channeling/ch3/README.md

0001 \page Examplech3 Example ch3
0002
0003 \author Alexei Sytov - INFN Ferrara Division (Italy) \n
0004  sytov@fe.infn.it
0005
0006 ## INTRODUCTION
0007 Example ch3 demonstrates the minimum requirements necessary to integrate the
0008 G4CoherentPairProduction process into a project, along with the G4ChannelingFastSimModel
0009 and G4BaierKatkov models, to simulate the physics of electromagnetic showers in
0010 an oriented crystal.
0011
0012 The key concept is the acceleration of electromagnetic processes (both radiation and
0013 pair production) in an oriented crystal, which can significantly reduce the effective
0014 radiation length [1,2]. Potential applications include electron/positron sources for
0015 accelerator experiments, as well as crystalline oriented calorimeters for collider and
0016 space applications [1,2].
0017
0018 This example serves as a guideline for users on how to add this physics
0019 to their existing Geant4 projects. It includes the minimum necessary options
0020 to incorporate this physics. Specifically, it requires registering
0021 G4FastSimulationPhysics and G4CoherentPairProductionPhysics in the main routine and
0022 adding a few lines of code in DetectorConstruction.
0023
0024 All of this physics does not depend on the physics list. In particular, the
0025 process G4CoherentPairProduction simulates only coherent part of pair production in
0026 the crystal volume, while the incoherent one should be simulated with
0027 standard Geant4 processes.
0028
0029 ## DESCRIPTION
0030
0031 The example simulates high energy photon interaction (typically above 10 GeV) with
0032 an oriented W crystal with <111> crystal axes aligned along the photon beam direction.
0033
0034 The structure of this example is very similar to the example ch1.
0035 ch3 includes a straight W crystal and a detector positioned behind it.
0036 The incoming photon beam is set up in macro run.mac.
0037
0038 One can also use the Geant4 GUI by launching the code without specifying a macro file.
0039 In this case, the visualization setup is automatically loaded through the vis.mac and
0040 init_vis.mac macro files. The initial beam distribution in this setup will be identical
0041 to that in run.mac.
0042
0043 The example does not include any input of the model or geometry parameters
0044 from the macro to keep it as straightforward as possible. The output is recorded
0045 into the file results.root. It consists of the spectrums of e-, e+
0046 and gamma arriving to the detector. To build these plots, one has to
0047 open this file in root and use
0048 ```cpp
0049 Spectrum_electrons->Draw()
0050 ```
0051
0052 ```cpp
0053 Spectrum_positrons->Draw()
0054 ```
0055
0056 and
0057
0058 ```cpp
0059 Spectrum_gamma->Draw()
0060 ```
0061
0062 for e-, e+ and gamma, respectively.
0063
0064 ## REFERENCES
0065
0066 -# V. N. Baier, V. M. Katkov, V. M. Strakhovenko. <a href="https://www.worldscientific.com/worldscibooks/10.1142/2216?srsltid=AfmBOopiXOyx7OWz8aPSFSC5kIKSJQs6wGF512V05177LJ_xX3mDfA7s#t=aboutBook">Electromagnetic Processes
0067 at High Energies in Oriented Single Crystals (World Scientific, Singapore, 1998).</a>
0068 -# L. Bandiera, V.V. Tikhomirov et al. <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.021603">Phys. Rev. Lett. 121, 021603 (2018).</a>