McXtrace - An X-ray ray-trace simulation package

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

The ILL_NeXT_Xray Instrument

NeXT (ILL) - the X-ray cone-beam tomography arm, operated simultaneously with and perpendicular to the neutron beam (companion to ILL_H521_NeXT.instr)

Identification

• Site: ILL
• Author: DRAFT, Peter Willendrup with Claude from public ILL / NeXT-Grenoble information
• Origin: ILL
• Date: September 2026

Description

DRAFT model of the X-ray imaging option of NeXT-Grenoble at the ILL.

Hardware (Tengattini et al., NIM A 968 (2020) 163939):
- source:   Hamamatsu L12161-07 sealed microfocus tube, W target, Be window,
up to 150 kV / 500 uA, minimum focal spot 5 um, 43 deg cone
- detector: Varex PaxScan 2530HE flat panel, CsI scintillator,
1792 x 2176 pixels of 139 um (portrait), up to 9 Hz (33 Hz bin 2)
- source-detector distance: >= 500 mm (set by the 43 deg cone covering the
~25 x 30 cm panel), four source positions 20 mm apart
-> SDD = 0.50, 0.52, 0.54, 0.56 m
- the sample sits on the common (neutron) rotation axis; the source-object
distance SOD sets the magnification M = SDD/SOD. The quoted 5 um
resolution needs M ~ 28, i.e. SOD ~ 18-20 mm.
- the ILL web page (2026) quotes a 20-300 kV source, i.e. the tube may have
been upgraded; kV > 150 is allowed here but flagged.

Geometry: the X-ray axis is the McXtrace z axis. At NeXT it is horizontal and
perpendicular to the neutron beam (neutrons travel along -x or +x here, depending
on the side of the source); the source/detector pivot (+-20 deg) is not modelled.

The sample defaults to the same object as in ILL_H521_NeXT: a vertical Fe rod,
radius 5 mm, for direct bimodal comparison (the neutron model gives T~0.4 at the
rod centre in white beam). An inner inclusion (e.g. an H2O-filled bore) can be added.

Detector: two ideal pixelated monitors on the flat-panel plane
Xray_counts:  photon counts (photon-counting response)
Xray_energy:  energy-weighted intensity [keV/s per pixel], a first-order model
of the energy-integrating CsI flat panel.
NOT modelled: CsI absorption efficiency vs energy, scintillator/optical blur,
focal-spot growth with tube power, heel effect, scatter from the sample
environment, and the 6 mm Pb / 10 mm + 5 mm B4C neutron shielding of the panel
(5 mm B4C over the active area transmits roughly 80-90 % at 40-150 keV).

ASSUMPTIONS (to be checked):
- Be exit window 0.2 mm (the L12161-07 datasheet value should be checked)
- focal spot = electron-beam footprint on the anode (square, focal_spot)
- anode take-off angle 12 deg (reflection-type microfocus tube, typical)
- Source_lab is a thick-target Kramers model; absolute intensity is indicative

Examples

(Test cases in bold)

• Test: kV=150 SOD=0.1 SDD=0.5 Detector: Xray_counts_I=176042000000

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
kV	kV	Tube acceleration voltage (<=150 for L12161-07; 20-300 per ILL web)	150
tube_current	A	Electron beam current (<= 500e-6)	100e-6
focal_spot	m	Focal spot size (square electron footprint on the anode)	5e-6
Emin	keV	Lowest photon energy simulated	5
anode	str	Anode material file	"W.txt"
take_off	deg	Anode take-off angle	12
Be_window	m	Be exit window thickness	0.2e-3
filter	str	Pre-filter material file (e.g. "Cu.txt", "Al.txt", "Sn.txt")	"Cu.txt"
filter_t	m	Pre-filter thickness (0: no filter)	0
SOD	m	Source - object (rotation axis) distance	0.1
SDD	m	Source - detector distance (0.50, 0.52, 0.54, 0.56)	0.5
sample	1	1: sample in beam, 0: flat field (open beam)	1
sample_mat	str	Sample (outer) material file	"Fe.txt"
sample_rho	g/cm3	Sample density (0: take nominal density from file)	0
sample_radius	m	Radius of the cylindrical sample	0.005
sample_height	m	Height of the cylindrical sample	0.05
incl_mat	str	Material of a coaxial inner cylinder ("NULL" for none)	"NULL"
incl_radius	m	Radius of the inner cylinder (0 for none)	0
incl_rho	g/cm3	Density of the inner cylinder (0: nominal)	0
sample_off	str	Optional OFF/PLY geometry for the outer sample, overrides the cylinder ("NULL": none)	"NULL"
omega	deg	Tomography rotation angle of the sample about the vertical axis	0
det_binning	1	Detector binning (1: 1792x2176 native, 2, 4, ...)	4

Links

• Source code for ILL_NeXT_Xray.instr.
• https://www.ill.eu/en/for-ill-users/instruments/instruments-list/next/
• A. Tengattini et al., NeXT-Grenoble, the Neutron and X-ray tomograph in Grenoble,
• Nucl. Instrum. Meth. A 968 (2020) 163939, doi:10.1016/j.nima.2020.163939
• NECSA_MIXRAD_Nikon_Tomo.instr (McXtrace examples) - similar lab-source tomograph

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

Generated for mcxtrace 3.9.0

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Last Modified: Monday, 05-Oct-2026 10:48:08 CEST