Test of a tuning system for Spoke cavity

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Test of a tuning system for Spoke cavity

• Nicolas GANDOLFO

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Spoke Cavity
Spoke SC cavity
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Spoke Cold Tuning System

• Spoke Cavity parameters
• Resonance 352 MHz
• Sensitivity 1 MHz/mm
• Bandwidth 250 Hz
• CTS parameters
• Resolution 2 nm
• Range 4 mm
• Nominal strength 600 kg
• Hostile environment
• Low pressure 10-7 mbar
• Cold temperature 2K
• X-Ray emission

3D View of the system on its Spoke cavity
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Mechanical study

• Components
• Main material Stainless Steel 304L
• Good mechanical behaviour at cryogenic
  temperatures
• Very low magnetic permeability
• Easy machining
• Good ratio quality/price
• Mechanical joints
• Ball joint Uniflon lubricant
• Standard bearings /!\
• Ball screw Stainless steel with MoS2 solid
  lubricant and ceramic balls
• Actuators
• Stepper motor Phytron
• Piezoelectric actuator type multistack

• CEA Soleil double lever arm principle

3D View
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Instrumentation diagram

• Bipolar stepper motor
• Driving by an constructor amplifier device
• Control from a computer
• Serial communication RS232
• Motor control software realized on LabView
• Regulation using a numeric PID and loopback
  information provides by RF electronic stage

f
?f
TCP/IP
PC Computer
LabView Software Control
RS232
Amplifier
M
PID
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Cryogenic test results

• Excellent repeatability
• Sensitivity found 0,95 Hz/pas (calculated
  1,38 Hz/pas)
• No mechanical hysteresis measurable
• Successful regulation with a stable frequency
  (variations lt ?f 50 Hz)

Motor control (in motorstep)
Frequency shift error (in Hz)
Curves showing CTS efficiency
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Piezoelectric actuators study
Noliac Piezoelectric actuators

• Specifications
• Dimensions 36x10x10 mm
• Vacuum compatibility (10-7 mbar)
• Strength capability 4 kN
• Stiffness 100 kN/mm
• Displacement range
• 36 µm _at_300K
• 3 µm _at_4K

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Piezoelectric actuators study

• Mechanical precautions !

• No shear, torsion, bending forces
• Hemispherical supports with high machining
  precision

• Nominal prestress of 40MPa
• Active tuning system for each actuator by heating
  an aluminum part which provides controlled
  strength

Next step Test _at_4K scheduled for begin of
2008