## Pulsed neutron scattering |

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Page 113

The flux in the epithermal region can therefore be expressed as A A' Thermal

energies: the Maxwellian

breaks down as soon as the neutron energy becomes within a few times kB T. T

is the effective temperature of the moderator. The neutron velocity becomes

comparable with that of the vibrating atoms. It can gain energy as well as lose it in

the collision. When the neutron energy is around kT it becomes equally likely to

gain or lose ...

The flux in the epithermal region can therefore be expressed as A A' Thermal

energies: the Maxwellian

**distribution**Our approach to neutron slowing-downbreaks down as soon as the neutron energy becomes within a few times kB T. T

is the effective temperature of the moderator. The neutron velocity becomes

comparable with that of the vibrating atoms. It can gain energy as well as lose it in

the collision. When the neutron energy is around kT it becomes equally likely to

gain or lose ...

Page 115

The epithermal l/k flux

for a polyethylene slab moderator at room temperature92.

Maxwellian. The joining region where the two functions mix can be described

well in practice by the function n0(A) = [1 - JWXpi(A) + y(A)nmax(A). The joining

function is the Fermi

wavelength and kw ...

The epithermal l/k flux

**distribution**can be smoothly joined on the Maxwellian**distribution**using the simple joining function of equation 3.19. These results arefor a polyethylene slab moderator at room temperature92.

**distribution**to theMaxwellian. The joining region where the two functions mix can be described

well in practice by the function n0(A) = [1 - JWXpi(A) + y(A)nmax(A). The joining

function is the Fermi

**distribution**I (3.19) 1 +exp[-(A-;.£)//H.]' /.£ is the joiningwavelength and kw ...

Page 233

Gaussian with the same FWHH (iv) convoluted with a Gaussian of the same RMS

width (t>) gives a very similar convolution (vi). results summed to give the

)dy. (6.8) Only in a few cases is this easy to obtain analytically. A general method

which can be applied in all cases is to represent the

Gaussians ...

**Distribution**(i) convoluted with (ii) gives the**distribution**(iii). A correspondingGaussian with the same FWHH (iv) convoluted with a Gaussian of the same RMS

width (t>) gives a very similar convolution (vi). results summed to give the

**distribution**nc(x) of figure 6.4 (iii). For normalized**distributions**nc(x) = lnl(x)n2(y-x)dy. (6.8) Only in a few cases is this easy to obtain analytically. A general method

which can be applied in all cases is to represent the

**distributions**by normalizedGaussians ...

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### Contents

HOW PULSED SOURCES WORK | 68 |

NEUTRON | 98 |

PULSED SOURCES VERSUS REACTORS | 150 |

Copyright | |

9 other sections not shown

### Common terms and phrases

absorber absorption accelerator atoms background beam tube beryllium Bragg reflection calculated cell collimation count-rate counter bank cross-section crystal analyser crystal monochromator curve defined density depends detector diffraction diffractometer direct geometry distance distribution dose effect efficiency elastic energy loss energy transfer epithermal equation fast neutrons figure of merit fission function give given Harwell hydrogen incident beam incident energy incident flight path incident neutron incoherent incoherent scattering intensity linac magnetic Maxwellian measured neutron beam neutron scattering neutron source nuclear nuclei phonon polarization proton pulse width pulsed neutron pulsed reactor pulsed source Q values radiation range ratio reciprocal lattice reciprocal space reflector resolution element resonance rotor sample scattered flight path scattering angle scattering length scattering vector Section shielding shown in figure shows single crystal slab moderator slit solid angle spectrometer spectrum spin spread target temperature thermal thickness time-of-flight transmission typical unit vanadium velocity vibrational wave-vector wavelength y-rays