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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. - PowerPoint PPT Presentation
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PS wirescanner calibration
Student Meeting10/03/2014
Carolina Bianchini
BE-BI-BL
10/03/2014 Carolina Bianchini 2
Outline
Wirescanner calibration
Calibration analysis
Conclusions
Calibration analysis...new method
10/03/2014 Carolina Bianchini
Wirescanner calibrationWire Scanners are devices used for beam-profile measurement in the LHC and its injectors.
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10/03/2014 Carolina Bianchini 4
Wire Scanners calibration is needed to correlate the potentiometer values with the projected position of the beam.
Wirescanner calibrationPS Wirescanner
10/03/2014 Carolina Bianchini 5
Wirescanner calibration
Laser Splitter Photodiode
Combiner
Wirescanner
PS Wirescanner calibration bench
10/03/2014 Carolina Bianchini 6
PS Wirescanner calibration procedure1. 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.
Wirescanner calibration
Bits (angular position)
Phot
odio
de s
igna
l
10/03/2014 Carolina Bianchini 7
Wirescanner calibration
Bits (angular position)
Phot
odio
de s
igna
lPS Wirescanner calibration procedure1. At each position, we have to find the center of the two peak
(in potentiometer bit).
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PS Wirescanner calibration procedureFor 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.
Wirescanner calibration
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PS Wirescanner calibration procedureThe 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).
Wirescanner calibration
10/03/2014 Carolina Bianchini
• 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. 10
Calibration analysis
10/03/2014 Carolina Bianchini
Calibration analysis The method developed by Emiliano follows these steps: 1. Laser signal is cut with fix threshold (|Max-Min|*40%).2. 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).
3. Plot the average between P1 and P2 vs the projected position.
4. Fit the previous curve with polynomial function.5. Generate calibration table.
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10/03/2014 Carolina Bianchini
Calibration analysis...new methodMy 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:1. I load data file to MatLab;2. I take the signal and I divide into IN and OUT profile;
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10/03/2014 Carolina Bianchini
3. I apply a threshold in order to clean the signal by the noise and I smooth the signal;
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Calibration analysis...new method
10/03/2014 Carolina Bianchini
4. I find 4 points where the signal is equal to the threshold (A, B, C, D).
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A B C D
Calibration analysis...new method
10/03/2014 Carolina Bianchini
5. I divide the signal into 2 different regions, A-B and C-D.6. 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.
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Calibration analysis...new method
10/03/2014 Carolina Bianchini
8. I calculate the average peak1, peak2 and I plot it vs position (in mm).
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Calibration analysis...new method
10/03/2014 Carolina Bianchini
9. I fit this curve with different polynomial order function and I choose the best polynomial result to generate the calibration table.
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Calibration analysis...new method
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15m/s IN
improvement
Posi
tion
diffe
renc
e (m
m)
Average absolute error107µm
Bits (angular position)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
29000 29500 30000 30500 31000 31500 32000 32500 33000 33500 34000
C1-C2
C1-C3
C2-C3
Average absolute error71µm
Average absolute error75µm
Calibration analysis...new method
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WS PS 146382 OLD METHOD (µm) EP METHOD (µm) NEW METHOD (µm)
10 m/s IN 105 85 78
15m/s IN 195 100 95
10 m/s OUT 116 85 79
15m/s OUT 107 75 71
Calibration analysis...new method
10/03/2014 Carolina Bianchini
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.
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Emiliano
Thanks to...