&SIGNAL: SIGNAL


ADD

  Signals from repeated simulations will be summed, wire by wire.

ANGULAR-INTEGRATION-POINTS

  The angular spread function is integrated using the Newton-
  Raphson technique with  2*n_angle+1  points.

  By default, n_angle is set to 2.

ANGULAR-SPREAD

  In the simplified ion tail model, you have the possibility
  to spread the ions that are produced in the avalanche, around
  the wire.

  The spread is to be provided as a probability distribution
  in terms of the angle PHI (in radians) between the incidence
  angle of the electron and the angle at which the ions start
  to drift away from the wire.

ATTACHMENT

  Attachment coefficients will be taken into account for signal
  calculations. They occur at two instances:

  - when computing the avalanche multiplication factor from the
    Townsend and attachment coefficients
  - when tracing the electron avalanche during the computation
    of the currents induced by the electrons

AVALANCHE

  Enables the avalanche setting chosen with AVALANCHE.
  NOAVALANCHE leads to a fixed multiplication factor of 1.

  Both ELECTRON-PULSE and DETAILED-ION-TAIL require Townsend
  coefficients. They use these coefficients, provided they are
  available, regardless of the setting of this option.

AVERAGE-SIGNAL

  Switching on this option makes that the total induced charge
  corresponds closely to the integral of the signal that is
  output by the program. This is less trivial than it may sound
  since signals can contain structure on a much smaller time
  scale than the binning of the signal.

  The averaging is done with an  2*n_average+1  point Newton-
  Raphson integration over a time bin centered at the point in
  time indicated in the output.

CROSS-INDUCED

  Requests the computation of the signal induced on the sense
  wires by the avalanches on different wires. Also currents
  induced by electrons that do not drift to a wire will be
  computed.

  The option is best used in conjunction with DETAILED-ION-TAIL.

DETAILED-ION-TAIL

  Adds an ion tail to the computed signal according to a more
  detailed model in which the ions do not necessarily start at
  the wire surface. Rather, they start where they are produced
  during the electron avalanche.

  This model is to be prefered in case the avalanche region is
  substantial or when the integrated charge is important. Otherwise,
  the simplified model will be faster.

DIFFUSION

  Varies the arrival times of the individual electrons from the
  clusters according to a Gaussian distribution.

ELECTRON-PULSE

  Adds an electron pulse to the computed signal.

  The electron pulse is computed by following the avalanche
  process along the electron drift line, this option therefore
  requires the presence of Townsend coefficients. Attachment
  coefficients, if present, will also be taken into account.
  Also the INTERPOLATE-TRACK option is not compatible with
  ELECTRON-PULSE.

INTERPOLATE-TRACK

  Enables the use of the prepared track, see PREPARE-TRACK.

  This option can not be used together with ELECTRON-PULSE
  nor with DETAILED-ION-TAIL.

  Default: Even if a prepared track is available, it will by
  default not be used for the signal calculation.

INTERPOLATION-ORDER

  In order to average the signal over a time bin, the
  signal is interpolated with polynomials of order  n_order,
  and then integrated using the Newton-Raphson technique
  over  2*n_average+1  points.

  The parameter  n_order  should not be chosen large since
  especially electron pulses rise very fast. This can easily
  give rise to interpolated values of the wrong sign.

  A value of 1 is therefore recommended, and is also default.

ION-ANGLES

  The shape of the ion tail is usually stored for a series of
  electron incidence angles. The reasons for this are that (a)
  similar ion tails are needed for electrons from possibly many
  clusters (b) the ion tail shape doesn't vary much between
  nearby electron incidence angles.

  The number of electron incidence angles for which a separate
  ion tail is calculated can be chosen with this keyword. A value
  of 1 would be suitable for cylindrically symmetric detectors,
  while a value of order 10-50 would be appropriate if one wishes
  to study stereo effects.

  Separate ion tails are always kept for the different wires on
  which the avalanche is produced and for the different wires on
  which the induced current is measured. A large setting therefore
  implies that a large volume of data has to be stored.

  [Default: 50]

ION-TAIL

  Adds an ion tail to the computed signal according to a simplified
  model in which the ions are assumed to come from the wire surface.

  You may, in this model, choose the spread around the wire of the
  ions that are produced in the avalanche. This can be achieved via
  the ANGULAR-SPREAD keyword.

ION-THRESHOLD

  In the detailed ion tail model, the ions are traced from the point
  where they were produced. This is done on a step-by-step basis of
  the electron drift line that generated the ions.

  To save CPU time, only steps are considered in which at least a
  certain fraction of the total number of ions is produced.

  This fraction should be set to 0 for chambers filled with, for
  instance, liquid Helium where the avalanche develops over a large
  part of the electron drift line.

  For conventional gaseous counters, 10**-3 to 10**-4 would be a
  more appropriate choice.

  The fraction is initially set to 0.

MONTE-CARLO-DRIFT

  Uses the Monte Carlo drifting routines rather the the default
  Runge-Kutta-Fehlberg integration routines. This option is useful
  if diffusion can cause electrons starting from the same starting
  point to reach significantly different end points.

  Since all electrons from a cluster are treated independently,
  and since options like INTERPOLATE-TRACK can not be used in
  conjunction with MONTE-CARLO-DRIFT, use of this option tends
  to make the computations longer.

  You may have to adjust the Monte Carlo parameters in the
  INTEGRATION-PARAMETERS statement when using this option.

  [Default is NOMONTE-CARLO-DRIFT]

NEW

  Means that summing of signals over repeated simulations does not
  take place.

SAMPLE-SIGNAL

  If this option is switched on, the signal that the program
  returns corresponds to the current at the point in time
  indicated in the output. Any fine structure smaller than the
  binning is lost.

Keyword index. Formatted on 10/11/98.