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English
Physics
Elementary Particles, Quantum Field Theory
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Chapter
Thermalization of Neutrons
Our first discussion of thermal neutron fields in Sec. 5.3 was based on the idealizing assumption that the neutrons were in a true state of thermal equilibrium and thus had a Maxwellian energy distribution wit...
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Activation by Epithermal Neutrons
The considerations begun in Chapter 11 will now be extended to the practically important case in which the neutron field contains both thermal and epithermal neutrons. The very same activity that can be excite...
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Neutron Sources
Because of their short lifetime, free neutrons do not occur in nature and must be artificially produced. A simple method consists of separating them from nuclei in which they are particularly loosely bound. Th...
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Standardization of Neutron Measurements
A great many investigations in neutron physics require precise absolute measurements. These absolute measurements are of two kinds: the absolute determination of source strengths and the absolute measurement o...
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Measurement of Cross Sections
In this chapter, a short survey will be given of the most important differential methods for determining cross sections. By differential methods is meant methods in which a substance is bombarded by a neutron bea...
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Slowing-Down Parameters
In this chapter, we consider stationary and non-stationary experiments for the study of neutron moderation and diffusion at energies above the thermal region. By far the most important of these experiments are...
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Applications of Elementary Diffusion Theory
In this chapter, we shall extend the elementary diffusion theory that was developed in Secs. 5.2. and 5.3 and apply it to some important special problems. We shall mainly be interested in the diffusion of ther...
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Investigation of the Diffusion, Absorption, and Thermalization of Neutrons by Non-Stationary Methods
During the last ten years non-stationary methods have gained increasing significance in neutron physics. This is because they frequently permit cleaner and more accurate measurements than stationary methods an...
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The Spatial Distribution of Moderated Neutrons
In this chapter we shall calculate the space and energy distribution of neutrons during the slowing-down process. Our goal will be to obtain the flux Φ (r, E) or the slowing-down density q (r, E) arising from giv...
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Measurement of the Thermal Neutron Flux with Probes
The neutron detectors discussed in the third chapter are not always suitable for determining the intensity of a stationary neutron field, but we can always use to advantage the so-called “radioactive indicator...
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Production and Nuclear Interaction of Neutrons
In the year 1930, Bothe and Becker discovered artificial nuclear γ-radiation. They bombarded Li, Be, B, and other light elements with α-particles from a polonium preparation and with a needle counter observed γ-r...
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Threshold Detectors for Fast Neutrons
Certain nuclear reactions, such as (n, 2 n) reactions, inelastic scattering, and some (n, p) and (n, α) reactions, occur only when the neutrons have energies above a particular threshold energy. In many cases, th...
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Neutron Detectors
Since the neutron is an electrically neutral particle, it does not interact with the usual detectors employed for ionizing radiation ; it is therefore detected indirectly using nuclear reactions that produce c...
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Investigation of the Energy Distribution of Slow Neutrons
In this chapter, we shall consider experiments for determining the stationary spectra of very slow (E < 10 ev) neutrons in bulk media. The main part of the chapter is centered around the discussion of various met...
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Neutron Fields
Let us consider sources in a scattering medium which emit neutrons with an energy E or with an energy distribution S (E). These neutrons exchange kinetic energy with the atoms of the scattering substance through ...
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Investigation of the Diffusion of Thermal Neutrons by Stationary Methods
In this chapter, we shall become familiar with stationary methods of determining the diffusion parameters of thermal neutrons. First we shall consider in Sec. 17.1 the classical methods of measuring the diffus...
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Slowing Down
As a rule, neutrons produced in nuclear reactions have energies far above the thermal energy range. When such fast neutrons collide with the atoms of a scattering medium, loss of energy occurs simultaneously w...
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Time Dependence of the Slowing-Down and Diffusion Processes
In this chapter, we shall study the behavior of neutron fields with nonstationary sources. In doing so we shall round out our discussion of the diffusion and slowing-down processes and in particular prepare ou...
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