1. Proposal of Piezo Goniometer for LHC Channeling experiment
M. Butcher, F. Loprete, R. Losito, A. Masi
Contents
Requirements for the LHC goniometer
The key point for closed loop control
The project guidelines
Realistic plan

2. Andrea Stevanato (CINEL) Alessandro Giustiniani
Acknowledgements
Andrea Stevanato (CINEL)
Clement Derrez
Alessandro Danisi
Mario Di Castro
Ricardo Picatoste
Alessandro Giustiniani
Sergio Calatroni
Giuseppe Bregliozzi
Walter Scandale
Vittorio Vaccaro
Benoit Salvant
Oliver Aberle

3. Slot for horizontal goniometer: Slot for vertical goniometer:
1–Requirements for the LHC goniometer
Slot for horizontal goniometer:
LSS7, DCUM Start: , B1, Closest Collimator slot: TCSM.D4L7.B1 (DCUM 19918)
Slot for vertical goniometer:
LSS7, DCUM Start: , B1, Closest Collimator slot: TCSM.6L7.B2 (DCUM 19844) 1 m from the device

4. Horizontal orientation:
1–Requirements for the LHC goniometer
Horizontal orientation:
Rotation about z-axis, Linear movement in y-axis z
View from side showing the Roll Angle
View from top showing the Yaw Angle θz θx x y y z
View from front showing the Pitch Angle θy x

5. Vertical orientation: Rotation about y-axis, Linear movement in z-axis
1–Requirements for the LHC goniometer
Vertical orientation: Rotation about y-axis, Linear movement in z-axis
Linear
Stage z
Crystal +
Holder
Yaw
Angle, θy
Roll
Angle, θx
Beam
0 mm x
Pitch
Angle, θy
Rotational
Stage y

6. 1–Requirements for the LHC goniometer
Linear Stroke: 60 mm
Linear resolution: 5 um
Total angular range : +/- 10 mrad
Yaw angle resolution: 0.1 µrad
Yaw angle accuracy over 70 mm travel: +/- 1 urad
Yaw angle overshoot : +/- 10 %
Yaw angle settling time: 20 ms
Yaw angle max speed in scan mode: 50 steps/s
(1 urad step size)
Pitch angle accuracy over 10 mm travel: few urad
Roll angle accuracy over 10 mm travel: few tens urad

7. Controlled in Closed loop Manually Adjusted at the commissioning
1–Requirements for the LHC goniometer
Maximum load: 300 g
Bake out temperature: 110 ° C (currently limited by the Curie temperature of the piezo actuator used)
Installation: quick plug support as for the LHC Collimators
Angle
Controlled in Closed loop
Measured in Real Time
Manually Adjusted at the commissioning
Yaw X
Roll
Pitch

8. Attocube FPS3010 2. The key point for closed loop control
Fabry-Perot Cavities CANNOT detect displacement SIGN
Different Sensitivity Regions (Blind Spots)
Added Extra Quadrature Signal
Better Sensitivity and Displacement Sign Recognition
Fiber
Object
Up to 30 pm resolution
±0.5 ppm Accuracy
0 to 10 cm Position Range
Source:

9. 2. The key point for closed loop control
Attocube FPS3010 accuracy according to the datasheet
+/-10 nm over 20 mm
+/- 5 nrad evaluated with uncertainty propagation law
Autocollimator measurement accuracy according to the datasheet:
+/- 0.5 µrad for any 100µrad measurement range.
+/- 1.2 µrad for the entire measurement range.
Fiber
Object

10. 2. The key point for closed loop control
Measured Background noise in the lab:
Attocube angular StdDev = 250 nrad
Autocollimator StdDev = 0.49 µrad
Fiber
Object

11. Size: compact for easy installation and maintenance
3–The project guidelines
Size: compact for easy installation and maintenance
Impact on the normal LHC operation: In parking position (NO MD) totally transparent
RF contacts to ensure the conductivity with the movable beam pipe section in parking position
On the beam pipe (including the movable section) a copper and NEG coating could be applied if needed
Movable beam pipe section
Stepping motor based linear movement for the movable beam pipe section

12. 3–The project guidelines
Crystal operation: compatibility with LHC nominal intensity beam under study
Impedance simulations in beam position are in progress
Crystal in beam position – Crystal support in grade 5 titanium

13. 3–The project guidelines
Size: compact for easy installation and maintenance
Weight: about 80 Kg

14. 3–The project guidelines
Linear stage: stepping motor based (i.e. last CINEL goniometer )
Range: 56 mm
Resolution: 5 um
Solution: linear guidance system based on linear roller ceramic bearings with cage in stainless steel AISI 316 L - One of the four guide systems is mounted on an elastic support to allow dilatation during the bake out

15. Rotational stage: closed loop controlled, piezo based
3–The project guidelines
Rotational stage: closed loop controlled, piezo based
Range: +/- 10 mrad
Accuracy: +/ urad
Solution: Piezo rotational stage controlled in closed loop using the Attocube FPS3010 interferometric measurement system based on 3 linear axes - A shutter is used to initialize the interferometric measurement system after a power cut
Piezo shutter with the small mirrors to initialise the interferometer sensor
Interferometer sensor heads
Insert 3D View of the piezo rotational stage + mirror + shutter + sensor heads
Piezo rotational stage based on flexure structure

16. 3–The project guidelines
Rotational stage: closed loop controlled, piezo based
Range: +/- 10 mrad
Accuracy: +/ urad
Solution: A gold coated mirror is placed on top of the rotational stage for angular feedback. The crystal holder is mounted on the bottom. They are aligned separately with respect to axis of the device.
Angular feedback mirror
Mirror installation tuning system
Piezo rotational stage
Crystal holder installation tuning system
Crystal holder
Crystal holder mounting screws

17. 3–The project guidelines
Rotational stage: closed loop controlled, piezo based
Mirror installation tuning system
Angular feedback mirror
Crystal holder installation tuning system
Piezo rotational stage
Crystal holder

18. 3–The project guidelines
Crystal Mounting procedure:
Solution:
Dismounting of the linear axis for the movable beam pipe
Insertion of the crystal holder through the CF150 flange (the exact mounting position is facilitated by a guiding system)
Fixation of the crystal holder screws through the DN100 flange of the beam pipe while the crystal holder is kept in position with a hand through the CF 150 flange
Mounting of the movable beam pipe linear axis

19. 3–The project guidelines4
1-2

20. Crystal Alignment procedure:
3–The project guidelines
Crystal Alignment procedure:
Solution:
The crystal holder should have a mirror that is well aligned with the crystal and targetable with an autocollimator through the CF 63 flange
The mirror should have a 12.7 mm diameter and be gold coated
In order to measure the pitch angle, an additional small mirror could be mounted on the crystal holder side and the angle measurement could be performed through the beam pipe
Gold coated mirror for yaw and roll alignment
INFN crystal support
Gold coated mirror for pitch alignment

21. 3–The project guidelines
Alignment procedure:
Installation of the device on an alignment bench (collimator support and autocollimator aligned w.r.t. the floor)
Compensation of the roll, yaw and pitch chamber angular errors using the adjustment screws of the goniometer support and the autocollimator to measure the angular errors with mirrors installed on the 4 tank reference edges.
Compensation range
Resolution
Yaw
+/- 17 mrad
0.5 urad
Pitch
+/- 14 mrad
0.4 urad
Roll
4.5 urad
Tank reference edges

22. Alignment procedure: 3–The project guidelines Goniometer support
View port to focus the angular feedback mirror
Tank pitch angular error compensation
Tank yaw angular error compensation
Tank roll angular error compensation

23. 3–The project guidelines
Alignment procedure:
Compensation of the mirror roll and yaw angular errors in beam position using the regulation screws on the top of the goniometer and the autocollimator to measure the angular errors (through the CF38 view port)
Compensation range
Resolution
Yaw
+/- 13 mrad
3 urad
Roll
5.50 urad
Mirror roll angular error tuning
Mirror yaw angular error tuning

24. Alignment procedure: 3–The project guidelines
Mirror yaw angular error tuning
Mirror roll angular error tuning
Tank reference edges
Crystal roll angular error tuning
Crystal pitch angular error tuning
Shutter yaw angular error compensation
Shutter roll angular error compensation
Tank reference edges
View port to focus the angular feedback mirror

25. Alignment procedure: Installation of the sensor head plate + shutter
3–The project guidelines
Alignment procedure:
Installation of the sensor head plate + shutter
With the shutter opened, maximization of the SNR (Signal to Noise Ratio) on each sensor head adjusting the screw of each flexible sensor head
Screws for the sensor head alignment

26. 3–The project guidelines
Alignment procedure:
With the shutter in closed position, adjustment of each small mirror to cover the related sensor laser beam through the proper tuning screw (this procedure can also be performed before the installation in the tank)
Shutter initialisation mirrors
Shutter mirror tuning screws

27. 3–The project guidelines
Alignment procedure:
With the shutter opened, compensation of the shutter installation roll and yaw angular errors in beam position using the adjustment screws on the top of the goniometer and the interferometric sensor to measure the angular errors. The goal is that the shutter does not perturb the sensor laser beams and the sensor head plate is perfectly parallel to the angular feedback mirror.
Compensation range
Resolution
Yaw
+/- 13 mrad
3 urad
Roll
5.50 urad
Shutter roll angular error compensation
Shutter yaw angular error compensation

28. Alignment procedure: Crystal holder installation
3–The project guidelines
Alignment procedure:
Crystal holder installation
Compensation of the crystal holder roll and pitch angular errors in beam position using the adjustment screws on the top of the goniometer and the autocollimator to measure the angular errors (through the CF63 flange and the beam pipe)
Compensation range
Resolution
Roll
+/- 13 mrad
3 urad
Pitch
Crystal pitch angular error tuning
Crystal roll angular error tuning

29. 3–The project guidelines
Alignment procedure:
Closing of the CF 63 flange
Closing of the tank upper cover

30. 3–The project guidelines
LHC Tunnel Installation procedure:
Alignment of the goniometer support with the survey
Installation of the goniometer using the quick plugs system
Compensation of the chamber roll, yaw and pitch angular errors using the adjustment screws of the goniometer support and the autocollimator to measure the angular errors with mirrors installed on the 4 tank reference edges (this step can eventually be skipped)
Compensation of the chamber roll and yaw angular error using the adjustment screws of the goniometer support and the autocollimator to measure the angular errors through the CF 38 view port focusing the feedback mirror

31. Sept 2013 Finalise the conceptual design
4–A realistic plan
February2013
Finalise the conceptual design
March 2013
Start the detailed design for the entire goniometer and the piezo stages
May 2013
End of the radiation tests on Piezo and sensors heads
Sept
2013
End of the detailed design – Green light for the production

32. March 2014 Horizontal and Vertical goniometer available at CERN
4–A realistic plan
Dec 2013
Horizontal and Vertical goniometer available at CERN
Jan 2013
Fully characterization of the prototype
Feb 2014
Goniometer ready to be installed in the LHC
March
2014
Commissioning and goniometer fully operational

33. 5–Conclusions and outlooks
Piezo actuators are potential candidates to be used for the LHC goniometers for the high achievable positioning resolution
Radiations effects on piezo actuators are being studied
Piezo goniometers can reach the positioning accuracy required by the LHC only in closed loop
The problem moves to the angular sensor used to close the loop. It has to fulfill the accuracy requirements and to be rad-hard
Interferometric sensors based on optical fiber have been chosen to fulfill the tight angular measurement accuracy and harsh environment robustness requirements

34. 5–Conclusions and outlooks
The design is made so that in parking position the device is completely transparent for the machine
The goniometer support uses the same quick plug concept as the LHC collimators
The current prototype is bakeable up to 110 degrees Celsius. The main limitation is given by the Piezo Curie Temperature. New Piezo actuators able to withstand bakeout temperatures up to 220 degrees Celsius are under study