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