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

The Tomography Instrument

Instrument to study tomographic imaging by means of the feature of OFF shape samples.

Identification

• Site: Templates
• Author: Peter Willendrup, based on work by Reynald ARNERIN
• Origin: Risoe
• Date: June 20th, 2008

Description

Instrument to study tomographic imaging by means of the feature of OFF shape samples.
The sample (geometry, an OFF file, default socket.off) is rotated by omega around the
vertical axis, and the transmitted beam is recorded on a 2D detector (monitor).

A tomography is a scan of omega over a full rotation. Settings suitable for a
full 3D reconstruction (72 projections of 4e6 rays each):
mcrun Tomography.instr omega=0:5:355 -n4e6 sigma_abs=1 -d TomoScan

Use the provided tomo_recon.py (numpy, scipy, matplotlib, pyqtgraph, h5py) in this folder to reconstruct a 3D
volume of the object from the scan directory: python tomo_recon.py TomoScan [--save]
(3 central slices + 3D isosurface; --save writes vol.nxs NeXus volume and surface.png;
--sirt 100 --median 3 gives fewer streaks than the default Hann FBP, see -h)

Examples

(Test cases in bold)

• Test: omega=0 -n4e6 Detector: monitor_I=1.0321e-09 monitor_ERR=7.92929e-13
• TestScan: mcrun Tomography.instr --scan_split=auto omega=0,355 -N72 -n4e6 Detector: monitor_I={72 values} monitor_ERR={72 values}

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
geometry	string	Name of the OFF file describing the sample shape	"socket.off"
omega	deg	Sample rotation around y	0
sigma_abs	barn	Sample absorption xs	1
frac_scatt	1	Fraction of neutrons to scatter in the sample	0
div_v	deg	Source vertical divergence (angular height)	1e-4
div_h	deg	Source horisontal divergence (angular width)	1e-4
source_w	m	Source width	0.4
source_h	m	Source height	0.2
det_w	m	Detector width	0.25
det_h	m	Detector height	0.15
opts	string	Monitor_nD options string	"x bins=128 y bins=64"

Links

• Source code for Tomography.instr.
• http://shape.cs.princeton.edu/benchmark/documentation/off_format.html

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

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Last Modified: Friday, 23-Oct-2026 18:32:10 CEST