# Presentation: 826165

## Analysis of Magnetic field Data andFPIX0 ADC calibration spread 

- G. Chiodini
- Sept 25, 2000
- Monday pixel meeting

## Summary

- Data with the magnetic field
- Are the data reliable?
- Data analysis method and errors evaluation
- Movement of the board
- Double fraction fluctuations
- Correlation between position and double fraction
- Global comparison between set 1, 2 and 3
- B variation along columns
- Double fraction for small track angle
- Empirical formula
- Validation of the model
-  b slope from the data
- Drift mobility estimations
- FPIX0 ADC calibration
- All detector improved Landau fit
- Single pixel improved Landau fit
- Channel-to Channel Landau spread
- Conclusions

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Are the data reliable?

-  Going throw the Logbook I conclude that the magnetic field   calibration are not worse than 10%, maybe they are much better:
-  Set 1 B up to 0.32 Tesla
-  Set 2 B up to 0.58 Tesla
-  Set 3 B up to 0.58 Tesla
-  The board move “apparently” due to the beam deflection( linear in B).
- _ __The incident track angle shift due the beam deflection is negligible. _
- The board move in x (long pixel dimension) and y (short pixel   dimension) when you change B and also during a run:
-   Static movement due to the coil and board support motion( quadratic in B )
-   Time dependent motion due to reaching of the thermal and mechanical    equilibrium of the system.
-  _The incident track angle change due to the board movement can be__   relevant:_

- for example if Y=50m and R=10cm we have deg

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Data analysis method

-  All the runs in magnetic field have been analyzed.
-  The runs are divided in set1, set2 and set3 each set with only one   geometry file.
-  Planes 8 and 9 dropped for set 1 and 3, for set 2 also planes 10 and 11
-  I applied the following cuts in the analisys:   for SSD:   type1.eq.1. .and.type2.eq.1. .and.type5.eq.1..and.type6.eq.1..and.
-    ntrks.eq.1. .and.width5.le.2..and.width6.le.2.
-    for SPD p-stop:   type7.eq.2..and.av_row7.gt.15..and.av_row7.lt.50..and.av_col7.gt.1.     .and. av_col7.lt.9..and.width.7.le.2.and.ncols7.eq.1.
-  The survived events are divide in groups of 200 events to “monitor”    in time the following quantities:   p-stop y residual, p-stop x residual, beam y slope, beam y position,   p-stop double fraction, Y plane 5 double fraction and Y plane 6    double fraction.

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Errors evaluation

-  The “instantaneous” measured quantity is an average between the   200 events.
-  The measured quantity is the average on all run.
-  The error on the measured quantity is given by the rms of  statistical   ensemble realized with the “instantaneous” measures.
-  This definition of the error is conservative and it assumes   that many unknown systematic errors dominate the dispersion in   time.
-  This definition of the error is  quite independent of the number of   events in the sub-samples

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Movement of the board

**Y-res**

**X-res**

**Y-slope**

**    ****Y-**
**position**

**-17.3A**

**-45A**

**-0A**

**45A**

**0A**

**17.3A**

**(Blow up**
**next page)**

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Double fraction fluctuations

**Double**
**SSD6**

**Double**
**SSD5**

**Double**
**P-stop**

**(Blow up**
**next page)**

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Data with B:  Correlation between position and double fraction (1)

- Data with B:  Correlation between position and double fraction (1)

**Double**
**P-stop**

**Y-res**

**V****bias****=-95V**

**V****bias****=-140V**

**V****bias****=**
**-175V**

**V****bias****=****-175V**

**V****bias****=-140V**

**V****bias****=-95V**

**20:50**
**10k**

**21:12**
**10k**

**21:30**
**10k**

**21:55**
**10k**

**22:22**
**10k**

**22:41**
**10k**

## Data with B: Correlation between position and double fraction (2)

- There is an evident correlation between motion of the board and double fraction only in set 3 at the largest magnetic field when Imag=45Amps.

## Data with B: global comparisons

**Y-res**

**X-res**

**Y-slope**

**Double**
**SSD6**

**Double**
**SSD5**

**Double**
**P-stop**

**    ****Y-**
**position**

**-17.3A**

**-45A**

**-0A**

**45A**

**0A**

**17.3A**

**0A**

**45A**

**-45A**

**-17.3A**

**-30A**

**17.3A**

**45A**

**30A**

**17.3A**

**8A**

**0A**

**-17.3A**

**-45A**

**-8A**

**8A**

**No bias ****sweep**

**Perturbative controlled access **

## Data with B: B variation along columns

**Double**
**P-stop**

**Double**
**P-stop**

**Column number**

- Uniform B?

- Uniform B?

- Set number 3

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Set 1

- In set 1 the minimum in the double fraction is not reached.
- The linear fit is not meaningful

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Set 2 and Set 3

- In set 2 and 3 the minimum in the double fraction is reached.
- The fit is done with the model explained later

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Comparisons between Set 1, 2 and 3 

- In the plots the data for set 2 and 3 has the minimum in the double fraction is shifted on B=0.

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Double fraction: empirical formula

- Double fraction: empirical formula

- Where:
- r = double / (single+double)
- Wcharge-sharing= effective charge sharing region
- a = constant term due to the diffusion
- b = linear coefficient due to the track inclination
-  = nominal track inclination
- 0 = unknown offset track inclination

- _The effect of the diffusion and track inclination sum up in quadrature __to give the double fraction_

- The effect of the magnetic field is to shift of the effective Lorentz angle  given by <Lorentz>B

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Double fraction: Validation of the model

- _ATLAS test beam: __the plot show the mean cluster size (not r!!!) vs track angle and look not very well fitted by a parabola. At angle ____ 5 deg a linear curve fit well the data     _

- _BTeV test beam_

- The fit with the model has a chi2 respect to the parabola only 50% better. I choose the fit with the model because the parameters has a physical interpretation.

- NB: The uncertainty on the track angle is quite big for ATLAS

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Double fraction: b slope from data

-  b decreases linearly with threshold.
-  b reaches a plateau for bias voltage bigger than 120V.
-  b extracted from 0-5 deg is less than the one extracted from 5-10 deg has expected.
-  I use b from left plot where rb(**this choice will give the smallest Lorentz angle**).
-  Anyway, only the simulation should be used to extract the Lorentz angle.

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Drift mobility estimation: Non linear model

- Drift mobility estimation: Non linear model

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Drift mobility estimation: Measurements

- For Qth=4700e- we can predict the ATLAS test beam Lorentz angle of 7.92.2deg to compare with their result of 9.00.4deg and my theoretical estimation of 8.76deg.

- For Qth=2500e- there is an average disagreement between measurements and theory of about 24.5%, instead for Qth=4700e- the agreement is about 5.5%.

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## FPIX0 ADC calibration:All detector improved Landau fit (1)

- Landau distribution convolutedwith a Gaussian curve

- For 280 m thick Si the theory predict (the fit for the FPIX0 p-stop gives): Emp/3.6eV=Qmp=21723e-        ( 24730-34029e- )  12.3% difference
- /3.6eV=1386e-                             ( 1526  31e- )  10 % difference
- g/3.6eV=1542e-                          ( 2913  54e-  )  almost two times bigger

- Fit accuracy:
- Qmp/Qmp about 0.12%
-  and  about 1.9%

**P2 = Q****mp****+0.223******
**P******
**P********g**

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## FPIX0 ADC calibration:All detector improved Landau fit (2)

- _No structure in time of the Landau parameters fit_

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## FPIX0 ADC calibration:Single pixel improved Landau fit

- Collection of 24 runs.
- Fit accuracy:
- Qmp/Qmp circa 0.8%
-  and  circa 10%

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## FPIX0 ADC calibration: Channel-to Channel Landau spread

- FPIX0 ADC calibration: Channel-to Channel Landau spread

- Rms channel to channel spread in the parameters fit:
- Qmp/Qmp about 3.9%
-  about 17%
-  about 14%

- Qmp+0.223=          24220 (2473029e- )
- = 1192( 1526  31e-)
- g  = 2929 2913  54e-)
-         2680after scaled to have the           Qmp at 21723 e-

- Results of the fit for all cells in one run

- <chi2>=2.26

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000

## Conclusions

- The B data could be affected by a large amount of systematic errors. Only a comparison with the simulation can clarify if we have seen only the board rotation or the B effect.
- The electron drift velocity saturation effect seems to be present in the data.
- No dependence of the mobility on Vbias can be extracted from the data.
- There is about 2400 e- of ADC spread maybe due to variation in the external ADC in a time scale of few second (it doesn’t affect the channel to channel relative adc noise in one events ).
- The FPIX0 8-bit nominal ADC information is a 45bit equivalent ADC

- Monday pixel meeting - G. Chiodini

- Sept 25, 2000