Call: MICROSCOPIC_AVALANCHE

x

x-Coordinate of the primary electron. See coordinates.

y

y-Coordinate of the primary electron. See coordinates.

z

z-Coordinate of the primary electron. See coordinates.

options

A String which may contain one or more of the following options and their negated versions (prefixed with NO):

ABORT-100: Kills avalanche tracing when it reaches a size of 100. By default, an avalanche is allowed to grow until it exhausts the memory allocated for it.
ABORT-1000: Kills avalanche tracing when it reaches a size of 1000. By default, an avalanche is allowed to grow until it exhausts the memory allocated for it.
ABORT-10000: Kills avalanche tracing when it reaches a size of 10000. By default, an avalanche is allowed to grow until it exhausts the memory allocated for it.
ABORT-100000: Kills avalanche tracing when it reaches a size of 100000. By default, an avalanche is allowed to grow until it exhausts the memory allocated for it.
MARK-ATTACHMENT: Marks the location where attachment occurs with representation ATTACHMENT. The electron will as a rule stop at these locations. This option is not active by default.
MARK-ELASTIC: Marks the locations of elastic interactions, using ELASTIC. This is nearly always the most common type of collision. This option is not active by default.
MARK-EXCITATION: Marks the locations of inelastic collisions where an excited state is produced. The point will be drawn using EXCITATION. This option is not active by default.
MARK-INELASTIC: Marks the locations of inelastic but non-exciting interactions. The position will be marked using INELASTIC. This option is not active by default.
MARK-IONISATION: Marks the locations where ionisations occur using IONISATION. This option is not active by default.
MARK-SUPER-ELASTIC: Marks the locations of super-elastic interactions using SUPER-ELASTIC. This option is not active by default.
PLOT-ELECTRON: Plots all electron trajectories. PLOT_DRIFT_LINE would only show the last electron trajectory calculated, not the entire avalanche.
PRINT: Switches on Magboltz printing. Use the DEBUG option to obtain details for each step.
SIGNAL: Requests calculation of the signals for the electrons in the avalanche. Please note that ion signals need to be added separately, as illustrated in the example below.

Note: switching on any of the MARK and PLOT options presumes that you have already opened a graphics window suitable for plotting the drift-line.

Example:

// Options and arguments Global options = `plot-electron, abort-100` Global emax = 200 Global estart = 0.1 Global xstart = -0.2+0.4*rnd_uniform Global ystart = 0.8

// Open a plot frame Call plot_drift_area // Microscopic avalanche Call microscopic_avalanche(xstart, ystart, 0, options, emax, estart, ... 0, 0, 0, edist, rates, n_electron, n_ion) Say "Electrons: {n_electron}, ions: {n_ion}"

// Retrieve the ion production point Call avalanche_information(`electrons`, ne) For ie From 2 To ne Do // No ion from the drift line starting point Call avalanche_information( ... `x-start`, ie, xion, `y-start`, ie, yion, `z-start`, ie, zion, ... `t-start`, ie, tion) Call drift_ion_3(xion, yion, zion) Call plot_drift_line Call add_signals(tion) // Offset with production time Enddo

// Close the plot Call plot_end

The locations where ions are produced are retrieved using AVALANCHE_INFORMATION and the ions are drifted with DRIFT_ION_3. The ion-induced signals are computed and added with ADD_SIGNALS.

e_maximum

Maximum kinetic energy in eV any electron in the avalanche is expected to reach.

The calculation of the avalanche as a whole is aborted when at any point an electron energy exceeds this value. The global variable OK will be set to False should this occur.

The trajectory will be inaccurate if the maximum energy is chosen too large.

A simple way to find suitable values for this parameter is running MAGBOLTZ with the PLOT-DISTRIBUTION-FUNCTIONS option switched on. Beware that e_maximum must be suitable over the entire drift path of the electron, including the avalanche region.

[Default: 200 eV]

e_start

Kinetic energy in eV of the primary electron at the start of the avalanche. The energy of secondary electrons is randomised according to a splitting function.

This energy must be strictly positive (non-zero) and less than e_maximum.

[Default: 2\ % of e_maximum.]

dir

Direction vector of the initial velocity of the primary electron. The initial direction has, in most gaseous detectors, little impact. The direction of secondary electrons is assumed to be isotropic.

The norm of the initial velocity is taken from e_start, not from the direction vector. The normalisation is arbitrary.

All three components must be specified. If all 3\ components of the direction vector are zero, then an isotropic random vector will be generated.

[A random direction is assumed if no direction is specified.]

distribution

On return an Histogram which contains the electron energy distribution sampled just prior to every interaction with the gas molecules.

If this argument is on entry an existing histogram, then new entries will be added to it. This can be used to force a scale and also to accumulate statistics across multiple calls.

If this argument is of another type on entry, then the current value will be deleted and a new histogram will be booked with 100\ bins and ranging from 0 to e_maximum.

rates

This procedure returns the detailed counts of the interactions in the form of a 1-dimensional Matrix.

The cross sections present in the vector vary with e_maximum since Magboltz eliminates, for reasons of efficiency, negligibly small cross section terms.

The various terms can be identified with the help of the CROSS_SECTION_IDENTIFIER procedure:

See the rates argument of the DRIFT_MICROSCOPIC_ELECTRON procedure for an example.

[Default: 0 microsec.]

Go to the top level, to Call, to MICROSCOPIC_AVALANCHE, to the topic index, to the table of contents, or to the full text.

Formatted on 21/01/18 at 16:55.

Call: MICROSCOPIC_AVALANCHE

x

y

z

status

time

options

e_maximum

e_start

dir

distribution

rates

n_electron

n_ion

delay