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

`Guide_gravity_shieldinglogger`

Component-
**Author:**Emmanuel Farhi -
**Origin:**ILL (France). -
**Date:**Aug 03 2001 -
**Version:**$Revision$ -
**Modification history:**- E. Farhi, from Gravity_guide by nslit. Lefmann (buggy).
- E. Farhi, focusing channels are now ok (Sept 4th, 2001).
- E. Farhi, 2D channel array. Correct focus bug (Dec 14th 2002)
- E. Farhi, Waviness+chamfers+nelements (Aug 19th 2003)

Models a rectangular straight guide tube centered on the Z axis, with gravitation handling. The entrance lies in the X-Y plane. The guide can be channeled (nslit,d,nhslit parameters). The guide coating specifications may be entered via different ways (global, or for each wall m-value). Waviness (random) may be specified either globally or for each mirror type. Side chamfers (due to substrate processing) may be specified the same way. In order to model a realistic straight guide assembly, a long guide of length 'l' may be splitted into 'nelements' between which chamfers/gaps are positioned. The reflectivity may be specified either using an analytical mode (see Component manual) or as a text file in free format, with 1st column as q[Angs-1] and 2nd column as the reflectivity R in [0-1]. For details on the geometry calculation see the description in the McStas component manual. There is a special rotating mode in order to approximate a Fermi Chopper behaviour, in the case the neutron trajectory is nearly linear inside the chopper slits, i.e. the neutrons are fast w/r/ to the chopper speed. Slits are straight, but may be super-mirror coated. In this case, the component is NOT centered, but located at its entry window. It should then be shifted by -l/2. Example: Guide_gravity(w1=0.1, h1=0.1, w2=0.1, h2=0.1, l=12, R0=0.99, Qc=0.0219, alpha=6.07, m=1.0, W=0.003) %VALIDATION May 2005: extensive internal test, all problems solved Validated by: nslit. Lieutenant Example values: m=4 Qc=0.02 W=1/300 alpha=6.49 R0=1WARNING:

Name | Unit | Description | Default |
---|---|---|---|

w1 |
m | Width at the guide entry | |

h1 |
m | Height at the guide entry | |

w2 | m | Width at the guide exit. If 0, use w1. | 0 |

h2 | m | Height at the guide exit. If 0, use h1. | 0 |

l |
m | length of guide | |

R0 | 1 | Low-angle reflectivity | 0.995 |

Qc | AA-1 | Critical scattering vector | 0.0218 |

alpha | AA | Slope of reflectivity | 4.38 |

m | 1 | m-value of material. Zero means completely absorbing. m=0.65 glass/SiO2 Si Ni Ni58 supermirror Be Diamond m= 0.65 0.47 1 1.18 2-6 1.01 1.12 for glass/SiO2, m=1 for Ni, 1.2 for Ni58, m=2-6 for supermirror. m=0.47 for Si | 1.0 |

W | AA-1 | Width of supermirror cut-off | 0.003 |

nslit | 1 | Number of vertical channels in the guide (>= 1) (nslit-1 vertical dividing walls). | 1 |

d | m | Thickness of subdividing walls | 0.0005 |

mleft | 1 | m-value of material for left. vert. mirror | -1 |

mright | 1 | m-value of material for right. vert. mirror | -1 |

mtop | 1 | m-value of material for top. horz. mirror | -1 |

mbottom | 1 | m-value of material for bottom. horz. mirror | -1 |

nhslit | 1 | Number of horizontal channels in the guide (>= 1). (nhslit-1 horizontal dividing walls). this enables to have nslit*nhslit rectangular channels | 1 |

G | m/s2 | Gravitation norm. 0 value disables G effects. | 0 |

aleft | 1 | alpha-value of left vert. mirror | -1 |

aright | 1 | alpha-value of right vert. mirror | -1 |

atop | 1 | alpha-value of top horz. mirror | -1 |

abottom | 1 | alpha-value of left horz. mirror | -1 |

wavy | deg | Global guide waviness | 0 |

wavy_z | deg | Partial waviness along propagation axis | 0 |

wavy_tb | deg | Partial waviness in transverse direction for top/bottom mirrors | 0 |

wavy_lr | deg | Partial waviness in transverse direction for left/right mirrors | 0 |

chamfers | m | Global chamfers specifications (in/out/mirror sides). | 0 |

chamfers_z | m | Input and output chamfers | 0 |

chamfers_lr | m | Chamfers on left/right mirror sides | 0 |

chamfers_tb | m | Chamfers on top/bottom mirror sides | 0 |

nelements | 1 | Number of sections in the guide (length l/nelements). | 1 |

nu | Hz | Rotation frequency (round/s) for Fermi Chopper approximation | 0 |

phase | deg | Phase shift for the Fermi Chopper approximation | 0 |

reflect | str | Reflectivity file name. Format [q(Angs-1) R(0-1)] | "NULL" |

Name | Unit | Description | Default |
---|---|---|---|

GVars |
- | .N_reflection: (1) Array of the cumulated Number of reflections. N_reflection[0] total nb of reflections, N_reflection[1,2,3,4] l/r/t/b reflections, N_reflection[5] total nb neutrons exiting guide, N_reflection[6] total nb neutrons entering guide. | |

pTable |

- Source code for
`Guide_gravity_shieldinglogger.comp`

.

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

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