WP8.1 UMI TunerA. Bosotti, N. Panzeri, R. Paparella, F. Puricelli

Updates since the last CARE meeting:• Life Time Test for PI-P889.90• Cryogenic calibration of a new force

sensor CELMI 142-500• Progress on the Blade Tuner

(presented by Nicola Panzeri)

Piezo Life-Time Test 1/2PROPERTIES PI P-888.90 Unit

Material PZT-PIC 255  

Length 36 mm

Cross section 100 mm2

Max. stroke 35 μm

Blocking force 3600 N

Res. frequency @ no load 40 kHz

Min. voltage -20 V

Max. voltage 120 V

Capacity - nominal 12,4 μF

Capacity - measured 13,6 μF

The purpose of this test is to investigate the behavior of piezoelectric ceramics in condition equivalent to 10 years of operation as actuator in active frequency tuner for ILC superconducting cavities (SC). To do this a Physik Instrumente PI P-888.90 PIC255 piezoelectric ceramic has been cooled down in LN2 and has been excited uninterruptedly for a month up to its limits, sustaining about 1.5x109 cycles of switching, up to nearly the maximum stroke, a good estimate of ten years as actuator for ILC cavities.

Main features and parameters of the piezo

Experimental apparatus block diagram Insert “functional” scheme

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

-20 0 20 40 60 80 100 120

Vpiezo [V]

Str

oke

[u

m]

before test

after test

Before After

Capacity [uF] 13.6 13.56

Res. Freq [kHz] 45.9 45.2

Max stroke [um] 40.2 38.3

Piezo Life-Time Test 2/2 Start 26 Nov 2004

Stop 20 Dec 2004

Hours 622

Cycles 1.505x109

Sine Wave Amplitude -20V ÷ +120 V

Frequency117 Hz for 4 days497 Hz for 6 days

997 Hz for 16 days

Average Preload 1.25 kN

Max Current [rms] < 200 mA

Average Temperature

81 K

Main features of the life time test

Hysteresis loops comparisons Solartron SM1 LVDT position transducer

Sensitivity@20kHz

= 149 mV/V/mm

Main piezo parameters checked

Cryogenic calibration of a new force sensor CELMI 142-500 1/3

Previous measurements have showed an unacceptable behavior of standard load cells when operated in a cryogenic environment.

Main problems were:

• Glue: plastic deformations appears at low temperature.

• Strain Gauge: high virtual load, high hysteresis.

Results:Unacceptable lack of stability, uniformity

and repeatability in the response

As a consequence a custom load cell, manufactured by CELMI srl (Buccinasco, Italy), has been realized and tested in order to verify the performances of

cryogenic-devoted sensitive elements (strain gauge & glue)Main features:

• Standard steel case (model 142), high transverse load resistance

• Strain gauge and glue suitable for cryogenic applications

CELMI load cell mod.142-500

Cryogenic calibration of a new force sensor CELMI 142-500 - 2/3

The setup developed for previous load cell test has been used

A stable liquid He T has not been reached because of the high heat transfer through the steel rod that exerts the force

• P = 1.4 10-3 mbar

• DUT T ranging from 6 to 15 K

• > 4000 calibration points

• 5 full range load sweeps, 0-200 kg

Cryogenic calibration of a new force sensor CELMI 142-500 - 3/3

This new sensor can be calibrated with an acceptable error,

the trend can be assumed to be:

kgmVVkgF out 5.7][71.4908.25][

Conclusions• After about one month of operation in LN2 environment under

extreme conditions, and after more than 1.5x109 oscillations driven between (nominal) operating voltage limits, the PI P 888.90 piezo is still working with almost the same characteristics.

• The test on CELMI prototype has proved that the glue and strain gauge sensors used can work in LHe cryogenic environment with good repeatability and sensitivity.

Future developments:• Realization of a new cell hosting the same sensitive elements but with

the proper shape and reduced dimensions• Testing and calibration of the new cell with a more accurate DUT

thermal stability - some solutions, already adopted for piezo tests, has been discarded due to the CELMI prototype size.

• A new insert to perform more accurate tests on piezos and force sensors has been designed and is under construction.