Piezo Studies and Temperature Measurements Ruben Carcagno May 11, 2005.

Piezo Studies and Temperature Measurements

Ruben Carcagno

May 11, 2005

5/11/2005 Ruben Carcagno - AAC Review 2

Background

• Fast tuners (e.g., piezo tuners) are needed to maintain high RF power efficiency in high gradient (e.g., 35 MV/m) SCRF cavities– Key component for cost reduction of ILC and

Proton Driver

• FNAL piezo tuner studies were done for the 3.9 GHz CKM deflecting cavity at A0.

• Experience and results are transferable to 1.3 GHz cavities for the ILC and Proton Driver. R&D in these areas will continue at HPTF.

5/11/2005 Ruben Carcagno - AAC Review 3

Detuning and RF Power

2

2/10

25.0

f

f

P

PΔf = cavity detuning (Hz)

f1/2 = cavity bandwidth

~ 200 Hz for 1.3 GHz TESLA cavities

~ 65 Hz for 3.9 GHz CKM cavities

m

Hz

l

f

000,2~

• RF power increase for field control due to detuning:

• Detuning highly sensitive to small changes in cavity shape• Example: 13-cell, 3.9 GHz CKM cavity (from FEA)

5/11/2005 Ruben Carcagno - AAC Review 4

Detuning Sources• Fast, small changes in cavity shape are caused by two

primary sources: • Lorentz Forces (electromagnetic):

Important for pulsed operation, high gradients (e.g., 35 MV/m) Highly repetitive Main detuning concern for ILC and Proton Driver Piezo compensation demonstrated at the Tesla Test Facility

Microphonics (vibration sources) Important for cw operation, narrow bandwidth Random Microphonics compensation less advanced than Lorentz FNAL work at A0 contributed to advances in the state of the art of

microphonics detuning compensation

2accEKf

5/11/2005 Ruben Carcagno - AAC Review 5

Detuning Compensation: Fast Tuners

PIEZOELECTRIC ACTUATORS• Commercially available from multiple

sources• Typically used at room temperature• Work at cryogenic temperatures with

reduced stroke. Characterization important • Actuator of choice in other labs for detuning

compensation studies

MAGNETOSTRICTIVE ACTUATORS• Being introduced as an alternative to

piezoelectric actuators for SCRF fast tuning• Newer technology for this application, single

source• Some labs are investigating this option

Fast tuners have been proposed for active detuning control by applying a counteracting force to the cavity

5/11/2005 Ruben Carcagno - AAC Review 6

Studies at 1.8 K3-cell 3.9 GHz CKM cavity

Piezo Actuator P-206-40 from Piezosystem Jena

Temperature Rings

• Microphonics Spectrum with pumps ON and OFF

• Vibration measurements with piezo as a sensor

• Piezo-RF detuning transfer function

• Manual microphonics detuning piezo compensation

• Quench and hot spot location using thermometry

5/11/2005 Ruben Carcagno - AAC Review 7

Manual Detuning Compensation

-600

-400

-200

0

200

400

600

800

1000

1200

0 0.5 1 1.5 2 2.5 3Time (s)

Res

onan

t F

req

uen

cy D

evia

tion

[H

z]

Without Compensation With Manual Compensation

(Offset added for visualization)

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90 100

Frequency (Hz)

Re

so

an

t F

req

. D

ev

iati

on

FF

T [

Hz]

Without Compensation

With Manual Compensation

• Cavity system support was not optimized to minimize microphonics

• Microphonics spectrum shows a strong detuning frequency at ~ 30 Hz

• Detuning compensation at 1.8 K was attempted by manually adjusting the piezo frequency, amplitude, and phase

• Detuning was reduced by more than a factor of three and maintained for several seconds

• The result was reproducible, showing the feasibility of using a piezo actuator to compensate microphonics detuning

5/11/2005 Ruben Carcagno - AAC Review 8

Studies at Room TemperatureAutomatic Microphonics Detuning Compensation

Piezo

Automatic compensation with an adaptive feedforward control method demonstrated in a 13-cell CKM cavity at room temperature.

For details, see:

R. Carcagno, L. Bellantoni, T. Berenc, H. Edwards, D. Orris, A. Rowe, “Microphonics Detuning Compensation in 3.9 GHz Superconducting RF Cavities,” 11th Workshop on RF-Superconductivity SRF 2003.

5/11/2005 Ruben Carcagno - AAC Review 9

Detuning Compensation Results• Automatic compensation

demonstrated for three induced frequencies (15 Hz, 27 Hz, and 45 Hz)

• More than 20 dB attenuation

• Mechanical Resonances quickly identified by driving piezo with white noise

0

0.5

1

1.5

2

2.5

3

3.5

0 100 200 300 400 500 600 700 800Frequency (Hz)

Res

onan

t F

req

. Dev

. FF

T (

KH

z) 230 Hz

375 Hz

5/11/2005 Ruben Carcagno - AAC Review 10

Piezo R&D – Next StepsILC and Proton Driver Support

Two Piezos

• Piezo R&D will continue with the HPTF Capture Cavity 2 test

• Integrate piezo with cavity tuner• Start with DESY design

• Studies at 2 K for ILC and Proton Driver:• Lorentz detuning compensation• Microphonic detuning compensation• Piezo characterization and reliability

under operating conditions• Integrate piezo control with LLRF

controls• Evaluate Alternatives (e.g.,

magnetostrictive actuators)• Increase collaboration efforts with other

Labs and institutions (e.g., DESY, ANL, JLab, Saclay, etc)

• Challenges• Piezo mechanical integration with

tuner (preload, reliability)• Mechanical resonances

(complicate control algorithms)• Cost/space reduction for mass

production and industrialization (power amplifiers, piezo size)

Capture Cavity 2 Tuner

5/11/2005 Ruben Carcagno - AAC Review 11

Fast Cavity ThermometryNew system based on smaller CERNOX sensors was developed at FNAL

Fast (10 kHz) temperature acquisition rate to study quench evolution

Traditional Carbon Glass RTDs used in SCRF thermometry (e.g., Cornell system) too large for small 3.9 GHz CKM cavity geometry

5/11/2005 Ruben Carcagno - AAC Review 12

Thermometry Results

Quench Operation(10 KHz data acquistion)

1.6

1.7

1.8

1.9

2

2.1

2.2

2.3

2.4

2.5

2.6

0 50 100 150 200 250 300 350 400

Time (ms)

Tem

per

atu

re (

K)

A

B

C

D

• Quench location clearly identified

• Hot spot shifts 90 degrees with cw polarization mode

• Increasing RF power resulted in quench at hot spot location

Lambda point

5/11/2005 Ruben Carcagno - AAC Review 13

Conclusions

• FNAL has already begun developing expertise in areas of piezo tuning and cavity thermometry

• R&D in these areas has resulted in advances in microphonics detuning compensation and the ability to pinpoint quench location in small cavities

• The focus of this work is now shifting towards ILC and Proton Driver support

• Piezo tuning development work will continue with the HPTF Capture Cavity 2 test

• Fast tuning (e.g., piezo) capability is critical for cost reduction efforts in high gradient SCRF machines (high RF power efficiency)