PS wirescanner calibration Student Meeting 10/03/2014 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 calibration Wire Scanners are devices used for beam-profile measurement in the LHC and its injectors. 3

10/03/2014 Carolina Bianchini 4 Wire Scanners calibration is needed to correlate the potentiometer values with the projected position of the beam. Wirescanner calibration PS Wirescanner

10/03/2014 Carolina Bianchini 5 Wirescanner calibration Laser Splitter PhotodiodeCombiner Wirescanner PS Wirescanner calibration bench

10/03/2014 Carolina Bianchini 6 PS Wirescanner calibration procedure 1.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) Photodiode signal

10/03/2014 Carolina Bianchini 7 2. Wirescanner calibration Bits (angular position) Photodiode signal PS Wirescanner calibration procedure 1.At each position, we have to find the center of the two peak (in potentiometer bit).

10/03/2014 Carolina Bianchini 8 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. Wirescanner calibration

10/03/2014 Carolina Bianchini 9 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). 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. 11

10/03/2014 Carolina Bianchini 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: 1.I load data file to MatLab; 2.I take the signal and I divide into IN and OUT profile; 12

10/03/2014 Carolina Bianchini 3.I apply a threshold in order to clean the signal by the noise and I smooth the signal; 13 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). 14 ABCD 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. 15 Calibration analysis...new method

10/03/2014 Carolina Bianchini 8.I calculate the average peak1, peak2 and I plot it vs position (in mm). 16 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. 17 Calibration analysis...new method

10/03/2014 Carolina Bianchini 18 15m/s IN improvement Position difference (mm) Average absolute error 107 µm Bits (angular position) Average absolute error 71 µm Average absolute error 75 µm Calibration analysis...new method

10/03/2014 Carolina Bianchini 19 WS PS OLD METHOD (µm)EP METHOD (µm)NEW METHOD (µm) 10 m/s IN m/s IN m/s OUT m/s OUT 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. 20

10/03/2014 Carolina Bianchini 21 Emiliano Thanks to...