the hw resonators in juelich - classe.cornell.edu · the hw resonators in juelich ... rfq...

Forschungszentrum JülichIn der Helmholtz-Gemeinschaft

Rolf StassenIKP/ COSY

11.06.2005SRF2005, Ithaca

1

The HW resonators in Juelich

• The Halfwave-Resonator• RF Main-coupler

• Tuner

• RF-Measurements • Cw operation

• Pulsed mode: mechanical resonances, LFD, I/Q-control

• Outlook



11.06.2005SRF2005, Ithaca

2

Accelerating facility COSY: new injector

Ion Source

RFQ

SuperconductingLINAC

DiagnosticsLine

Transfer Line

50 MeV H , D- -

New injectorbased on SC-HWR

Cyclotron Julic: Limits quantity of polarized particles (2E10)

• pulsed operation (2 Hz, 500 µs beam)

• beam-current = 2mA

• Injection-energy = 2.5 MeV/u

• 20 resonators 160 MHz, ß = 0.11

• 24 resonators 320 MHz, ß = 0.2

• 4 resonators (same type) each cryostat @4K

• final-energy 52 MeV (H-) / 56 MeV (D-)

• Eacc = 8 MV/m (Bpeak=80mT, Epeak=38MV/m)

• Focusing quadrupoles and diagnostic outside

the cryostats



11.06.2005SRF2005, Ithaca

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HWR Parameter (160MHz, ß=0.11)

Beamports

1.125 m

26G / Ω

245R/Q / Ω

4.8Epeak/Eacc

10.4Bpeak/Eacc / mT/MV/m

4 Accessports (chemical preparation,

HPR)

Used for couplers and additional

pumping

D=180mm B-Field

λβ str

z

acc

dzztzEE

∫∞

∞−=))(,(



11.06.2005SRF2005, Ithaca

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RF main coupler

• Inductive coupling mounted from the top

• 4 kW Peakpower (10ms, 10Hz, 100% Reflection)

• 150 W avg. power

• adjustable:106 < Qext <109

• 2 RF windows (warm/cold)

• < 5 mW/cm2 RF heating on the cold window with a vapu. Ge-layer

coldwindow

warmwindow

~80 c

m



11.06.2005SRF2005, Ithaca

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ACCEL: preferred circular shape by

spinning

ZANON: milling elliptical shape into a20mm Niobium-Plate

Two different prototypes from two manufactures

1. difference:

Fabrication of endplates



11.06.2005SRF2005, Ithaca

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Two different prototypes from two manufactures (2)

2. difference:

quantity and position of weldings

ACCEL:

Four halfcells + endplates

ZANON:

Eight pieces + endplates



11.06.2005SRF2005, Ithaca

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Preparation for both cavities done by ACCEL

• Ultrasonic cleaning• 120µm BCP in closed pumped system (temperature

controlled), cleaning and filling with pure water• High pressure rinsing via

access-ports (30min each port)• Drying by pumping in clean-room

• No heat treatment• No baking



11.06.2005SRF2005, Ithaca

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4K-Measurement: Multipacting

• First Multipacting barrier at some mW (Eacc ~ keV)

• Conditioning with 5W RF-Power for about 3 weeks

Two-point MPnear beamports

Tuningrange: +/- 1mm (+/- 120kHz)Initial tension possible

• Stepper motor• Piezo actuators: compen-

sation of LFD • All active parts outside the

cryostat

For details see Poster TuP32: R.Eichhorn



11.06.2005SRF2005, Ithaca

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Qo-Epeak

ACCEL / ZANON

1,E+07

1,E+08

1,E+09

1,E+10

0 10 20 30 40Epeak [MV/m]

Q0

0 1 2 3 4 5 6 7 8

Eacc [MV/m]

max. qualityfactor due to limited magnetic shielding

MP at circularendplates

Quench

BCS-qualityfactor

Pulsed operation

(10ms, 2Hz):

Eacc = 7.5 MV/m

(Epeak = 36 MV/m)



11.06.2005SRF2005, Ithaca

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Mechanical Eigenmodes

279265

242

223

211

198154

48

00 50 100 150 200 250 300 350 400 450 500

Frequency / Hz

mech

anic

al osc

ilation-

am

plit

ude (

a.u

.)

1) FFT of phase-signal after step-function at Piezo-Tuner2) Sinusoidal excitation

230 Hz211 Hz

160 Hz154 Hz

67 Hz48 Hz

ZANONACCEL



11.06.2005SRF2005, Ithaca

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Mechanical resonances in pulsed operation

Preflected

Pforward

Accelerating field

Change of resonancefrequency

Excitation of strongest mechanical eigenmode(211 Hz)



11.06.2005SRF2005, Ithaca

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Lorentz-Force-Detuning

Change of resonance-frequencywith Piezo-Feedforward

Change of resonance-frequencywithout Piezo-Feedforward

Piezo- Feedforward

Eacc = 3,1 MV/m

=> LFD = 60 Hz

Pulse-length: 25msLimited by mechanical

inertia

Static detuning:∆f = -k * Eacc²

ZANON: 6 Hz/(MV/m)²ACCEL : 10 Hz/(MV/m)²

First ANSYS®-Simula-tion: 1 Hz/(MV/m)²

Field-probe



11.06.2005SRF2005, Ithaca

13

02468

10

E-F

ield

/ M

V/m

Frequency-control

beam

Analogue I/Q-control

TP3TP2TP1

Field accuracy:

Achieved Goal(worst case)

+/- 0,6% Amplitude (+/- 0,5%)+/- 1,4° Phase (+/- 0,5° )

I/Q-control

TP1: Activating the I/Q-control, frequency-control switched off

TP2: Triggering the highfield-pulsTP3: I/Q-control and pulsing switched offTP4: Activating the frequency-control loop

TP4

Phase (+14Hz)

Phase (-14Hz)Amplitude (+14Hz)

Amplitude (-14Hz)



11.06.2005SRF2005, Ithaca

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Conclusion and next steps

Cavities

LHe Reservoir

RF Power Input

RF Field Probe

Cavity Alignment

MagneticShielding

Cryostat Vessel

Additional Pumping

MLI Insulation

Shield Cooling (part. Removed)

Thermosyphon

Girder

Piezo & StepperMotor (Tuner) Rupture Disc

Pumping Port (Insulating Vacuum)

Tuner

LHe 4 K inHe 50 K out

Beam Axis

• 8 MV/m possible but up to now not serious in a 7000 h/a linacoperation

• Mechanical stability requires modifications

• RF-conditioning, baking, (He-processing)

• 2K-operation• Installation of one prototype

including lHe-cover in the new cryostat

Thanks to:R. Eichhorn, F. Esser, B. Laatsch, G. Schug, H. Singer

MAC members:B. Aune, A. Facco, D. Proch, U. Ratzinger,S. Schriber, K. Shepard, M. Vretenar

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