The plastic scintillant of doping neutron-sensitive material boron and the method for measurement thermal neutron thereofTechnical field
The invention belongs to actinometry field, the plastics being specifically related to a kind of neutron-sensitive material boron that adulterates dodgeBright body and the method measuring thermal neutron thereof.
Background technology
Plastic scintillant is typically done substrate by polystyrene, is blended into other organic additive and makees scitillating material, thenMaking plus Wavelength shifter, it has, and detection efficient is high, photoyield is high, and signal pulse width is narrow, machinabilityCan good, adaptive capacity to environment is strong, stable mechanical performance, the advantage such as with low cost and be widely used in radiation and surveyIn amount work, but owing to the main component of plastic scintillant is C, H, O, they cut with neutron interactionFace is relatively low, typically cannot be directly used to the monitoring field of neutron, to this end, the period of the day from 11 p.m. to 1 a.m also needs doping or embedding in Tan CeEnter other materials and export to increase optical signal, just can be used for soon as embedded one layer of ZnS:Ag film at plastic scintillantNeutron measurement.
Owing to ZnS:Ag film is light tight, the method therefore embedding ZnS:Ag film in plastic scintillant can be lostA lot of photons, causes detection efficient and sensitivity to decline.
Summary of the invention
Present invention aims to problems of the prior art, it is provided that one can be used for thermal neutronThe plastic scintillant of the doping neutron-sensitive material boron measured, and use this boron-doping Plastic scintillation bulk measurementThe method of thermal neutron.
Technical scheme is as follows: the plastic scintillant of a kind of neutron-sensitive material boron that adulterates, by polyphenylSubstrate made by ethylene, is blended into scitillating material and Wavelength shifter, wherein, mixes and contain in described polystyrene substrateThe raw material of boron, the incorporation of the raw material containing boron accounts for the 5%-10% of plastic scintillant gross mass.
Further, the plastic scintillant of the neutron-sensitive material boron that adulterates as above, wherein, described containsOrganoboron compound chosen by the raw material having boron, during preparing plastic scintillant by organoboron compound byCorresponding proportion mixes in polystyrene substrate and is sufficiently mixed.
Boron-doping plastics are dodged by the method for the Plastic scintillation bulk measurement thermal neutron of above-mentioned doping neutron-sensitive material boronBright body is connected with photomultiplier tube, and is sealed in opaque shell, forms probe；Probe is placed inMeasure in environment, incident neutron and the raw material generation nuclear reaction containing boron in plastic scintillant, nuclear reactionWhole energy losses in boron-doping plastic scintillant, are made material be in excited state, de excitation by the alpha-particle releasedTime release photon, photon numbers be proportional to alpha-particle loss energy, i.e. the quantity of nuclear reaction, also with regard to direct ratioIn incident neutron number, the record photomultiplier tube electric impulse signal amount in the unit interval can calculate neutronFluence, thus realize the measurement of neutron fluence, it is multiplied by fluence-dose conversion coefficient and can get neutron DE.
Beneficial effects of the present invention is as follows: neutron sensitive material boron is mixed in plastic scintillant by the present invention,Neutron can effectively be measured by the material of boracic.The side of this employing boron-doping Plastic scintillation bulk measurement thermal neutronMethod is cheap, applied range, and its detection efficient is far above embedding ZnS:Ag film in plastic scintillantMethod.
Accompanying drawing explanation
Fig. 1 is boron-doping plastic scintillant structure and nuclear reaction schematic diagram；
Fig. 2 is the schematic diagram of plastic scintillator detector.
Detailed description of the invention
With embodiment, the present invention is described in detail below in conjunction with the accompanying drawings.
The key component of scintillator detector has scintillator, collection optical system, the phototube of detection lightPart (such as photomultiplier tube), and give the potentiometer of each electrode power supply of photomultiplier tube, they are closed in oneIn individual opaque shell, being referred to as probe, this belongs to the known features of this area.Wherein plastic scintillantPrimary structure is typically done substrate by polystyrene, is blended into other organic additive and makees scitillating material, adds shiftingRipple agent is made, and these materials are not had an effect with thermal neutron containing C, H, O, and the most general plastics dodgeBright body cannot be directly used to measure thermal neutron.
Neutron can will embed a certain proportion of neutron-sensitive with a lot of material generation nuclear reactions in plastic scintillantAfter material, incident neutron reacts, and reaction can pass to plastic scintillant material makes it excite, during de excitationReleasing photon, photon is transferred to photomultiplier tube through Wavelength shifter, by follow-up electricity after being converted into the signal of telecommunication and amplifyingRoad record.Photon numbers is directly proportional to the energy of absorbed, and the reaction of nuclear reaction can be certain, number of photonsAmount is the most just proportional to number of neutrons.
As it is shown in figure 1,10N+ is there is in B with neutron10B=α+7The nuclear reaction of Li+2.792Mev,10B and neutronReaction cross-section is higher, and the cross section of thermal neutron is 3840 targets, therefore contains10During the material of B can effectively be measuredSon, method is while preparing former plastic scintillant, adds the microgranule of boracic.The present invention is at Plastic scintillationMixing the raw material containing boron in the polystyrene substrate of body, the incorporation of the raw material containing boron accounts for plastic scintillantThe 5%-10% of gross mass.The described raw material containing boron can choose organoboron compound, such as trialkylborane,Hydroxyl borine etc., is mixed the raw material containing boron in polystyrene substrate by corresponding proportion and is sufficiently mixed.
As in figure 2 it is shown, boron-doping plastic scintillant 1 is connected with photoconduction 2, the most again with photomultiplier tubeConnecting, and be sealed in opaque shell, form probe, in figure, K is photocathode, and F is for focusing onPole, D1～D10For dynode, A is anode.Probe is placed in measurement environment, incident neutron and plasticsThe raw material generation nuclear reaction containing boron in scintillator, due to the extremely short range of alpha-particle, nuclear reaction is releasedAlpha-particle can make material be in excited state by whole energy losses in plastic scintillant, will necessarily during de excitationReleasing photon, photon numbers is proportional to the energy of alpha-particle loss, and i.e. the quantity of nuclear reaction, is the most just proportional toIncident neutron number, thus realize the measurement of neutron fluence, it is multiplied by fluence-dose conversion coefficient and can get neutron agentThe Radiation Protection Quantities such as amount equivalent.
Embodiment
Boron-doping plastic scintillant is made substrate by the polystyrene mixing the raw material containing boron, be blended into scitillating material andWavelength shifter forms, and concrete preparation method is to make substrate with the polystyrene of the trialkylborane containing corresponding proportionAdd the first solute and three ditolyls and the second solute PoPo post polymerization are made boron-doping plastic scintillant block, thenCleaved molding obtains boron-doping plastic scintillant.
As it is shown in figure 1, incide the reaction occurred in boron-doping plastic scintillant by neutron；By boron-doping plasticsScintillator and collection optical system, the photoelectric device (such as photomultiplier tube) of detection light, and give photomultiplier transitThe potentiometer managing each electrode power supply is enclosed in an opaque shell, forms probe, internal structure of popping one's head inAs shown in Figure 2.Being placed in by probe in measurement environment, incident neutron occurs with the boron in boron-doping plastic scintillantReaction, nuclear reaction release alpha-particle by whole energy losses in boron-doping plastic scintillant, extreme portions energyPassing to the first solute makes it excite three ditolyls, launches the fluorescence of wavelength 350-400nm during its de excitation,Second solute PoPo absorbs the light that this fluorescence emission wavelengths is longer, and main peak position wavelength is at 423nm, and photon is through lightLead and be transferred to photomultiplier tube, amplified by signal amplification circuit and record after being converted into electric impulse signal, and thisThe quantity of individual electric pulse is proportional to the neutron number of times with boron generation nuclear reaction, is the most just proportional to incident neutronQuantity, the electric impulse signal amount of record unit time can calculate the fluence of neutron, it is achieved neutron fluenceMeasure.The number of pulses that one neutron ultimately forms and the ratio of boron-doping, photomultiplier tube model and photoelectricity timesIncrease pipe duty relevant, determine and photomultiplier tube circuit in boron-doping ratio-dependent, photomultiplier tube modelIn the case of having designed, can simulate by the method for Monte Carlo and calculate and come by the method for experimental verificationArrive.
Obviously, those skilled in the art can carry out various change and modification without deviating from this to the present inventionBright spirit and scope.So, if the present invention these amendment and modification belong to the claims in the present invention andWithin the scope of its equivalent technology, then the present invention is also intended to comprise these change and modification.