Constructing a Allpix Squared Sensor Simulation
Based on documentation written by Elliott P Wright.
Following this is an Allpix Squared tutorial for checking sensor functionality, demonstrated using a 224 x 512 pixel matrix (MALTA-like) with a test beam of pions.
Launching Allpix2
To open Allpix Squared, you must first move to the directory containing your Allpix configuration files (e.g. your home directory). Type the following command into the command line:
apptainer shell /cvmfs/unpacked.cern.ch/gitlab-registry.cern.ch/allpix-squared/allpix-squared:latest
Getting Started
I would recommend starting by looking at the example.conf and example_detector.conf configuration files given in allpix-squared/examples/ .
example_detector.conf gives an example of how to set up a detector's position and orientation. In this case, the type of detector is cmsp1, the design of which can be found under allpix-squared/models/cmsp1.
example.conf describes how to initialise a simulation of 10000 events, each of which producing a 120GeV 10$\mu$m pion beam.
To start a full simulation, cd into the directory containing the relevant .conf file. To run the file (e.g. to run example.conf), type:
allpix -c <file.conf> .
Once this has run, now look for the output folder in the same directory as <file.conf>. If this is present, you can examine the files in the ROOT Object Browser using:
rootbrowse
Then navigate to the examples folder. You have now demonstrated Allpix Squared functionality. With this in mind, we can now move on to building our own sensor based on the Allpide model.
Constructing a Sensor Test Beam Simulation
To begin with, we take the Allpide model from the featured Allpix models and change the relevant parameters to match those in the table below.
| Name | Value | Unit |
|---|---|---|
| Sensor Dimension | 20 x 10 | mm$^2$ |
| Pixel Pitch | 36.4 x 36.4 | $\mu$m$^2$ |
| Pixel Matrix | 512 x 224 | |
| Sensor Thickness | 100 | $\mu$m |
| Sensor Excess | 0.6816 x 0.9232 | mm$^2$ |
: Table of Sensor Parameters
You will then need to add the following line in the main simulation configuration file:
model_paths = "./allpix-squared/<detector_files>/"
Where <detector_files> is the directory where allpide is stored. This allows Allpix to know where you want it to check for pre-defined detectors.
Other Notes
NOTE: Allpix Squared also provides the possibility to utilize a full electrostatic TCAD simulation for the description of the electric field.
Root tutorial found at: https://root.cern.ch/root/htmldoc/guides/users-guide/Trees.html
To look for histogram data, go to PixelHit/<detector>/pixel/local_center_/X().