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PS wirescanner calibration. Student Meeting 10/03/2014. Carolina Bianchini BE-BI-BL. Outline. Wirescanner calibration. Calibration analysis . Calibration analysis...new method. Conclusions. Wirescanner calibration.

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Presentation Transcript
slide1

PS wirescanner calibration

Student Meeting

10/03/2014

Carolina Bianchini

BE-BI-BL

slide2

Outline

Wirescanner calibration

Calibration analysis

Calibration analysis...new method

Conclusions

wirescanner calibration
Wirescanner calibration

Wire Scanners are devices used for beam-profile measurement in the LHC and its injectors.

slide4

Wirescanner calibration

PS Wirescanner

Wire Scanners calibration is needed to correlate the potentiometer values with the projected position of the beam.

slide5

Wirescanner calibration

PS Wirescanner calibration bench

Wirescanner

Splitter

Laser

Combiner

Photodiode

slide6

Wirescanner calibration

PS Wirescanner calibration procedure

We move the system along the vertical axis with fix step and we record, at each position, the profile of the laser-beam. We repeat these measurement at two different speed: 10m/s and 15m/s.

Photodiode signal

Bits (angular position)

slide7

Wirescanner calibration

PS Wirescanner calibration procedure

At each position, we have to find the center of the two peak (in potentiometer bit).

Photodiode signal

Bits (angular position)

2.

slide8

Wirescanner calibration

PS Wirescanner calibration procedure

For each scanned position we plot the potentiometer center of the laser beams as function of the position.

We fitted it with a polynomial curve.

3.

slide9

Wirescanner calibration

PS Wirescanner calibration procedure

The best polynomial curve order is chosen minimizing the average difference between the fit and the real values and looking for the best average of the peaks distance.

4.

We generate a table to correlate the motor angular position (in bit) vs the projected position (in mm).

c alibration analysis
Calibration analysis
  • Actually the calibration data analysis is performed using a Java application written by BE/BI/SW.
  • The calibration data analysis is carried out in 3 steps:
    • Identification of the signals obtained during the measurements;
    • Identification of the two laser peaks. The first peak is the absolute minimum value of the signal registered by the photodiode. The second peak is found as the second minimum value in the region lowered by at least 40% of the previous peak value.

- Generation of the tables.

calibration analysis
Calibration analysis

The method developed by Emiliano follows these steps:

  • Laser signal is cut with fix threshold (|Max-Min|*40%).
  • Average values in the first and in the second couple of points where the threshold is equal to the signal are calculated (P1 and P2).
  • Plot the average between P1 and P2 vs the projected position.
  • Fit the previous curve with polynomial function.
  • Generate calibration table.
calibration analysis new method
Calibration analysis...new method

My expected work as technical student is to develop a program with new mathematical routines and fit functions which will standardize calibrations quality assurance.

During my first 3 months I have developed an alternative method in MATLAB to better perform the calibration data fit.

I follow these logical steps:

  • I load data file to MatLab;
  • I take the signal and I divide into IN and OUT profile;
slide13

Calibration analysis...new method

  • I apply a threshold in order to clean the signal by the noise and I smooth the signal;
slide14

Calibration analysis...new method

  • I find 4 points where the signal is equal to the threshold (A, B, C, D).

A

B

C

D

slide15

Calibration analysis...new method

  • I divide the signal into 2 different regions, A-B and C-D.
  • In each region I apply another smooth (lower order) and I use a Gaussian fit to calculate the center of the peak. I obtain 2 values, peak1 and peak2.
slide16

Calibration analysis...new method

  • I calculate the average peak1, peak2 and I plot it vs position (in mm).
slide17

Calibration analysis...new method

  • I fit this curve with different polynomial order function and I choose the best polynomial result to generate the calibrationtable.
slide18

Calibration analysis...new method

Average absolute error

107µm

15m/s IN

Average absolute error

75µm

Position difference (mm)

Bits (angular position)

Average absolute error

71µm

improvement

conclusions
Conclusions
  • New routines seems to improve PS & PSB calibration reliability.
  • First attempt done in MatLab showed good results, taking into account the electronic noise in the potentiometer reading.
  • Different filters are still under studying.
  • Once the procedure will be tested on all the PS & PSB calibrations, a final software will be developed in Python.
slide21

Thanks to...

Emiliano

21