Structure for slow neutron detection and method for slow neutron energy spectrum measurement

A method for energy spectrum measurement of slow neutrons, using a structure for slow neutron detection, comprising the following steps:

• S1) placing the structure for slow neutron detection on a moving equipment with a detector unit of the structure configured to face the movement direction of the equipment directly to obtain the number of slow neutrons reaching different depths within a shielding barrel, and obtaining slow neutron depth distribution spectrum based on the number of slow neutrons at different depths, wherein the slow neutron depth distribution spectrum is divided into N channels;
• and
• S2) dividing the energy range of slow neutrons to be detected into N portions corresponding to 0-E1, E1-E2, . . . , EN-1-EN according to the relationship between neutrons' energies and the maximum depths of the slow neutrons that can be reached within the shielding barrel obtained through simulation, wherein EN=E and E is the maximum energy of slow neutrons that can be shielded by the shielding barrel, then the number of slow neutrons in the Nth channel of the slow neutron depth distribution spectrum is generated by the neutrons with energy in the range of EN-1-EN, and obtaining the contribution of neutrons with energy in the range of EN-1-EN to the number in N channels of the slow neutron depth distribution spectrum by combining the probability ratio of neutrons with energy in the range of EN-1-EN reaching different depths within the shielding barrel obtained through simulation and the number in the Nth channel of the slow neutron depth distribution spectrum;
• and
• S3) the number in the (N−1)th channel of the slow neutron depth distribution spectrum is generated by neutrons with energy in the ranges of EN-2-EN-1 and EN-1-EN, wherein the contribution of the neutrons with energy in the range of EN-1-EN to the number in the (N−1)th channel of the slow neutron depth distribution spectrum is obtained by step S2, and the contribution of the neutrons with energy in the range of EN-2-EN-1 to the number in the (N−1)th channel of the slow neutron depth distribution spectrum is equal to the number in the (N−1)th channel of the slow neutron depth distribution spectrum minus the number contributed by neutrons with energy in the range of EN-1-EN in the (N−1)th channel;
• and obtaining the contribution of neutrons with energy in the range of EN-2-EN-1 to the numbers in the first (N−1) channels of the slow neutron depth distribution spectrum by combining the probability of neutrons with energy in the range SDU-PA240001-US 18 of EN-2-EN-1 reaching different depths within the shielding barrel obtained through simulation and the number in the (N−1)th channel of the slow neutron depth distribution spectrum, wherein the first (N−1) channels comprising the 1st, 2nd, . . . , (N−2)th, and (N−1)th channel;
• and
• S4) the number in the (N−2)th channel of the slow neutron depth distribution spectrum is generated by neutrons with energy in the ranges of EN-3-EN-2, EN-2-EN-1 and EN-1-EN, wherein the contribution of the neutrons with energy in the range of EN-1-EN to the number in the (N−2)th channel of the slow neutron depth distribution spectrum is obtained by step S2, the contribution of the neutrons with energy in the range of EN-2-EN-1 to the number in the (N−2)th channel of the slow neutron depth distribution spectrum is obtained by step S3, and the contribution of the neutrons with energy in the range of EN-3-EN-2 to the number in the (N−2)th channel of the slow neutron depth distribution spectrum is equal to the number in the (N−2)th channel of the slow neutron depth distribution spectrum minus the number contributed by the neutrons with energy in the range of EN-2-EN-1 and EN-1-EN in the (N−2)th channel, and obtaining the contribution of neutrons with energy in the range of EN-3-EN-2 to the numbers in the first (N−2) channels of the slow neutron depth distribution spectrum by combining the probability of neutrons with energy in the range of EN-3-EN-2 reaching different depths within the shielding barrel obtained through simulation and the number in the (N−2)th channel of the slow neutron depth distribution spectrum, wherein the first (N−2) channels comprising the 1st, 2nd . . . , (N−3)th, and (N−2)th channel, and similarly, the slow neutron energy spectrum can be obtained after the contributions of neutrons in different energy ranges to all channels of the slow neutron depth distribution spectrum in the shielded barrel were obtained;
• and in step S1, assuming that the movement direction of all slow neutrons is perpendicular to the bottom surface of the shielding barrel of the structure for slow neutron detection, then the relationship between the ratio of the maximum depth of neutrons reaching within the shielding barrel to the width of the shielding barrel, the neutron energy and the speed of shielding barrel is described by:
• d
• max
• w
• =
• v
• n
• ·
• t
• w
• =
• v
• n
• ·
• 1
• v
• =
• 1
• v
• ·
• 2
• ⁢
• E
• k
• m
• 0
• (
• 1
• )
• wherein dmax is the maximum depth of a neutron reaching within the shielding barrel, w is the width of the shielding barrel along the movement direction, vn is the speed of a neutron, v is the speed of the shielding barrel, Ek is the kinetic energy of a neutron, and mo is the rest mass of a neutron;
• and
• when the speed of the shielding barrel remains constant, there is a monotonic positive correlation between the kinetic energy of neutrons and the ratio of the maximum depth of neutrons reaching within the shielding barrel to the width of the shielding barrel, thus the energy of slow neutrons can be distinguished based on that to obtain the spectrum of slow neutrons.