Multichannel Neutron Collimator for TRT Nemtsev, G. E.; Rodionov, R. N.; Khafizov, R. R. ...
Plasma physics reports,
12/2022, Volume:
48, Issue:
12
Journal Article
Peer reviewed
The project is described of the neutron camera for the tokamak with reactor technologies (TRT). The neutron camera is a multichannel neutron collimator covering the plasma neutron source with ...observation chords. The neutron camera is a system designed for measuring the profile of fusion neutron source in the poloidal cross section of the tokamak. The system conceptual design is proposed, which includes ten measuring channels of collimators that monitor the plasma in the radial direction. For more detailed covering the plasma neutron source with observation lines, it is proposed that the system will also be equipped with several vertical collimators. The channels of collimators are located inside the vacuum chamber ports, being partly introduced into the facility cryostat volume. Such a solution makes it possible to improve the coverage of the plasma volume by observation lines. It is proposed to use stainless steel and high-density borated polyethylene as materials for the collimators. It is planned to use diamond detectors and scintillators based on stilbene and lanthanum chloride as neutron detectors. The plasma neutron source is simulated in this work. Using radiative transport calculations, the neutron fluxes and spectra in the channels of collimators were obtained. The neutron camera of the TRT facility will make it possible to measure the profiles of neutron sources in DD and DT plasmas, as well as the ratios of emission intensities of DD and DT neutrons, neutron spectra, total neutron yields, and other parameters.
IMAT is a new cold neutron imaging and diffraction instrument located at the second target station of the pulsed neutron spallation source ISIS, UK. A broad range of materials science and materials ...testing areas will be covered by IMAT. We present the characterization of the imaging part, including the energy-selective and energy-dispersive imaging options, and provide the basic parameters of the radiography and tomography instrument. In particular, detailed studies on mono and bi-dimensional neutron beam flux profiles, neutron flux as a function of the neutron wavelength, spatial and energy dependent neutron beam uniformities, guide artifacts, divergence and spatial resolution, and neutron pulse widths are provided. An accurate characterization of the neutron beam at the sample position, located 56 m from the source, is required to optimize collection of radiographic and tomographic data sets and for performing energy-dispersive neutron imaging via time-of-flight methods in particular.
A moderator device to produce a uniform thermal neutron field has been designed by Monte Carlo methods using the MCNP6.1 code. It uses a 241Am/9Be neutron source of 111 GBq activity and high-density ...polyethylene (HDPE) moderator. The main tasks developed were to evaluate the geometry of the moderator and to select the neutron source position, in order to optimize the thermal neutrons flux in the irradiation area, and to assess the dose rate. In the system, named FANT (Fuente Ampliada de Neutrones Térmicos), the neutron moderation and backscattering processes are effective to obtain quite uniform thermal fluence rates above 1000 cm−2 s−1 in a cylindrical irradiation chamber of 32 cm diameter and 34 cm length. The device has been built in the neutron measurements hall of the Energy Engineering Department of Universidad Politécnica de Madrid (UPM), performing several measurements to characterize the neutron field and validate the calculations.
FANT can be employed hereafter in different applications requiring a neutron field with a substantial thermal component, like testing and calibration of neutron detectors and neutron dosimeters, or the use NAA (Neutron Activation Analysis) methods for detection of trace substances or materials.
•A thermal neutron source built using a 111 GBq 241Am/9Be source and HDPE moderator.•Designed by Monte Carlo (MCNP6) based on neutron moderation and backscattering.•Effective thermal neutron fluence rates above 1000 cm−2 s−1 and quite uniform.•Cylindrical irradiation chamber of 32 cm diameter and 34 cm length.•Suitable for testing and calibration of neutron instruments, or for NAA.
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced ...Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of \(\sim 1.7\,{\rm{s}}\) with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of \({40}_{-8}^{+8}\) Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 \(\,{M}_{\odot }\). An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at \(\sim 40\,{\rm{Mpc}}\)) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position \(\sim 9\) and \(\sim 16\) days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.
We report the most precise determination of the S01 neutron-neutron effective range parameter (rnn) from neutron-neutron quasifree scattering in neutron-deuteron breakup. The experiment setup ...utilized a collimated beam of 15.5 MeV neutrons and an array of eight neutron detectors positioned at angles sensitive to several quasifree scattering kinematic configurations. The two neutrons emitted from the breakup reaction were detected in coincidence and time-of-flight techniques were used to determine their energies. The beam-target luminosity was measured in-situ with the yields from neutron-deuteron elastic scattering. Rigorous Faddeev-type calculations using the CD Bonn nucleon-nucleon potential were fit to our cross-section data to determine the value of rnn. The analysis was repeated using a semilocal momentum-space regularized N4LO+ chiral interaction potential. We obtained values of rnn=2.86±0.01(stat)±0.10(sys) fm and rnn=2.87±0.01(stat)±0.10(sys) fm using the CD Bonn and N4LO+ potentials, respectively. Our results are consistent with charge symmetry and previously reported values of rnn.
Ultra-intense MeV photon and neutron beams are indispensable tools in many research fields such as nuclear, atomic and material science as well as in medical and biophysical applications. For ...applications in laboratory nuclear astrophysics, neutron fluxes in excess of 10
n/(cm
s) are required. Such ultra-high fluxes are unattainable with existing conventional reactor- and accelerator-based facilities. Currently discussed concepts for generating high-flux neutron beams are based on ultra-high power multi-petawatt lasers operating around 10
W/cm
intensities. Here, we present an efficient concept for generating γ and neutron beams based on enhanced production of direct laser-accelerated electrons in relativistic laser interactions with a long-scale near critical density plasma at 10
W/cm
intensity. Experimental insights in the laser-driven generation of ultra-intense, well-directed multi-MeV beams of photons more than 10
ph/sr and an ultra-high intense neutron source with greater than 6 × 10
neutrons per shot are presented. More than 1.4% laser-to-gamma conversion efficiency above 10 MeV and 0.05% laser-to-neutron conversion efficiency were recorded, already at moderate relativistic laser intensities and ps pulse duration. This approach promises a strong boost of the diagnostic potential of existing kJ PW laser systems used for Inertial Confinement Fusion (ICF) research.
Small‐angle neutron scattering (SANS) has increasingly been used by the structural biology community in recent years to obtain low‐resolution information on solubilized biomacromolecular complexes in ...solution. In combination with deuterium labelling and solvent‐contrast variation (H2O/D2O exchange), SANS provides unique information on individual components in large heterogeneous complexes that is perfectly complementary to the structural restraints provided by crystallography, nuclear magnetic resonance and electron microscopy. Typical systems studied include multi‐protein or protein–DNA/RNA complexes and solubilized membrane proteins. The internal features of these systems are less accessible to the more broadly used small‐angle X‐ray scattering (SAXS) technique owing to a limited range of intra‐complex and solvent electron‐density variation. Here, the progress and developments of biological applications of SANS in the past decade are reviewed. The review covers scientific results from selected biological systems, including protein–protein complexes, protein–RNA/DNA complexes and membrane proteins. Moreover, an overview of recent developments in instruments, sample environment, deuterium labelling and software is presented. Finally, the perspectives for biological SANS in the context of integrated structural biology approaches are discussed.
Small‐angle neutron scattering (SANS) provides structural information on biological macromolecules in solution that is perfectly complementary to the information obtained using other structural biology techniques, including crystallography, nuclear magnetic resonance and electron microscopy. Compared with its sister technique small‐angle X‐ray scattering, SANS allows specific and individual information to be obtained on subunits within important heterogeneous biological assemblies such as multiprotein or protein–RNA/DNA complexes as well as solubilized membrane proteins.
Instrumentation for time‐resolved small‐angle neutron scattering measurements with sub‐millisecond time resolution, based on Gähler's TISANE (time‐involved small‐angle neutron experiments) concept, ...is in operation at NIST's Center for Neutron Research. This implementation of the technique includes novel electronics for synchronizing the neutron pulses from high‐speed counter‐rotating choppers with a periodic stimulus applied to a sample. Instrumentation details are described along with measurements demonstrating the utility of the technique for elucidating the reorientation dynamics of anisometric magnetic particles.
Instrumentation for sub‐millisecond time‐resolved small‐angle neutron scattering measurements at NIST is described and applied to the reorientation dynamics of elongated hematite nanoparticles.
The Monte Carlo ray-tracing simulation package McStas is verified by modeling two double axis neutron diffractometers, KARL and KANDI-II, located at the Israel Research reactors IRR-1 and IRR-2, ...respectively. The advantage of simulating these instruments is their simple design and small number of components. We focus on the simulation of a Soller slit collimator as well as Pyrolytic Graphite and Copper single crystal monochromators. The simulation is compared to neutron flux measurements, performed via activation analysis along the neutron beam as well as observed diffraction patterns from different powder samples. Calculated diffraction patterns are found to agree with observations to within 20%–50% in reflection peak width, while calculated attenuation of the neutron beam agrees to within 20% when the entire instrument is considered, and can show a discrepancy of up to 60% for individual components. Finally, a possible optimization of the neutron flux in the KARL diffractometer is presented.
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