Radial Strip Detector

This example simulates a radial strip detector, which features a trapezoidal shape and strips fanning out radially from a common focal point. Such detectors are planned to be deployed in the end-cap regions of the ATLAS Inner Tracker (ITk). This example uses the model of a specific ITk module, called the R0. You can see the radial detector used in this simulation by enabling the VisualizationGeant4 module.

Detector models for radial strip detectors are implemented in the RadialStripDetectorModel class. A radial strip detector model is defined using four parameters for each strip row. In addition, its geometry has to be defined as radial_strip.

type = "monolithic"
geometry = "radial_strip"
number_of_strips = 1026, 1026, 1154, 1154
angular_pitch = 0.19309mrad, 0.19309mrad, 0.17169mrad, 0.17169mrad
inner_pitch = 74.4um, 78.1um, 73.6um, 78.5um
strip_length = 19mm, 24mm, 29mm, 32mm

In this simulation example, the detector is hit by a beam of 5.4 GeV electrons. A simple linear electric field model is used. Deposited charge carriers are grouped during the propagation stage by use of the charge_per_step parameter. The CapacitiveTransfer module handles the simulation of cross-talk by transferring a portion of collected charge to adjacent strips in the same row. Charge threshold during the digitization phase is set to approximately three times the value of electronic noise.

The granularity parameter controls the number of bins for in-pixel histograms. As the typical strip length of several centimeters would, by default, lead to exceedingly large histograms, the granularity parameter is set to 80 4. This corresponds to a typical strip pitch of 80 um in the x direction and to 4 strip rows (in the y direction) of the radial strip detector.