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

The FRMII_SPODI_MULTI Instrument

Simple monochromator diffractometer for powders

Identification

• Site: FRMII
• Author: V. Kochetov, C. Hauf, M. Hoelzel, A. Senyshyn
• Origin: MLZ, Garching, Germany
• Date: August 24, 2026

Description

SPODI is a high-resolution thermal neutron diffractometer at the research
reactor Heinz Maier-Leibnitz (FRM II) especially dedicated to structural
studies of complex systems. Unique features like a very large monochromator
take-off angle of 155 degrees and a 5 m monochromator-sample distance in its
standard configuration achieve both high-resolution and a good profile shape
for a broad scattering angle range of 160 degrees. Two-dimensional data are
collected by an array of 80 vertical position sensitive 3He detectors
typically during 40 resolution steps of 0.05 degrees.

List of available wavelengths in A delivered by germanium monochromator:
Reflection    Take-off 155 degrees, L2=5m      Take-off 135 degrees, L2=2.8m
Ge 331            2.536 A                           2.396 A
Ge 551            1.549 A                           1.463 A
Ge 771            1.111 A                           1.050 A

The implemented model corresponds to the standard setup with the take-off angle
of 155 degrees, Ge 551 reflection giving rise to the wavelength of ~1.5482 AA,
and L2 of 5 m.

Examples

(Test cases in bold)

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
lambda	A	Wavelength; if 0, calculated from HKLmono and TOA	1.5482
HKLmono	str	Miller indices of the Ge-monochromator reflection	"551"
TOA	deg	Take-Off Angle; if 0, calculated from HKLmono and lambda	0
L2	m	Distance from the monochromator to the sample	5.0
Dsample	m	Sample diameter	8e-3
Hsample	m	Sample height	40e-3
Powder	str	LAZ/HKL/PCR/CIF file for powder description	"Na2Ca3Al2F14.laz"
Holder		Flag to enable (1) / disable (0) the vanadium sample holder	0
StartTheta	deg	Start angle of the detector system relative to the beam	0
ResStep	deg	Resolution step in degrees (standard is 0.05 deg)	0.05
iResStep	deg	Index number of resolution step (between 0 and 39 for standard 0.05 deg)	0

Links

• Source code for FRMII_SPODI_MULTI.instr.
• M. Hoelzel, A. Senyshyn, N. Juenke, H. Boysen, W. Schmahl and H. Fuess, Nucl. Instr. and Meth. in Ph A 667 (2012) 32-37

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

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Last Modified: Friday, 11-Sep-2026 15:00:09 CEST