Fast neutron spectrometer and detector

Patent metadata

Field	Value
Publication number	US-11169285-B2
Application number	US-201916630613-A
Country	US
Kind code	B2
Filing date	Jul 9, 2018
Priority date	Jul 13, 2017
Publication date	Nov 9, 2021
Grant date	Nov 9, 2021

Abstract

A device for measuring the energy of neutrons incident in a first direction is provided. The device comprises a gas between a cathode and an anode, the anode comprising a matrix array of electron detectors, the first direction being orthogonal to the anode-cathode direction.

First claim

The invention claimed is:

1. A device for measuring the energy of neutrons incident in a first direction having an energy greater than 5 MeV, the device comprising a gas between a cathode and an anode, the anode comprising a matrix array of electron detectors, the first direction being orthogonal to the anode-cathode direction, and the device further comprising a circuit configured for:
a) measuring the number, the positions, and the times of arrival of electrons;
b) determining, from the positions and times of arrival, the angle θ′ between the first direction and the direction of an ionized trace left by a nucleus of said gas after collision with one of the neutrons; and
c) determining the energy of the neutron from the number of electrons and the angle θ′.

2. The device as claimed in claim 1 , wherein said circuit is configured to, in step c):
determine, from the number of electrons N e , the ionization energy of the trace E i , via the relationship E i =N e *ΔE, where ΔE is the energy required to create an electron-ion pair in the gas; and
determine the energy E n of the neutron via the relationship:

E
n

=

A
⁢

⁢

E
P

cos
2

⁢

θ
′

wherein E p respects the relationship E p =E i /Q(E i ), Q(E i ) being the nuclear recoil quenching factor associated with the ionization energy of the trace E i , and
A is a constant coefficient dependent on the ratio between the mass of the neutron and the mass of said nucleus.

3. The device as claimed in claim 1 , further configured for measuring the energy of neutrons incident in a second direction, the second direction being parallel to the anode-cathode direction, wherein said circuit is configured to:
a) measure the number, the positions, and the times of arrival of the electrons;
b′) determine, from the positions and times of arrival, the angle θ between the second direction and the direction of an ionized trace left by a nucleus of said gas struck by one of the neutrons; and
c′) determine the energy of the neutron from the number of electrons and the angle θ.

4. The device as claimed in claim 3 , wherein said circuit is configured to:
determine, from the number of electrons N e , the ionization energy of the trace E i , via the relationship E i =N e *ΔE, where ΔE is the energy required to create an electron-ion pair in the gas; and
determine the energy E n of the neutron via the relationship:

E
n

=

A
⁢

⁢

E
P

cos
2

⁢
θ

wherein E p respects the relationship E p =E i /Q(E i ), Q(E i ) being the nuclear recoil quenching factor associated with the ionization energy of the trace E i , and
A is a constant coefficient dependent on the ratio between the mass of the neutron and the mass of said nucleus.

5. The device as claimed in claim 3 , further comprising a rotary holder having an axis of rotation orthogonal to the first direction and to the second direction, a rotation of one quarter of a revolution about the axis of rotation making the device pass from an orientation in which the first direction is parallel to the direction of incidence of the neutrons to an orientation in which the second direction is parallel to the direction of incidence of the neutrons.

6. The device as claimed in claim 1 , wherein the cathode and the anode are located on opposite sides of a cylindrical field cage arranged to produce a uniform electric field.

7. The device as claimed in claim 6 , wherein the field cage has a diameter between 10 and 35 cm and a length between 15 and 35 cm.

8. The device as claimed in claim 1 , wherein the gas is a mixture of helium 4 and of CO 2 comprising between 4 and 6% CO 2 .

9. The device as claimed in claim 1 , wherein the precision of the measurement of the times of arrival of the electrons is between 16 and 40 ns.

10. A method for measuring the energy of neutrons incident in a direction having an energy greater than 5 MeV, the method comprising:
a) providing a gas between a cathode and an anode, the anode comprising a matrix array of electron detectors;
b) orienting the anode-cathode direction orthogonal to the direction of incidence of the neutrons;
c) measuring the number, the positions, and the times of arrival of electrons coming from gas on the matrix array;
d) determining, from the positions and times of arrival, the angle θ′ between the direction of incidence of the neutrons and the direction of an ionized trace left by a nucleus of said gas after collision with one of the neutrons; and
e) determining the energy of the neutron from the number of electrons and from the angle θ′.

11. The method as claimed in claim 10 , wherein step e) comprises:
determining, from the number of electrons N e , the ionization energy of the trace E i , via the relationship E i =N e *ΔE, where ΔE is the energy required to create an electron-ion pair in the gas; and
determining the energy E n of the neutron via the relationship:

E
n

=

A
⁢

⁢

E
P

cos
2

⁢

θ
′

wherein E p respects the relationship E p =E i /Q(E i ), Q(E i ) being the nuclear recoil quenching factor associated with the ionization energy of the trace E i , and
A is a constant coefficient dependent on the ratio between the mass of the neutron and the mass of said nucleus.

12. The method as claimed in claim 10 , further comprising successively:
b′) orienting the anode-cathode direction parallel to the direction of incidence of the neutrons; and
f) implementing steps c), d) and e).

Assignees

• Centre Nat Rech Scient

Inventors

• Santos Daniel
• Guillaudin Olivier
• Sauzet Nadine

Classifications

• G01T3/008

  using an ionisation chamber filled with a gas, liquid or solid, e.g. frozen liquid, dielectric (G01T3/006 takes precedence) · CPC title

• G01T3/001 Primary

  Spectrometry · CPC title

• G01T5/06 Primary

  Bubble chambers · CPC title