IONFLUCT¶

Summary

Calculates ionisation energy losses of charged hadrons, muons, and electrons/positrons with ionisation fluctuations.

See also DELTARAY

For any SDUM but PRIM–ION:

WHAT(1) ≥ 1.0:: switches the restricted energy loss fluctuations for hadrons and muons on
≤ -1.0:: switches the restricted energy loss fluctuations for hadrons and muons off
= 0.0:: ignored
Default: : restricted energy loss fluctuations for hadrons and muons are activated if option DEFAULTS is missing or if it is used with SDUM = CALORIMEtry, EET/TRANSmut, HADROTHErapy, ICARUS, NEW–DEFAults or PRECISIOn.

With any other SDUM value, they are not activated.
WHAT(2) ≥ 1.0:: switches the restricted energy loss fluctuations for electrons and positrons on
≤ -1.0:: switches the restricted energy loss fluctuations for electrons and positrons off
= 0.0:: ignored
Default: : restricted energy loss fluctuations for electrons and positrons are activated if option DEFAULTS is missing or if it is used with SDUM = CALORIMEtry, EM–CASCAde, HADROTHErapy, ICARUS, NEW–DEFAults or PRECISIOn.

With any other SDUM value, they are not activated.
WHAT(3) :: If WHAT(1)≥ 1.0 (resp. WHAT(2)≥ 1.0), WHAT(3) represents the accuracy parameter for the ionisation fluctuation algorithm [Fas97a] (see Transport of charged hadrons and muons) for hadrons and muons (resp. electrons and positrons). The accuracy parameter can take integer values from 1 to 4 (corresponding to increasing levels of accuracy)
< 0.0:: resets to default
Default: = 1.0 (minimal accuracy)
WHAT(4) =: lower bound (or corresponding name) of the indices of the materials in which the restricted energy loss fluctuations are activated

(“From material ``WHAT(4)``…”)
Default: = 3.0
WHAT(5) =: upper bound (or corresponding name) of the indices of the materials in which the restricted energy loss fluctuations are activated

(“…to material ``WHAT(5)``…”)
Default: = WHAT(4)
WHAT(6) =: step length in assigning indices

(“…in steps of ``WHAT(6)`` ”)
Default: = 1.0
SDUM: : blank

For SDUM = PRIM–ION: generation of primary ionisation electrons is switched on

(or switched off, if WHAT(3) < 0)

Delta rays below threshold for explicit generation are generated anyway: for close collisions down to the threshold, and for distant collisions down to an internally computed value, such as to match the input 1\(^{st}\) ionisation potential and the average number of primary ionisations per unit length.

WHAT(1) =: effective 1\(^{st}\) ionisation potential (eV) (meaningless for model 1)
Default: : No default
WHAT(2) =: number of primary ionisations per cm for a mimimum ionising particle (assumed to be a \(\mu^+\) at

\(\beta \gamma = 3\)). For gases it must be the value at NTP.

If set = 0 (valid value), only primary electrons related to close collisions will be produced and WHAT(1) and WHAT(3) will be meanigless.
Default: : No default
WHAT(3) =: primary ionisation model type (1, 2, 3 or 4).

0 is ignored if a previous call set a value > 0, otherwise it forces the default. A value < 0 switches off primary ionisation production
Default: = 1.0
WHAT(4) =: lower bound (or corresponding name) of the indices of the materials in which the choices represented by WHAT(1), (2) and (3) apply

(“From material ``WHAT(4)``…”)
Default: = 3.0
WHAT(5) =: upper bound (or corresponding name) of the indices of the materials in which the choices represented by WHAT(1),(2) and (3) apply

(“…to material ``WHAT(5)``…”)
Default: = WHAT(4)
WHAT(6) =: step length in assigning indices

(“…in steps of ``WHAT(6)`` ”)
Default: = 1.0
SDUM: = PRIM–ION

Warning : the following section describes a feature that is not yet implemented

For SDUM = SECO–ION: generation of secondary ionisation electrons is switched on, or off if WHAT(3) \(<0\) (not yet available in the code)

WHAT(1) =: average energy spent per ion couple (eV).
Default: : No default
WHAT(2) =: number of secondary ionisations per cm for a mimimum ionising particle (assumed to be a \(\mu^+\) at

\(\beta \gamma = 3\)). For gases it must be the value at NTP.

If set = 0 (valid value), only primary electrons related to close collisions will be produced and WHAT(1) as well as WHAT(3) will be meanigless.
Default: : No default
WHAT(3) =: secondary ionization flag.

0 is ignored if a previous call set a value > 0, otherwise it forces the default. A value < 0 switches off primary ionisation production
Default: = 1.0
WHAT(4) =: lower bound (or corresponding name) of the indices of the materials in which the choices represented by WHAT(1), (2) and (3) apply

(“From material ``WHAT(4)``…”)
Default: = 3.0
WHAT(5) =: upper bound (or corresponding name) of the indices of the materials in which the choices represented by WHAT(1),(2) and (3) apply

(“…to material ``WHAT(5)``…”)
Default: = WHAT(4)
WHAT(6) =: step length in assigning indices

(“…in steps of ``WHAT(6)`` ”)
Default: = 1.0
SDUM: = SECO–ION
Default: (option IONFLUCT not given): ionisation fluctuations are simulated or not depending on option DEFAULTS as explained above. Explicit primary ionisation events are never simulated by default.

See also Table 7.1 at.

Notes

The energy loss fluctuation algorithm is fully compatible with the DELTARAY option. (See Example below).
Primary ionisation electron energies are stored in COMMON ALLDLT at each step in the selected materials.

Use with care and possibly for gases only. The number of primary ionisations electrons can quickly escalate, particularly when multiply charged ions are involved. No COMMON saturation crash should occur since the code is piling up all the remaining primary electrons into the last COMMON location if no further one is available, however CPU penalties can be severe if used without wisdom.

Example (number-based):

*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
IONFLUCT         0.0       1.0       3.0       7.0      16.0       3.0
IONFLUCT         1.0       0.0       2.0       8.0      10.0       2.0
DELTARAY       1.E-3       0.0       0.0      10.0      11.0
*  The special FLUKA algorithm for ionisation fluctuations is activated
*  with accuracy level 3 for photons and electrons in materials 7, 10, 13 and
*  16 (Nitrogen, Aluminum, Silver and Mercury). The same algorithm is activated,
*  at an accuracy level = 2, for materials 8 and 10 (Oxygen and Aluminum), but
*  in the latter material only for ionisation losses with energy transfer
*  < 1 MeV. Losses with larger energy transfer will result in explicit delta
*  electron production. In material 11 (Iron),  delta rays will be produced if
*  the energy transfer is larger than 1 MeV, but fluctuations for lower energy
*  transfers will be ignored.

The same example, name based:

IONFLUCT         0.0       1.0       3.0  NITROGEN   MERCURY       3.0
IONFLUCT         1.0       0.0       2.0    OXYGEN  ALUMINUM       2.0
DELTARAY       1.E-3       0.0       0.0  ALUMINUM      IRON