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Validation of the TCF-Parameters for the ALTRO-Chip (ALICE TPC Readout) Simon Feigl, ALICE Offline Project CERN, Summer Student Lectures August 12, 2008 Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC) Outline

SLIDE 1

Validation of the TCF-Parameters for the ALTRO-Chip (ALICE TPC Readout)

Simon Feigl, ALICE Offline Project

CERN, Summer Student Lectures

August 12, 2008

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 2

Outline

Outline ALICE’s Time Projection Chamber Shape of Readout Signal AliRoot Class AliTPCCalibTCF Preliminary Results, Tasks, Problems Abbreviations: ALICE ....... A Large Ion Collider Experiment TPC ....... Time Projection Chamber TCF ....... Tail Cancellation Filter ALTRO ....... ALICE TPC ReadOut

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 3

Outline

Outline ALICE’s Time Projection Chamber Shape of Readout Signal AliRoot Class AliTPCCalibTCF Preliminary Results, Tasks, Problems Abbreviations: ALICE ....... A Large Ion Collider Experiment TPC ....... Time Projection Chamber TCF ....... Tail Cancellation Filter ALTRO ....... ALICE TPC ReadOut

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 4

Time Projection Chamber

Gas atoms are ionized by high energy particles Resulting free electrons accelerate in the electric field towards the endcaps Electrons are detected by the multi-wire proportional chambers at the endcaps

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 5

Read Out Chambers Layout

≈ 570.000 pads divided into 36 sectors

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 6

Read Out Signal Shape

Signal shape results not only from the electrons

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 7

Read Out Signal Shape

Signal shape results not only from the electrons Induced signals also from ions moving to:

Pad Plane Cathode Gate

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 8

ALTRO-Chip & Fitting

To reach the desired shape the signal is fitted Fitfunction is based on a sum of exponentials Leads to 6 fit-parameters

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 9

ALTRO-Chip & Fitting

To reach the desired shape the signal is fitted Fitfunction is based on a sum of exponentials Leads to 6 fit-parameters

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 10

ALTRO-Chip & Fitting

To reach the desired shape the signal is fitted Fitfunction is based on a sum of exponentials Leads to 6 fit-parameters

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 11

AliRoot Class

AliRoot class AliTPCCalibTCF:

Extract pulses out of RAW-files Select only “proper” Pulses (selection rules!) Sum pulses per pad, calculate mean Fit (mean) pulse, save parameters Check quality of fit

Tasks:

Sum pulses per Sector, calculate mean & parameters Do this with a significant amount of data to get good statistics Compare parameters of sector to parameters of pads in the sector Adjust pulse selection rules prudently Choose parameters, store them (in the right format) and send them to the ALTRO-Database.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 12

Distribution of Parameters

Example: Distribution of one parameter in four selected sectors: Leadoff calculations suggest that one set of parameters for all pads in one sector is sufficient (difference between pads is insignificant compared to pulse-to-pulse fluctuations) However, more data from all pads has to be analysed (is needed resp.) to complete the study adequately.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 13

Distribution of Parameters

Example: Distribution of one parameter in four selected sectors: Leadoff calculations suggest that one set of parameters for all pads in one sector is sufficient (difference between pads is insignificant compared to pulse-to-pulse fluctuations) However, more data from all pads has to be analysed (is needed resp.) to complete the study adequately.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 14

Problems

Unproper summed pulses emerge (e.g. Gate Signal): enhance pulse selection rules.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 15

Problems

Unproper summed pulses emerge (e.g. Gate Signal): enhance pulse selection rules. Invalid pad addresses appear: add exclusion of these addresses to selection rules.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 16

Problems

Unproper summed pulses emerge (e.g. Gate Signal): enhance pulse selection rules. Invalid pad addresses appear: add exclusion of these addresses to selection rules. More RAW-data is needed to get decent statistics.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 17

Problems

Unproper summed pulses emerge (e.g. Gate Signal): enhance pulse selection rules. Invalid pad addresses appear: add exclusion of these addresses to selection rules. More RAW-data is needed to get decent statistics. By now there have also been pads missing in the analysis.

Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

SLIDE 18

Looking forward to Sep. 10

summer students rule Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)

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Looking forward to Sep. 10

summer students rule Simon Feigl, ALICE Offline Project Validation of TCF-Parameters (ALICE TPC)