[ Identification | Description | Input parameters | Output parameters | Links ]

The Virtual_mcnp_input Component

This component uses a file of recorded neutrons from the reactor monte carlo code MCNP as a source of particles.

Identification

• Author: Chama Hennane and E. Farhi
• Origin: ILL
• Date: June 28th, 2006
• Version: 1.15
• Modification history:
  • EF, July 25th 2006: bug fixes.

Description

This component generates neutron events from a file created using the
MCNP Monte Carlo code for nuclear reactors. It is used to
calculate flux exiting from hot or cold neutron sources.
Neutron position and velocity is set from the file. The neutron time is
left at zero.

Note that axes orientation may be different between MCNP and McStas.
The component has the ability to center and orient the neutron beam to the Z-axis.
It also may change the coordinate system from the MCNP frame to the McStas one.
The verbose mode is highly recommended as it displays lots of useful informations.
To obtain absolute intensity, set 'intensity' and 'nps' parameters.
The source total intensity is 1.054e18 for LLB/Saclay (14 MW) and 4.28e18 for
ILL/Grenoble (58 MW).

Format of MCNP events are :

  position_X position_Y position_Z dir_X dir_Y dir_Z Energy Weight Time

energy is in Mega eV, time in shakes (1e-8 s),
positions are in cm and the direction vector is normalized to 1.

%BUGS
We recommend not to use parallel execution (MPI/Threads) with this component.

EXAMPLE:
To generate PTRAC files using MCNP/MCNPX, add at the end of your input file:
  ptrac         file = asc
                max  = -1000000   // number of neutrons to generate and stop
                write = all
                event = sur
                filter = 2001,jsu // surface id
To create a 'source' from a MCNP simulation event file for the ILL:
COMPONENT source = Virtual_mcnp_input(
   file = "H10p", intensity=4.28e18, nps=11328982,
   verbose = 1, autocenter="translate rotate rescale")

WARNING: This is a contributed Component.

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
file	str	Name of the MCNP PTRAC neutron input file. Empty string "" unactivates component	0
autocenter	str	String which may contain following keywords. "translate" or "center" to center the beam area AT (0,0,0) "rotate" or "orient" to center the beam velocity along Z "change axes" to change coordinate system definition "rescale" to adapt intensity to abs. units. with factor intensity/nps. Other words are ignored.	0
repeat_count	1	Number of times the source must be generated. 0 unactivates the component	1
verbose	0|1	Displays additional informations if set to 1	0
intensity	n/s	Intensity multiplication factor	0
MCNP_ANALYSE	1	Number of neutron events to read for file pre-analysis. Use 0 to analyze them all.	10000
surface_id	1	Index of the emitting MCNP surface to use. -1 for all.	-1
nps	1	Number of total events shot by MCNP to generate the PTRAC as indicated at the end of the MCNP 'o' file as 'source particle weight for summary table normalization' or alternatively 'nps = '.	0
smooth	0/1	Smooth sparsed event files for file repetitions.	1

Output parameters

Name	Unit	Description	Default
hfile
head	char	header buffer
rep
begin_neutrons
do_rotate
do_translate
bx
by
bz
angle2z	double, rad	rotation angle required to orient beam along Z axis
mean_x	double	\
mean_y	double	source center coordinates
mean_z	double	/
old_surface
surface
informed_event
informed_surface
min_x
min_y
min_z
max_x
max_y
max_z
min_vx
min_vy
min_vz
max_vx
max_vy
max_vz
n_count_extrapolated
repeat_cnt

Links

• Source code for Virtual_mcnp_input.comp.
• MCNP
• MCNP -- A General Monte Carlo N-Particle Transport Code, Version 5, Volume II: User's Guide, p177

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[ Identification | Description | Input parameters | Output parameters | Links ]

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Fri May 11 08:41:09 2012

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Last Modified: Friday, 11-May-2012 10:41:09 CEST