Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra Determination

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A.; Zaka i-Issou ou, A.-A.; Fallo , M.; Po a, A.; Algo a, A.; Tain, J.L.; Valencia, E.; Rice, S.; Guadilla, V.; Ag amun , J.; Äys ö, Juha; Bow y, M.; Bui, V.M.; Caballe o-Folch, R.; Cano-O , D.; Co mon, S.; Cucoanes, A.; Elomaa, Viki-Veikko; E onen, Tommi; Es é ez, E.; Es ienne, M.; Fa elly, G.F.; F aile, L.M.; Ganioglu, E.; Ga cia, A.; Gelle ly, W.; Gomez-Ho nillos, M.B.; Go lyche , V.; Hakala, Jani; Jokinen, A i; Jo dan, M.D.; Kankainen, Anu; Konde , F.G.; Lebois, M.; Ma inez, T.; Mendoza, E.; Molina, F.; Mon ane , A.; Moo e, Iain; Náche , E.; O igo, S.; Pen ilä, Heikki; Pé ez, A.B.; Podolyak, Zs.; Regan, P.H.; Rissanen, Juho; Rubio, B.; Shiba, T.; Sonzogni, A.; Vedia, V.; Webe , Ch is ine; Wilson, J. B iz, J. A., Zaka i-Issou ou, A.-A., Fallo , M., Po a, A., Algo a, A., Tain, J.L., Valencia, E., Rice, S., Guadilla, V., Ag amun , J., Äys ö, J., Bow y, M., Bui, V.M., Caballe o-Folch, R., Cano-O , D., Co mon, S., Cucoanes, A., Elomaa, V.-V., E onen, T., . . . Wilson, J. (2016). To al Abso p ion Spec oscopy o Fission F agmen s Rele an o Reac o An ineu ino Spec a De e mina ion. Ac a Physica Polonica B, 47(3), 755-762. h ps://doi.o g/10.5506/APhysPolB.47.755 2016 Vol. 47 (2016) ACTA PHYSICA POLONICA B No 3 TOTAL ABSORPTION SPECTROSCOPY OF FISSION FRAGMENTS RELEVANT FOR REACTOR ANTINEUTRINO SPECTRA DETERMINATION∗ J.A. B iza, A.-A. Zaka i-Issou oua, M. Fallo a, A. Po aa A. Algo ab,c, J.L. Tainb, E. Valenciab, S. Riced, V. Guadillab J. Ag amun b, J. Äys öe, M. Bow yd, V.M. Buia R. Caballe o-Folch , D. Cano-O g, S. Co mona, A. Cucoanesa V. Elomae, T. E onene, E. Es é ezb, M. Es iennea G.F. Fa ellyd, L.M. F aileh, E. Ganioglui, A. Ga ciag W. Gelle lyd, M.B. Gomez-Ho nillos , V. Go lyche J. Hakalae, A. Jokinene, M.D. Jo danb, A. Kankainene F.G. Konde j, M. Leboisk, T. Ma inezg, E. Mendozag F. Molinab, A. Mon ane b, I. Moo ee, E. Náche l, S. O igob H. Pen iläe, A.B. Pé ezb, Zs. Podolyakd, P.H. Regand J. Rissanene, B. Rubiob, T. Shibaa, A. Sonzognim,n, V. Vediah C. Webe e, J. Wilsonk o he IGISOL Collabo a ione aSUBATECH, CNRS/IN2P3 — Ecole des Mines de Nan es Uni e si é de Nan es, Nan es, F ance bIFIC, CSIC — Uni e si y o Valencia, Valencia, Spain cMTA ATOMKI, Deb ecen, Hunga y dUni e si y o Su ey, Guild o d, UK eIGISOL — Uni e si y o Jy äskylä, Jy äskylä, Finland Uni e si a Poli ecnica de Ca alunya, Ba celona, Spain gCIEMAT, Mad id, Spain hUni e sidad Complu ense de Mad id, Mad id, Spain iDepa men o Physics, Is anbul Uni e si y, Is anbul, Tu key jA gonne Na ional Labo a o y, A gonne, USA kIns i u de Physique Nucléai e, O say, F ance lIns i u o de Es uc u a de la Ma e ia (CSIC), Mad id, Spain mB ookha en Na ional Labo a o y, Up on, USA nNa ional Physical Labo a o y, Tedding on, UK (Recei ed Decembe 18, 2015) ∗P esen ed a he XXXIV Mazu ian Lakes Con e ence on Physics, Piaski, Poland, Sep embe 6–13, 2015. (755) 756 J.A. B iz e al. The con ibu ion o each ission agmen o he eac o an ineu ino spec a was de e mined using he summa ion me hod based on he exis ing in o ma ion on ission yields and decay da a con ained in nuclea da abases and he eac o e olu ion code MURE. The be a decay o some o he main con ibu o s has been s udied using he To al Abso p ion Spec oscopy (TAS) echnique du ing wo expe imen al campaigns a he IGISOL acili y, in Jy äskylä (Finland). Resul s on he decay o 92Rb, he mos impo an con ibu o in he 4–8MeV ene gy egion a e epo ed. The s a us o he analysis o he second expe imen is p esen ed as well. DOI:10.5506/APhysPolB.47.755 1. In oduc ion Nuclea eac o co es a e in ense sou ces o an ineu inos, o ins ance, in s anda d 900 MWe P essu ized Wa e Reac o s (PWR) he e a e p oduced a ound 1021 an ineu inos pe second. This huge lux allows o s udying neu ino physics despi e he low in e ac ion c oss sec ion ha hose elu- si e pa icles o e o he expe imen alis s. The an ineu ino de ec ion is usually done h ough he in e se be a decay p ocess in which he incoming an ineu ino in e ac s wi h a p o on p oducing a neu on and a posi on νe+p→n+e+.(1) This mechanism is used in eac o an ineu ino expe imen s such as Double Chooz (F ance) [1], Daya Bay (China) [2] and RENO (Sou h Ko ea) [3]. Two de ec o s a e used in hose expe imen s, one nea he eac o o measu e he emi ed an ineu ino spec a and one a ≈1–2 km o measu e he oscilla ed an ineu ino spec a. In his way, he magni ude o he oscilla ion pa am- e e θ13 is s udied. Howe e , he Double Chooz expe imen ook da a only wi h he a de ec o om 2011 o Decembe 2014 when he nea de ec o was inally ins alled and ope a i e. Fo his eason, he da a analysis o es- ima e he oscilla ion pa ame e θ13 demanded an al e na i e de e mina ion o he emi ed an ineu ino spec a. A smalle a e o emi ed an ineu inos han p edic ed was ound o di e en expe imen s loca ed a sho dis ances om he eac o co e, whe e no neu ino oscilla ion is expec ed o occu . This is he so-called “ eac o anomaly” [4] and mo i a ed he sea ch o a new ype o neu inos, he s e ile neu inos. The esul s o he h ee neu ino expe imen s [1–3] p esen ed an unex- plained dis o ion in he posi on ene gy spec a in he 4–8MeV egion [5]. I is e iden when plo ing he measu ed e sus expec ed a io o he nea de- ec o s (excep o Double Chooz as he nea de ec o was no a ailable ye ) whe e no oscilla ion is supposed o occu . The o igin o his dis o ion emains o be cla i ied. Fo hese wo main easons, an al e na i e de e mi- na ion o he emi ed an ineu ino spec a om a nuclea eac o is needed. To al Abso p ion Spec oscopy o Fission F agmen s Rele an o Reac o . . . 757 Usually, he e a e wo ways o accomplish such ask, i s , he con e - sion me hod [6], in which he measu ed in eg al be a spec a a e con e ed in o an ineu ino spec a unde ce ain assump ions. Second, he summa- ion me hod [7], in which one adds he indi idual con ibu ions om each decay b anch o he ission agmen s. The la e me hod allows o calcu- la ing eac o an ineu ino spec a when no in eg al be a spec um has been measu ed and i is he only me hod use ul as a p edic i e ool o u u e nuclea eac o s. Fo hese easons, ou g oup decided o use he summa- ion me hod as a ool o calcula ing an ineu ino spec a. Howe e , he summa ion me hod equi es eliable in o ma ion on he be a decay o , a leas , he mos ele an con ibu o s. This means ha he in o ma ion on he nuclea da abases should be eliable in e ms o Q alues, be a eeding dis ibu ions, ypes o be a ansi ion (allowed, 1s o bidden, 2nd o bidden, e c.) and ission yields o each issionable iso ope. 1.1. Pandemonium e ec and o al abso p ion spec oscopy echnique High esolu ion spec oscopy based on HPGe de ec o s is he main ech- nique used o s udying be a decay p ope ies o nuclei h ough he measu e- men o he gamma ays om he de-exci a ion o he daugh e nucleus. The low e iciency o hese de ec o s o he de ec ion o high-ene gy gamma- ays and he high agmen a ion o he de-exci a ion pa hs om le els loca ed a high exci a ion ene gies make di icul he measu emen o be a eeding a high exci a ion ene gies. This expe imen al di icul y was i s unde lined by Ha dy e al. [8] and i is usually e e ed o as Pandemonium e ec . I causes an unde es ima ion o eeding o le els a high exci a ion ene gies and an o e es ima ion o le els a low exci a ion ene gies. As a conse- quence, he a e age gamma ene gies a e unde es ima ed and he a e age be a and neu ino ene gies a e o e es ima ed in he nuclea da abases o nuclei which we e s udied using High Resolu ion Spec oscopy echniques. The usual way o o e come his e ec is he To al Abso p ion Spec oscopy (TAS) echnique. Using a la ge scin illa ion c ys al o high in insic e iciency and ideally co e ing 4πsolid angle, one is sensi i e o he ull de-exci a ion cascade and, he e o e, he be a eeding a he han he indi idual gamma ays. The impac o his e ec on he calcula ion o he eac o decay hea due o he gamma and be a adia ion emi ed a he eac o co es was p esen ed in Re . [9]. Those TAS esul s on he decay o 102,104−107Tc, 105Mo, and 101Nb nuclei [9,10] we e ound ema kably ele an in he de e mina ion o he eac o an ineu ino spec a as well as i was p esen ed in Re . [11]. Figu e 2 o ha a icle shows he a io o he an ineu ino spec a calcula ed wi h and wi hou he new TAS da a o he ou main issionable iso opes. 758 J.A. B iz e al. The impac was up o 8% o 239,241Pu, a ound 3.5% o 238U and 1.5% o 235U in he ene gy ange om 0 o 6 MeV. One obse es as he new TAS esul s displace some s a is ics in he ene gy spec a om high neu ino ene gies (2< E < 6 MeV) o lowe ene gies (E < 2MeV). 2. Expe imen s An e alua ion o he mos ele an con ibu o s o he eac o an ineu- ino spec a was done using he summa ion me hod [7], he nuclea da a conside ed in Re . [11] and he MCNP U ili y o Reac o E olu ion (MURE) [12]. In he simula ions, i was assumed a 450 days i adia ion pe iod and a s anda d uel composi ion o PWR eac o s o 52% 235U, 33% 239Pu, 6% 241Pu and 8.7% 238U. The esul s a e shown in Table I and we e al eady published in Re . [13]. They indica ed 92Rb as he mos ele an case in he ene gy egion o 4–8MeV wi h special impo ance a 6–8MeV. The mos easible cases om he expe imen al poin o iew among hose shown in Table I we e selec ed unde he c i e ia o p oduc ion yields and decay p ope ies. Two expe imen s we e ca ied ou de o ed o s udy hem oge he wi h o he cases o ele ance o eac o decay hea calcula ions. TABLE I Main con ibu o s o a s anda d PWR an ineu ino ene gy spec um compu ed wi h he MURE code [12], coupled wi h he lis o nuclea da a gi en in Re . [11], assuming a uel composi ion o 52% 235U, 33% 239Pu, 6% 241Pu and 8.7% 238U, o a 450 day i adia ion pe iod and using he summa ion me hod desc ibed in [11]. Values a e gi en in pe cen age ( able om Re . [13]). 4–5MeV 5–6MeV 6–7MeV 7–8MeV 92Rb 4.74 11.49 24.27 37.98 96Y 5.56 10.75 14.10 142Cs 3.35 6.02 7.93 3.52 100Nb 5.52 6.03 93Rb 2.34 4.17 6.78 4.21 98mY 2.43 3.16 4.57 4.95 135Te 4.01 3.58 104mNb 0.72 1.82 4.15 7.76 90Rb 1.90 2.59 1.40 95S 2.65 2.96 94Rb 1.32 2.06 2.84 3.96 To al Abso p ion Spec oscopy o Fission F agmen s Rele an o Reac o . . . 759 2.1. Jy äskylä 2009 expe imen Se e al ubidium and b omine iso opes we e s udied in his expe imen pe o med a he IGISOL acili y [14] in he Uni e si y o Jy äskylä in 2009. P o on-induced ission on an u anium a ge was he p oduc ion mechanism o ob ain he adioac i e iso opes. The JYFLTRAP double Penning ap was used o ex ac a e y clean beam o 92Rb using he mass-selec i e bu e gas cooling echnique [15]. The pu i y o he beam is a key issue o TAS measu emen s since he emo al o con amina ions in he analy- sis induces di icul - o-es ima e sys ema ic unce ain ies o he be a- eeding dis ibu ion. The Rocinan e TAS spec ome e , composed o 12 BaF2c ys- als a anged in a cylind ical shape o diame e 25 cm and heigh 25 cm, was used. A silicon de ec o was placed close o he measu emen poin o ag on he be a pa icles and emo e con ibu ions o he TAS spec a om he oom backg ound. Figu e 1(le ) shows schema ically he expe imen al se up and a pic u e o he TAS de ec o used. Fig.1. (Le ) The Rocinan e To al Abso p ion Spec ome e used in he 2009 ex- pe imen a IGISOL acili y a he Uni e si y o Jy äskylä. (Righ ) DTAS de ec o used in he 2014 expe imen . 2.1.1. Resul s on 92Rb decay The da a analysis was pe o med using TAS β- agged spec a o supp ess he oom backg ound con amina ion. The analysis was pe o med ollowing he TAS da a analysis desc ibed in Re . [16]. The esul s ob ained o 92Rb decay ha e been ecen ly published in Re . [13]. The eeding dis ibu ion om his analysis has been con olu ed wi h he esponse o ou de ec o o his pa icula decay in o de o ob ain he ecalcula ed spec um ha is shown in compa ison wi h he expe imen al one in Fig. 2(a). 760 J.A. B iz e al. Fig.2. (a) Compa ison o expe imen al and econs uc ed spec a ound in ou TAS analysis o 92Rb decay ( igu e om Re . [13]). (b) The same as (a) when ixing he di ec g ound s a e eeding o he alue o 95.2% epo ed in Re . [17]. A ele an esul is he di ec g ound s a e eeding. We ob ain a 87.5(25)% eeding in con as wi h he p e iously epo ed alue o 95.2(7)% in ENSDF da abase [17]. Ou alue p o ides he bes ep oduc ion o he expe imen al spec um, χ2= 630, and i one ixes he g ound s a e eeding in ou analysis o he 95.2% epo ed in Re . [17], he alue o he χ2g ows o 2048 and he ep oduc ion o he expe imen al spec um is much wo se, specially in he low-ene gy egion, as i can be seen in Fig. 2(b). The esul ing eeding dis ibu ion is shown in Fig. 3(le ) in compa ison wi h he p e ious knowl- edge on his decay om high esolu ion s udies as egis e ed in ENSDF da abase [17]. We can obse e ha he eeding placed a s a es be ween 800 and 2000 keV we e p e iously unde es ima ed. The impac o ou esul s on he calcula ion o he an ineu ino spec a is p esen ed in Fig. 3( igh ). The plo shows he a io be ween he an ineu ino spec a calcula ed wi h and wi hou ou esul s on 92Rb o he ou main issionable iso opes, 235,238U and 239,241Pu. Th ee di e en se s o nuclea da a we e e alua ed and he esul s a e shown in Fig. 3(b). The cu e showing alues la ge han 1 o he a io wi h/wi hou he new TAS da a in he 5-8 MeV ene gy egion (black cu e in he online e sion) is he one whe e mo e impac is ound, as expec ed, since an old e sion o he ENSDF da abase was used in Re . [19]. I eaches an impac o up o 27% co ec ion o he case o 235U. The o he wo da ase s explo ed show e y simila esul s and gi e alues smalle han 1 in he 5–8 MeV ene gy egion. Those cu es co espond o he da a se used in Re . [11] ( ed line in he online e sion) and ha om Re . [18] (g een line in he online e sion) which is basically he mos upda ed ENSDF da abase [17]. Fo hose wo da ase s, co ec ions o 4.5% o 235U, 3.5% o 239Pu, 2% o 241Pu, and 1.5% o 238U a e ound. To al Abso p ion Spec oscopy o Fission F agmen s Rele an o Reac o . . . 761 U 238 2 4 6 8 10 U 235 Pu 239 Pu 241 Ra io (w/wo new da a) Ene gy (MeV) 2 4 6 8 10 1.25 1.15 1.1 1.05 1 0.95 1.2 1.25 1.15 1.1 1.05 1 0.95 1.2 Fig.3. (Le ) Compa ison o be a eeding dis ibu ion o 92Rb decay ound in ou wo k [13] wi h he in o ma ion in he ENSDF da abase [17]. (Righ ) Ra io o he an ineu ino spec a calcula ed wi h and wi hou he new TAS in o ma ion on 92Rb decay o he ou main issionable iso opes. Th ee se s o nuclea da a a e e alua ed: Re . [11] in ed, Re . [18] in g een and Re . [19] in black ( igu es om Re . [13]). 2.2. Jy äskylä 2014 expe imen The second expe imen was ca ied ou in 2014 a he IGISOL acili y as well [20], a e he upg ade o he acili y o he new IGISOL-4 [21]. The new DTAS de ec o [22], de eloped o he u u e DESPEC expe imen a FAIR Facili y in GSI, Da ms ad (Ge many), was i s used in his expe imen . I is composed o 18+1 NaI(Tl) c ys als o dimensions 15 ×15 ×25 cm3. A pic u e o he expe imen al se up can be seen in Fig. 1 ( igh ). The measu emen o 12 nuclei in e es ing om he poin o iew o an ineu ino spec a de e mina ion was done oge he wi h 11 cases in e es ing o eac o decay hea calcula ions. The da a analysis is cu en ly on-going including calib a ions and es o he Gean 4 simula ions. These simula ions desc ibe he expe imen al se up in a de ailed way wi h he aim o ob aining he esponse o he TAS de ec o o he adia ion in ol ed in he decays o s udy. The alida ion o hese simula ions is done by he compa ison o expe imen al and simula ed spec a o calib a ion sou ces. 3. Summa y and conclusions An al e na i e de e mina ion o he eac o an ineu ino spec a is e- qui ed by eac o neu ino expe imen s. The summa ion me hod needs eli- able in o ma ion om nuclea da abases. Howe e , he be a decay o some ission agmen s s udied using he high esolu ion spec oscopy su e s om he Pandemonium e ec . The use o he TAS echnique p o ides a way o de e mine eeding dis ibu ions in a mo e eliable manne . 762 J.A. B iz e al. The mos ele an con ibu o s o he eac o an ineu ino spec a we e de e mined using he summa ion me hod and he eac o e olu ion code MURE. 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