Commit 67b5f68b authored by Simon Spannagel's avatar Simon Spannagel
Browse files

Merge branch 'beamWaisteConvention' into 'master' 

Adjust beam waist treatment to standard convention

See merge request allpix-squared/allpix-squared!1039
parents 30cb9013 a16843b8

AUTHORS.md

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@@ -18,6 +18,7 @@ The following authors, in alphabetical order, have developed or contributed to A 
* Bogdan-Mihail Blidaru, Heidelberg University, [mblidaru](https://gitlab.cern.ch/mblidaru)

* Marco Bomben, Université de Paris, [mbomben](https://gitlab.cern.ch/mbomben)

* Koen van den Brandt, Nikhef, [kvandenb](https://gitlab.cern.ch/kvandenb)

* Ben Bruers, DESY, [bbrueers](https://gitlab.cern.ch/bbrueers)

* Carsten Daniel Burgard, DESY, [cburgard](https://gitlab.cern.ch/cburgard)

* Maximilian Felix Caspar, DESY, [mcaspar](https://gitlab.cern.ch/mcaspar)

* Liejian Chen, Institute of High Energy Physics Beijing, [chenlj](https://github.com/chenlj)
@@ -49,6 +50,7 @@ The following authors, in alphabetical order, have developed or contributed to A 
* Andre Sailer, CERN, [sailer](https://gitlab.cern.ch/sailer)

* Tasneem Saleem, Synchrotron SOLEIL, [TasneemSaleem](https://github.com/TasneemSaleem)

* Arka Santra, Weizman Institute, [asantra](https://gitlab.cern.ch/asantra)

* Christian Scharf, HU Berlin, [cscharf](https://gitlab.cern.ch/cscharf)

* Enrico Jr. Schioppa, Unisalento and INFN Lecce, [schioppa](https://gitlab.cern.ch/schioppa)

* Sebastian Schmidt, FAU Erlangen, [schmidtseb](https://github.com/schmidtseb)

* Sanchit Sharma, Kansas State University, [SanchitKratos](https://github.com/SanchitKratos)

src/modules/DepositionLaser/DepositionLaserModule.cpp

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@@ -450,8 +450,10 @@ std::pair<ROOT::Math::XYZPoint, ROOT::Math::XYZVector> DepositionLaserModule::ge 
    // Lambda to generate a smearing vector

    auto beam_pos_smearing = [&](auto size) {

        auto [v1, v2] = orthogonal_pair(beam_direction_);

        double dx = allpix::normal_distribution<double>(0, size)(event->getRandomEngine());

        double dy = allpix::normal_distribution<double>(0, size)(event->getRandomEngine());



        // Beam waist is equal to 2*sigma

        double dx = allpix::normal_distribution<double>(0, size / 2.)(event->getRandomEngine());

        double dy = allpix::normal_distribution<double>(0, size / 2.)(event->getRandomEngine());

        return v1 * dx + v2 * dy;

    };

src/modules/DepositionLaser/README.md

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@@ -38,6 +38,8 @@ For a `cylindrical` beam, all tracks are parallel to the set beam direction. 
For a `converging` beam, track directions would have isotropic distribution (but with a limit on a max angle between the

track and the set beam direction).



The transversal width of the Gaussian beam is defined by the beam waist $`w_0`$, which describes the minimal beam width. The beam width in turn is defined as the distance between the point of maximum intensity and the point where the intensity drops to $`\frac{1}{e^2}`$. For a Gaussian-distributed intensity, the intensity drops to $`\frac{1}{e^2}`$, if $`x=2\sigma`$, see the probability distribution function of the normal distribution. The beam waist therefore equals $`2\sigma`$.



**NB**: convention on global time zero for this module contradicts the general convention of the Allpix Squared.

For this module, global t=0 is chosen in such a way that the mean value of temporal distribution is *always* positioned at

*4 standard deviations*  w.r.t. the global t=0.
@@ -63,7 +65,7 @@ and temporal distribution. 
* `source_position`: a 3D position vector.

* `beam_direction`: a 3D direction vector.

* `beam_geometry`: either `cylindrical` or `converging`

* `beam_waist`: standard deviation of transversal beam intensity distribution at focus. Defaults to 20 um.

* `beam_waist`: parametrises the transversal width of the beam by the beam waist $`w_0=2\sigma`$ described above. Defaults to 20 um.

* `focal_distance`: needs to be specified for `converging` beam. This distance is *as it would be in air*. In silicon, beam

  shape will effectively stretch along its direction due to refraction and the actual focus will be further away from the

  source.