Two-dimensional Position-sensitive Neutron Detector Research Articles

Simulations and systematic neutron beam characterisations on two-dimensional position-sensitive neutron detector multi-wire proportional counter with delay-line readout

A two-dimensional position-sensitive neutron detector multi-wire proportional counter (MWPC) was systematically characterised on dedicated detector test station V17 at reactor BER2 of HZB. Performances including characteristic anode curve, characteristic drift curve, detection efficiency, efficiency homogeneity, horizontal position resolution, vertical position resolution, counting rate capability, and gamma sensitivity were measured. In addition, systematic simulations were conducted based on the detector configurations. These systematic studies are presented here for the first time. They assist in obtaining a greater understanding of detector performances, form the methodology for detector characterisations by reactor neutron beams, and can be used as references for neutron detector research and applications.

Development of an FRP System which is a Two-dimensional Position-sensitive Neutron Detector

Development of an FRP System which is a Two-dimensional Position-sensitive Neutron Detector

Imaging of a spatial distribution of preferred orientation of crystallites by pulsed neutron Bragg edge transmission

A pulsed neutron transmission coupled with a two-dimensional position sensitive neutron detector gives a time-of-flight spectrum at each pixel of the detector, which depends on the total cross-sections of materials. In order to extract quantitative information of the preferred orientation included in the Bragg scattering total cross-section data, a spectral analysis software for the 2D imaging has been developed, and the transmission data of an unbent iron plate were analyzed. The 2D images with respect to the preferred orientation were successfully obtained, and the effectiveness of spectroscopic neutron transmission imaging was indicated.

Development of material evaluation method by using a pulsed neutron transmission with pixel type detectors

A spectroscopic neutron imaging is attractive in the research field of energy-selective neutron radiography. Imaging using the time-of-flight (TOF) method at a pulsed neutron source is very suitable for such spectroscopic measurements. We developed new two-dimensional position sensitive neutron detectors (2D-PSNDs) aiming at high detection efficiency, high counting rate and high time resolution which are the most important 2D-PSND performances for the spectroscopic imaging. These detectors consist of independent 6Li-glass (Ce) scintillator pixels, and have been used in various pulsed neutron transmission experiments. As a result, we have succeeded in developing various new imaging techniques; crystallographic, nuclide-selective and thermographic imaging.

Two-dimensional position sensitive neutron detector

A two-dimensional position sensitive neutron detector has been developed. The detector is a3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 A neutrons. The detector is tested with 0.5 bar3He + 1.5 bar krypton gas mixture in active chamber and 2 bar4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in theQ range of 0.02-0.25 A−1.

Development of position-sensitive neutron detector based on scintillator

For evaluating neutron optical devices, we have developed the two-dimensional position-sensitive neutron detectors (PSND) of the crossing fibre array type. In parallel, we have studied the PSNDs of the direct coupling type with flat panel photomultiplier tubes for responding to various spatial resolutions with high detection efficiency. This paper views and reports on the recent status of development of PSNDs based on neutron scintillators in neutron optics group.

Recent development of position-sensitive neutron detectors employing wavelength-shifting cross-fiber

For evaluating neutron optical devices, we have designed and tested two-dimensional position-sensitive neutron detectors (PSND) which employ two wavelength-shifting fiber arrays optically coupled to a scintillator plate. Feasibility on applications of the PSND having a 50×50 mm 2 sensitive area and a pixel size of 0.4×0.4 mm 2 has been tested at pulsed neutron sources. While, for realizing the large sensitive area, another PSND having a 128×128 mm 2 sensitive area and a 0.5×0.5 mm 2 pixel size with a dynode coding technique were developed and tested.

Fast two-dimensional position-sensitive detection of neutrons in a time-of-flight reflectometer

A two-dimensional position-sensitive neutron detector with a maximum count rate of 500kHz is described. The high counting rate is obtained by making use of dedicated electronics for data handling. The electronics convert the wire charges of a position-sensitive photomultiplier into a position using internal look-up tables. Timing modules are presented for neutron time-of-flight (TOF) determination and for dynamic measurements with an independent time-base. The position and TOF information are stored by a fast Data Handling Module. The detector is calibrated with a grid of 256×256 channels, using channel widths of 0.25mm.The maximum error in position determination is 0.25mm.This error is reduced to less than 0.05mm when the electronics are used one dimensionally instead of two dimensionally. The total detector resolution was determined to be 0.6mm.

Two-dimensional position-sensitive [formula omitted]-neutron detector for reflectometry and high-resolution diffractometry

A two-dimensional position-sensitive neutron detector has been developed at the Geesthacht Neutron Facility (GeNF). The detector is a 3 He and CF 4 filled multiwire proportional counter with delay line readout and has a sensitive area of 300 mm ×300 mm and a high detection efficiency for wavelengths λ>0.15 nm. It is an important component of the new diffractometer ARES at GeNF which is dedicated to the analysis of residual stresses. The detector design to achieve excellent linearity, detection homogeneity and a spatial resolution of about 2 mm ×2 mm has been described.

Neutron measurements on the MK 200N-1 type two-dimensional delay-line position- sensitive detector with the new OTDCV1.11 time-to-digital converter

Neutron scattering test of the MK 200N-1 type two-dimensional position-sensitive neutron detector with the new OTDC V1.11 TDC at the Budapest Research Reactor is described. The obtained results verify the expected high quality of the detector system.

The 30 m Small-Angle Neutron Scattering Instruments at the National Institute of Standards and Technology

Two high-resolution, general-purpose, small-angle neutron scattering instruments have been constructed at the National Institute of Standards and Technology's Center for Neutron Research. The instruments are 30 m long and utilize mechanical velocity selectors, pinhole collimation and high-data-rate two-dimensional position-sensitive neutron detectors. The incident wavelength, wavelength resolution and effective length of the instruments are independently variable, under computer control, and provide considerable flexibility in optimizing beam intensity and resolution. The measurement range of the instruments extends from 0.0015 to 0.6 Å−1 in scattering wavevector, corresponding to structure in materials from 10 Å to nearly 4000 Å. The design and characteristics of the instruments, and their modes of operation, are described, and data are presented which demonstrate their performance.

Performance of the neutron polarimeter NPOL2 for ( [formula omitted], [formula omitted]) polarization transfer measurements

A high performance neutron polarimeter NPOL2 has been constructed to measure polarization transfer observables D ij for neutron kinetic energies of T n = 150–400 MeV. The NPOL2 system consists of 6 planes of two-dimensional position-sensitive neutron detectors with a size of 1 × 1 × 0.1 m 3. Neutron polarization is determined from the azimuthal distribution of the elastic n + p scattering in the scintillator material. The effective analyzing powers ( A y;eff ) of NPOL2 have been calibrated by using the polarized neutrons from the 0° 2H( p , n )pp reaction at T p = 146, 228, 296, 346 and 392 MeV as well as by using the polarized neutrons from the 0° 6Li( p , n ) 6Be(g.s.) reaction at T p = 228 MeV. The A y;eff values of NPOL2 have reasonable values, typically 0.223 ± 0.012 and 0.132 ± 0.004 for ( n ,n) and ( n ,p) channels, respectively, at T n = 291 MeV. The figure-of-merit value defined as ε D.S.( A y;eff ) 2 is over 4 × 10 −4 for the wide neutron kinetic energy region of T n = 200–400 MeV, where ε D.S. is the double scattering efficiency.

Facility for the (p, n) polarization transfer measurement

We have designed and constructed a facility to measure the complete polarization transfer coefficient D ij for the (p, n) reaction at intermediate energies. The facility consists of a beam swinger dipole magnet used for angular distribution measurements and a 100 m tunnel for the neutron energy measurement by the time-of-flight method. Typical neutron energy resolution is about 1.85 MeV for 290 MeV neutrons including a contribution of 1 MeV due to the target thickness. The background associated with this tunnel system was carefully investigated and found to be negligibly small. A dipole magnet for the neutron spin rotation is installed in the neutron flight path to measure the longitudinal polarization as well as the induced polarization. The neutron polarimeter which consists of 6 planes of the two-dimensional position-sensitive neutron detectors with a size of 1 m × 1 m × 0.1 m has been constructed. Its effective left-right analyzing power 〈 A y eff〉 has been calibrated at 194, 290 and 384 MeV. The figure-of-merit value defined by 〈 A y eff〉 2 × ε DS at 290 MeV is 4.05 × 10 −4, where ε DS is the double scattering efficiency.

Construction and performance of one- and two-dimensional large position-sensitive liquid and plastic scintillation detectors — an application to a neutron polarimeter

Large one- and two-dimensional position-sensitive neutron detectors have been developed. Their shapes are a long block and a square and their sizes are 100×10×7.5 cm 3 and 100×100×10 cm 3 for one- and two-dimensional detectors, respectively. Both liquid and plastic scintillators are employed as detector materials. Position resolutions are examined by using monoenergetic neutron beams with energies of 61.6 MeV. The obtained position resolutions in FWHM are 3–5 cm and 4–14 cm for one- and two-dimensional detectors, respectively. Position resolutions are poor near the corner of the two-dimensional detector irrespective of scintillator materials. Scintillation light responses have been compared with predictions of Monte Carlo calculations. Neutron polarimeters at an intermediate energy have been developed by utilizing the position sensitivity of these detectors.

A New Position-Sensitive Detector for Thermal and Neutrons

A new two-dimensional position-sensitive neutron detector is described. It is based on (n,γ) neutron resonance capture in a foil with subsequent detection of internal conversion electrons with a high-density proportional chamber. Large-area detectors with a 1 mm spatial resolution are feasible. A detection efficiency of 50% is possible for thermal neutrons using gadolinium-157 foil and for epithermal neutrons using hafnium-177.

A new position-sensitive detector for thermal and epithermal neutrons

A new two-dimensional position-sensitive neutron detector is described. It is based on (n, γ) neutron resonance capture in a foil with subsequent detection of internal conversion electrons with a high-density proportional chamber. Large-area detectors with a 1 mm spatial resolution are feasible. A detection efficiency of 50% is possible for thermal neutrons using gadolinium-157 foil and for epithermal neutrons using hafnium-177.