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神龙一号装置光激中子源用于中子共振测温可行性研究

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中子共振测温与传统的测温技术相比,具有很多优势由于其短时间响应特性和中 子的强穿透性,可用于冲击波温度测量但国内尚无高强度的白光中子源,无人研究中 子共振测温技术为研究神龙一号装置用于中子共振测温的可行性,本文采用mc模拟 软件nuka和mcnPS,做了如下一些工作: 第一!根据神龙一号装置加速的电子束流特性和采用的韧致辐射叠层担靶,计算得 到目前神龙一号装置的光中子产额为1.34X100每电子脉冲(mcnPS)和1.55xl0,.每 电子脉冲(fluka),为连续谱分布,在0.1一IMeV间出现峰;脉冲宽度为85ns;在角度 上基本呈各向同性分布 第二!计算了不同材料的辐射靶在神龙一号装置电子束流特性下的中子产额,均在 10.2量级左右,得到天然铀和天然针金属靶的中子产额大于其他材料,其中天然铀的产 额最高铀靶中子产额随厚度的增加而增加,在scm左右趋于饱和,达7.47x1012每电 子脉冲 第三!计算被!重水和石蜡三种慢化剂对光中子的慢化结果,得到慢化叠层担靶产 生的光中子,使leV一100eV间的中子强度最大的慢化剂厚度分别为10一12cm!12一16cm 和2一2.scm,由慢化导致的脉冲时间展宽在次微秒到微秒两级,石蜡导致的脉冲时间展 宽将比其他两种小一个数量级对铀靶光中子的最佳慢化厚度为2.5一3cm 第四!计算了叠层担靶和7cm厚的铀靶产生的光中子经过最佳厚度的石蜡慢化后 穿过Icm厚的钨片的透射谱,均可观测到-82W的21.O6ev共振峰计算得到的离靶sm 处的透射谱显示:叠层担靶的透射谱在共振峰附近的计数为几到几十n*m一p.一难 在实验上测量出共振峰:铀靶的透射谱在共振峰附近的计数为5一6xl护n*m-2*ps一-, 可以从实验上测量到共振峰 第五!根据洛斯阿拉莫斯测量冲击温度的装置,计算神龙一号装置采用7cm的铀 靶产生的光中子经过3cm的石蜡慢化后透过M样本的透射谱,可以观测到.82w的 21.06eV共振峰和其展宽的趋势,在距靶sm处的计数还高于洛斯阿拉莫斯的情形 第六!为验证计算的结果,实验测量了神龙一号装置产生的光中子产额,计算结果 显示产额约为1012个每电子脉冲,与计算结果基本符合 根据以上的计算和实验的验证,证明神龙一号装置采用7cm的铀靶,加上最优的 慢化,是可以用于中子共振测温的 关键词:中子共振测温!神龙一号!Mc模拟!可行性研究!MCNPS!FLUKA神龙一号装置光激中子源用于中子共振测温可行性研究 Abstraet ThetemPeraturemeasuremeniusingneutronresonaneesPectrumhasmanyadvantages eomP硕ngtraditionaltee俪quesoftemPeraturemeasuremeni.Thisteehniquecantakethe shocktemPeral泊re,beeauseofitsshortresPondingtimeandthePenetratingofneutron.But there15nooneeanstu勿thisteehniquewiththeabseneeofhighstrengthwhiteneutron source.ToinvestigatethefeasibilityofneutronresonaneetemPeraturemeasuremeniusing Dragon一I,thisPaPerdoesmanyworksasfollowsthroughMCsimulationcodeMCNPSand FLUKA二 Firstl又theeomputedneutronproduetion151.34x100pereleetronpulse(MeNPS)and 1.ssx一0pereleetronpulse(rLu以),aeeoraingtotheeleetronbeameharaeteristiesof nowstateandusingthemulti一layerTatarget.ThePhoto一neutronhasaeoniinuousenergy sPeetrumwithaPeakbetween0.IMeVandIMeV,andanisotroPydistribution.ItsPulse width1585ns. Secondly,theneutronProduetionsofmanymaterialshadbeeneomPutedwiththe eleetronbeameharaeteristiesofnragon一x,theresultsdisp一盯theyare1012ma助itudes,and theProduetionofnaturaluraniumandnaturalthoriumarehigherthantheothers.The Produetionofnaturaluraniumeanbeelilianeedwiththeinereasingoftargetthie玩ess,and 即proachasaturationatscmofthethie知esswithavalueof7,47XlolZpereleetronpulse. 仆irdly,themoderationofPhoto一eutronwiththreemoderators一beryllium,heavywater andParaffin一showsthattheoPtimalthicknessofmoderatorstogainmaximumresonance neutron(from1eVto100eV)strengthare10一1Zem!12一16emandZ一2.sem,resPeetively. AndthebroadeningofneutronPulsewidtheausedbymoderation15fromsub一microseeondto mieroseeond,thebroadeningofParaffin15onemagnitudelowerthantheothers.TheoPtimal thieknessOfParaffinforneutronsProdueedbynaturaluranium15be七刀een2.semand3.oem. Fourthl苏thetransmissionsPectrumofneutronsProducedbymulti一layerTatargetand 7emUtargetPenetratingthrougha1emtUngstenlayer砍eroPtimalmoderationofParaffin hadbeensimulated,fromwhiehtheresonaneediPof21.06eVeanbeseen.Buttheeounts aroundresonaneedipfrommulti一l盯er几啤etare加mseveraltoseve耐tensn*cm.2*s一l, andit15diffieulttomeasuretheresonaneediPonexPeriment.Fortunately,theeountsfromU t哩etares一6x2oZn*em.2*.一l,theresonaneedipeanbemeasuredone却eriment. Fifthly,theneutrontransmissionsPectrumofDragon一1using7emUtargetand3em ParaffinmoderatorPassingthroughtheMosamPlehadbeenealeulated,aeeordingtothe神龙一号装置光激中子源用于中子共振测温可行性研究 samPlesetusedbyLosAlamos.TheZI.06eVresonaneePeakof182wanditsbroadening trendeanbeseen,andtheeountsofDragon一115higherthanLosAlamos. Sixthiy,theneutronProductionhadbeenmeasuredusingsilveractivationdeteetor,in ordertocheekuPthesimulatedresult.Themeasuredneutronproduction15aroundlolZper eleetronPulse,aceordswiththesimulatedresult. TheeonelusioneanbeseenthattheDragon一1eanbeusedfortemPeraturemeasurement usingneutronresonaneesPectrumwitha7emUtargetanda3emParaffinmoderator,through theworksabove. KeyWbrds:TemPeraturemeasuremeniusingneutronresonaneesPectrum!Dragon一I! MCsimulation!feasibilitystudy!MCNPS!FLUKA 111 人.神共一号装置光弹中珊用型鱼些鲤迥型里色一一一一一 目录 第一章!弓}言..................................................................................................................1 第二章!神龙一号装置光中子特性模拟.........,............,........................,.....,.,6 2.1!蒙特卡罗方法介绍及模拟光中子的可行性研究[22!231......................................6 2.2!神龙一号光中子特性.................................................................................................8 2.2.1!计算模型与物理参数设置......................................................................................8 2.2.2!神龙一号装置光中子产额..................................,.............................................9 2.2.3!神龙一号装置光中子能谱......................................................................................9 2.2.4!光中子脉冲特性...............................................................................,..............10 2.2.5!光中子角分布........................................................................................................n 2.2.6!韧致辐射本底特性................................................................................................12 2.3!加速器大厅中子空间分布.......................................................................................14 第三章!神龙一号装置用于中子共振测温可行性初步研究........................................18 3.1!多材料光中子产额计算...........................................................................................18 3.1.1!单层靶与叠层靶的光中子产额比较....................................................................18 3.1.2!多种材料的光中子产额比较................................................................................18 3.1.3!铀靶光中子产额随厚度的变化............................................................................20 3.2!光中子慢化计算.......................................................................................................20 3.2.1!中子慢化规律[29!30].........................................................................................20 3.2.2!担靶光中子慢化计算及结果................................................................................22 3.2.3!铀靶光中子慢化计算与结果................................................................................24 3.3!中子透射谱计算.......................................................................................................25 3.3.1!担靶中子透射谱....................................................................................................26 3.3.2!铀靶中子透射谱....................................................................................................29 3.4!用于中子共振测温可行性分析...............................................................................32 3.4.1!洛斯阿拉莫斯应用中子共振测温的装置及结果................................................32 3.4.2!对比计算模型........................................................................................................33 3.4.3!中子透射谱............................................................................................................34 3.4.4!时间道宽和慢化剂慢化时间的影响....................................................................35 3.4.5!从理论推导的中子注量简单分析........................................................................36 3.5!结论....................................................................................................,................37 第四章!神龙一号中子产额测量....................................................................................39 4.1!活化法及等效率测量原理.......................................................................................39 4.1.1!活化法基本原理....................................................................................................39 4.1.2!等效率测量原理....................................................................................................40神龙一号装置光激中子源用于中子共振测温可行性研究 4.2.1!坪特性测量.................,....................................................................................42 4.2.2!分辨时间测量...............................................................................................,..42 4.2.4!中子灵敏度测量....................................................................................................44 4.3!中子产额测量...........................................................................................................47 4.3.1!灵敏度修正............................................................................................................47 4.3.2!测量计数及数据处理............................................................................................49 第五章!总结与展望........................................................................................................50 致谢..............................................................................................................................52