1. BWS Design meeting Jose Luis Sirvent PhD. Student XX/03/2014
Beam Wire Scanner: Optical position sensor assembly and performance tests
BWS Design meeting
Jose Luis Sirvent
PhD. Student
XX/03/2014

2. Position Sensors and Secondary Particle Shower Acquisition
Resolver
X Axis: Optical position sensor
Y Axis: Diamond Detector
Y Axis  Diamond Detector measurements
X Axis  Optical position sensor measurements

3. 1. Optical Position Sensor Working Principle
Primary Electronics: Control LD power and adapt PD signal to be acquired by ADC.
Optical Circulator: Directs the light form the LD to the sensor system and the reflected signal to the PD.
Optical Feedthrough: Overcomes the vacuum barrier.
Lens system: Focuses the light from ~9um (fibre core) to ~20um (reading spot) and collects reflections.
Encoder disc: Made of Soda-lime glass with high reflectivity Cr. Tracks.
Characteristics: All optic sensor system (in tunnel) working with SMF 1310nm
Photodiode Signal

4. 1. Assembly Tests: Focusers Housings and Caps
We have 4 sets:
2 x Schaffter + Kirrchoff
2 x Thorlabs + Asphericon
Focusers fixation system:
Schaffter + Kirrchoff : deg.
Thorlabs + Asphericon: 2 Screws + Pressure

5. 1. Assembly Tests: Disc Holder
The disc holder consist of two pieces:
A) Shaft attachment
B) Compressing Ring
There was an small problem in the compressing ring:
Manufacturing drawings: Step to fit disc Diam. ~ 39.9 mm
Physical piece: Step to fit disc Diam. ~ mm
Solved modifying the piece  Thanks William!
To Consider:
Materials dilatation:
Different design
2. Amount of pressure on screws:
Special tool for fixation
3. Mounting references:
The disk should always be mounted in
the same angular position. Key in disk?.
If calibration is always performed
alignment by eye is OK.

6. 1. Assembly Tests: Adjustment tools and Caps
Good:
The micrometric screws took some time to arrive
The pieces fit perfectly
To Consider:
The caps are very thick and for the focuser clamping with the screw quite a lot of strength is needed. The screw could be damaged or what is worse, the focusers housing while fixed in the crown.
We’ll perform a small modification on the caps making a slit after the adjusting screw

7. 1. Assembly Tests: The whole system in the Crown
Good:
The focuser systems (housing and adjusting elements) fits perfectly and slides softly
The micrometric screws adjusting range is correct
The space for mounting the SMF and the slits are not forcing the fibre to bend
To consider:
The fixing screws are not the best ones (not flat and scratch the focusers housing)
Too much strength needed to fix/release the cap to the focuser housing, if adjusted and dismounted the adjustment could be lost.
The fibres are quite rigid and need free space to bend (We’ll have space enough to not force them?)
SMF UHV
Feedthroughs
High Temp
Patchcords

8. 1. Assembly Tests: Complete system mounted and fibre routing
Good:
The Focusers are perfectly aligned with the disc (90 degrees) and in the correct track (I cannot verify if completely in the centre…)
To consider:
The fibre routing is not trivial, it’s quite rigid and we should avoid force it to bend too much.
The use of a flexible tube to route the fibre would be a good idea (protection & routing)
We are using now 1m of special UHV SMF for High Temp (Too long, we’d need a loop inside)

9. 2. Performance Tests: The Set-Up used
CH_1
CH_2

10. 2. Performance Tests: The Software used
Matlab-Based Script with user interface for quick tests:
Standalone operation
Analyses the two channels independently
Extracts position information
Checks that every pulse has been correctly detected
Extracts disc eccentricity (position error)
Applies calibration curves, corrected positions
Checks the calibration reliability/repetitivity
Extracts errors after calibration
Available on-line with demo files and user guide:

11. 2. Performance Tests: Channel 1: Pulses detected correctly & 10um Track in good conditions
Scan Region
Revolution - Scan Region
Complete Revolution

12. 2. Performance Tests: Channel 2: Pulses detected correctly & 10um Track in good conditions

13. 2. Performance Tests: Disc Eccentricity Detected & Calibration curves: Prototype
Complete Revolution
5e-4 Rad
Scan Region
Revolution - Scan Region

14. 2. Performance Tests: Disc Eccentricity Detected & Calibration curves: Prototype
Complete Revolution
5e-4 Rad
Scan Region
Revolution - Scan Region
Projected Error Eccentricity Fork 10cm (P.E.):
P.E= 2.5e-4 * 0.1m = 25mm
Disc centre offset (e):
2.5e-4 = e / 0.5D
D =  e = 17mm

15. 2. Performance Tests: Disc Eccentricity Detected & Calibration curves: Lab. Test-Bench
2e-3 Rad
P.E. = 100mm
e = 68mm

16. 2. Performance Tests: Disc Eccentricity Correction (1x Scan region): Prototype
P.E. = 0.601mm

17. 2. Performance Tests: Disc Eccentricity Correction (4 x Scan region): Prototype
P.E. = 1.1mm

18. 2. Performance Tests: Disc Eccentricity Correction (1x Revolution – Scan Region): Prototype
P.E. = 1.501mm

19. 2. Performance Tests: Disc Eccentricity Correction (3x Revolution – Scan Region): Prototype
P.E. = 1.8mm