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.

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			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
    /process/had/rdm/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.

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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
	     
 



