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&DRIFT: TRACK: SRIM

LATERAL-STRAGGLING

Requests lateral straggling be applied at each step of the SRIM track generation.

[By default, switched on.]

LONGITUDINAL-STRAGGLING

Requests longitudinal straggling be applied at each step of the SRIM track generation. Slight range variations may remain as a result of path length variations if lateral straggling is in effect.

Since longitudinal straggling is SRIMs way to introduce energy loss fluctuations, this option should be switched off when energy loss fluctuations are introduced by other means. See for this the FLUCTUATION-MODEL options.

[By default, switched on.]

FAST-VAVILOV

Requests the use of the fast Vavilov random number generator, which is equivalent to the RND_VAVILOV_FAST.

The alternative is the use of the precise Vavilov generator, which internally is the same as RND_VAVILOV.

In most cases, the additional precision afforded by using the precise generator is not justified by the overall precision of the energy loss generator.

[Default is the fast generator.]

GROUPING

SRIM is aimed at low energy nuclear particles which deposit large numbers of electrons in a gas. It would neither be practical nor useful in most cases to treat each of these electrons individually. Garfield therefore by default groups the electrons such that, in all, one will have of order MXCLUS/2 clusters.

You may override this by manually specifying a grouping size.

[Automatic grouping is default.]

ENERGY

The kinetic energy of the particle traversing the chamber.

The kinetic energy Ekin is related to the energy E by the relation E\ =\ Ekin\ +\ m, where m is the mass of the particle. In high energy physics, it is usual to quote the energy E of a particle, not the kinetic energy.

The kinetic energy can either be a number, in which case it is assumed to be in MeV, or a number followed by a unit (eV, keV, MeV or GeV).

[No default; mandatory parameter]

MASS

Refer to the Heed MASS specification.

[By default, the mass found in the SRIM table.]

CHARGE

Refer to the Heed CHARGE specification.

[By default, the charge found in the SRIM table.]

particle

Refer to the Heed particle specification.

FLUCTUATION-MODEL

Depending on the energy of the particle traversing the gas, various energy loss fluctuation models may be applicable. The SRIM output does not specify the model to use.

By default, Garfield uses a combined model which is described in http://cern.ch/rjd/Garfield/vavilov.ps This model uses the Landau distribution for small steps, the Vavilov distribution for medium steps and the Gaussian distribution for long steps. The parameters of these distributions are automatically updated according to the particle properties (mass, charge and kinetic energy) and the gas properties (A, Z and the density rho).

The following models are available:

Whenever using a Vavilov distribution, whether by using the "combined" model or by requesting the Vavilov distribution explicitly, you have the choice between two generators, a fast one (FAST-VAVILOV) and a more precise one (PRECISE-VAVILOV).

When explicitly requesting the use of the Vavilov distribution, beware of the limitations in applicability which are explained in the note cited above. The permissible parameter range is that of the RND_VAVILOV or RND_VAVILOV_FAST procedure, depending on the choice of generator.

Please note that range fluctuations should be switched off with the NOLONGITUDINAL-STRAGGLING option if energy loss fluctuations are introduced.

[Default: the combined model.]

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