Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities...

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Innovative Tuner Designs for Low-β β β SRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Transcript of Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities...

Page 1: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Innovative Tuner Designs for Low-ββββ SRF Cavities

Zachary A. Conway

Argonne National Laboratory

Physics Division-Linac Development Group

Page 2: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Outline

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� Why use a tuner?

� Cavity mechanical properties

� Low-β cavity tuner examples

Page 3: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Tuner Requirements

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CW Pulsed

Fast Tuning

Slow Tuning � Center Cavity Frequency

� Microphonics

� He Pressure

Fluctuations

� Resonant Vibrations

� Over Couple –

Additional RF Power $$$

Operating Mode

� Lorentz Detuning

� Over Couple –

Additional RF Power $$$

� Center Cavity Frequency

Page 4: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Why use a tuner?

� Accelerator cavities must be operated with a stable phase and amplitude

� High beam loading – Reduced dependence on RF frequency errors

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Page 5: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Mechanical Considerations

� Design to minimize microphonics (can be extremely effective if

considered early)

– Decoupled the RF accelerating mode from common mechanical vibrations

• cw operation - helium pressure fluctuations (M. Kelly, THIOB04, QWR)

• pulsed operation - Lorentz detuning (W. Schappert, FRIOA01)

– Do as much as you can then use a tuner and overcouple to control RF field

� For example

– cw operation – balance contributions to ∆f

– pulsed operation - fabricate with a high rigidity

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xdxExHfV

32

00

2

00 )()(∫∆

−∝∆ rrrr

εµ

Slater Perturbation Theorem

Page 6: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Cavity Mechanical Design

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Page 7: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

ββββ = 0.5 345 MHz Triple-Spoke Cavity

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measured ∆∆∆∆f/∆∆∆∆P = -12.4 Hz/torr∆∆∆∆f/∆∆∆∆P = -6.3 Hz/torr

∆∆∆∆f/∆∆∆∆P = -2.5 Hz/torr∆∆∆∆f/∆∆∆∆P = -0.5 Hz/torr

Room temperature test results

Z.A. Conway, SRF2005, TUA06T. Schultheiss & J. Rathke, AES, Modeling

1)

4)

2)

3)

Page 8: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

ββββ = 0.077 72MHz Quarter-Wave Cavity

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Z

Displacement (mm) 0 0.25 0.5 1

Δfp-p (Hz) 0.2 15 33 66

Peak-to-Peak Frequency Deviation For A Center Conductor Offset From Electrical Center Along Z.

Frequency Shift Due To Pendulum-Like Oscillations of Center Conductor

X

Possible to eliminate microphonics due to pendulum mode if done correctly. (J.R. Delayen 1987)

Page 9: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Types of Tuners In Use/Development Today

� Mechanical

– Course slow tuners

• Control The Applied Force

• Control The Applied Displacement

– Fine fast tuners

• Piezo electric

• Magnetostrictive

� Electromagnetic: Voltage Controlled Reactance (VCX)

– Limited application range without further R&D

• Stored Energy < 25 J

• Frequency < ~100 MHz

– No plans to use in future accelerators

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Page 10: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Tuners Which Control The Applied Force

� Tuner compresses cavity by squeezing at the

beam ports

� This design separates the mechanically

compliant course tuner from the rigid fast tuner

� ANL approach has essentially no direct

interaction with the clean assembly10

Tuning BarsWire Rope Bellows

Fast Tuner Aperture

Helium Gas Input

Page 11: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Helium Gas Actuated Slow Tuner Performance

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Am

plitu

de (d

B, a

rb)

Pha

se S

hift

(Deg

rees

)

Slow Tuner Response

Slow Tuner Transfer Function

The pneumatic tuner is quite fast >2500 Hz/sec

Zinkann et al, PAC’05, WPAT082

Page 12: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Piezoelectric Fast Tuner

Fast Tuner Cross SectionNb Ring and Button Welded To Cavity

17 c

m

Nb Wall Helium JacketWith 6.75” CF Flange

Belleville Washers

G-10 Thermal Breaks

Piezo Actuators

Differential Screw

Nb RingNb Button

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Fast Tuner On HWR Cavity

Liquid Nitrogen Out

Kelly et al, LINAC2010, THP057

Page 13: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

-180

-135

-90

-45

0

45

90

135

180

0 20 40 60 80 100 120 140 160 180 200

Re

spo

nse

Re

lati

ve

Ph

ase

Sh

ift

(De

gre

es)

Vibration Frequency (Hz)

Fast Tuner Performance on HWR

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0

10

20

30

40

50

60

70

0 20 40 60 80 100 120 140 160 180 200

RF

Fre

qu

en

cy V

ari

ati

on

Am

pli

tud

e (

arb

.)

Vibration Frequency (Hz)

Page 14: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Examples of Low-ββββ Tuners For CW Operation

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Page 15: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Tuner Examples

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ISAC-II Cryomodule @ TRIUMF

760

800

840

880

920

5:19:41 PM 5:21:07 PM 5:22:34 PM 5:24:00 PM 5:25:26 PM

Time, h-m-s

Pre

ssu

re, T

orr

-27000

-23000

-19000

-15000

Tu

ner

Po

siti

on

, ste

p

PressureTuner Position

630

800

850

900

Pre

ssur

e (T

orr)

Time (min)

� Lever connected to tuning plate

� Tuner resolution = 0.04Hz/step

(5nm/step)

� Laxdal et al, SRF2011 THIOB06

Bottom View Of Cavity

Page 16: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Tuner Examples

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352 MHz β = 0.17 Halfwave

EURISOL R&D

at 293 K.110 kHz tuning range68 kHz/mm

For a similar β = 0.31 cavity at 293 K.150 kHz tuning range227 kHz/mm

Facco et al, PRST-AB 9, 110101 (2006)

Page 17: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Plunger Tuners

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Spiral2IPN-Orsay

� Can in principle be used on nearly

any cavity with a properly placed

port.

� Moveable niobium rod

� Cooled with helium bath

� Large tuning range = 90kHz

High RRR Niobium PlungerOlry, SRF09, THOBAU04

Page 18: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Example of Low-ββββ Tuner For Pulsed Operation

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Page 19: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

FNAL’s Single Spoke Cavity Tuning

� FNAL developed spoke cavities for a pulsed

high-intensity proton accelerator

� The cavities are reinforced, increasing their

rigidity and minimizing Lorentz detuning, I.

Gonin (FNAL)

� G. Apollinari, SRF’05, TUP34

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325 MHz Single-Spoke

Page 20: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

FNAL’s Single Spoke Cavity Tuner

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TFlat-Top=1ms

Eacc=30MV/m

TFill=1,2ms

Detuning, Hz

Time

Piezo OFF

Piezo ON

Schappert, Pischalnikov, FRIOA01

Page 21: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Summary

� When designing your cavity it pays to couple your

electromagnetic with your mechanical simulations

Majority of frequency detuning effects can be minimized or

even eliminated by design (neglect can lead to an unusable

system)

� Tuner designs should be tailored to applications; many

designs work but vary in cost, complexity and flexibility

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Page 22: Innovative Tuner Designs for Low-ββββSRF Cavities Tuner Designs for Low-ββββSRF Cavities Zachary A. Conway Argonne National Laboratory Physics Division-Linac Development Group

Thank You

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� Scott Gerbick, Mark Kedzie, Mike Kelly, Peter Ostroumov,

Sergey Sharamentov Ken Shepard, and Gary Zinkann (ANL)

� Jean Delayen (ODU)

� Alberto Facco (MSU/INFN-LNL)

� Robert Laxdal (TRIUMF)

� Yuriy Pischalnikov and I. Gonin (FNAL)

� John Rathke and Tom Schultheiss (AES)