Neutron Imaging Plate Research Articles

2-D Evaluation of Bred Tritium Using Neutron Imaging Plate

Tritium breeding performance of a fusion blanket is a key parameter for the self-sufficient fueling of a fusion reactor, and thus designed to validate the performance of a neutronics experiment. Measuring the 2-D distribution of bred tritium is challenging via conventional methods such as $\beta $ -ray counting from an irradiated lithium sample using a liquid scintillation counter (LSC) and a single-crystal diamond detector with a thin 6LiF film, because they are point detectors which require many measurements. In this article, 2-D distribution of the low quantity produced tritium was evaluated with a neutron imaging plate (NIP) with a Gd convertor by estimating the loss of neutrons via a capture reaction by Li. Deuterium–deuterium (DD) fusion neutrons were generated using a compact fusion device at an average neutron production rate of $1.5 \times 10 ^{5}$ n/s by applying high voltages. A neutron image with “shadows” projected by thermal neutron capture reactions of 6Li(n, $\alpha$ ) and 10B(n, $\alpha$ ) was successfully obtained. The experimentally evaluated values were confirmed to be consistent with the total number of capture reactions calculated using a neutron transport code. The results suggest that the approach could be a facile method for the 2-D evaluation of bred tritium.

Analysis of the detective quantum efficiency of a neutron image plate detector

The aim of the present note is to derive a general formula for a detective quantum efficiency (DQE) of a neutron image plate detector which includes all essential parameters of the system. Relying on that formula, the effects of a variety of processes involved in the formation of an output signal are discussed and estimated. The theoretical value of the DQE is compared with the experimental one measured for the commercial neutron image plate BAS-IP ND 2025 (FUJIFILM).

Preparation for a neutronics experiment using a discharge fusion device and an imaging plate neutron detector

Tritium breeding ratio (TBR) is one of the most important parameters determining the tritium self-sufficiency of a deuterium-tritium fusion reactor. A neutronics experiment is planned to measure the spectral neutron fluences two-dimensionally (2D) using a discharge-type compact fusion neutron source and a neutron imaging plate (NIP), respectively. We report a calibration method for the NIP and optimization of the discharge condition to enhance the neutron production rate. A linear relationship between the neutron fluence in the NIP and photostimulated luminescence (PSL) per area was obtained in the range of the neutron fluence from 103 to 107 n/cm2. A neutron production rate higher than 107 n/s was successfully achieved by the optimized discharge condition. It is shown that a quantitative 2D measurement by the NIP is feasible using the linear relationship and a correlation coefficient on the energy spectrum.

Neutron imaging on the VR-1 reactor

Training reactor VR-1 is a low power research reactor with maximal thermal power of 1 kW. The reactor is operated by the Faculty of Nuclear Science and Physical Engineering of the Czech Technical University in Prague. Due to its low power it suits as a tool for education of university students and training of professionals. In 2015, as part of student research project, neutron imaging was introduced as another type of reactor utilization. The low available neutron flux and the limiting spatial and construction capabilities of the reactor's radial channel led to the development of a special filter/collimator insertion inside the channel and choosing a nonstandard approach by placing a neutron imaging plate inside the channel. The paper describes preliminary experiments carried out on the VR-1 reactor which led to first radiographic images. It seems, that due to the reactor construction and low reactor power, the neutron imaging technique on the VR-1 reactor is feasible mainly for demonstration or educational and training purposes.

Photostimulated luminescence properties of neutron image plates

The luminescence properties of two commercial neutron-sensitive image-plates based on Gd2O3-doped BaFBr:Eu2+ storage phosphors are examined. These are white Fuji plates and blue Fuji plates (BAS-ND) with Gd2O3 content by weight of 34% and 50%, respectively. Both plates show two maxima in the photostimulation spectrum near 500nm and 600nm, with the ratio of the peak responses (I600nm/I500nm) 1.39 and 0.53 for the white and blue plates respectively. The optimum wavelengths for photostimulation for the two phosphors are therefore different. The response of the blue plate is only 25% that of the white plate, if each is stimulated at its optimum wavelength.

Simulation of Fast Neutron Radiography with a Time-of-Flight System

A novel fast neutron imaging method with Time-of-Flight was analyzed, which can provide a way to improve ratio of signal to noise for discrimination of scattered particles from the background, especially for bulky sample examination. For the same system spatial resolution, the length of each unit in scintillator detector array can be increased to improve detection efficiency, which is higher than for the traditional neutron image plate obviously. Key parameters such as detection efficiency and spatial resolution have been simulated by means of a Monte-Carlo method, and the ratio of signal to noise effect was estimated from MC and experimental results. Spatial resolution and contrast of compound sample have been calculated.

BioDiff - a neutron diffractometer for protein crystallography

The research reactor Heinz Maier-Leibnitz (FRM II) is a modern high flux neutron source which feeds some 30 state of the art neutron beam instruments. Currently 24 are operational, others in commissioning or under construction. The newly built neutron single crystal diffractometer BIODIFF is especially designed to collect data from crystals with large unit cells. The main field of application is the structural analysis of proteins, especially the determination of hydrogen atom positions. BIODIFF is a joint project of the Jülich Centre for Neutron Science (JCNS) and the FRM II. Typical scientific questions addressed are the determination of protonation states of amino acid side chains (see e. g. [1,2]) and the characterization of the hydrogen bonding network between the protein active centre and an inhibitor or substrate. BIODIFF is designed as a monochromatic instrument. By using a highly orientated pyrolytic graphite monochromator (PG002) the diffractometer is able to operate in the wavelength range of 2.4 Å to about 5.6 Å. Contaminations of higher order wavelengths are removed by a neutron velocity selector. To cover a large solid angle the main detector of BIODIFF consists of a neutron imaging plate in a cylindrical geometry with online read-out capability. A fast Li/ZnS scintillator CCD camera is available for additional detection abilities. An optical CCD-camera pointing at the sample position is used to quickly align the crystal with respect to the neutron beam. The main advantage of BIODIFF is the possibility to adapt the wavelength to the size of the unit cell of the sample crystal while operating with a clean monochromatic beam that keeps the background level low. BIODIFF is equipped with a standard Oxford Cryosystem "Cryostream 700+" which allows measurements in the temperature regime from 90 K up to 500 K (see Figure underneath).

Thermal neutron imaging with CsBr storage phosphors

The storage phosphor material CsBr:Eu2+ has been investigated for use in thermal neutron imaging. CsBr:Eu2+ imaging plates were prepared in a polycrystalline form by cold pressing starting powders. These as-prepared materials show only small photostimulated luminescence intensity under thermal neutron irradiation, but the luminescence intensity can be increased by incorporating separate neutron converters, in the form of lithium, boron or gadolinium containing compounds. An imaging plate containing 5% 10B2O3 as a neutron converter has 50% the photostimulated luminescence intensity of a commercial Fuji neutron imaging plate. Thermal neutron imaging was shown to be possible with the CsBr:Eu2+-based imaging plates, and the differences in thermal neutron and X-ray images were clearly observed.

LiF crystals as high spatial resolution neutron imaging detectors

Abstract Neutron imaging by color center formation in LiF crystals was applied to a sensitivity indicator (SI) as a standard samples for neutron radiography. The SI was exposed to a 5 mm pinhole-collimated thermal neutron beam with an LiF crystal and a neutron imaging plate (NIP) for 120 min in the JRR-3M thermal neutron radiography facility. The image in the LiF crystal was read out using a laser confocal microscope. All gaps were clearly observed in images for both the LiF crystal and the NIP. The experimental results showed that LiF crystals have excellent characteristics as neutron imaging detectors in areas such as high spatial resolution.

Neutron radiography using neutron imaging plate

The aims of this research are to study properties of a neutron imaging plate (NIP) and to test it for use in nondestructive testing (NDT) of materials. The experiments were carried out by using a BAS-ND 2040 Fuji NIP and a neutron beam from the Thai Research Reactor TRR-1/M1. The neutron intensity and Cd ratio at the specimen position were approximately 9x10(5) ns/cm(2) s and 100 respectively. It was found that the photostimulated luminescence (PSL) readout of the imaging plate was directly proportional to the exposure time and approximately 40 times faster than the conventional NR using Gd converter screen/X-ray film technique. The sensitivities of the imaging plate to slow neutron and to Ir-192 gamma-rays were found to be approximately 4.2x10(-3) PSL/mm(2) per neutron and 6.7x10(-5) PSL/mm(2) per gamma-ray photon respectively. Finally, some specimens containing light elements were selected to be radiographed with neutrons using the NIP and the Gd converter screen/X-ray film technique. The image quality obtained from the two recording media was found to be comparable.

Optimisation of lithium borate–barium chloride glass-ceramic thermal neutron imaging plates

Glass-ceramic thermal neutron imaging plates (NIPs) recently reported have been further developed for use in neutron radiography. The plate consists of nanocrystallites of the storage phosphor BaCl 2:Eu 2+ embedded within a neutron-sensitive lithium borate glass-matrix. A new generation of samples, enriched with both 10B and 6Li with thicknesses in the range 280–500 μm have been studied. Neutron images were read out using a Fuji BAS2500 imaging plate scanner and the quality of the images obtained was comparable to those recorded on a commercial NIP. Details of the response to neutron-irradiation as well as the obtained spatial resolution of the images are presented. The neutron absorption and radiation hardness of the materials studied is also measured.

Biophysical reactions affect of the protonation state of amino acids in protein

Protonation is the key to elucidate a function of protein.Neutron crystallographic analysis is a powerful method that can observe the protonation states of amino acid residues in a protein molecule. However the neutron crystallographic technique was very difficult method, because of low flux neutron source mainly. Recently, a neutron imaging plate and an elastically bent perfect Si monochromator enabled neutron experiment. As the result, neutron structural biology has been progressed greatly in these ten years. In this report, we explain the various biological reactions affected by the protonation state on protein molecules by our studies on neutron crystallographic analysis. Furthermore, we also introduce our recent study on the protonation of cubic insulin molecule.

Photostimulated luminescence from BaCl2:Eu2+ nanocrystals in lithium borate glasses following neutron irradiation

A glass-ceramic thermal neutron imaging plate material is reported. The material consists of a neutron sensitive 2B2O3–Li2O glass matrix containing nanocrystallites of the storage phosphor BaCl2:Eu2+. When doped with 0.5mol% Eu2+, the neutron induced photostimulated luminescence (PSL) conversion efficiency of the B10 enriched glass-ceramic is around 60% of that a commercial neutron imaging plate, while the γ sensitivity is an order of magnitude lower than that of the commercial plate. A Eu2+-concentration series shows that the PSL efficiency for x rays is optimized at 0.01mol% Eu2+. Thermoluminescence measurements indicate trap depths in BaCl2:Eu2+ ranging from 0.55to2.7eV.

Measurements of small organic molecules on the single crystal neutron diffractmeters for biomolecules at JAERI

Our group has two single-crystal neutron diffractometers, named BIX-3 and BIX-4, in the JRR-3 reactor-hall at JAERI. Although these diffractometers were designed for bio-macromolecules, these can be applied for diffraction measurement of small organic and organometallic molecules by changing the wavelength of incident neutron beam shorter. Since BIX-3 and BIX-4 have a large neutron imaging plate as a detector, they can efficiently collect the Bragg reflections of organic crystal which has relatively large unit cell. The longest value of cell dimension was 50 Å. In typical measurement, the crystal size is 1–3 mm 3, the measurement time is 1–2 weeks and the minimum d-value is 0.85 Å. In this presentation, we introduce the performance of BIX-3 and BIX-4 as diffractometers for small organic molecules.

Structure and neutron imaging characteristics of lithium borate–barium chloride glass-ceramics

A glass-ceramic has been developed which can be used as a thermal neutron imaging plate (NIP) for neutron radiography. The plate consists of nanocrystallites of the storage phosphor BaCl 2:Eu 2+ embedded within a neutron sensitive lithium borate glass-matrix. Details of their preparation and structure are discussed. Neutron images were read out using a Fuji BAS2500 imaging plate scanner and the quality of the images obtained is comparable to those recorded on a commercial NIP. Details of the response to neutron and X-irradiation as well as the obtained spatial resolution of the images are presented. The neutron activation of the materials studied is also calculated.

Weissenberg-type neutron diffraction camera and its application to the structural and magnetic phase transitions of KMnF3

A Weissenberg-type neutron diffraction camera (W-NDC) equipped with a neutron imaging-plate (NIP) has been developed. The W-NDC gives Weissenberg-type and rotational diffraction patterns at low-temperature (10 K<T<300 K) and high-temperature (300 K<T<800 K) regions. To reduce background counts of the NIP diffracted from the aluminum containers and the specimen holder, a radial slit with several polymer sheets coated with 6LiF powder is continuously oscillated around the specimen during measurements. A test structural analysis for a single crystal NaCl suggests that the integrated intensities of reflections obtained from the Weissenberg-type diffraction patterns adequately satisfy a structural refinement by means of a least square method, though a fading effect of the photon energy stored in the NIP should be regarded during measurements. Structural and magnetic phase transitions in KMnF3 have been studied by using the W-NDC, to eliminate an inconsistency for temperature, and to enable an ordering of the phase transition as reported.

Lithium borate glass ceramics as thermal neutron imaging plates

Abstract A new glass ceramic composed of a lithium borate glass matrix containing Eu-doped BaCl 2 crystals has been developed for thermal neutron radiography, and has been tested for sensitivity to γ-radiation. It is shown to exhibit photostimulated luminescence (PSL) upon X- and γ-irradiation. The PSL arises from orthorhombic BaCl 2 nanocrystallites in the glass ceramics, which also contain a PSL-inactive phase of cubic BaCl 2 . The relative PSL efficiency of the glass ceramics has a strong dependence on gamma energy, which correlates with relative half-thickness. The effect of fluoride doping in the glass ceramics has been found to substantially increase the PSL, which ranges from ∼0.6% without fluoride doping to ∼8% with 0.2 F:Cl concentration, all relative to Fujifilm’s commercial neutron imaging plate BAS-ND.

Preparation and optimization of ceramic neutron image plates based on BaFBr : Eu2+ and GdF3

Commercially available neutron image plates (NIPs) consist of a mixture of a powdered x-ray storage phosphor and a neutron converter, both embedded in an organic binder supported on a polymer sheet. The initiation of the storage mechanism in the phosphor is caused by conversion electrons generated in the neutron converter due to neutron absorption and activation and its subsequent decay. The organic binder phase just provides mechanical stability to the NIP but reduces its efficiency through two effects: first by the absorption of low energy electrons and second by introducing an inactive volume fraction to the layer. Avoiding the organic fraction, for example by preparing a ceramic NIP without binder, could increase the efficiency and spatial resolution without a loss in mechanical stability. In the following, two processes for preparation of ceramic NIPs are reported, both delivering ceramic NIPs consisting solely of GdF3, as the neutron converter and BaFBr : Eu2+, as the storage phosphor. The correlation between the sintering parameters and volume fraction of the neutron converter is investigated with respect to high efficiency and high spatial resolution. The generally observed antidromic behaviour between these two quantities was observed in this study also.

Advances in detectors for single crystal neutron diffraction

Parallax error severely limits the use of gas detectors for neutron and X-ray single-crystal diffractometry. This is particularly the case in Neutron Macromolecule Crystallography (NMC), where a large solid angle is needed. High-resolution cylindrical detectors based on Neutron Image Plates provide a large angular coverage but they are gamma sensitive and do not allow time-resolved measurements. We describe the principle of a gas counter, the multi-blade Microstrip Gas Chamber (MSGC), which has the potential to design parallax-free cylindrical detectors. It contains radial MSGC plates, providing a partitioning of the gas volume and a segmentation of the signal readout. The axial coordinate is measured by reading out the charge signal on the anodes and the trans-axial coordinate is deduced from the electron drift distance measured optically using the time difference between the primary and the avalanche light. Expected characteristics are a sub-millimeter position resolution, a sub-microsecond time resolution, and a global counting rate greater than 10 7 s - 1 .

Novel materials and concepts for neutron image plates

Neutron image plates (NIPs) are used for two-dimensional, position-sensitive detection of neutrons. Commercially available neutron image plates consist of a mixture Gd 2O 3 and BaFBr:Eu 2+. In this contribution we present a system of converter ( 6LiF) and storage phosphor (KCl:Eu 2+), which exhibits a high efficiency for the detection of neutrons, while at the same time features a low γ-sensitivity due to the low atomic numbers. Two different morphologies of image plates based on KCl:Eu 2+– 6LiF were fabricated: ceramic (C-NIPs) and pixelated NIP (Pix-NIPs) . For these NIPs a neutron equivalent of 1/20 neutron per photon for soft γ-rays was found while the equivalent for hard γ-quanta is 1/400 neutron per absorbed photon. The detective quantum efficiency (DQE) of a C-NIP consisting of KCl:Eu 2+– 6LiF amounts to 38%, a value which is comparable to commercially available neutron image plates. Pix-NIPs represent a novel structure in which the scattered light is confined to square cells embedded in the image plate. Due to this light confinement, the resolution of such an image plate is primarily independent of scattering properties of the NIP and is mainly a function of the size of the cell structure used.