1. 12 dec 2006fast timing Simulation workshop U.Chicago 1 LITRANI LIght TRansmission in ANIsotropic media. A general purpose Monte-Carlo program simulating light propagation in isotropic or anisotropic media. Xavier Gentit Presented by P.L e Dû mail gentit@hep.saclay.cea.fr web : http://gentit.home.cern.ch/gentit/ DAPNIA/SPP * CEN Saclay * BP n° 2 F91191 Gif-sur-Yvette * France

2. 12 dec 2006fast timing Simulation workshop U.Chicago 2 General features Developped for –CMS PbWO4 crystals and alveola –GLAST experiment with a CsI calorimeter LITRANI, a general simulation for the propagation of optical photons. The first motivation was the responsibility of the Saclay CMS group in the calibration of the calorimeter, but the program is quite general and may be of interest each time you have to handle with optical photons.

3. 12 dec 2006fast timing Simulation workshop U.Chicago 3 What is LITRANI? Litrani is a general purpose Monte-Carlo program, built upon ROOT, simulating light propagation in any type of set-up which may be represented by the shapes provided by the old geometry of ROOT. The geometry of Litrani is flat: it is not possible to place a volume inside an other volume. Each shape may be made of a different materials. Dielectric constant, absorption length and diffusion length of materials may depend upon wavelength. Dielectric constant and absorption length may be anisotropic.

4. 12 dec 2006fast timing Simulation workshop U.Chicago 4 What is LITRANI ? (2) Each plane face of a volume may be either partially or totally in contact with an other face of an other volume, or covered with some revetment having defined characteristics of absorption, reflection and diffusion. When in contact with an other face of an other volume, the possibility exists to have a thin slice of width d and index n between the 2 faces. The program has various sources of light: spontaneous photons, photons coming from an optical fibre, photons generated by the crossing of particles, photons generated by the crossing of gamma rays of energy of 0.1 to 1 Mev or photons generated by an high energy electromagnetic shower. The time and wavelength spectra of emitted photons may reproduce any scintillation spectrum.

5. 12 dec 2006fast timing Simulation workshop U.Chicago 5 What is LITRANI ? (3) As detectors, you can have phototubes, APD, or any general type of surface or volume detectors. The aim is to follow each photon until it is absorbed or detected. Quantities of interest to be delivered by the program are the proportion of photons detected, and the time distribution for the arrival of these, or the various ways photons may be lost. For APDs, the simulation goes until the generation of the electronic pulse. The program takes into account the variation of the physical parameters as a function of the wavelength.

6. 12 dec 2006fast timing Simulation workshop U.Chicago 6 Software environment LITRANI is written in C++ and is based on ROOT, this new splendid programming environment provided by René Brun and his team. The actual version of LITRANI is working on Windows NT/2000/XP and Linux (tested on lxplus.cern.ch with Scientific Linux and gcc 3.2.3, and on daplxa177 at Saclay with Linux RedHat RHEL 4 (SLC4) and gcc 3.4.5). Starting from the Linux version, it should be quite easy for you to prepare versions for other unix systems. All sources and Makefiles are provided. On Windows XP, this version of LITRANI has been compiled and linked ( with VC++7.1 ) with the "Dev" "Win32gdk" version of ROOT : 5.13/06. Use it with the same ROOT version or recompile and relink it with your version of ROOT. Litrani uses features of the TSpectrum class of ROOT not available in the old versions of ROOT. Do not go below ROOT 5.12/00.

7. 12 dec 2006fast timing Simulation workshop U.Chicago 7 Installation (1) Go to download of the version for Windows. Go to download of the version for linux. The version of LITRANI is now 3.5. Please notice that there is a relatively big step between this version and the versions with number beginning with 2. Read the page concerning changes from version 2 to version 3. Notice that the general introduction to LITRANI found below gives a good idea of what LITRANI is. But if you look for an exhaustive description of the capabilities of LITRANI, you will find it in the "class description" of all classes of LITRANI.

8. 12 dec 2006fast timing Simulation workshop U.Chicago 8 Installation (2) 1.A general introduction into LITRANI in C++ including the installation. 2.A presentation of SplineFit: the way to provide parameter dependence in LITRANI. 3.A list of examples CINT macros, to learn how to use LITRANI. These example are available with the downloaded package. Study them carefully, beginning with Transm1.C, which is the simplest one. Notice that all examples begin with a call to the function InitLitrani.C(). It is a good idea to also proceed like this in your CINT code. 4.A detailed presentation of all classes of LITRANI. 5.The list of recent news about LITRANI. New since version 3.4 of LITRANI: class TLitSpectrum. And big new since version 3.5: the possibility to handle gammas of energy between 0.1 and 1.0 Mev. Look at class TPhotoElecCompton. 6.A presentation of the physics behind the program. 7.Copyrights. You will find from here pointers towards the following topics :

9. 12 dec 2006fast timing Simulation workshop U.Chicago 9 Learning Litrani with examples This is a welcome feature of Litrani that you can learn it by studying examples. These heavily commented examples are distributed with Litrani as a CINT macros, in the directory "Macros", Do not forget that Litrani uses sometimes values which vary as a function of a parameter, like index of refraction varying as a function of wavelength. For defining such quantities, look at the CINT macros provided in the directory "FitMacros" of the package SplineFit.

10. 12 dec 2006fast timing Simulation workshop U.Chicago 10 Examples of CINT macros for Litrani Description Transm1.C The simplest example.Transmission study inside a TSBRIK Transm2.C idem, more elaborated Transm3.C Transmission study inside a CMS crystal with negativ birefringent material Anibm1.C Setup with beam of muons and APD AniFibre.C Simulation of a fibre with varying incident angle DamAnibm1.C Setup with beam of muons and APD, damaged crystal DamAnibm2.C Identical, except that the damages have not been done by electromagnetic showers DamTransm1.C Transmission study inside a TSBRIK with damaged crystal GLASTWithPINs.C Simulation of a GLAST CsI(Tl) crystal with 4 PINs GLASTWithPMs.C Simulation of a GLAST CsI(Tl) crystal with phototubes OxCryst.C Variation of Collection Efficiency with Generated x position TransCone1.C Transmission study inside a conical shape CMSgif_light.C Very precise description of a CMS barrel crystal with varying radiation damages CMSDrc_light.C Variation of the above CMSEcalECVPT.C Very precise description of a CMS end-cap crystal with Vacuum photo-triode Gamma.C Example of use of gamma beam, class TPhotoElecCompton InitLitrani.C Used by all examples! Study it first. LitDemos.C Allow to test all the above examples by clickin buttons

11. 12 dec 2006fast timing Simulation workshop U.Chicago 11 My conclusions (P.Le Dû) LITRANI is a simple and user frienly tool for various applications –MCP optimisation (Cerenkov light) –PET devices with LSO/LaBR3 crystals and various photodetectors…. We are looking to use it: –For the optimization of the timing detectors of the ATLAS diffractive roman pot experiment (Christophe ) –For the french medical imaging (PET) Contacts with ESI (Yves Lemoigne) INNOTEP collaboration (Clermont,Lyon, Grenoble,Marseille,Saclay) CERIMED (Marseille Imaging platform) Expect some results for the next workshop