Electron scattering benchmark (T. O'Shea and B. Faddegon)

GEOMETRY DEFINITION

The geometry is described in the enclosed documument : NRCC_electron_scat.pdf

A "World" volume contains a "Frame" made of Air.
The Frame contains : ExitWindow, ScatterFoil, MonitorChbr, Bag.
The Bag contains a Gas volume, which contains 2 aluminium Rings.
The Scoring plane is the end-plane of the Frame

The default geometry is constructed in DetectorConstruction class. The parameters of the ScatterFoil (material and thickness) must be defined via 2 UI commands : see the macro scatter.mac

PHYSICS LIST

Physics lists can be local (eg. in this example) or from G4 kernel physics_lists subdirectory.

Local physics lists:

"local" standard EM physics with current 'best' options setting. these options are explicited in PhysListEmStandard
"standardSS" standard EM physics with single Coulomb scattering instead of multiple scattering

From geant4/source/physics_lists/builders:

"emstandard_opt0" recommended standard EM physics for LHC
"emstandard_opt1" best CPU performance standard physics for LHC
"emstandard_opt2" alternative models
"emstandard_opt3" current state of art for EM physics analog to "local"above

Physics lists and options can be (re)set with UI commands

Please, notice that options set through G4EmProcessOPtions are global, eg for all particle types. In G4 builders, it is shown how to set options per particle type.

PRIMARY GENERATOR : mono-enegetic pencil beam

The primary kinematic consists of a single particle which hits the detector perpendicular to the input face (ExitWindow). The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can be changed via the G4 build-in commands of ParticleGun class. (see the macros provided with this example)

The incident beam has a Gaussian-shaped spatial distribution. The rms of the Gaussian can be define with an UI command built in PrimaryGeneratorMessenger.

VISUALIZATION

The Visualization Manager is set in the main () (see eelectronScattering.cc). The initialisation of the drawing is done via the commands in vis.mac In interactive session:

PreInit or Idle > /control/execute vis.mac

The example has a default view which is a longitudinal view of the detector.

The tracks are drawn at the end of event, and erased at the end of run. Optionaly one can choose to draw all particles, only the charged, or none. This command is defined in EventActionMessenger class.

TRACKING

One can limit 'by hand' the step lenght of the particle. As an example, this limitation is implemented as a 'full' process : see StepMax class and its Messenger. The 'StepMax process' is registered in the Physics List.

DETECTOR RESPONSE

At the end of a run, from the histogram(s), one can study different physics quantities, via the histograms defined below.

An ascii file corresponding to histo 4 (see below) is automatically written.

List of the built-in histograms

The test contains 4 built-in 1D histograms, which are managed by the HistoManager class and its Messenger. The histos can be individually activated with the command :

/analysis/h1/set id nbBins  valMin valMax unit

where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..) (see the macros xxxx.mac).

1 "(charged particles): projected angle at Scoring plane"
2 "(charged particles): dN/dS at Scoring plane"
3 "(charged particles): d(N/cost)/dS at Scoring plane"
4 "(charged particles): normalized d(N/cost)/dS at Scoring plane"
5 "(charged particles); scattering angle theta"
6 "(charged particles); measured scattering angle theta"

The histograms can be viewed using ROOT or PAW.

One can control the name and format of the histograms file with the command:

/analysis/setFileName  name  (default nrccBenchmark)

It is possible to choose the format of the histogram file : root (default), xml, csv, by using namespace in HistoManager.hh

It is also possible to print selected histograms on an ascii file:

/analysis/h1/setAscii id

All selected histos will be written on a file name.ascii (default nrccBenchmark)

HOW TO START ?

Execute electronScattering in 'batch' mode from macro files e.g.
```
% electronScattering   myMacro.mac
```

Execute electronScattering in 'interactive' mode with visualization e.g.

% electronScattering
Then type your commands, for instance :
Idle> control/execute vis.mac
Idle> run/beamOn 5
....