1 – Moderator
2 – Fourier Chopper
3 – Guide Tube
4 – Main Detector
5 – Sample Position
6 – 90°-Detector
7 – PSD Detector
8 – VME Control and Operative Visualization/Analysis
9 – VME Station (OS/9) Data Acquisition
10 – EtherNet Data Transfer

11 - Background chopper

 

 

Instrument Responsibles:
Simkin Valery
Russia, Moscow reg., Dubna, Joliot-Curie str., 6
tel. +7 (49621) 6-21-32
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Bobrikov Ivan
Russia, Moscow reg., Dubna, Joliot-Curie str., 6
tel. +7 (49621) 6-65-80
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

HRFD Group Staff

 

Main research fields:
1. Precision analysis of polycrystal structure;
2. Monocrystal diffraction peaks shape analysis with Δd/d ≈ 0.001;
3. Internal stress analysis in bulk items and materials.

Poster

 

Description of HRFD

 

A disk chopper intended to reduce the background of recycled neutrons is located in a ring corridor of the IBR-2 reactor. A Fourier-chopper modulating intensity of a primary beam with a frequency up to ~102.4 Hz is positioned at a distance of about 8.5 m from the moderator. The beam on a sample is formed by a mirror focusing neutron guide with an entrance window of 15 × 200 mm2 and an exit window of 15 × 100 mm2. Detectors are arranged around the sample position at fixed distances and scattering angles.

From the main detectors at 2θ=152° and 2θ=90° signals are sent to the correlation electronics, which makes it possible to obtain high-resolution spectra. The position-sensitive detector placed at 2θ=30° is intended for registration of diffraction peaks with large dhkl.

HRFD was constructed in collaboration with PNPI RAS and VTT (Finland) with due regard to operational experience of the first Fourier-diffractometer SFINKS at the steady-state reactor VVR-I in Gatchina. In early 1992 a neutron beam was formed and in June, 1992, first high-resolution diffraction spectra were obtained.

 

Fig.1. HRFD group (1996). From left to right: V.G.Simkin, N.R.Shamsutdinov, A.M.Balagurov, V.Yu.Pomjakushin, Yu.V.Taran, V.B.Zlokazov.

 

Fig.2. Preparation to a neutron experiment at HRFD. From left to right: V.G.Simkin, I.A.Bobrikov, S.N.Bushmeleva.

 

 

Fig.3. High-temperature vacuum furnace at HRFD.

 Fig.4. Curved mirror neutron guide.

 Fig.5. The old model of the Fourier chopper. V.G. Simkin checking the device (2008).

Рис. 6 Fourier chopper. (2016)

 

 

 

Fig.7. Comparison of neutron diffraction patterns of the YBa2(Cu,Fe)3O6.3 powder sample obtained in a high-resolution mode at HRFD (a) and with a resolution usual for an IBR-2 diffractometer (b). 

 

Fig.8. 2D spectrum ((La,Pr)0.3Ca0.7MnO3) obtained with HRFD using PSD detector at Т = 10 К. The horizontal axis is the analyzer time channels (channel width – 64 µs) and the vertical axis is angle groups.

 

Basic Parameters

 

Neutron beam cross-section at sample position 15 × 100 mm
Moderator - sample distance ~ 29.6 m
Chopper - sample distance 21.14 m
Fourier-chopper (disk-type) Al-alloy
- outer diameter 540 mm
- slit width, number of slits 0.7 mm, 1024
- max speed of rotation 6000 rpm
- max modulation frequency 102.4 kHz
- effective pulse width ≈ 10 µs
Main detectors at 2θ = 90° and 2θ = 152° 6Li, time-focusing
Detector for large dhkl 3He, PSD, Δx ≈ 1.8 mmм,
2θ ≈ 30°
Aperture of the main detectors: 0.16 sr (2θ = 152°),
0.04 sr (2θ = 90°)
Wavelength range 0.9 - 8 Å
dhkl range;  
- high resolution 0.7 - 4 Å
- medium resolution 1 - 16 Å
Neutron flux at sample position 1.3×107 n/cm2/s
Standard sample volume ~ 1 cm3
Resolution (Δd/d) for 2θ = 152°, d = 2 Å ~ 0.001

 

Typical Spectra

 

Fig. 1. Spectrum of Al2O3 standard obtained at the Fourier-chopper rotation rate of 4000 rpm and channel width of 4 μs.

 

Sample environment

 

The available sample environment equipment:

 

1) Air furnace (from RT up to 500 °С);
2) Vacuum furnace (from RT up to 1300 °С);
3) Closed-cycle helium refrigerator (from RT up to 2.4 К);
4) Closed-cycle helium refrigerator (from 300 °С up to 8 К);
5) Electromagnet (up to 0.95 T) (it is necessary to clarify with a responsable person);
6) Goniometer GKS-100;
7) Galvanostat-potentiostat: 0-10V, 0-15А;

 

Possibility to prepare samples in inert atmosphere (Argon, Helium)
Possibility to make X-Ray phase analysis if necessary.

 

Publications

 

1) Balagurov, A. M., Bobrikov, I. A., Bokuchava, G. D., Zhuravlev, V. V.& Simkin, V. G. Correlation Fourier Diffractometry: 20 Years of Experience at the IBR-2 Reactor (2015). Phys. Part. Nucl. 46, 249–276. [pdf]
 
2) A.M. Balagurov "High-resolution Fourier diffraction at the IBR-2 reactor" (2005) Neutron News 16, 8-12. [pdf]