Difference: SWGuidePixelDigitization (22 vs. 23)

Revision 232019-05-09 - PaulJeanSchutze

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META TOPICPARENT name="SWGuideTrackerDigitization"
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SimHits.png Track_split.png
Changed:
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  • The track segment is split into many parts (about 100) each with charge $q_i$ which is fluctuated according to the G4 dEdx fluctuation formula.
  • Each point charge is drifted to the detector surface under the influence of the B-field ($2^{nd}$ order Lorentz force used).
  • The point charge is diffused with a Gaussian smearing.
  • All charges within a single pixel limit are collected to give the pixel charge $Q_n$.
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The process can logically be split into the sensor response and the readout chip response, which is also reflected in the structure of the code.

The sensor response is packed into the accumulateSimHits function and performs these steps:

  • The track is split into many segments (length of 10 um) each with charge $q_i$ which is fluctuated according to the G4 dEdx fluctuation formula.
  • Each negative point charge is drifted to the detector surface under the influence of the B-field ($2^{nd}$ order Lorentz force used, with Lorentz angle read from a DB - optionally overwritten via the configration).
  • The point charge is diffused with a Gaussian smearing. Based on the drift distance, the charge is expanded to a 2D Gaussian cloud.
  • A numerical integration over this cloud calculates the charge propagated to each individual pixel ($Q_n$) within 3sigma of the cloud.
  • A cluster charge re-weighting is performed to describe the effects arising from radiation damage.

The actual digitization process is implemented in the digitize function:

 
  • Noise is added. There are two types of noise: detector noise & readout noise. The $1^{st}$ one determines which pixel is above threshold and is read out. The $2^{nd}$ one determines the noise contributions to the signal at the ADC input.
  • A threshold is applied and the charge is converted to ADC counts (integer).
  • Inefficiencies and miss-calibration are applied.
 
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