Boron Neutron Capture Therapy

Physics of Atomic Nuclei - Fundamentals of boron neutron capture therapy of malignant tumors are outlined, and the current status of the development of epithermal-neutron sources on the basis of...     

A Compact in situ Polarized3He System for Neutron Scattering

<正>This study investigates the performance of a new compact（55 cm×56 cm×48 cm） in situ spin-exchange optical pumping ³He neutron spin filter（NSF） system developed at the China Spallation Neutron Source. The enclosed NSF cell, filled with ³He at 2.53 bar, achieved an initial ³He polarization of approximately 60%.     

Measuring Neutron Lifetime on an IBR-2 Pulsed Neutron Source

A new method of measuring neutron lifetimes on pulsed neutron sources based on changes in the neutron spectrum during the time of the neutron transit along a rather large path length due to their decay is proposed. The main advantage of this method is the use of relative measurements. Simulating the experiment made it possible to explore the influence of background and neutron losses caused by both the interaction with residual gas and the different level of detector efficiency on the systematic errors. All parameters can be measured experimentally.     

Proton-Accelerator Driven High-Flux Pulsed Neutron Source for Beam Research

Physics of Particles and Nuclei Letters - Parameters of the optimum alternative of a high-flux pulsed neutron source (fourth-generation neutron source in Dubna), which is foreseen to replace the...     

基于自由电子激光的小型太赫兹源初步设计

介绍了基于自由电子激光的太赫兹源的研究情况,提出了一种小型自由电子激光太赫兹源设计方案.采用独立调谐双腔热阴极微波电子枪,不需要α-磁铁及其他束团压缩装置,能够达到所需的束流品质,达到减小系统尺寸的目的.加速结构采用对称输入耦合器和同轴吸收负载输出耦合器,减少加速器的横向尺寸.采用混合永磁型波荡器,孔耦合输出的稳定球面光学谐振腔.介绍了该方案的初步设计和仿真计算.     

Concept of the Fourth-Generation Neutron Source in Dubna

The principles of designing a subcritical neutron-multiplying system with reactivity modulation, which can be used as the target in a superbooster with a linear proton accelerator, are described. Calculations demonstrate that the output neutron-flux density of a pulse can be expected to reach 10¹⁷ cm^–2 s^–1 at maximum and 2 × 10¹⁴ cm^–2 s^–1 on average. The pulse duration of thermal neutrons can be 200–300 and 20–30 μs depending on the moderator and the corresponding pulse duration of the proton accelerator.     

Maxwellian Averaged Neutron Capture Cross Sections in 56Fe and 57Fe

Measurements of the keV-neutron capture cross sections and radiative γ-ray spectrum of 56Fe and 57Fe are performed based on a 7 Li（p,n）7 Be reaction neutron source. The incident neutron spectrum on a capture sample is measured by means of a time-of-flight （TOF） method with a 6Li-glass detector. The radiative capture 7-rays emitted from an iron CS Fe or 57 Fe） or standard gold （197Au） sample are detected by a large anti-Compton NaI（TI） spectrometer covered with a heavy shield. The capture yields of samples are obtained by applying a pulse-height weighting technique to the corresponding capture γ-ray pulse-height spectrum. The Maxwellian averaged neutron capture cross sections of 56Fe and 5T Fe are derived according to the present capture cross section results.     

Tritium Fuel Cycle for Muon-Catalyzed Intense Neutron Source (MC INS)

The paper presents a schematic design of a Tritium Fuel Cycle for Muon-Catalyzed Intense Neutron Source (MC INS) capable of producing 14 MeV neutrons. Based on the assumption that the fuel mixture should be used in a liquid phase different approaches are proposed to incorporate a DT cell (synthesizer) into the MC INS facility. Estimations of the total tritium inventory in the MC INS facility are given. The calculations of the DT cell operation temperature regime using the code FLOW-3D^(R) are presented. The capability to remove the thermal energy released in the DT cell of the proposed design is shown. The MC INS design is analyzed from the viewpoint of tritium safety requirements. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Munich Compact Light Source: initial performance measures

While large‐scale synchrotron sources provide a highly brilliant monochromatic X‐ray beam, these X‐ray sources are expensive in terms of installation and maintenance, and require large amounts of space due to the size of storage rings for GeV electrons. On the other hand, laboratory X‐ray tube sources can easily be implemented in laboratories or hospitals with comparatively little cost, but their performance features a lower brilliance and a polychromatic spectrum creates problems with beam hardening artifacts for imaging experiments. Over the last decade, compact synchrotron sources based on inverse Compton scattering have evolved as one of the most promising types of laboratory‐scale X‐ray sources: they provide a performance and brilliance that lie in between those of large‐scale synchrotron sources and X‐ray tube sources, with significantly reduced financial and spatial requirements. These sources produce X‐rays through the collision of relativistic electrons with infrared laser photons. In this study, an analysis of the performance, such as X‐ray flux, source size and spectra, of the first commercially sold compact light source, the Munich Compact Light Source, is presented.     

Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi(Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm~3.     

Reaction Rate of Radiative Capture of a Neutron by a 2H Nucleus

Russian Physics Journal - Within the framework of the modified potential cluster model with forbidden states, n2H radiative capture is considered at energies from 10 meV (0.01 eV) to 10 MeV. It is...     

Physical design of target station and neutron instruments for China Spallation Neutron Source

The China Spallation Neutron Source(CSNS)is the first accelerator-based multidiscipline user facility to produce pulsed neutrons by tungsten target under collision of a pulsed proton beam with a beam power of 100 kW at a repetition rate of 25 Hz.In this paper,we focus on the physical design of CSNS target station and neutron instruments.Under optimized design,the flat tungsten target and the compact target-moderator-reflector coupling enhance effective cold and thermal neutron output from moderators.Three wing-type moderators supply four different characteristics of neutrons to 19 beamlines primarily for neutron scattering applications.Layout of neutron instruments are conceptually planned for total 20 beamlines,the configuration and specification have been determined for three day-one neutron instruments.All designs are optimized for the Phase I of 100 kW with a upgradable capacity to 500 kW.     

Analysis of radiation environmental safety for China's Spallation Neutron Source(CSNS)

The China Spallation Neutron Source(CSNS)is going to be located in Dalang Town,Dongguan City in the Guangdong Province.In this paper we report the results of the parameters related with environment safety based on experiential calculations and Monte Carlo simulations.The main project of the accelerator is an under ground construction.On top there is a 0.5 m concrete and 5.0 m soil covering for shielding,which can reduce the dose out of the tunnel's top down to 0.2 μSv/h.For the residents on the boundary of the CSNS,the dose produced by skyshine,which is caused by the penetrated radiation leaking from the top of the accelerator,is no more than 0.68 μSv/a.When CSNS is operating normally,the maximal annual effective dose due to the emission of gas from the tunnel is 2.40×10-3 mSv/a to the public adult,and 2.29×10-3 mSv/a to a child,both values are two orders of magnitude less than the limiting value for control and management.CSNS may give rise to an activation of the soil and groundwater in the nearest tunnels,where the main productions are 3H,7Be,22Na,54Mn,etc.But the specific activity is less than the exempt specific activity in the national standard GB13376-92.So it is safe to say that the environmental impact caused by the activation of soil and groundwater is insignificant.To sum up,for CSNS,as a powerful neutron source device,driven by a high-energy high-current proton accelerator,a lot of potential factors affecting the environment exist.However,as long as effective shieldings for protection are adopted and strict rules are drafted,the environmental impact can be kept under control within the limits of the national standard.     

Composite Surface Integral Transforms in Neutron Therapy of Cancer

Composite surface finite integral transforms are applied to formulate the optimal ballistic property for a temporally tuned multibeam neutron cancer 3D therapy as a single-valued dynamical system. By invoking Pontryagin's maximum principle, with the operation functions of the beams constituting the control vector, it is proved, in an inverse problem formulation, that for every spatial configuration of the neutron beams, there exists an optimal temporal control vector satisfying an a priori system of linear homogeneous Volterra integral equations of the first kind and convolution type. A version of this newly advanced, temporally optimalized, multibeam 3D irradiation therapy, with a linearized ballistic property, is shown to result from a shooting-type solution to a related, semihomogeneous dual system of linear integral equations of the first kind. A criterion for the controllability of this optimization problem has also been established.     

Analysis of some Elements in Fuel Oil by using Neutron Capture Gamma Ray Spectroscopy

The analysis of some elements in fuel oil was done by using neutron capture gamma ray spectroscopy. The gamma rays emitted after the reaction of (n, γ) from the fuel oil atoms bombarded with the thermal neutrons emitted from a ²⁵²Cf source were investigated in the energy interval 0 … 10 MeV. The impurity elements in the sample were determined.     

High-Resolution Neutron Diffractometer Based on the IN-06 Pulsed Neutron Source at the Institute for Nuclear Research,Russian Academy of Sciences

A high-resolution neutron diffractometer has been fabricated on the basis of an IN-06 pulsed neutron source at the Institute for Nuclear Research, Russian Academy of Sciences. The diffractometer incorporates two blocks of detectors with helium neutron counters and time-of-flight (TOF) focusing at scattering angles of 156°–165°. A block of new-type high-efficiency scintillation detectors of thermal neutrons based on a ZnS(Ag)/LiF scintillator and silicon photomultipliers with TOF focusing is developed and tested. Test measurements are performed, and the diffractometer resolution is estimated. The diffraction pattern of nonmagnetic NiCrAl alloy is measured and used to determine the phase composition by means of the Rietveld method. It is demonstrated that the given setup can be applied to phase analysis.     

Theoretical Optimization of Neutron and Physical Characteristics of a Multiplying Pulsed Neutron Source Based on a Proton Accelerator

Physics of Particles and Nuclei Letters - The neutron source operating at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research (JINR, Dubna, Russia), based on an IBR-2M...