Thermal Neutron Beam Research Articles

Construction and Application of T2-3 Thermal Neutron Beam Port in JRR-3

We present the reconstruction of T2-3 beam port in the guide hall of JRR-3. A new T2-3 is a multi-purpose thermal neutron beam port, named “MUSASI” with two monochromatic beam used for extreme condition experiments under high fields or at ultra-low temperatures, development and performance tests of neutron detectors and optical devices for J-PARC, and industrial use such as residual stress analysis, etc. A sufficient beam time in a unit of 25 days is provided for internal and outside users. We request neutron community to join this project and suggestion/criticism aimed to effective use of this beam line, oriented to complementary use of JRR-3 with J-PARC.

Design and performance of a thermal-neutron double-crystal diffractometer for USANS at NIST

An ultra-high-resolution small-angle neutron scattering (USANS) double-crystal diffractometer (DCD) is now in operation at the NIST Center for Neutron Research (NCNR). The instrument uses multiple reflections from large silicon (220) perfect single crystals, before and after the sample, to produce both high beam intensity and a low instrument background suitable for small-angle scattering measurements. The minimum detector background to beam intensity ratio (noise-to-signal, N/S) forq≥ 5 × 10−4 Å−1is 4 × 10−7. The instrument uses 2.38 Å wavelength neutrons on a dedicated thermal neutron beam port, producing a peak flux on the sample of 17300 cm−2 s−1. The typical measurement range of the instrument extends from 3 × 10−5 Å−1to 5 × 10−3 Å−1in scattering wavevector (q), providing information on material structure over the size range from 0.1 µm to 20 µm. This paper describes the design and characteristics of the instrument, the mode of operation, and presents data that demonstrate the instrument's performance.

Evaluation of the divergence of a thermal neutron beam using a Position Sensitive Detector

The divergence of the thermal neutron beam available at the main outlet channel of the Argonauta Reactor in the Instituto de Engenharia Nuclear has been measured by using a Position Sensitive Detector. The measurement process addressing a proper beam characterization has been conducted under several geometric arrangements, including attempts to reduce the beam divergence by using a honeycomb-type gadolinium collimator. Since the detector presents finite resolution, each measured position spectrum is a convolution of the true Rocking Curve expressing the beam divergence with the function that describes the detector response. Therefore, those spectra have been submitted to an unfolding process to recover the concealed Rocking Curve. Prior to undertake this task however, the detector Line Spread Function - LSF was determined as required by the unfolding process. This was done by taking the response of the detector to a line source simulated by a narrow slit-collimator placed at several distances from the detector window. After a Lorentzian fitting to the acquired position spectra, the related FWHM were plotted against the source-detector distance. An extrapolation to zero furnishes then the width of the unknown LSF expressed as a normalized Lorentz function, which was then incorporated to a computer program developed to perform the unfolding. The final Rocking Curve emerges then as a normalized Lorentzian function properly defined by its width and a zero offset, showing that the beam diverges about 2.2 cm in 1 meter. The honeycomb collimator could not reduce this divergence due to its low aspect ratio.

New prompt k0 and partial cross section values measured in the cold neutron beam of Budapest Research Reactor

A complete series of measurements have been performed in the thermal neutron beam at the Budapest Research Reactor to determine the prompt k0 factors for every stable element. After the installation of the cold neutron source, the flux of the beam increased by more than an order of magnitude, which made possible to determine the k0 and cross-section values having low cross-sections with a better accuracy. The paper presents the new data for the first set of low-cross-section elements and they are compared to the best literature data.

The crossed geometry of two super mirror polarisers—a new method for neutron beam polarisation and polarisation analysis

Abstract We propose a new arrangement of super mirror polarisers to polarise a white cold or thermal neutron beam. With this method, the dependence of the neutron polarisation on angle and wavelength is suppressed efficiently. For such a neutron beam, the average polarisation can be measured with a precision of better than 10 - 3 using opaque spin filters. Average polarisation values of 0.997 for a cold neutron beam can be obtained. Furthermore, the method can be used for efficient polarisation analysis. Here, however, the precision is limited to a few times 10 - 3 by depolarisation effects. We present the method and results of experimental tests.

Space–time torsion contribution to quantum interference phases

The field of neutron interferometry achieved one of its most significant successes with the detection of the influence of gravity in the quantum mechanical phase of a thermal neutron beam. From the latest experimental readouts in this context an intriguing discrepancy has been elicited. Indeed, theory and experiment dissent by one per cent, and though this fact could be a consequence of the mounting of the experimental device, it might also embody a difference between the way in which gravity behaves in classical and quantum mechanics. In this work the effects, upon the interference pattern, of space–time torsion will be analyzed heeding its coupling with the spin of the neutron beam. It will be proved that, even with this contribution, there is enough leeway for a further discussion of the validity of the equivalence principle in nonrelativistic quantum mechanics.

Levels of [formula omitted] populated in average resonance neutron capture

The primary γ rays and energy levels in Yb 174 were investigated in average resonance neutron capture using tailored neutron beams at 2 and 24 keV and a pair spectrometer at the High Flux Reactor at Brookhaven. A thermal neutron beam was also used. Nearly 300 levels with spin up to J = 4 are reported below 4 MeV. The distribution of radiative strength in this nucleus was derived and is analyzed with a giant dipole resonance and single-particle strength models. The neutron binding energy in Yb 174 was determined at 7464.4 ( 3 ) keV .

Characterization of the wavelength spectrum of guided neutron beams

A simple method is introduced for the determination of the effective temperature of neutron beams. It is mathematically derived that the thermal equivalent neutron flux measured with a thin foil made from a 1/v-nuclide is proportional to the product of the real flux and the average wavelength. The real flux can be determined using fully absorbent materials. From the ratio of the two fluxes the average wavelength and the effective temperature can be determined. The method has been tested in thermal and cold neutron beams.

High flux neutron imaging for high-speed radiography, dynamic tomography and strongly absorbing materials

We present NEUTROGRAPH, a new instrument for high-flux neutron radiography and tomography at the Institut Laue-Langevin in Grenoble, France. It has been operational since October 2002. With a high-intensity thermal neutron beam of about 3×10 9 n cm −2 s −1, NEUTROGRAPH is dedicated to real-time, snapshot and stroboscopic radiography with time resolution down to a few microseconds, as well as dynamic tomography on a sub-minute time scale. The high intensity also allows the visualization of thick and strongly absorbing materials. This allows investigation of larger samples with extremely low contrast, as in some fields of material science and archaeology. Various experiments have been carried out during the last 2 years. We present the large spectrum of applications and we describe the properties of a detector system dedicated to these types of experiments. Furthermore, we describe an algorithm to eliminate the effects of scintillator degradation in intense neutron fluxes.

Performance of a pixel detector suited for slow neutrons

Semiconductor pixel radiation detector systems have recently made significant progress achieving excellent spatial resolution, high sensitivity, wide dynamic range and low noise. The hybrid silicon pixel device of Medipix type developed at CERN was originally designed for position sensitive single X-ray photon detection. We have adapted this device to a position sensitive detector of slow neutrons by covering the detector surface with a 6LiF neutron converter. Neutrons are converted to tritons and alpha particles which are subsequently detected by the silicon pixel detector. The basic parameters of such a pixel neutron sensitive device were investigated using thermal neutron beams. Tests for neutron imaging applications and comparison with currently used devices for neutron radiography (CCD camera with scintillator, imaging plates) were performed. The aim of this article is to demonstrate the exceptional good spatial resolution for neutrons (up to 8.5 lp/mm in the case of Medipix-2 option), reasonable neutron detection efficiency with very low sensitivity to background gamma radiation, low noise, perfect linearity and wide dynamic range. Results and future prospects are presented in this article.

Implementation of neutron tomography around the Algerian Es-Salam research reactor: preliminary studies and first steps

During the last three years a static neutron radiography facility has been designed and installed around one of the horizontal neutron beam channels of the Es-Salam research reactor. In order to extend the field of application of neutron radiography, a development project is actually undertaken. The purpose of this project is the implementation of neutron tomography (NT). The Es-Salam research reactor provides a 10 9 n/cm 2 s thermal neutron beam for the installation of a tomography facility. The aim of this Tomography facility will be to visualize dynamic processes and to implement fast reconstruction methods. A first step in this direction was the design and the realization of an exposition cell, a beam-catcher, a turn table and a neutron beam collimation system. All electronic parts of the detection system will be provided and installed within the frame work of a Technical Cooperation Project (TCP) with the International Atomic Energy Agency (IAEA). This paper describes the estimation procedure of the main design parameters according to the measurement of the beam properties for final tomography station as well as the composition and the performance of the proposed detection system. Moreover, the influence of physical parameters of the irradiation in-pile parts on the image quality and acquisition process is discussed.

Neutron beam design for low-intensity neutron and gamma-ray radioscopy using small neutron sources

Two small neutron sources of /sup 252/Cf and /sup 241/Am-Be radioisotopes were used for design of neutron beams applicable to low-intensity neutron and gamma-ray radioscopy (LINGR). In the design, Monte Carlo code (MCNP) was employed to generate neutron and gamma-ray beams suited to LINGR. With a view to variable neutron spectrum and neutron intensity, various arrangements were first examined, and neutron-filter, gamma-ray shield, and beam collimator were verified. Monte Carlo calculations indicated that with a suitable filter-shield-collimator arrangement, thermal neutron beam of 3900 ncm/sup -2/s/sup -1/ with neutron/gamma ratio of 7 /spl times/ 10/sup 7/, and 25 ncm/sup -2/s/sup -1/ with very large neutron/gamma ratio, respectively, could be produced by using a /sup 252/Cf (122 /spl mu/g) and a /sup 241/Am-Be (37 GBq) radioisotopes at the irradiation port of 35 cm from the neutron sources.

New neutron imaging facility at the NIST

The design objective of the thermal neutron radiography facility at the National Institute of Standards and Technology (NIST) Center for Neutron Research was to provide a large beam diameter and a high fluence rate in order to produce images of dynamic systems. A thermal neutron beam with a 14 cm diameter thimble was chosen. The beam was initially filtered by a 10 cm thick single crystal bismuth filter cooled with liquid nitrogen. The beam exiting the port is shaped using either a 1 cm or 2 cm diameter pinhole to form a uniform high fluence rate beam at the sample. The resulting neutron beam at the sample has an L/ D ratio of 280 with a fluence rate of 1.84×10 7 cm −2 s −1 and 560 with a fluence rate of 4.75×10 6 cm −2 s −1 uniformly spread over a 26 cm diameter beam. To capture the neutron beam image a scintillator and CCD camera is used. The current neutron camera system is limited to a 2.5 s frame rate; however, a high frame rate detector system based on amorphous silicon will allow frame rates to meet the design goal. Samples can be rotated and translated in situ for radiography and tomography applications. This facility became operational in early 2003. Since then the facility has been translated backwards by ≈2.13 m and 5 cm of bismuth was added to the filter. The design of this facility and the impact of the later changes are discussed.

Porphyrin-Mediated Boron Neutron Capture Therapy: A Preclinical Evaluation of the Response of the Oral Mucosa

Preclinical studies are in progress to determine the potential of boron neutron capture therapy (BNCT) for the treatment of carcinomas of the head and neck. Recently, it has been demonstrated that various boronated porphyrins can target a variety of tumor types. Of the porphyrins evaluated so far, copper tetracarboranylphenyl porphyrin (CuTCPH) is potentially a strong candidate for clinical use. In the present investigation, the response of the oral mucosa to CuTCPH-mediated boron neutron capture (BNC) irradiation was assessed using the ventral surface of the tongue of adult male Fischer 344 rats, a standard rodent model. CuTCPH was administered by intravenous infusion, at a dose of 200 mg/kg body weight, over a 48-h period. Three days after the end of the administration of CuTCPH, biodistribution studies indicated very low levels of boron (<2 microg/g) in the blood. Levels of boron in tongue tissue were 39.0 +/- 3.8 microg/g at this time. This was the time selected for irradiation with single doses of thermal neutrons from the Brookhaven Medical Research Reactor. The estimated level of boron-10 in the oral mucosa was used in the calculation of the physical radiation doses from the 10B(n,alpha)7Li reaction. This differs from the approach using the present generation of clinical boron carriers, where boron levels in blood at the time of irradiation are used for this calculation. Dose-response curves for the incidence of mucosal ulceration were fitted using probit analysis, and the doses required to produce a 50% incidence of the effect (ED50 +/- SE) were calculated. Analysis of the dose-effect data for CuTCPH-mediated BNC irradiation, compared with those for X rays and thermal neutrons alone, gave a compound biological effectiveness (CBE) factor of approximately 0.04. This very low CBE factor would suggest that there was relatively low accumulation of boron in the key target epithelial stem cells of the oral mucosa. As a consequence, with low levels of boron (<2 microg/g) in the blood, the response of the oral mucosa to CuTCPH-mediated BNCT will be governed primarily by the radiation effects of the thermal neutron beam and not from the boron neutron capture reaction [10B(n,alpha)7Li].

Study of a 5 MeV electron linac based neutron source

A compact neutron source, based on a 5 MeV electron linac, has been designed for Neutron Radiography/Boron-Neutron-Capture-Therapy (BNCT) applications. Although a higher electron energy is generally needed to produce an intense neutron beam, in this paper the use of Be and BeD 2 photoneutron targets will be proposed, leading to thermal neutron beams of 8.48 × 10 7 n/cm 2/s/mA and 1.23 × 10 8 n/cm 2/s/mA, respectively. Optimization of the parameters involved in neutron production (e-γ conversion, moderator and reflector performances) has been studied by means of the MCNP-4C2 code.

Confined propagation of thermal neutrons using nanotubes

We study the possible confined propagation of thermal neutrons along carbonnanotubes (CNTs) behaving as waveguides with total transverse cross sectionΩtot atnanometre scales. Our approach extends previous proposals regarding similar phenomena along waveguideswith Ωtot in the micron scale and it receives additional motivation by recent studies on the possiblefocusing of x-rays at the nanoscale. We consider single wall and multiwall CNTs(SWCNTs and MWCNTs). A proper description of the confined propagationappears to require quantum mechanics. All (or most) thermal neutrons wouldpropagate along the MWCNT (the most favourable possibility) in the fundamentalmode. We estimate various possible loss mechanisms in the intensity of thermalneutron beams propagating confined along the CNT: nuclear absorption anddiffuse scattering, bending losses and tunnelling effects across the walls of theCNT. According to our purely theoretical model, and due to the smallness ofΩtot, the transmitted neutron flux through a sole MWCNT would berather small (roughly, about one or a few per hour across the wholeΩtot, for an incoming flux outside the MWCNT of1014 neutrons cm−2 s−1). We also discuss the potential interest of the confined propagation of thermal neutrons atthe nanoscale and the possibility of the latter phenomenon in other types of nanotubes(NTs) different from CNTs.

Low efficiency 2-dimensional position-sensitive neutron detector for beam profile measurement

A gas-filled position-sensitive wire detector has been developed for monitoring thermal neutron beams with flux up to 10 7 n/cm 2/s over an area ≈80 cm 2. It is filled with CF 4(4 atm) and a small quantity of 3He, has 1.2 mm spatial resolution, 0.1% efficiency (at 0.18 nm) and can achieve a count rate of 350 kHz. Experiments at the 30 MW HANARO reactor showed that the fabricated PSD is a very useful and convenient tool for adjusting neutron monochromators, especially focusing monochromators, and for monitoring monochromatic beams. It can be used for various neutron optics experiments.

Combination of the vascular targeting agent ZD6126 with boron neutron capture therapy

The aim of this study was to evaluate the antitumor efficacy of the vascular targeting agent ZD6126 (N-acetylcochinol-O-phosphate) in the rodent squamous cell carcinoma (SCC) VII carcinoma model, in combination with boron neutron capture therapy (BNCT). Sodium borocaptate-(10)B (BSH, 125 mg/kg, i.p.) or l-p-boronophenylalanine-(10)B (BPA, 250 mg/kg, i.p.) was injected into SCC VII tumor-bearing mice, and 15 min later, ZD6126 (100 mg/kg, i.p.) was administered. Then, the (10)B concentrations in tumors and normal tissues were measured by prompt gamma-ray spectrometry. On the other hand, for the thermal neutron beam exposure experiment, SCC VII tumor-bearing mice were continuously given 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating (P) cells in the tumors, followed by treatment with a (10)B-carrier and ZD6126 in the same manner as the above-mentioned (10)B pharmacokinetics analyses. To obtain almost similar intratumor (10)B concentrations during neutron exposure, thermal neutron beam irradiation was started from the time point of 30 min after injection of BSH only, 90 min after BSH injection for combination with ZD6126, 120 min after the injection of BPA only, and 180 min after BPA injection for combination with ZD6126. Right after irradiation, the tumors were excised, minced, and trypsinized. The tumor cell suspensions thus obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without BrdU labeling (quiescent [Q] cells) was determined using immunofluorescence staining for BrdU. Meanwhile, the MN frequency in total (P + Q) tumor cells was determined from the tumors that were not pretreated with BrdU. The clonogenic cell survival assay was also performed in mice given no BrdU. Pharmacokinetics analyses showed that combination with ZD6126 greatly increased the (10)B concentrations in tumors after 60 min after BSH injection and after 120 min after BPA injection. The concentrations of (10)B from BSH in normal tissues were also raised by combination with ZD6126, although not so clearly as those in tumors. Combination with ZD6126 had almost no effect on the concentrations of (10)B from BPA in normal tissues. The clonogenic surviving fractions of total tumor cells and the MN frequencies of both total and Q tumor cells were reduced and increased by combination with ZD6126, respectively, whether BSH or BPA was employed. However, the degrees of these changes in the clonogenic surviving fractions and the MN frequencies were more obviously observed in tumors from BSH-injected mice than from BPA-injected mice, and in Q tumor cells than in total tumor cells regardless of the employed (10)B-carrier. Combination with ZD6126 was regarded as more promising in BSH-BNCT than BPA-BNCT, and more effective for enhancing the sensitivity of the Q tumor cells than that of the total tumor cells. This resulted in the decrease in the extended difference in the sensitivity between the total and Q tumor cells caused by the use of (10)B-carrier for BNCT.

Development of a non-destructive neutron radiography technique to measure the three-dimensional soot deposition profiles in diesel engine exhaust systems

A technique was developed to non-destructively measure the three-dimensional soot deposition thickness profiles in diesel engine exhaust components using a digital neutron imaging technique. In this technique, the test component positioned on a rotating platform is exposed to a thermal neutron beam from a nuclear reactor and the flux transmitted through the test object is measured using a digital neutron imaging system. The thickness of the diesel soot is then determined by analyzing the attenuation of this neutron flux. The technique was applied here to an aluminum pipe that was fouled for approximately 12 h by diesel exhaust from a diesel generator. The analysis of the neutron images indicated that the average soot thickness in the fouled pipe decreased nonlinearly along the pipe. It was also found that the measurements using this technique were within 16% of the direct destructive measurements of the thickness determined after sectioning the pipe.

The usefulness of 2-nitroimidazole-sodium borocaptate- 10B conjugates as 10B-carriers in boron neutron capture therapy

We evaluated the usefulness of five new 10B-compounds (TX-2016, TX-2017, TX-2018, TX-2041, and TX-2042) as 10B-carriers in boron neutron capture therapy (BNCT). They are 2-nitroimidazole-sodium borocaptate- 10B (BSH) conjugates, that is, hybrid compounds that have both hypoxic tumor cell sensitizing unit under γ-ray irradiation, 2-nitroimidazoles, and thermal neutron-sensitizing unit, BSH. 10B distribution analyses in tumors and blood indicated that TX-2041 has the most favorable characteristics for localizing a sufficient amount of 10B into tumors and keeping the 10B concentration high during neutron beam irradiation. In addition, TX-2041 showed a significantly higher radio-sensitization effect with reactor thermal neutron beams than BSH on both total (=proliferating (P) + quiescent (Q)) and hypoxia-rich Q cell populations in solid tumors. Further, TX-2041 clearly demonstrated a radio-sensitization effect with γ-rays on both cell populations, which could never be achieved by BSH. 10B-carriers with a hypoxic tumor cell-sensitizing effect on tumors with γ-rays as well as the potential to selectively localize and keep 10B in tumors, such as TX-2041, are promising for use in actual BNCT.