end of CY07)

Capture cavity 2 in its final location for the injector

Type 3+ cryomodule

A used 3-MW Klystron,

10-MW, 1.5-ms modulatorCC2 RF system

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f NML Schedule (Phase-2 & 3)NML Schedule (Phase-2 & 3)

Phase - 2 (FY08) Testing of 1st and 2nd Cryomodule without Beam,

Prepare Facility for Beam• Receive, Install, Power, Cool-down 1st Cryomodule• Install New Gun and Relocate Injector to NML• Extend Cave• Install Beam Lines and Dumps• Install Additional RF Systems needed for CCI and Gun• Receive, Install, Power, Cool-down 2nd Cryomodule• Begin Building Extension needed for Phase-3

Phase - 3 (FY09) Testing of Full RF Unit with Beam

• Complete Building Extension• Begin Testing with Beam• Install 3rd Cryomodule• Upgrade Cryomodule RF system to 10 MW

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f Two CMs with beamTwo CMs with beam

The existing building is perfect for testing two cryomodules with ILC-like beam. The building can be extended to fit 3 cryomodules.

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f ILC-like beam?ILC-like beam?

3.2 nC/bunch @3 MHz, up to 3000 bunches @ 5Hz

Bunch length: 300-μm rms Transverse emittance: not important (~5 μm) Energy: 30-40 MeV (to avoid overfocusing in

the CM operating at 31 MV/m) Need “known and frozen” beam parameters at

the cryomodule entrance

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f

(CC-1)

13m

Existing Fermilab PhotoinjectorExisting Fermilab Photoinjector

The existing photoinjector and the laser will be moved to NML in 2008.

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f Fermilab Photo InjectorFermilab Photo Injector

The PhotoInjector has been in operation since late 90’s and has been a training ground for SCRF technology

Provides 17MeV bunches (up to few hundred) at 1 MHz rate at 1 pulse/sec Two 1.3-GHz klystron-based RF systems power the RF Gun and Capture Cavity RF systems will be moved to NML in 2008

Capture Cavity and beamline

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f Existing rf gunExisting rf gun

Very high dark current

rf break down for pulses longer than 300us

We will not use this gun cavity at NML

RF Gun prior to solenoid installation

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f

P. Piot

(CC-1, CC-2)

(intended initially for ILC crab cavity tests)

22m

Proposed NML Injector LayoutProposed NML Injector Layout

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f NML injector layoutNML injector layout

1 – Gun cavity, 2 – Coaxial rf coupler, 3 – dark current kicker, 4 – laser mirror cross, 5 – current monitor & BPM, 6 - collimator, 7 – Tesla cavity (CC1), 8 – Tesla cavity (CC2)

1 23

4

5

6

7

8

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f NML cathode systemNML cathode system

Gun Transfer

Transport System

GUN

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f Fermilab plans for the rf gunFermilab plans for the rf gun

We are planning to copy (and improve) a DEZY-PITZ gun

RF gun sub-systems needed at NML: Cathode system -- need new, will be supplied by

INFN Milano UV laser system -- exists, needs upgrades Gun cavity – need new, will be supplied by DESY Focusing solenoids – need new Coaxial coupler – need new Dark current kicker – need new Laser mirror cross – need new RF system (5-MW or more, 1.5-ms modulator) –

exists (needs updrades) Water, temperature control system -- exists

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f Cathode systemCathode system

The cathode system is being provided to us by INFN-Milano.

Two sub-systems: A stand-alone vacuum chamber for cathode

preparation with Cs and Te sources A cathode loading chamber connected to the gun

cavity.

Discussions underway on how to redesign the cathode socket (and spring) in the gun cavity. Goal: reduce the dark current Would like to “hide” the rf contact spring See next slides

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f RF spring contact (from D. Sertore, INFN)RF spring contact (from D. Sertore, INFN)

•Two different spring types have been used, in the same insert!•The insert was designed for a WELDED Watch-band type spring.

Watch-band type•CuBe hard, silver coated spring•Difficult to weld (becomes hard)•Critical number of convolutions

Cantend coil spring•CuBe uncoated. •Available coated with Ag, Au etc…•Welded by the manufacturer

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f Our latest proposal to INFN and DESYOur latest proposal to INFN and DESY

Two springs – one for centering and one locking

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f UV laser systemUV laser system

Already have at photoinjector Needs some upgrading Will be moved to NML in Jan 2008 Can run a single gaussian pulse or stacked (4) pulses

at 3MHz

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f Gun cavityGun cavity

Have all DESY drawings at Fermilab. Do not yet have a complete set of procedures (brazing, tuning etc) Would like to make some modifications to design: cathode

socket, rf probe, reduce max. fields Will take time to develop expertise.

DESY has agreed to make a gun cavity for us at DESY. Currently negotiating small changes to their design

(cathode)

We will start making our own gun cavity and the coupler shortly after DESY will start the manufacturing. KEK STF has asked us to supply a gun cavity for them. No

official agreement yet.

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f RF probe - possible locationRF probe - possible location

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f Focusing solenoidsFocusing solenoids

Will make two identical solenoids (like main solenoid above) instead of two different ones Present bucking coil design interferes with a possible rf probe

installation at the gun cavity cathode wall. Solenoids can be ordered from Danfysik (they have drawings,

fixtures) $30k each PS needed: 500A, 50V, 10 ppm 27k Eur

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f Laser mirrorLaser mirror

Have drawings from DESY Laser mirror alignment will be difficult because

coaxial coupler inner diameter is small

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f RF systemRF system

Already have a 5MW Klystron at the photoinjector TH 2104C

Need a new 1.5-ms modulator and a pulse transformer Planning to build at Fermilab

Plan to run the gun at 40 MV/m at the cathode From DESY simulations: gradient ≈ 23 MV/m·(P[MW])1/2

For 40 MV/m need about 3 MW. For conditioning need more power.

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f Water systemWater system

Temperature stability is crucial: Average power at 1ms flattop, 5 Hz: 15 kW Simulations freq. shift: -23 kHz per one-degree C

Plan temperature control to 1F (0.5 degree C)

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f Overall summaryOverall summary

Would like to have beam at NML in Apr 2008 The rf gun will be capable of providing ILC-like

beams. For 4-stacked laser pulses at 40 MV/m @ cathode 3.2 nC per bunch 4.2 MeV kinetic energy at gun exit 4-μm rms norm emittance 2.4 mm rms bunch length 1.2% rms momentum spread