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Temps de capture des neutrons thermiques par les noyaux de bore 10 dans un scintillateur plastique dopé au bore

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Temps en µs

Ilj1 :1<= Gxuìh g*xqh fdswxuh g*xq qhxwurq gh 4 PhY gdqv xq vflqwloodwhxu sodvwltxh grsì dx eruh

Oh fkurqrjudpph vxu od jxuh :143 suìvhqwh vfkìpdwltxhphqw o*hqfkdñqhphqw ghv ìyëqhphqwv txh vxelw xq qhxwurq udslgh sìqìwudqw gdqv xq vflqwloodwhxu sodvwltxh grsì dx Eruh hw whuplqdqw vrq klvwrluh hq ìwdqw fdswxuì sdu xq qr|dx gh Eruh 431 Vhxohv ohv suhplëuhv froolvlrqv gh wkhupdolvdwlrq jìqëuhqw vx!vdpphqw gh vljqdo srxu íwuh sulvhv hq frpswh sdu od fkdñqh gh phvxuh/ f*hvw fh txl fruuhvsrqg dx slf dsshoì wkhupdolvdwlrq vxu od jxuh :1431 Oh whpsv txl vìsduh o*lpsxovlrq gh wkhupdolvdwlrq gh fhoxl txl fruuhvsrqg ã od fdswxuh gx qhxwurq hvw xqh grqqìh vwdwlvwltxh1 Lo uhsuìvhqwh oh whpsv plv sdu oh qhxwurq srxu qlu gh shuguh vrq ìqhujlh sdu froolvlrqv +q/s, ìodvwltxhv txl qh jìqëuhqw sdv dvvh} gh skrwrqv gh vflqwloodwlrq srxu txh oh vljqdo vrlw h{sorlwdeoh1 Lo frpsuhqg ìjdohphqw oh whpsv qìfhvvdluh srxu txh oh qhxwurq/ xqh irlv wkhupdolvì/ vrlw fdswxuì sdu xq qr|dx gh Eruh 431 Oh skìqrpëqh píph gh wkhupdolvdwlrq hvw uìjl sdu ohv orlv vwdwlvwltxhv hw gìshqg ìjdohphqw gh o*ìqhujlh gx qhxwurq lqflghqw1 Hq hhw/ soxv o*ìqhujlh gx qhxwurq hvw idleoh soxv od suredelolwì tx*lo vrlw fdswxuì dxjphqwh +Fi1 frxueh gh vhfwlrq h!fdfh gh uìdfwlrq +q/k, ghv qhxwurqv vxu ghv qr|dx{ gh Eruh 43,1

:1519 H!fdflwì joredoh gh gìwhfwlrq

Dq gh frpsduhu ohv h!fdflwìv gh gìwhfwlrq ghv vflqwloodwhxuv sodvwltxhv grsìv dx Eruh ã fhoohv ghv vwuxfwxuhv xwlolvdqw ghv gìwhfwhxuv ã Kìolxp 6/ xqh ìwxgh frpsdudwlyh d ìwì frqgxlwh vxu o*dwholhu D1F1F1 +Dwholhu gh Frpsdfwdjhv ghv Frtxhv hw hperxwv, gh

(n,n) (n, )α

Ilj1 :143= Fkurqrjudpph gh o*klvwrluh g*xq qhxwurq gdqv xq vflqwloodwhxu sodvwltxh grsì dx Eruh

FRJHPD od Kdjxh1 Od jìrpìwulh dgrswìh hvw od píph srxu ohv ghx{ w|shv gh gìwhfwhxuv/ hooh hvw suìvhqwìh vxu od jxuh :1441 Hq idlw/ vhxo oh pdwìuldx gh gìwhfwlrq d ìwì prglì1 Hq olhx hw sodfh gh o*Kìolxp 6 gdqv ohv vwuxfwxuhv gìwhfwulfhv/ oh vflqwloodwhxu sodvwltxh/ grsì ã 8 ( hq pdvvh gh Eruh qdwxuho d ìwì vlpxoì1

Od fhooxoh gh phvxuh hvw frqvwlwxìh gh 6 eorfv gh ;5 gìwhfwhxuv lqvwdooìv hq txlqfrqfh vxu ghx{ udqjìhv1 O*remhfwli hvw gh frxyulu o*dqjoh vrolgh pd{lpdo dq g*dyrlu xqh h!fdflwì gh gìwhfwlrq ghv qhxwurqv wkhupltxhv od soxv lpsruwdqwh srvvleoh1 Dlqvl/ oh glphqvlrqqhphqw ghv ìsdlvvhxuv gh sro|ìwk|oëqh hvw who txh od pdmrulwì ghv qhxwurqv sìqìwudqw gdqv oh glvsrvlwli vrlw wkhupdolvìh dx qlyhdx ghv gìwhfwhxuv ã Kìolxp 61 Gh soxv/ xqh ìsdlvvhxu vxssoìphqwdluh gh sro|ìwk|oëqh d ìwì sodfìh ghuulëuh ohv gìwhfwhxuv ã Kìolxp 6 dq gh vhuylu gh uì hfwhxu +doeìgr, dx{ qhxwurqv txl vhudlhqw sdvvìv xqh suhplëuh irlv vdqv lqwhudjlu dx wudyhuv ghv ghx{ udqjìhv gh gìwhfwhxuv fdu q*ìwdqw sdv vx!vdpphqw wkhupdolvìv1 Fh glvsrvlwli shuphw dlqvl g*dpìolruhu o*h!fdflwì gh gìwhfwlrq/ hq dxjphqwdqw od suredelolwì g*lqwhudfwlrq ghv qhxwurqv dyhf ohv gìwhfwhxuv1

Ohv uìvxowdwv vrqw suìvhqwv srxu ohv wurlv eorfv gh gìwhfwhxuv vxu od jxuh :1451 Od iruph hq duf gh fhufoh gh o*h!fdflwì gh gìwhfwlrq surylhqw gx idlw txh oh iþw gh gìfkhwv gdqv ohtxho od vrxufh gh qhxwurqv xqlirupìphqw uìsduwlh hvw vlpxoìh hvw prlqv orqj txh ohv gìwhfwhxuv1 Od shuwh gh frpswdjh surylhqw grqf g*xq hhw sxuhphqw jìrpìwultxh1 Gdqv fh fdv/ o*h!fdflwì gh gìwhfwlrq hvw pd{lpdoh srxu ohv gìwhfwhxuv vlwxìv dx fhqwuh gx eorf1

Gdqv oh fdv rü vhxov ghv vflqwloodwhxuv sodvwltxhv grsìv dx Eruh vhudlhqw xwlolvìv/ o*h!0 fdflwì joredoh gh gìwhfwlrq ghv qhxwurqv wkhupltxhv hvw doruv dpìolruìh sdu xq idfwhxu 433 srxu od suhplëuh udqjìh gh gìwhfwhxu hw 43 srxu od vhfrqgh udqjìh sdu udssruw dx píph glvsrvlwli xwlolvdqw ghv gìwhfwhxuv ã edvh g*Kìolxp 61 Oh skìqrpëqh gh fuhxvhphqw gh x{ dssdudñw ìjdohphqw wuëv qhwwhphqw oruv gh fhwwh ìwxgh1 Lo hvw soxv lpsruwdqw srxu ohv vflq0 wloodwhxuv txh srxu ohv gìwhfwhxuv ã jd} ã Kìolxp 6 hq udlvrq gh od soxv judqgh rsdflwì ylv ã ylv ghv qhxwurqv wkhupltxhv grqw glvsrvhqw ohv vflqwloodwhxuv sodvwltxhv grsìv dx Eruh sdu udssruw dx{ gìwhfwhxuv xwlolvdqw o*Kìolxp 61

Gdqv oh fdguh gh fhwwh ìwxgh/ vhxoh od vhqvlelolwì dx{ qhxwurqv wkhupltxhv d ìwì vlpxoìh1

:151 VLPXODWLRQ QHXWURQLTXH Ã O*DLGH GH PFQS

Ilj1 :144= Jìrpìwulh gx glvsrvlwli gh gìwhfwlrq gh o*D1F1F1 vlpxoìh sdu PFQS

Od srvvlelolwì gh gìwhfwlrq ghv qhxwurqv udslghv sdu ohv vflqwloodwhxuv sodvwltxhv q*d sdv ìwì sulvh hq frpswh1

Xqh udslgh frpsdudlvrq hqwuh ohv gìwhfwhxuv ã Kìolxp 6 hw ohv vflqwloodwhxuv sodvwltxhv grsì dx Eruh shuphw vxu oh wdeohdx :15 gh frqvwdwhu txh o*rsdflwì dx{ qhxwurqv wkhupltxhv hvw phloohxuh srxu ohv vflqwloodwhxuv txh srxu ohv gìwhfwhxuv ã edvh g*Kìolxp 61

Kìolxp 6 Vflqwloodwhxu grsì dx Eruh

Vhfwlrq h!fdfh gh fdswxuh 8733 eduq 6;33 eduqv

Qrpeuh gh qr|dx{ fleohv sdu fp :/47143

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8/8<143

#$%

Rsdflwì srxu 4 fp g*ìsdlvvhxu 65 ( ;; (

Rsdflwì srxu 9/8 fp g*ìsdlvvhxu <4/67 ( <</<< (

Wdeohdx :15= H!fdflwì gh gìwhfwlrq ghv qhxwurqv wkhupltxhv srxu ohv gìwhfwhxuv ã edvh gh vflqwloodwhxuv sodvwltxhv grsìv dx Eruh hw ohv gìwhfwhxuv ã edvh g*Kìolxp 6

Fh wdeohdx mxvwlh grqf o*dsshoodwlrq gh Eodfn Qhxwurq Ghwhfwru srxu fhv gìwhfwhxuv/ sxlvtxh <</<< ( ghv qhxwurqv sìqìwudqw gdqv fh vflqwloodwhxu qh uhvvruwhqw sdv gx gìwhf0 whxu1 Fhv uìvxowdwv rqw ìwì rewhqxv srxu xq gìwhfwhxu ã Kìolxp 6 jrq ìv ã 7 eduv hw xq grsdjh gx vflqwloodwhxu sodvwltxh hq Eruh 43 gh 4 ( hq pdvvh sdu udssruw dx sro|vw|uëqh1 Hq frqfoxvlrq/ ohv vlpxodwlrqv qhxwurqltxhv juåfh dx frgh PFQS rqw shuplv g*rs0 wlplvhu oh gldpëwuh ghv gìwhfwhxuv srxu txh od pdmrulwì ghv qhxwurqv lqflghqwv +grqw oh vshfwuh hq ìqhujlh hvw frqqxh, vrlw wkhupdolvìh hw grqf qdohphqw fdswxuìh sdu xq qr|dx gh Eruh 431 O*h!fdflwì gh gìwhfwlrq ghv qhxwurqv wkhupltxhv hvw soxv lpsruwdqwh srxu

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