中子蒸发与裂变碎片关联性研究

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1、EffectofFrictiononNeutronEmissioninFissionofHeavynucleiMay16-12,2006Shanghai,ChinaJing-DongBao,YingJiaDepartmentofPhysics,BeijingNormalUniversity1.Theparameterization2.Stochasticcalculationforangulardistributionoffissionfragment3.Effectoffrictiononneutronemiss

2、ion4.Summary1.{c,h,α}parameterizationofnuclearshapewherecistheelongation,i.e.,thedistanceoftwocentersoffragments;histheneckparameter;αistheasymmetricalparameter..AsetofLangevinequationstestparticles:.StochasticRunge-KuttaalgorithmTime-dependentfissionrate（　　）t

3、estparticlespassingoverthesaddlepointfirsttimetestparticlespassingoverthesaddlepointmulti-timesJ.D.Bao,Y.Jia:PRC69,027602(2004).passingoverthescission*DuringtheMonte-Carlosimulatingstep,wecomparetimestepandhalfdecayperiodofneutronisarandomnumberbetween0and1，th

4、enemissionofaneutron;*Thenuclearinertialenergydecreaseswiththeemissionofneutron。AngulardistributionoffissionfragmentEffectiverotationalmomentdefinedatsaddle-pointandisalwaysarandomvariable!isthetemperatureatthesaddlepoint,calculatedbyLangevinsimulation3.One-bo

5、dywellpluswindowfrictioniswindowareaThewellformulaisappliednearthegroundstate;thewindowformulaisaddressedwhenthesystemarrivesatthesaddlepoint.Ingeneral,wehave:Neutronemissionpre-scissionforTh224Otherquestions:Thetwo-dimensionalfissionrateis(20-30%)largerthanth

6、atofonedimensioniftheneckisconsidered;DependenceofTransportcoefficientsontemperatureneedstoconsiderinfurtherwork.Thesaddle-pointdriftsintoinsidewellandthefissionbarrierdecreaseswiththeemissionofneutron4.SummaryThelimitationofdiffusionmodel：itisnotsuitabletoqua

7、si-fissionproblem,becauseanequilibriumshapeisnecessary.Underdampedmotionbeforesaddle-pointandoverdampedfromsaddle-pointtoscissionpoint;(3)Temperatureatsaddle-pointdeterminedbythecaseoftestparticleleavingsaddlepointlasttime;(4)Oscillatingtimearoundsaddle-pointi

8、sthelongestdynamicaltimescale,butitisinfluencedstronglybyneutronemission.Thanks!