Disclosure of Invention
The invention aims to solve the problem that the D-D/D-T neutron yield D (D, n) is measured by adopting an adjoint particle method at present3He or T (d, n)4The technical problem that the detector is damaged by radiation in the He reaction process along with the radiation of a plurality of neutrons and alpha particles, performance degradation is caused, and reliable beam monitoring data are obtained is very unfavorable is solved.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a neutron beam monitoring system based on a silicon carbide detector is characterized by comprising a vacuum accompanying target tube, a silicon carbide detector and an analysis processing system;
the vacuum accompanying target tube is internally provided with a target, the other end of the vacuum accompanying target tube is externally sleeved with an insulating ring, and the outer side of the insulating ring is provided with a beam limiting diaphragm;
the silicon carbide detector and one end face of one end of the vacuum accompanying target pipe, which is sleeved with the insulating ring, are arranged oppositely, and an aluminum foil is arranged between the silicon carbide detector and the vacuum accompanying target pipe;
3-6 back scattering diaphragms are arranged in the vacuum accompanying target pipe along the axial direction of the vacuum accompanying target pipe;
the backscatter diaphragms, the beam limiting diaphragms, the aluminum foils and the silicon carbide detectors are all arranged coaxially with the targets;
and the analysis processing system is connected with the silicon carbide detector and is used for analyzing and processing signals generated by the accompanying particles entering the silicon carbide detector to obtain the number of the accompanying alpha particles.
Further, the diameter of each backscattering diaphragm is sequentially reduced along the moving direction of the neutron beam.
Further, the number of the back scattering diaphragms is 6, and the diameter ratio of each back scattering diaphragm along the moving direction of the neutron beam is 20-12: 18-10: 16-10: 15-6: 7-2: 1.
further, the distance between the silicon carbide detector and the target is larger than the diameter of the beam limiting diaphragm.
Furthermore, the distance between every two adjacent backscattering diaphragms is 400-600 mm, and the distance between the backscattering diaphragm at the tail end of the moving direction of the neutron beam and the inner end face of one end, provided with the target, of the vacuum accompanying target tube is 1200-1800 mm.
Further, the length of the vacuum accompanying target tube is 1200-2000 mm; the thickness of the aluminum foil is 0.8-2 μm.
Further, the silicon carbide detector is a Schottky diode type silicon carbide detector or a P-I-N type silicon carbide detector.
Compared with the prior art, the invention has the following beneficial effects:
1. the neutron beam monitoring system based on the silicon carbide detector adopts the silicon carbide detector, and the silicon carbide detector can meet the beam monitoring requirement and can obtain rich detailed information.
2. The silicon carbide detector has 2-3 orders of magnitude higher radiation resistance to alpha particles than a silicon detector, has better radiation resistance to neutrons in a use environment, and has longer service life than the conventional Au-Si surface barrier detector.
3. The diameter of the vacuum accompanying target tube provided with 3-6 back scattering diaphragms is gradually reduced along the moving direction of the neutron beam, which is beneficial to reducing the influence of scattering alpha particles on beam monitoring.
4. The monitoring system of the invention is used for monitoring steady-state and pulse fast neutron beam current of an accelerator device, in particular to D (D, n)3He or T (d, n)4The average energy of the neutron beam generated by the He nuclear reaction is 2.5MeV or 14MeV, because of D (D, n)3He and T (d, n)4The He reaction process is accompanied with the radiation of a plurality of neutrons and alpha particles, the radiation damage to the detector is particularly obvious, and the monitoring system has extremely small damage and particularly obvious effect.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
The invention provides a neutron beam monitoring system based on a silicon carbide detector, which is used for monitoring the neutron beam which is shot to a target 8 by a D particle beam through an accelerator, and the included angle between the D particle beam and the axis of the target 8 is 90 degrees, 135 degrees or 155 degrees. As shown in fig. 1 and 2, the angle θ between the D particle beam and the axis of the target 8 is 155 °, and the angle θ includes a vacuum accompanying target tube 1, a silicon carbide detector 2, and an analysis processing system 3. Wherein, the vacuum is followed target pipe 1 one end inside and is equipped with target 8, and the outside cover of the other end is equipped with insulator ring 4 and beam limiting diaphragm 5, and beam limiting diaphragm 5 is closer to the tip that the vacuum was followed target pipe 1 than insulator ring 4, and carborundum detector 2 sets up with the vacuum is followed target pipe 1 cover one end terminal surface of establishing insulator ring 4 relatively, and carborundum detector 2 sets up with the vacuum is followed through aluminium foil 7 interval between the target pipe 1. The vacuum accompanying target tube 1 is internally provided with 3 anti-scattering diaphragms 6 along the axial direction thereof, the diameters of the 3 anti-scattering diaphragms 6 are sequentially reduced along the moving direction of the neutron beam, and the 3 anti-scattering diaphragms 6, the beam limiting diaphragm 5, the aluminum foil 7 and the silicon carbide detector 2 are all coaxially arranged with the target 8.
The analysis processing system 3 connected to the silicon carbide detector 2 includes a preamplifier 301, a main amplifier 302, a multi-channel analyzer 303, a bias power supply 304, a single-channel analyzer 305, and a scaler 306, and the analysis processing process of the analysis processing system is the same as the analysis processing method of the existing monitoring system, and is used for analyzing and processing the signal generated by the accompanying particles entering the silicon carbide detector 2, and the accompanying particles enter the silicon carbide detector 2 to generate a signal, and are analyzed and processed by the analysis processing system to obtain the accompanying alpha particle number.
In other embodiments of the present invention, if the included angle between the D-particle beam and the axis of the target 8 is 90 ° or 135 °, the monitoring system of the present invention can be directly used, and only the parameter setting is adjusted accordingly.
In addition, the number of the backscattering diaphragms 6 in the vacuum-assisted target tube 1 can be generally set to 3-6, the above embodiment is set to 3, but it is a preferable mode, if the number is set to 6, the diameter of each backscattering diaphragm 6 is also reduced in sequence along the moving direction of the neutron beam, and the preferable diameter ratio is 20-12: 18-10: 16-10: 15-6: 7-2: 1.
in addition, in order to optimally design the monitoring system, the distance between adjacent backscattering diaphragms 6 can be set to be 400-600 mm, and the distance between the backscattering diaphragm 6 at the tail end of the neutron beam current movement direction and the inner end face of the vacuum accompanying target tube 1 is set to be 1200-1800 mm. The length of the vacuum accompanying target tube 1 is set to 1200-2000 mm, and the thickness of the aluminum foil 7 is set to 0.8-2 μm.
The distance l between the silicon carbide detector 2 and the target 8 and the diameter of the beam limiting diaphragm 5 are both one of the parameters of neutron yield, and r < < l needs to be met, and the parameter setting is only an optimal scheme when the included angle theta between the D particle beam and the axis of the target 8 is 155 degrees.
The working principle of the monitoring system of the invention is as follows:
the D particle beam accelerated by the accelerator bombards on the target 8 of T-Ti, and D reacts with T to generate 14MeV neutrons and 3.5MeV alpha (alpha)4He) particles in which neutrons are generated in one-to-one correspondence with alpha particles, the emission time is the same, and the emission direction is opposite, so that the emitted neutrons can be tracked by monitoring the accompanying alpha particles. The emitted alpha particles sequentially pass through the vacuum accompanying target tubes 1 and the anti-scattering diaphragms 6, are collimated by the beam limiting diaphragm 5 and then reach the silicon carbide detector 2, and in order to reduce the influence of the scattered D particles on the silicon carbide detector 2, an aluminum foil 7 is shielded in front of the silicon carbide detector 2.
The silicon carbide detector 2 used in the invention can adopt a Schottky diode type silicon carbide detector or a P-I-N type silicon carbide detector, and the following concrete preparation methods of the Schottky diode type silicon carbide detector and the P-I-N type silicon carbide detector are provided.
The preparation method of the Schottky diode type silicon carbide detector comprises the following steps:
(1) preparing homoepitaxy on the upper surface of the N-type silicon carbide substrate by using a chemical vapor deposition method;
(2) cleaning and polishing the lower surface of an N-type silicon carbide substrate, placing the N-type silicon carbide substrate on an electron beam evaporation platform, enabling the lower surface of the N-type silicon carbide substrate to face upwards, preparing a nickel/gold electrode on the lower surface of the N-type silicon carbide substrate, carrying out vacuum annealing at 900 ℃ to obtain ohmic contact, and thickening the nickel/gold electrode by using an electroplating method;
(3) cleaning and polishing the homoepitaxy surface on the upper surface of the N-type silicon carbide substrate, placing the surface on an electron beam evaporation platform, preparing a nickel electrode on the homoepitaxy surface, obtaining a preset electrode pattern by using a mask plate, evaporating a gold layer at a wiring disc exposed by the mask plate, and thickening the gold layer to obtain a chip;
(4) and protecting the wiring position of the chip by using a mask, and sequentially manufacturing silicon oxide and silicon nitride dielectric layers on the nickel electrode.
The preparation method of the P-I-N type silicon carbide detector comprises the following steps:
(1) preparing homoepitaxy on the upper surface of the N-type silicon carbide substrate by using a chemical vapor deposition method;
(2) growing an aluminum-containing P layer on the homoepitaxy on the N-type silicon carbide substrate by using a chemical vapor deposition method, wherein the aluminum-containing P layer has an aluminum doping concentration of 2 x 1019cm-3The thickness of the P layer is 0.3 mu m;
(3) cleaning and polishing the lower surface of the N-type silicon carbide substrate, placing the lower surface on an electron beam evaporation platform, preparing a nickel/gold electrode on the lower surface of the N-type silicon carbide substrate, carrying out vacuum annealing at 900 ℃ to obtain ohmic contact on the lower surface, and thickening the ohmic contact by using an electroplating method;
(4) cleaning and polishing the homoepitaxy surface, preparing a nickel electrode with the thickness of 50nm on the cleaned and polished homoepitaxy surface by using an electron beam evaporation platform, annealing in argon at 900 ℃ to obtain ohmic contact on the upper surface, obtaining a preset electrode pattern by using a mask plate during manufacturing, evaporating a gold layer at a wiring plate, and thickening the gold layer to obtain a chip;
(5) and protecting the front surface connecting disc of the chip by using a mask plate, and sequentially manufacturing silicon oxide and silicon nitride dielectric layers on the front surface of the chip.
The neutron beam monitoring system based on the silicon carbide detector can be applied to monitoring the steady state and the pulse fast neutron beam of an accelerator device, in particular to the pulse fast neutron beam D (D, n)3He or T (d, n)4The average energy of the neutron beam generated by the He nuclear reaction is 2.5MeV or 14MeV, as shown in figure 3, the monitoring system of the invention is adopted to measure T (d, n) for a certain pulse fast neutron beam4The typical particle-coupled method is used for monitoring the neutron beam current of the He nuclear reaction. The clear observation is made in the vicinity of the 250 channels4The He particle peak, which can be used to infer neutron yield, was fitted with a Gaussian function, and the energy resolution of the silicon carbide detector was 8% calculated by dividing the full width at half maximum (FWHM) by the peak centroid, while the proton peak of the D (D, n) p product near channel 141 was also detected because the deuterium content of the tritium target increased after a period of use. FIG. 4 is a comparison of the measurement results of the Au-Si surface barrier detector and the silicon carbide detector, which are well matched, and the linear determination coefficient of the fitting result is as high as 99%. Proved by verification, the silicon carbide detector 2 can well meet the requirement of test precision, and the error is within 1%. Therefore, the monitoring system of the invention not only can meet the requirement of test precision, but also can effectively improve the radiation resistance of alpha particles, and has longer service life.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.