Last version:
FLUKA 2023.3.3, January 31st 2024
(last respin 2023.3.3)
flair-2.3-0d 13-Sep-2023

News:

-- Fluka Release
( 31.01.2024 )

FLUKA 2023.3.3 has been released.
Next FLUKA Course
The 23rd FLUKA course
will be held at the Lanzhou University, China, on June 1-8, 2024

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# IONFLUCT

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

For any SDUM's but PRIM-ION:

```     WHAT(1) >= 1.0 : restricted energy loss fluctuations (for hadrons
and muons) switched on
=< -1.0 : restricted energy loss fluctuations (for hadrons
and muons) switched 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,
With any other SDUM value, they are not activated.
```

```     WHAT(2) >= 1.0 : restricted energy loss fluctuations (for electrons
and positrons) switched on
=< -1.0 : restricted energy loss fluctuations (for electrons
and positrons) switched 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,
With any other SDUM value, they are not activated.
```

```     WHAT(3) : If WHAT(1) (resp. WHAT(2)) >=1, WHAT(3) represents the accuracy
parameter for the ionisation fluctuation algorithm (see [Fas97a])
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
```

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 1st ionisation potential and the average number of primary ionisations per unit length.

```     WHAT(1) = effective 1st ionisation potential (eV)
(meaningless for model 1)
No default
```

```     WHAT(2) = number of primary ionisations per cm for a mimimum ionising
particle (assumed to be a muon+ 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.
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
```

```     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
```

```     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.
```

Notes:

• 1) The energy loss fluctuation algorithm is fully compatible with the DELTARAY option.

• 2) 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....+....8
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
```