Blade and Piezo Tuners Overview

1
Blade and Piezo Tuners Overview
1m

• Justin Keung
• University of Pennsylvania
• January 16, 2007

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Lorentz Detuning

• As the cavity accelerating gradient increases,
  the pressure due to radiation becomes significant
• Recall

• Cross section of one-cell cavity
• Red line represents the cavity design contour
• Blue line shows the deformed shape
• Cavity deformation causes change in natural
  resonant frequency
• Piezo Tuner to compensate

Estimation of Lorentz Detuning and Related Tuning
Characteristics of ICHIRO Cavity, T. Higo et al.,
KEK, 2006
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Mechanical Resonance

• Entire cryomodule can vibrate at mechanical modes
• (your hand can feel the cryomodule vibrate!)
• Changes the shape of the cavities periodically
• Resting cavity resonates at 42Hz, beam arrival
  excites a 180Hz resonance
• The 180Hz resonance decay constant is about 0.7
  second
• ILC will have only 0.2 seconds between beam
  pulses
• Piezo Tuner to compensate

ILC FAST TUNER RD PROGRAM at FNAL, Status Report
CC2 Piezo Test Preliminary Results, Ruben
Carcagno et al., 2006
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What are Tuners?

• Piezoelectric Crystals and Blade Tuner
• Changing the natural frequency of the cavity
  (tuning) by changing its size
• 22.5MHz -15 per 1mm of the cavity flange to
  flange distance
• Piezos tuners fast
• Actively control cavity tuning (10-6 s time
  scale)
• The same piezo crystals concurrently measures the
  noise and compensates for it
• Blade tuners slow
• One time tuning, after cavity cools to 2K

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Piezos and Blade Tuner
Top left complete Piezo and Blade Tuner Top
right blade tuner unmounted Bottom left piezo
tuner unmounted Bottom right Piezo tuner mounted
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Blade Tuner In Action
Time lapsed video of the blade tuner changing the
natural frequency of the cavity (orange line
shifting). The blue line represent the frequency
away from 1.3GHz, in units of 135kHz/mV. Blade
tuner has tuning range of 30.8MHz-2. One step
of the motor moves the screw forward/backward by
1.6nm-2, and changes the resonant frequency by
2.3Hz-2
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Piezo Tuner Actuator
Representation of the before (left) and after
(right) the piezo tuner changing the natural
frequency of the cavity (orange line
shifting). Actual measurement done with locating
the frequency of the peak before and after the
application of piezo voltage. 150V applied on
the 9 stack (of the 91 stack) moves the
frequency at the peak by 18kHz-12.5.
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Piezo Tuners Sensor
Signal is a result of hammering the table. Blue
signal from monitor piezo, 2mm. Green same
signal from drive piezo, 6mm. (smaller amplitude,
but signal received) This demonstrates the
plausibility of using the same piezo to both
sense/actuate.
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Piezo Sensor Actuator
This board, using the actuator piezo, is able to
extract the same signal as the sensor piezo. This
board also controls the actuator piezo.