UNDERGROUND PHYSICS ADVANCED EXAMPLE - DMX UserRequirements.txt - Alex Howard, e-mail: alexander.howard@cern.ch, 29/11/01. Introduction: This document is an initial introduction to the Dark Matter Example - DMX. A single liquid xenon cell is simulated within Geant4 and the scintillation light produced from interactions from various calibration species is recorded as hits in a PhotoMultiplier Tube (PMT). The output is then written to an ASCII file for future off-line analysis. ------------------------------------------------------------------------------- User Requirements: General UR 1.1: Configure the run management UR 1.2: Configure the event loop Geometry: Experimental set-up: UR 2.1: A "cavern" of dimensions 5m x 6m x 3m with concrete walls is defined as the World Volume. In the centre of the cavern a steel vacuum vessel containing liquid and gaseous xenon is placed. The internal construction of the vessel accurately reproduces an existing prototype Dark Matter detector which allows experimental comparison. The active detector volume is defined by a series of metal rings, complemented by a cover mirror and a PMT immersed in the liquid. Two grids and a thermalising copper shield are also incorporated. The liquid/gas interface is located 6mm away from the mirror surface. A Am241 calibration source is suspended from one of the grids in the liquid phase, above the PMT. XXX================XXX mirror XXX________________XXX gas phase XXX XXX XXX XXX liquid phase XXX XXX XXX.......U........XXX grid + calibrator XXX................XXX grid XXX| |XXX | ___------___ | || PMT || || || An accurate simulation of the above set-up should be carried. UR 2.2: Record the energy deposited in the sensitive volume of the xenon chamber (liquid phase). UR 2.3: Produce scintillation photons with different time constants and light yields depending upon the species of particle causing the excitation - either nuclear recoil or electron recoil type interactions. UR 2.4: Implement reflectivities and transmission probabilities for all materials concerned. UR 2.5: Ray trace the scintillation back to the PMT and record hit times, positions and number of photons. PHYSICS: The following areas of physics should be included: UR 3.1: · Low Energy Electromagnetic - to 250eV for both e and photons Maximum energy range around 10 MeV for any particle UR 3.2: · Compton Scattering UR 3.3: · Photoelectric Effect UR 3.4: · Bremsstrahlung UR 3.5: · Rayleigh Scattering - for both optical photons and hard X-rays/Gammas UR 3.6: · Electromagnetic ionisation UR 3.7: · Delta Rays Produced discretely down to 250eV to allow secondaries and tertiaries to be properly handled UR 3.8: · Heavy Ion Transport - to 250eV for protons, alphas and nuclei Allows separate scintillation time and yield compared to gammas (electrons) UR 3.9: · Radioactive Decay - induced All materials are sensitive to induced activity as a consequence of photo-nuclear or neutron capture UR 3.10: · Radioactive Decay - sources Specific nuclei can be decayed within the geometry to reproduce experimental calibration the experiment UR 3.11: · Neutron tracking from medium energy (few MeV) to thermal capture Discretely transported through-out the volume to give full detector response for both neutron capture activation and elastic and inelastic interaction in the target volume UR 3.12: · Scintillation light production and ray-tracing to PMT Optical photon transport introduced to allow realistic detector response to be produced. ParticleSource: UR 4.1: Implement a generic particle source that allows various particles, ions and nuclei to be fired or decayed anywhere within the volume. UR 4.2: Allow confinement of the particle source to within given volumes and randomly select particle or ion production within that volume. UR 4.3: Allow various source shapes - point, sphere and cylinder have been implemented. UR 4.4: !!!! not in ours !!! Allow spectrum of energies to be chosen as well as a monoenergetic particle type. Radioactive Decay Module: UR 5.1: Allows specific ions to be decayed within set nuclear limits and energies and positions - linked to Particle Source above. UR 5.2: Can control induced activity to specific volumes. UR 5.3: Allows increased functionality in terms of choice of weighting for the decay and other non-analogue MC techniques. Analysis: UR 6.1: Outputs to file "hits.out" the event number (Evt #), the energy deposited in the liquid phase (Etot, MeV), the number of hits in LXe (LXe hits), the time of the first hit (LXeTime, ns), the number of PMT hits (PMT hits), the average PMT hit time relative to the first hit in LXe (PmtTime, ns), the first particle to hit the LXe (First hit) and flags the type of particles depositing energy - gamma, neutron, electron, positron, proton, other (Flags). UR 6.2: The "First hit" and "Flags" described above constitute a record of particle type history important for identifying and differentiating between elastic and inelastic neutron interactions. Visualisation: UR 7.1: Visualise the experimental set-up. UR 7.2: Visualise tracks in the experimental set-up. UR 7.3: Allow the choice between scintillation light, PMT photocathode hits, and full tracking to be displayed. UR 7.4: Allow the user to choose specific track colours for gammas, neutrons, charged-plus and charged-minus tracks. UR 7.5: Allow output to stored interactive files using the HEPREP interface which can then be read into Wired and other XML packages. User Interface: UR 8.1: Allow control of the particle source via the /dmx/gun control: Command directory path : /dmx/gun/ Guidance : Particle Source control commands. Sub-directories : Commands : 1) List * List available particles. 2) particle * Set particle to be generated. 3) direction * Set momentum direction. 4) energy * Set kinetic energy. 5) position * Set starting position of the particle. 6) ion * Set properties of ion to be generated. 7) type * Sets source distribution type. 8) shape * Sets source shape type. 9) centre * Set centre coordinates of source. 10) halfz * Set z half length of source. 11) radius * Set radius of source. 12) confine * Confine source to volume (NULL to unset). 13) angtype * Sets angular source distribution type 14) energytype * Sets energy distribution type 15) verbose * Set Verbose level for gun UR 8.2: Control verbosities via: The user should have the ability to change several features including a) verbosities can be controlled for /control/verbose /run/verbose /tracking/verbose /hits/verbose /grdm/verbose /dmx/gun/verbose UR 8.3: Control the output to the screen into Modulo N events: using printModulo control. Command /dmx/printModulo Guidance : Print events modulo n Range of parameters : EventNb>0 Parameter : EventNb Parameter type : i Omittable : False UR 8.4: Draw commands controlled via /dmx/draw/: DM Example draw commands. Sub-directories : Commands : 1) drawColours * Tracks drawn by Event (standard colours) or by Step (custom colours) 2) drawTracks * Which tracks to draw in the event 3) drawHits * Set flag to draw hits in PMT. 4) neutronColour * Colour of neutron in the event 5) gammaColour * Colour of gamma in the event 6) opticalColour * Colour of gamma in the event 7) chargedplusColour * colour of chargedplus in the event 8) chargedminusColour * colour of chargedminus in the event UR 8.5: Control the files to be saved - PMT hits and event summary in terms of energy deposit and number of photon hits observed. Command /dmx/savePmt Guidance : Set flag to save (x,y,z) of hits in PMT into file 'pmt.out' Default = false Parameter : savePmtFlag Parameter type : b Omittable : False Command /dmx/saveHits Guidance : Set flag to save hits in each run into file 'hits.out' Default = true Parameter : saveHitsFlag Parameter type : b Omittable : False UR 8.6: Allow the suppression of physics processes within specific volumes in order to optimise running of the neutron transport code. Gammas may be killed in the concrete wall in order to reduce processing time significantly. Command /dmx/KillGammasInConcrete Guidance : Kills gammas produced by neutrons in the concrete wall Default = false Parameter : KillGammasFlag Parameter type : b Omittable : False Default value : 0 CUTS: UR 9.1: User can apply special cuts to time and step length to tracks. If the global time is exceeded then the track is killed. UR 9.2: Allow gammas to be killed in the concrete wall in order to optimise processing time for neutron transport. ------------------------------------------------------------------------------ Background Information/Links Information on the experimental side of this project can be obtained from the following: Who we are: Imperial College High Energy Physics Group -> http://www.hep.ph.ic.ac.uk/ Imperial College Astrophysics -> http://astro.ic.ac.uk/ Dark Matter collaboration and existing experimental programme: Boulby Collaboration Home Page -> http://hepwww.rl.ac.uk/ukdmc/ Full Users Requirement Document A draft of the full users requirement document for the advanced example can be downloaded/viewed at the following: Word Document -> http://icva.hep.ph.ic.ac.uk/~howard/g4_project/urd_draft1.doc Web Page -> http://icva.hep.ph.ic.ac.uk/~howard/g4_project/urd_draft1.htm