1. Piezo Tuning System (PTS)
developed at Saclay

2. Saclay Piezo Tuning System (PTS)
Purpose:
Design of a new PTS that can be mounted on a TTF cavity
(present design of cavity and He tank without any modification)
Fabrication of 2 PTS
Tests
RF power tests of C45 TTF cavity in CRYHOLAB (WP10 – Bernard Visentin)
Mechanics + electronics development:
G. Devanz – E. Jacques - S. Leducq – M. Luong (DAPNIA/SACM)
Bo Wu (DAPNIA/SIS)

3. Mechanical principle of the present TTF tuner
Mechanical studies
Mechanical principle of the present TTF tuner
Design by M. Maurier and P. Leconte based of the MACSE tuner design
DLscrew
DLarms
DLcavity
Double lever system: ratio ~ 1/17
Stepping motor with Harmonic Drive gear box
Screw – nut system
D Zmax = ± 5 mm and D Fmax = ± 2.6 MHz
theoretical resolution: dz = 1.5 nm !
Orientation of the forces:
the cavity is always compressed
the tuner fixations are stretched
fixation on
Cavity
fixation on
He tank
fixation on
He tank

4. Mechanical studies Stiffness increased by reversing the forces
The piezo support is pulled
Fpull≈ Fcav/2
Fcav < 10 kN
Fcompress
Present piezo TTF tuner:
The piezo actuator shall be kept in compression by its support: Fcompress
The effective preload strength on the stack is:
Fpreload ≈ Fcompress - Fcav/2
The stiffness of the whole tuning system is degraded by the piezo support which shall have a flexibility to allow piezo elongation and a good preload control.
Reversing the strength direction: by stretching the cavity, the strength would be applied on the stack only by the cavity extension. A higher tuner stiffness would be conserved.

5. suppressing the asymmetry
Mechanical studies
suppressing the asymmetry
A second lever can be added in order to obtain a symmetric movement allowing long tuning range keeping strengths parallel to the axis of the cavity.
SOLEIL and Super-3HC cryomodules have such tuner design without piezos.
(the Super-3HC tuner)

6. Mechanical studies piezos frame
2 flexible steel foils for transverse force transmission and axial piezo stroke transmission
Transverse force due to lever system
Load applied by the cavity elasticity
Helium tank fixation
Flexibility of the support for lowering the transverse forces
piezos frame
2 piezos actuators
Piezo actuator size:
L= 30 to 36 mm
2 piezo stacks in a symmetric position guided by 2 flexible steel foils for axial stroke transmission without friction

7. Mechanical studies
Question: do we need a system to equilibrate the load between the 2 piezos stacks mounted on the tuner ?
piezos support
=> Our first design is without any adjustment system.
A precise machining of the pieces + the toppling of the tuner components should allow to equilibrate the compression load on the 2 piezos.
Conical support
piezo
Spherical support glued on the piezo stack
Experience will tell us if an adjustment system is necessary
Length (51 mm) precisely machined
(+0.005, -0)
Once the two conical supports are machined, these 5 elements will be matched together

8. Mechanical studies piezos support Do we need a preloading system ?
Requirement for the tuner design: the cavity shall be always stretched (suppression of the mechanical plays for minimizing the backslash).
Typical force applied by the cavity is about 2000 N (0.5 to 1 mm deformation).
It is possible to increase this force up to about 7000N (cavity stretched by about 2 mm from zero point at cold) while keeping the cavity in elastic deformation (in the whole range 300K-2 K).
In that case, if the force is equally distributed, each piezo should see about 1600 N, which is an interesting preload value.
First design without any preloading system

9. A pneumatic jack was used to apply forces up to about 7000N
2 PTS fabricated
Tests on a bench at 300K
A pneumatic jack was used to apply forces up to about 7000N
Results:
Stiffness estimation : 35 kN
The flexibility is mainly due to the ball bearing housings
Working of the “slow” tuner: OK
(stepper motor, gear box, mechanical lever, …)

10. Tests on C45 TTF cavity at 300K
Control system developed at Saclay for the integrated tests in CRYHOLAB
Phase
Demodulator
Arbitrary waveforms
Generator
Demultiplexer
Multiplexer PC
GPIB
RS232
i/o 6602
N.I.
Digital Scope
RF Amplifier
(Solid state,IOT,on klystron)
Capacitance meter
RF Control System
Motor Driver
Piezo Driver
Piezo Sensor
Signal Conditionning
FM Demodulator
Locking Amplifier
Tuner
Piezo
Actuator
Motor
Sensor
RF coupler
RF pick-up
trig 1 2 3
Trig

11. Tests on C45 TTF cavity at 300K
After RF power test of C45 cavity in CRYHOLAB (WP10 – Bernard Visentin) the tuner was mounted on the cavity for tests in the laboratory.
Tests program outside CRYHOLAB
(no precise RF measurements available):
Identification and characterization of the mechanical modes: F, Q, piezo to piezo transfer function
Influence of the cavity stretching force on the piezo sensor response (by moving the stepper motor)
Tests performed with NOLIAC piezos PZT-S2
(pz29) L=30mm, 10x10mm

12. Piezo to piezo transfer function
PTS
Signal generator
Piezo driver gain G X
Piezo actuator
9-cells
cavity
Piezo sensor Y
GPIB
Oscilloscope
Harmonic analysis
X(w) = G sin(w)
Steady state of linear system
Y(w)=|Y| sin(w+f)
PC+Labview
X : piezo actuator voltage
Y : piezo sensor voltage
Transfer function H(w) = Y(w)/X(w)

13. Tests on C45 TTF cavity at 300K
Amplitude and phase signal of the transfer function of one piezo to the other.
The tests are still in progress (linearity, influence of the stretching of the cavity, …)
Quality factors of several modes are being determined

14. Tests on C45 TTF cavity at 300K
The cavity will be mounted in CRYHOLAB at the end of week 42
Tests at 300 K in CRYHOLAB:
end of October - beginning of November
Analysis of the CRYHOLAB environment influence on the mechanical modes (main coupler fixation, insulating vacuum, helium tank vacuum, etc.)
RF measurements will allow the analysis of the piezos to detuning transfer function

15. Piezo to detuning transfer function
PTS X
Piezo actuator
9-cells
cavity Y
Piezo sensor
Electrical
Mechanical RF
X : piezo actuator voltage
Y : cavity detuning
electric
Transfer function H(w) = Y(w)/X(w)

16. Tests on C45 TTF cavity in CRYHOLAB (WP10)
The cavity will be cooled down for integrated RF power tests in CRYHOLAB at mid of November.
These tests are scheduled until the end of the year.