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Measu emen o ission yields and isome ic yield a ios a IGISOL
Pomp, S ephan; Ma e a, And ea; Rakopoulos, Vasileios; Al-Adili, Ali; Lan z, Ma ias;
Solde s, And eas; Jansson, Kaj; P oko ie , Alexande ; E onen, Tommi; Go elo , Dmi y;
Jokinen, A i; Kankainen, Anu; Moo e, Iain; Pen ilä, Heikki; Rin a-An ila, Sami
Pomp, S., Ma e a, A., Rakopoulos, V., Al-Adili, A., Lan z, M., Solde s, A., Jansson, K.,
P oko ie , A., E onen, T., Go elo , D., Jokinen, A., Kankainen, A., Moo e, I., Pen ilä,
H., & Rin a-An ila, S. (2018). Measu emen o ission yields and isome ic yield a ios
a IGISOL. In F.-J. Hambsch, N. Ca jan, & I. Rusko (Eds.), Scien i ic Wo kshop on
“Nuclea Fission Dynamics and he Emission o P omp Neu ons and Gamma Rays“
(Theo y-4) (A icle 00017). EDP Sciences. EPJ Web o Con e ences, 169.
h ps://doi.o g/10.1051/epjcon /201816900017
2018
Measu emen o ission yields and isome ic yield a ios a
IGISOL
S ephan Pomp1,,And ea Ma e a1,Vasileios Rakopoulos1,Ali Al-Adili1,Ma ias Lan z1,And eas
Solde s1,Kaj Jansson1,Alexande V. P oko ie 1,Tommi E onen2,Dimi i Go elo 2,A i Jokinen2,
Anu Kankainen2,Iain D. Moo e2,Heikki Pen ilä2, and Sami Rin a-An ila2
1Uppsala Uni e si y, Depa men o Physics and As onomy, Box 516, 75120 Uppsala, Sweden
2Uni e si y o Jy äskylä, Depa men o Physics, P.O. Box 35 (YFL), 40014 Jy äskylä, Finland
Abs ac . Da a on ission yields and isome ic yield a ios (IYR) a e ools o s udy he
ission p ocess, in pa icula he gene a ion o angula momen um. We use he IGISOL
acili y wi h he Penning ap JYFLTRAP in Jy äskylä, Finland, o such measu emen s
on 232Th and na U a ge s. P e iously published ission yield da a om IGISOL conce n
he 232Th(p, ) and 238U(p, ) eac ions a 25 and 50 MeV. Recen ly, a neu on sou ce, using
he Be(p,n) eac ion, has been de eloped, ins alled and es ed. We summa ize he esul s
o (p, ) ocusing on he i s measu emen o IYR by di ec ion coun ing. We also p esen
i s esul s o IYR and ela i e yields o Sn and Sb iso opes in he 128-133 mass ange
om na U(n, ) based on γ-spec ome y. We ind a s agge ing beha iou in he cumu-
la i e yields o Sn and a shi in he independen ission yields o Sb as compa ed o
cu en e alua ions. Plans o he u u e expe imen al p og am on ission yields and IYR
measu emen s a e discussed.
1 In oduc ion
Fission yields (FY) a e a key obse able o s udies o he ission p ocess. They a e measu ed o
example using he 2E o he 2E-2 - echnique [1], echniques in ol ing con en ional mass spec ome-
e s like LOHENGRIN [2,3] o using i adia ion echniques in combina ion wi h γ-spec ome y [4].
The challenges in he men ioned echniques a e connec ed o he achie able mass esolu ion (2E and
2E-2 echnique), limi s in he achie able exci a ion ene gies in he issioning nucleus (in he case
o LOHENGRIN), o he necessi y o su icien ly long li e imes o he s udied ission p oduc s in
combina ion wi h he equi emen o well-known decay da a (when using γ-spec ome y).
An al e na i e me hod o measu e ission yields is p o ided by he usage o he ISOL- echnique
(Iso ope Sepa a ion On-Line) in combina ion wi h a Penning ap o mass sepa a ion. Wi h his
app oach independen iso opic FY can be measu ed o a ange o issioning sys ems wi h di e en
exci a ion ene gies and, since he me hod is based on di ec ion coun ing, wi hou equi emen s on
γ-decay schemes.
Fu he mo e, he high mass esol ing powe p o ided by Penning aps make i possible o mea-
su e isome ic yield a ios (IYR). This is hen, again, no based on he measu emen o gamma decays
e-mail: [email p o ec ed]
© The Au ho s, published by EDP Sciences. This is an open access a icle dis ibu ed unde he e ms o he C ea i e Commons
A ibu ion License 4.0 (h p://c ea i ecommons.o g/licenses/by/4.0/).
EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
bu on di ec ion coun ing, esol ing he g ound s a e mass om he mass o he isome ic s a e. Rou-
inely achie able mass esol ing powe s co espond o a esolu ion o abou 0.5 MeV in exci a ion en-
e gy. New de elopmen s like he Phase-Imaging Ion-Cyclo on-Resonance echnique [5] can achie e
a esolu ion o 50 keV. This opens he doo o bo h high-quali y FY da a and measu emen s o a wide
ange o IYR o a ious ission sys ems.
The IYR may be used o deduce he angula momen um dis ibu ions o he ission agmen s.
This allows hus o s udy he amoun o ene gy a ailable in he ission p ocess ha is con e ed in o
o a ional ene gy. The ini ial spin also in luences he p oduc ion o ission neu ons and gamma ays
in he de-exci a ion p ocess o he agmen [6]. The e o e, IYR, measu ed o a ange o issioning
sys ems and ac oss all masses, p o ide impo an in o ma ion and cons ain s o modelling he ission
p ocess and i s dynamics.
I has also been poin ed ou ha he di e ences be ween calcula ed and measu ed an ineu ino
p oduc ion a Daya Bay may be due o a lack o knowledge on IYR [7,8].
Las bu no leas , i should be men ioned ha , due o high N/Z a io and low a e age p omp -
neu on emission mul iplici y, neu on-induced ission o 232Th and 238U is an e icien way o p oduce
exo ic nuclei. Using a neu on-p oduc ion a ge wi hin an ISOL acili y and he 232Th(n, ) eac ion is
he mos p omising way o p oduce e y neu on- ich nuclei especially in he ligh mass egion, close
o 78Ni, o u he s udies wi h a Penning ap.
2 Expe imen al
The measu emen s discussed he e ha e been pe o med a he IGISOL acili y, loca ed a he Accel-
e a o Labo a o y o he Uni e si y o Jy äskylä, Finland. He e we gi e a b ie ou line o he acili y.
De ails can be ound in Re s. [9,10].
The K-130 cyclo on deli e s a p o on beam o he ission chambe . In he p esen ed cases his
beam is used o bo h (p, ) and (n, ) eac ion s udies. In he i s case a 25 MeV beam di ec ly in e ac s
wi h 232Th o na U a ge s o induce (p, ) eac ions. In he (n, ) case, a 30 MeV beam is used o c ea e
neu ons in a hick Be yllium a ge ia he Be(p,n) eac ion. The Be a ge is loca ed inside he ission
chambe and he neu ons hen induce (n, ) eac ions in he na U a ge loca ed a ew cm downs eam
he neu on p oduc ion a ge . Fu he de ails on he neu on con e e a e gi en below and in Re .
[11].
Helium is used as bu e gas o slow down he ission p oduc s and lush hem owa ds a a-
dio equency (RF) ion guide whe e hey a e s epwise accele a ed o 30 kV owa ds a magne ic mass
sepa a o . The ime spen by he ions in he bu e gas un il ex ac ion owa ds he magne is on he
o de o a ew ens o milliseconds.
The ions p oduced in his way a e dominan ly in he 1+cha ge s a e. The ela i e ac ion o
ions in he 1+s a e may a y om elemen o elemen in a non- i ial way and can be measu ed in
dedica ed s udies. An example is gi en below. De ails o he beha iou o he a ge cell ha is used in
he (p, ) case, i.e., he s opping e iciency o he di e en ions and po en ial bias o di e en ission
p oduc masses o hei o al kine ic ene gies (TKE), ha e been s udied in Re . [12]. I was ound ha
such dependences a e weak and he associa ed unce ain ies a e small compa ed o o he sys ema ic
unce ain ies. A simila s udy o he (n, ) case is cu en ly in p og ess.
A e ex ac ion om he ission chambe by he ion guide and a second acuum chambe wi h
ex ac ion elec odes, a dipole magne is used o selec ions o an isoba ic mass chain. The mass
esol ing powe , M/∆Mo he magne is abou 500.
A e he magne , he ions pass h ough a swi ch ya d whe e hey can ei he be de lec ed o a γ- ay
measu emen s a ion, o owa ds he adio equency coole and bunche (RFQ). A e decele a ion
and cooling, sho ion bunches o abou 10 µs du a ion a e inally eleased owa ds a se up o wo
2
EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
bu on di ec ion coun ing, esol ing he g ound s a e mass om he mass o he isome ic s a e. Rou-
inely achie able mass esol ing powe s co espond o a esolu ion o abou 0.5 MeV in exci a ion en-
e gy. New de elopmen s like he Phase-Imaging Ion-Cyclo on-Resonance echnique [5] can achie e
a esolu ion o 50 keV. This opens he doo o bo h high-quali y FY da a and measu emen s o a wide
ange o IYR o a ious ission sys ems.
The IYR may be used o deduce he angula momen um dis ibu ions o he ission agmen s.
This allows hus o s udy he amoun o ene gy a ailable in he ission p ocess ha is con e ed in o
o a ional ene gy. The ini ial spin also in luences he p oduc ion o ission neu ons and gamma ays
in he de-exci a ion p ocess o he agmen [6]. The e o e, IYR, measu ed o a ange o issioning
sys ems and ac oss all masses, p o ide impo an in o ma ion and cons ain s o modelling he ission
p ocess and i s dynamics.
I has also been poin ed ou ha he di e ences be ween calcula ed and measu ed an ineu ino
p oduc ion a Daya Bay may be due o a lack o knowledge on IYR [7,8].
Las bu no leas , i should be men ioned ha , due o high N/Z a io and low a e age p omp -
neu on emission mul iplici y, neu on-induced ission o 232Th and 238U is an e icien way o p oduce
exo ic nuclei. Using a neu on-p oduc ion a ge wi hin an ISOL acili y and he 232Th(n, ) eac ion is
he mos p omising way o p oduce e y neu on- ich nuclei especially in he ligh mass egion, close
o 78Ni, o u he s udies wi h a Penning ap.
2 Expe imen al
The measu emen s discussed he e ha e been pe o med a he IGISOL acili y, loca ed a he Accel-
e a o Labo a o y o he Uni e si y o Jy äskylä, Finland. He e we gi e a b ie ou line o he acili y.
De ails can be ound in Re s. [9,10].
The K-130 cyclo on deli e s a p o on beam o he ission chambe . In he p esen ed cases his
beam is used o bo h (p, ) and (n, ) eac ion s udies. In he i s case a 25 MeV beam di ec ly in e ac s
wi h 232Th o na U a ge s o induce (p, ) eac ions. In he (n, ) case, a 30 MeV beam is used o c ea e
neu ons in a hick Be yllium a ge ia he Be(p,n) eac ion. The Be a ge is loca ed inside he ission
chambe and he neu ons hen induce (n, ) eac ions in he na U a ge loca ed a ew cm downs eam
he neu on p oduc ion a ge . Fu he de ails on he neu on con e e a e gi en below and in Re .
[11].
Helium is used as bu e gas o slow down he ission p oduc s and lush hem owa ds a a-
dio equency (RF) ion guide whe e hey a e s epwise accele a ed o 30 kV owa ds a magne ic mass
sepa a o . The ime spen by he ions in he bu e gas un il ex ac ion owa ds he magne is on he
o de o a ew ens o milliseconds.
The ions p oduced in his way a e dominan ly in he 1+cha ge s a e. The ela i e ac ion o
ions in he 1+s a e may a y om elemen o elemen in a non- i ial way and can be measu ed in
dedica ed s udies. An example is gi en below. De ails o he beha iou o he a ge cell ha is used in
he (p, ) case, i.e., he s opping e iciency o he di e en ions and po en ial bias o di e en ission
p oduc masses o hei o al kine ic ene gies (TKE), ha e been s udied in Re . [12]. I was ound ha
such dependences a e weak and he associa ed unce ain ies a e small compa ed o o he sys ema ic
unce ain ies. A simila s udy o he (n, ) case is cu en ly in p og ess.
A e ex ac ion om he ission chambe by he ion guide and a second acuum chambe wi h
ex ac ion elec odes, a dipole magne is used o selec ions o an isoba ic mass chain. The mass
esol ing powe , M/∆Mo he magne is abou 500.
A e he magne , he ions pass h ough a swi ch ya d whe e hey can ei he be de lec ed o a γ- ay
measu emen s a ion, o owa ds he adio equency coole and bunche (RFQ). A e decele a ion
and cooling, sho ion bunches o abou 10 µs du a ion a e inally eleased owa ds a se up o wo
Figu e 1. Expe imen al equency dis ibu ion spec um o he egion o mass A=81. The iden i ica ion o he
peaks is based on a equency o mass calib a ion. The igu e shows he posi ions o 81As, 81Ge, and 81mGe
(dashed black), and he Gaussian i s used o ex ac he IYR (do ed ed).
consecu i e Penning aps, JYFLTRAP. In he aps he ions a e s o ed inside a magne ic ield and hei
eigenmo ion is manipula ed by applying a RF ield ha selec s di e en q/m a ios in he s a ic 7.0 T
magne ic ield. The selec ed ions hen pass h ough a 1.5 mm wide ape u e and a e ex ac ed owa ds
a mul ichannel pla e (MCP). The las s ep allows o addi ional ime-o - ligh measu emen s which
can sup ess impu i ies wi h he same q/m a io. The o al ime om p oduc ion o he ission p oduc
un il egis a ion on he MCP a ies depending on he se ing o he expe imen , e.g., collec ion and
cooling imes in he RFQ. These se ings can be changed depending on he measu emen needs, e.g.,
desi ed mass esol ing powe . Typically his o al ime is on he o de o a ew hund ed ms. The e o e,
decay co ec ions ha e o be applied o he aw da a.
The case o 81Ge is he mos di icul measu emen discussed in his pape . The mass di e ence
be ween isome and g ound s a e is only 679 keV and he IYR is small. The isome ic s a e hus shows
up as a small bump almos comple ely imme sed in he mass peak ela ed o he g ound s a e o 81Ge.
Peak posi ions a e calcula ed ela i e o a e e ence peak, 81As in his case, and all peaks a e i ed
wi h Gaussian dis ibu ions (see Fig. 1).
I u ns ou ha applying Gaussian i s does no always ep oduce he expe imen al da a su icien ly
well and he peaks migh ha e sys ema ic dis o ions depending on se ings o he Penning ap. While
his has, in gene al, a negligible e ec on he IYR, i is desi able o apply he co ec shapes in he
i ing p ocess, especially in cases wi h o e lapping peaks. To his end, a me hod using Gaussian
p ocesses o i impe ec models wi h non-linea leas squa es and using a p io dis ibu ion has been
de eloped in Uppsala [13]. The me hod has, howe e , no ye been applied in he esul s p esen ed in
his pape .
3 Resul s and discussion
3.1 P o on-induced ission a 25 MeV
O e he pas yea s a se ies o measu emen s o FY om he (p, ) eac ion on 232Th and na U ha e
been pe o med by he IGISOL g oup [14].
F om some o hese da a IYR could be ex ac ed o six nuclei, each om he wo issioning sys-
ems. These measu emen s ep esen he i s IYR ob ained by di ec ion coun ing. Fu he mo e, nine
3
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Theo y-4
Table 1. IYR o he six s udied nuclei om (p, ) a 25 MeV o he wo s udied issioning sys ems. Unce ain ies
a e s a is ical only. The IYR a e gi en as Ym/(Ym+Yg.s.).
Spin
g.s.
Spin
isom.
∆M
(keV)
IYR o na U
om [17]
IYR o na U IYR o 232Th
81Ge (9/2+) (1/2+) 679 - 0.03±0.01 0.08±0.02
96Y0−8+1140 - 0.55±0.01 0.61±0.02
97Y(1/2−) (9/2)+667 0.71 0.73±0.02 0.78±0.02
128Sn 0+(7−) 2091 0.52 0.58±0.02 0.46±0.01
129Sb 7/2+(19/2−) 1851 - 0.47±0.04 0.46±0.01
130Sn 0+(7−) 1946 0.34 0.54±0.02 0.38±0.01
ou o he wel e measu emen s a e he i s IYR measu emen s o he s udied sys em. P elimina y
esul s we e p esen ed ecen ly [15]. He e we b ie ly summa ize e ised esul s. A mo e de ailed
publica ion is in p og ess [16].
In Table 1 we gi e he spin assignmen s o he six nuclei in hei g ound s a e and hei s udied
isome , hei mass di e ence, and ou measu ed IYR wi h hei s a is ical unce ain ies. Da a om
he only o he measu emen o IYR in he (p, ) eac ion ob ained by Tanikawa e al. [17] by means o
γ-spec ome y a e also included in he able. The IYR a e gi en as he yield o he me as able s a e
o e he o al yield.
The 81Ge case is he only one ou o he six cases whe e he isome ic s a e has lowe spin compa ed
o he g ound s a e. This is consis en wi h he compa a i ely low obse ed IYR. When compa ing
he wo Y ium cases, we no e ha 96Y shows a la ge di e ence in spin be ween g ound s a e and
isome han 97Y and has as small IYR. In he case o 128Sn and 130Sn we ind ha , a leas o he
na U eac ion, simila IYR may be expec ed since g ound s a e and isome ic s a e ha e he same spin
assignmen s in bo h cases. These obse a ions indica e ha ou esul s a e consis en wi h each o he .
Ou da a a e in easonable ag eemen wi h he da a om Tanikawa e al. [17] excep in he 130Sn case
whe e Re . [17] gi es a alue ha is much lowe and close o ou esul o he Tho ium case bu also
much lowe han hei IYR o 128Sn.
Ou mos s iking obse a ion is ela ed o di e ences in he IYR be ween he wo s udied is-
sioning sys ems. We see a endency ha he 232Th(p, ) eac ion gi es highe IYR, compa ed o he
na U(p, ) eac ion, o nuclei in he ligh -mass egion whe eas he opposi e end is seen in he hea y-
mass egion. Mos no ably he IYR o 128Sn and 130Sn a e signi ican ly lowe o 232Th(p, ) compa ed
o na U(p, ). A possible explana ion o his obse a ion migh be linked o di e en scission con igu-
a ions due o di e ences in ission mode a ios; o 232Th he supe -long mode is ound o be s onge
compa ed o 238U a compa able exci a ion ene gies in he compound sys em [18].
3.2 Rela i e yields and isome ic a ios o (n, ) eac ions
The neu on-induced ission da a ha e been ob ained using a hick (6 mm) Be yllium a ge . This
implies only mino di e ences in he ene gy spec a compa ed o he cha ac e ized 5-mm hick wa e -
cooled Be a ge [11,19]. The idea behind he de elopmen o his a ge is mo i a ed by he newly
ins alled MCC30/15 cyclo on ha is designed o deli e a 30 MeV p o on beam wi h cu en s up o
100 µA. This would lead o a powe o 3 kW on he a ge ha needs o be cooled, bu could also
be used o c ea e a neu on lux ha induces a ission a e ha is high enough o ensu e easonable
measu emen imes o IFY measu emen s o e a wide mass ange. Cha ac e iza ion campaigns a
The S edbe g Labo a o y in Uppsala and in Jy äskylä showed ha he design goal o eaching a o al
4
EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
Table 1. IYR o he six s udied nuclei om (p, ) a 25 MeV o he wo s udied issioning sys ems. Unce ain ies
a e s a is ical only. The IYR a e gi en as Ym/(Ym+Yg.s.).
Spin
g.s.
Spin
isom.
∆M
(keV)
IYR o na U
om [17]
IYR o na U IYR o 232Th
81Ge (9/2+) (1/2+) 679 - 0.03±0.01 0.08±0.02
96Y0−8+1140 - 0.55±0.01 0.61±0.02
97Y(1/2−) (9/2)+667 0.71 0.73±0.02 0.78±0.02
128Sn 0+(7−) 2091 0.52 0.58±0.02 0.46±0.01
129Sb 7/2+(19/2−) 1851 - 0.47±0.04 0.46±0.01
130Sn 0+(7−) 1946 0.34 0.54±0.02 0.38±0.01
ou o he wel e measu emen s a e he i s IYR measu emen s o he s udied sys em. P elimina y
esul s we e p esen ed ecen ly [15]. He e we b ie ly summa ize e ised esul s. A mo e de ailed
publica ion is in p og ess [16].
In Table 1 we gi e he spin assignmen s o he six nuclei in hei g ound s a e and hei s udied
isome , hei mass di e ence, and ou measu ed IYR wi h hei s a is ical unce ain ies. Da a om
he only o he measu emen o IYR in he (p, ) eac ion ob ained by Tanikawa e al. [17] by means o
γ-spec ome y a e also included in he able. The IYR a e gi en as he yield o he me as able s a e
o e he o al yield.
The 81Ge case is he only one ou o he six cases whe e he isome ic s a e has lowe spin compa ed
o he g ound s a e. This is consis en wi h he compa a i ely low obse ed IYR. When compa ing
he wo Y ium cases, we no e ha 96Y shows a la ge di e ence in spin be ween g ound s a e and
isome han 97Y and has as small IYR. In he case o 128Sn and 130Sn we ind ha , a leas o he
na U eac ion, simila IYR may be expec ed since g ound s a e and isome ic s a e ha e he same spin
assignmen s in bo h cases. These obse a ions indica e ha ou esul s a e consis en wi h each o he .
Ou da a a e in easonable ag eemen wi h he da a om Tanikawa e al. [17] excep in he 130Sn case
whe e Re . [17] gi es a alue ha is much lowe and close o ou esul o he Tho ium case bu also
much lowe han hei IYR o 128Sn.
Ou mos s iking obse a ion is ela ed o di e ences in he IYR be ween he wo s udied is-
sioning sys ems. We see a endency ha he 232Th(p, ) eac ion gi es highe IYR, compa ed o he
na U(p, ) eac ion, o nuclei in he ligh -mass egion whe eas he opposi e end is seen in he hea y-
mass egion. Mos no ably he IYR o 128Sn and 130Sn a e signi ican ly lowe o 232Th(p, ) compa ed
o na U(p, ). A possible explana ion o his obse a ion migh be linked o di e en scission con igu-
a ions due o di e ences in ission mode a ios; o 232Th he supe -long mode is ound o be s onge
compa ed o 238U a compa able exci a ion ene gies in he compound sys em [18].
3.2 Rela i e yields and isome ic a ios o (n, ) eac ions
The neu on-induced ission da a ha e been ob ained using a hick (6 mm) Be yllium a ge . This
implies only mino di e ences in he ene gy spec a compa ed o he cha ac e ized 5-mm hick wa e -
cooled Be a ge [11,19]. The idea behind he de elopmen o his a ge is mo i a ed by he newly
ins alled MCC30/15 cyclo on ha is designed o deli e a 30 MeV p o on beam wi h cu en s up o
100 µA. This would lead o a powe o 3 kW on he a ge ha needs o be cooled, bu could also
be used o c ea e a neu on lux ha induces a ission a e ha is high enough o ensu e easonable
measu emen imes o IFY measu emen s o e a wide mass ange. Cha ac e iza ion campaigns a
The S edbe g Labo a o y in Uppsala and in Jy äskylä showed ha he design goal o eaching a o al
Figu e 2. P elimina y esul s o ela i e cumula i e FY o Sn (le ) and independen FY o Sb ( igh ) in he
na U(n, ) eac ion. The semi-open ci cle indica es ha only he g ound s a e is included in he da a poin , and he
open ci cles indica e ha only he isome could be measu ed. The solid ed line ep esen s calcula ions using he
GEF code weigh ed wi h he neu on ene gy spec um. The blue squa es a e e alua ed da a om ENDF/B-VII a
14 MeV.
lux o mo e han 2·1012 n/s /s can be achie ed wi h a 100 µA p o on cu en . The neu on lux wi h
ene gies abo e 1 MeV would ac ually be 2–3·1012 n/s /s [11].
The da a p esen ed he e we e, howe e , ob ained wi h he K-130 cyclo on and a p o on cu en
o only 1 µA since he MCC30/15 was no a ailable du ing he measu emen campaign in Decembe
2016. This mean ha we could no achie e su icien in ensi ies o ge good measu emen s a is ics
using JYFLTRAP. Ins ead he ission p oduc s we e di ec ed o a γ-spec ome y s a ion whe e he
p esen ed esul s we e ob ained. Ne e heless, he measu ed da a he e a e he i s (n, ) da a measu ed
a IGISOL.
Acco ding o he cha ac e iza ion da a he e ec i e neu on ene gy spec um is a he wide. The
e ec i e neu on ene gy, de e mined by weigh ed a e aging o he neu on ene gy spec um wi h he
ission c oss sec ion o he na U a ge , is 12.4±8.8 MeV. Abou (97±1)% o all ission e en s a e
om 238U(n, ). Acco ding o calcula ions wi h he GEF code [20], i s chance ission con ibu es
wi h 55%, second chance wi h 31%, hi d and ou h chance ission wi h 8 and 6%, espec i ely. The
p e- ission emission o o he pa icles is negligible. We could also measu e he a io o he 1+/2+
cha ge s a es. Fo Sn we ob ain 1.19±0.17 and o Sb 2.78±0.42. I should be no ed, howe e , ha
he di e en p obabili ies o each he 1+s a e do no a ec he esul s p esen ed below.
He e we summa ize he p elimina y esul s om he Decembe 2016 campaign. A mo e de ailed
publica ion has been submi ed [21]. Figu e 2 shows he measu ed ela i e ission yields o Sn and
Sb in he mass ange be ween 128 and 133.
The measu ed FY o Sn a e cumula i e. The measu ed FY o Sn da a can be sub ac ed om
he Sb da a and, he e o e, he Sb yields a e independen FY. The igu e shows a compa ison o he
measu emen esul s o e alua ed da a and calcula ions using he GEF code. No e ha we no malize
o he a ea unde he espec i e dis ibu ions since ou measu ed da a a e no on an absolu e scale.
The discussion is, he e o e, based on he obse ed shapes only. In he Sn case, we obse e a s uc u e
wi h a ela i ely low yield o 131Sn and a high yield in 132Sn. This is no p edic ed by GEF o p esen
in he e alua ed da a. The yield o he Sb iso opes is peaked a mass 132. The end in he yields is
oughly ep oduced by GEF bu is in sha p con as o he da a in he ENDF e alua ion which shows
a peak in he yield a mass 130.
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EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
Table 2. Isome ic yield a ios in he na U(n. ) eac ion as ob ained in he p esen measu emen compa ed o
calcula ions wi h he GEF code and he ENDF/B-VII and JENDL-4.0 e alua ions.
Spin
g.s.
Spin
isom.
This wo k GEF ENDF/B-VII.1 JENDL 4.0
129Sn 3/2+11/2−0.37±0.13 0.63 0.15±0.12 0.68±0.43
130Sn 0+(7−)0.64±0.48 0.49 0.48±0.49 0.70±0.46
131Sn (3/2+) (11/2−)0.43±0.19 0.69 0.48±0.45 0.81±0.51
130Sb (8−) (4,5)+0.81±0.43 0.68 0.43±0.41 0.43±0.28
132Sb (4+) (8−)0.25±0.10 0.49 0.61±0.41 0.61±0.20
Table 2 shows he de i ed IYR a io o i e cases compa ed o GEF calcula ions and e alua ed
da a. Compa ed o he IYR da a in he (p, ) case, he s a is ical unce ain ies a e a he la ge. We
expec his o imp o e conside ably when using JYFLTRAP in o hcoming campaigns.
We no e ha ou da a a e consis en when compa ing, e.g., 129Sn and 131Sn whe e he g ound
s a e and he isome ca y he same spin assignmen s. We also no e ha he IYR is in e sed when
compa ing he wo Sb iso opes. This is consis en wi h he spin assignmen s in hese wo cases which
a e also in e sed be ween hei espec i e g ound s a e and isome . Since he e alua ions also gi e
la ge unce ain ies i is no possible o obse e any clea disc epancy. Also he esul s om he GEF
code a e in ough ag eemen wi h he measu ed da a. The only excep ions migh be 129Sn and 132Sb
whe e he measu ed IYR seem o be signi ican ly lowe han he GEF p edic ions.
4 Ou look
Fu u e wo k will ocus on con inued s udies on he s opping e iciencies in he ission ion guide
and measu emen o he anspo e iciency o he sys em using, e.g., 252C (SF). This will allow
he FY da a o be discussed on an absolu e scale. We also plan o implemen he Phase-Imaging
Ion-Cyclo on-Resonance echnique o achie e 50 keV mass esolu ion. This will open up o mea-
su emen o a wide ange o IYR o many di e en issioning sys ems and a de ailed s udy o he
o igin angula momen um gene a ion in nuclea ission.
This wo k has been suppo ed by he Eu opean Commission wi hin he CHANDA p ojec (con ac 605203),
he Swedish Radia ion Sa e y Au ho i y (SSM), and by he Swedish Nuclea Fuel and Was e Managemen Co.
(SKB).
Re e ences
[1] A. Al-Adili e al., hese p oceedings
[2] S. Julien-La e iè e e al., hese p oceedings
[3] A. Bail, e al., Phys. Re . C 84, 034605 (2011)
[4] H. Naik, e al., Nucl. Phys. A 941, 16 (2015)
[5] S. Elisee , e al., Phys. Re . Le . 110, 082501 (2013)
[6] I. S e cu, e al., Phys. Re . C 88, 044603 (2013)
[7] A.A. Sonzogni, e al., Phys. Re . Le . 116, 132502 (2016)
[8] F.P. An, e al., Phys. Re . Le . 118, 251801 (2017)
[9] H. Pen ilä, e al., Eu . Phys. J. A 44, 147 (2010)
[10] D. Go elo , e al., Nucl. Ins . Me h. Phys. Res. B 376, 46 (2016)
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EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
Table 2. Isome ic yield a ios in he na U(n. ) eac ion as ob ained in he p esen measu emen compa ed o
calcula ions wi h he GEF code and he ENDF/B-VII and JENDL-4.0 e alua ions.
Spin
g.s.
Spin
isom.
This wo k GEF ENDF/B-VII.1 JENDL 4.0
129Sn 3/2+11/2−0.37±0.13 0.63 0.15±0.12 0.68±0.43
130Sn 0+(7−)0.64±0.48 0.49 0.48±0.49 0.70±0.46
131Sn (3/2+) (11/2−)0.43±0.19 0.69 0.48±0.45 0.81±0.51
130Sb (8−) (4,5)+0.81±0.43 0.68 0.43±0.41 0.43±0.28
132Sb (4+) (8−)0.25±0.10 0.49 0.61±0.41 0.61±0.20
Table 2 shows he de i ed IYR a io o i e cases compa ed o GEF calcula ions and e alua ed
da a. Compa ed o he IYR da a in he (p, ) case, he s a is ical unce ain ies a e a he la ge. We
expec his o imp o e conside ably when using JYFLTRAP in o hcoming campaigns.
We no e ha ou da a a e consis en when compa ing, e.g., 129Sn and 131Sn whe e he g ound
s a e and he isome ca y he same spin assignmen s. We also no e ha he IYR is in e sed when
compa ing he wo Sb iso opes. This is consis en wi h he spin assignmen s in hese wo cases which
a e also in e sed be ween hei espec i e g ound s a e and isome . Since he e alua ions also gi e
la ge unce ain ies i is no possible o obse e any clea disc epancy. Also he esul s om he GEF
code a e in ough ag eemen wi h he measu ed da a. The only excep ions migh be 129Sn and 132Sb
whe e he measu ed IYR seem o be signi ican ly lowe han he GEF p edic ions.
4 Ou look
Fu u e wo k will ocus on con inued s udies on he s opping e iciencies in he ission ion guide
and measu emen o he anspo e iciency o he sys em using, e.g., 252C (SF). This will allow
he FY da a o be discussed on an absolu e scale. We also plan o implemen he Phase-Imaging
Ion-Cyclo on-Resonance echnique o achie e 50 keV mass esolu ion. This will open up o mea-
su emen o a wide ange o IYR o many di e en issioning sys ems and a de ailed s udy o he
o igin angula momen um gene a ion in nuclea ission.
This wo k has been suppo ed by he Eu opean Commission wi hin he CHANDA p ojec (con ac 605203),
he Swedish Radia ion Sa e y Au ho i y (SSM), and by he Swedish Nuclea Fuel and Was e Managemen Co.
(SKB).
Re e ences
[1] A. Al-Adili e al., hese p oceedings
[2] S. Julien-La e iè e e al., hese p oceedings
[3] A. Bail, e al., Phys. Re . C 84, 034605 (2011)
[4] H. Naik, e al., Nucl. Phys. A 941, 16 (2015)
[5] S. Elisee , e al., Phys. Re . Le . 110, 082501 (2013)
[6] I. S e cu, e al., Phys. Re . C 88, 044603 (2013)
[7] A.A. Sonzogni, e al., Phys. Re . Le . 116, 132502 (2016)
[8] F.P. An, e al., Phys. Re . Le . 118, 251801 (2017)
[9] H. Pen ilä, e al., Eu . Phys. J. A 44, 147 (2010)
[10] D. Go elo , e al., Nucl. Ins . Me h. Phys. Res. B 376, 46 (2016)
[11] A. Ma e a, e al., Eu . Phys. J. A 53, 173 (2017)
[12] A. Al-Adili, e al., Eu . Phys. J. A 51, 59 (2015)
[13] P. Helgesson and H. Sjös and, in manusc ip
[14] H. Pen ilä, e al., Eu . Phys. J. A 52, 104 (2016)
[15] V. Rakopoulos, e al., o appea in Eu . Phys. J. (P oceedings o ND2016)
[16] V. Rakopoulos, e al., in manusc ip
[17] M. Tanikawa, e al., Z. Phys. A 347, 53 (1993)
[18] I.V. Ryzho , e al., Phys. Re . C 83, 054603 (2011)
[19] A. Solde s, e al., Nucl. Da a Shee s 119, 338 (2014)
[20] K.-H. Schmid , e al., Nucl. Da a Shee s 131, 107 (2016)
[21] A. Ma e a, e al., submi ed o Eu . Phys. J.
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EPJ Web o Con e ences 169, 00017 (2018) h ps://doi.o g/10.1051/epjcon /201816900017
Theo y-4
