&DRIFT: TRACK


FROM

  The coordinates of the starting point of the track.

  This would usually be a set of 3 numbers. If you omit
  the z-coordinate, 0 is assumed.

  [No default, in cm.]

TO

  The coordinates of the end point of the track. If the
  particle undergoes multiple scattering or energy loss
  (HEED model), then the end point merely serves to compute
  the initial direction of the particle.

  When both TO is used and DIRECTION and RANGE, then the
  information provided with TO is taken.

  This would usually be a set of 3 numbers. If you omit
  the z-coordinate, 0 is assumed.

  [No default, in cm.]

DIRECTION

  The direction in which the particle starts moving from
  the starting point.

  When using DIRECTION, you must also use RANGE. You should
  not use TO however in this case, since TO overrules the
  information from DIRECTION and RANGE.

  This would usually be a set of 3 numbers. If you omit
  the z-coordinate, 0 is assumed.

  [No default, in cm.]

RANGE

  This is the maximum distance the particle is allowed to
  travel from the starting point. The range is measured by
  projection onto the DIRECTION, i.e. the additional length
  that results from multiple scattering is not taken into
  account.

  The RANGE should be chosen sufficiently large to avoid
  having the particle cut prematurely, but not too large
  either - this would cause overflow in HEED's internal
  buffers.

  [No default, in cm.]

FIXED-NUMBER

  Requests the simple model in which a fixed number of
  electrons or ions is generated at equally spaced points
  along the track.


  The track is straight in this model.

  Since this the only model that doesn't depend on external
  information, this is the initial default.

Additional Information on:

  • LINES

  • EQUAL-SPACING

      Requests a model in which the number of clusters
      generated along a straight track is always exactly
    
           mean * length
    
      where "mean" is the mean number of clusters per cm as
      entered with the PARAMETER statement in the gas section
      and where "length" is the distance between the start
      and end points of the track. The clusters are deposited
      with a constant spacing.
    
      The cluster size distribution is respected.
    
      This model can only be selected if the mean number of
      clusters and the cluster size distribution have been
      entered in the gas section.
    

    EXPONENTIAL-SPACING

      Requests a model in which the number of clusters
      generated along a straight track is Poisson distributed
      with a mean of:
    
      mean * length
    
      where "mean" is the mean number of clusters per cm as
      entered with the PARAMETER statement in the gas section
      and where "length" is the distance between the start
      and end points of the track. The spacing between the
      clusters is exponentially distributed.
    
      The cluster size distribution is respected.
    
      This model can only be selected if the mean number of
      clusters and the cluster size distribution have been
      entered in the gas section.
    

    WEIGHTED-DISTRIBUTION

      This model generates single electron or ion deposits
      (i.e. no clusters) at positions that follow a user
      specified distribution. The model can be used to
      simulate certain background conditions.
    
      The deposits are generated in random sequence.
    

    Additional Information on:

  • WEIGHTING-FUNCTION
  • SAMPLES

  • SINGLE-CLUSTER

      A single cluster is generated on each track. The cluster
      size is taken from the information entered in the gas
      section.
    
      This model differs from FIXED-NUMBER with a number of samples
      set to 1 in that the cluster in SINGLE-CLUSTER is at a random
      location while it would be in the middle of the track when
      using FIXED-NUMBER.
    
      This model can be seen as a rough approximation to photon
      from e.g. an Fe 55 source, provided an adequate cluster size
      distribution is entered.
    

    HEED

      This option calls the Heed program to take care of cluster
      generation. This program simulates the ionisation of the gas
      molecules by a particle.
    
      The particle knock an electron out of an atom. The electron
      may have sufficient energy to cause further ionisations (in
      that case we speak of a delta electron) or it may start drifting
      towards the anode. The atom returns to its ground state by either
      emitting an Auger electron or by fluorescence photons. The Auger
      electrons are treated like the ionisation electrons. The photons
      can be absorbed in other atoms.
    
      When using the Heed interface, you must define the gas mixture
      to Heed in the gas section. Then, you should specify on the
      TRACK statement what kind of particle traverses the chamber.
      Clustering information entered in the gas section through the
      PARAMETER and CLUSTER statements is not used.
    

    Additional Information on:

  • particle
  • MASS
  • CHARGE
  • ENERGY
  • MULTIPLE-SCATTERING
  • DELTA-ELECTRONS
  • TRACE-DELTA-ELECTRONS

  • Keyword index. Formatted on 10/11/98.