Modular Apparatus for Nuclear Reactions Spectroscopy (MARS): Characterization and First Application to Determine 12C(6Li,4He)14Ng.s Nuclear Reaction Cross Sections

Eu . Phys. J. Plus (2025) 140:367
h ps://doi.o g/10.1140/epjp/s13360-025-06305-0
Regula A icle
Modula appa a us o nuclea eac ions spec oscopy (MARS): cha ac e iza ion
and i s applica ion o de e mine 12C(6Li,4He)14Ng.snuclea eac ion c oss sec ions
L. Ga ido-Gómez1,a, A. Vegas-Díaz1,2,M.A.G.Al a ez
1,J.P.Fe nández-Ga cía
1, B. Fe nández1,2, F. J. Fe e 1,2,
D. Lopez-Ai es3
1Depa amen o FAMN, Uni e sidad de Se illa, Apa ado 1065, 41080 Se illa, Spain
2Cen o Nacional de Acele ado es, Uni e sidad de Se illa, Jun a de Andalucía-CSIC, 41092 Se illa, Spain
3Ins i u e o T ansu anium Elemen s ITU, Eu opean Commission - Join Resea ch Cen e, Box 2340, 76125 Ka ls uhe, Ge many
Recei ed: 23 Feb ua y 2025 / Accep ed: 6 Ap il 2025
© The Au ho (s) 2025
Abs ac This wo k p esen s MARS (Modula appa a us o nuclea eac ions spec oscopy) and i s cha ac e iza ion p io o i s
i s applica ion o measu e 6Li+12C nuclea eac ions. Measu emen s we e pe o med a he 3 MV andem accele a o o he CNA
(Na ional Accele a o Cen e ), in Se ille, Spain. The 6Li p ojec iles we e accele a ed a ene gies a ound he 6Li+12C Coulomb
ba ie (Vcm
B∼3.0 MeV - cen e o mass and Vlab
B∼4.5 MeV - labo a o y ame). Using a 6Li2+ beam, we measu ed a 13
labo a o y ene gies om 4.00 o 7.75 MeV. Thus, we p esen he exci a ion unc ion o 12C(6Li,4He)14Ng.s. eac ion, a 2 backwa d
angles (110.0◦and 140.0◦). The p ojec ile dissocia ion, leading o his eac ion, inc eases wi h he bomba ding ene gies a ound he
Coulomb ba ie . This dissocia ion is a o ed a an op imum ene gy Eop
b≥VB+|Qbu|,whe eVBis he Coulomb ba ie o he
sys em, and |Qbu|is he module o Q- alue o he 6Li dissocia ion in o 4He+2H. This esul co obo a es a sys ema ic analysis o
weakly bound p ojec iles eac ing on se e al a ge s [1].
1 In oduc ion
Fi s nuclei, iso opes o hyd ogen (H) and helium (He), o igina ed du ing p imo dial nucleosyn hesis as a esul o he big bang,
wi h e y low yield a es o exo ic 7Be and weakly bound s able 7Li nuclei [2]. Hea ie nuclei o igina ed much la e , du ing s ella
nucleosyn hesis, by nuclea eac ions o ligh e elemen s, om iso opes o hyd ogen H (Z 1) and helium He (Z 2),in hes a s’
bi h, li e, and dea h. The la e wi h he consequen nucleosyn hesis o hea ie nuclei in supe no ae e en s [3]. Thus, all ma e
known in he Uni e se o igina es om nuclea eac ions. Measu emen s and analysis o nuclea eac ions a e key o unde s anding
he yield a e and abundance o elemen s in he cosmos, he dynamics o s ella bodies, and he di e en As ophysics scena ios
[2–9].
Rega ding he abundance o ligh elemen s in he cosmos, he e is a gap be ween He and C, whe e he abundances o Li, Be and
B elemen s a e e y low and he nuclei wi h masses A 5andA8 a e no s able. The u h abou such abundances mus be
ela ed o he nuclei s uc u e and eac ion dynamics and hei p obabili y o being o med o dissocia ed in nuclea eac ions.
Di e en wo ks epo ed on Li nuclea eac ions. Fo example, P ei e and collabo a o s [10] epo ed on he c oss sec ion o
he eme ging 4He (alpha pa icles), de i ed om 6Li dissocia ion in o 4He and 2H, peak a he g azing angle. Maye and Schneide
[11] es ablished an ene gy h eshold abo e which he Ru he o d dec ease is accompanied by a s ong inc ease in he eac ion c oss
sec ion o 6Li on 12C, a bomba ding ene gies below 5.50 MeV, analyzing he sca e ing angle a 165.0◦. Capu o e al. epo ed he
6Li b eakup exci a ion unc ion, a 170.0◦, o he6Li+144Sm sys em [12]. Luong and collabo a o s [13] epo ed he p edominance
o ans e eac ions, a sub-ba ie ene gies, in igge ing he b eakup o 6, 7Li eac ing on 144Sm and 207,208,209Pb a ge s. Pandi
e al. [14] de e mined he nuclea eac ion cap u e as dominan (∼70%) o he 7Li+93Nb. The sys ema ic cap u e o and he
inclusi e p oduc ion o α(c oss sec ion) o eac ions in ol ing 7Li, o e a wide mass ange, was also epo ed. The elas ic sca e ing
angula dis ibu ions o 6, 7, 9, 11Li impinging on 64Zn, 120Sn and 208Pb hea y a ge s, a bomba ding ene gies a ound he espec i e
Coulomb ba ie s, ha e been p e iously analyzed [1,15–17]. The sys ema ic op ical model (OM) analysis and he espec i e op ical
po en ials (OP) we e shown o s ongly co ela e wi h he p ojec ile nuclea s uc u e and i s b eakup p obabili y. A an op imum
bomba ding ene gy, dependen on he Q- alue o he p ojec ile b eakup and he Coulomb ba ie o he sys em, he p ojec ile ends
o dissocia e ( h ough b eakup and/o ans e eac ions). This ac equi es adap ing he OM o he p ojec ile s uc u e. S able igh ly
bound nuclei eac ions equi e sho - ange Coulomb and nuclea po en ials; weakly bound nuclei eac ions equi e accoun ing o
e y s ong sho - ange nuclea abso p i e p ocesses; and exo ic nuclei eac ions equi e sho - and long- ange Coulomb and nuclea
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367 Page 2 o 12 Eu . Phys. J. Plus (2025) 140:367
Fig. 1 MARS elec onic sys em
based on CAEN SpA desk op and
VME modules
po en ials, o accoun o ex eme abso p ion p ocesses, which ex end o longe dis ances, a away om he nuclea sho - ange
in e ac ion [15–17].
In his con ex , we p opose o in es iga e u he he 6Li nuclea eac ions. We concen a e on he p oduc ion o 4He, de i ed
om he dissocia ion o 6Li in o 4He and 2H, h ough b eakup o ans e o 2H (cap u e - incomple e usion) o he 12C, ligh e
a ge , ha o ms 14N, in he g ound and exci ed s a es. This in es iga ion is p oposed as a unc ion o he bomba ding ene gy and
he de ec ion angle. I comple es and imp o es p e ious da a [11,18].
The MARS spec ome e bene i s om he s a e-o - he-a in adia ion de ec ion, digi al signal p ocessing, and da a acquisi ion.
Today, his s a e-o - he-a links wo main ea u es: (i) he inc easing use o digi al echniques in p ocessing pulses om de ec o s
and (ii) he inc easing end o digi izing pulses close o adia ion de ec o s [19,20]. Among he 3 majo da a acquisi ion s anda ds
used in nuclea and pa icle Physics, VME (VERSA module eu oca d) [19] bus modules communica e h ough digi al signals bussed
o e he backplane, and da a ans e occu s by di ec memo y access. Wi hin VME, he pa ame e s a e se h ough he so wa e,
allowing o au oma ed con ol. The GUI (G aphical use in e ace) is loca ed on an embedded compu e wi hin a VME bus module.
O e coming he limi s o adi ional analog acquisi ion chains, new wa e o m digi ize s ha e been de eloped [21–25]. They consis
o models ha di e in sampling equency, esolu ion, numbe o channels, o m ac o , and memo y size. Fu he de elopmen s
include DPP (Digi al pulse p ocessing) algo i hms [26–29], ins alled in an FPGA (Field p og ammable ga e a ay), allowing online
analysis and new acquisi ion me hods ha go beyond he simple wa e o m eco d. Thus, a DPP-equipped digi ize p o ides a ully
digi al eplacemen o mos adi ional modules. Digi ize s a e a ailable in VME and desk op o m ac o s and ep esen he la es
in pulse p ocessing and da a acquisi ion sys ems.
MARS in eg a es de ec ion, elec onic, and da a acquisi ion in a e y compac sys em. The elec onic sub-sys em combines
desk op (p eampli ie s) and VME (digi ize , among o he modules) o m ac o s. MARS consis s o 16 channels spec ome e o
s udying cha ged pa icles ou going nuclea eac ions.
In Sec . 2, we p esen MARS as a spec ome e . In Sec . 3, we p esen MARS cha ac e iza ion: (i) on a labo a o y bench wi h
emula ed elec onic pulses; (ii) coupled o a eac ion chambe and a silicon de ec o i adia ed by a adioac i e iple alpha sou ce;
and (iii) coupled o a eac ion chambe , placed in one o he expe imen al beam lines a he CNA [30], o measu e 6Li+12C nuclea
eac ions. In Sec . 4, we p esen he i s esul s o he applica ion o MARS o he 6Li+12C measu emen s. Finally, in Sec . 5,we
d aw ou main conclusions.
2 MARS desc ip ion
MARS (Modula appa a us o nuclea eac ions spec oscopy) is a compac and po able spec ome e ha can measu e he angula
and ene gy dis ibu ions o cha ged pa icles eme ging om nuclea eac ions. I s design allows di e en ypes o digi ize , i mwa e,
and hen acquisi ion sys ems o be applied. In pa icula , he di e en i mwa e allows o di e en pulse analysis echniques.
MARS de ec ion sys em is composed o 16 o ally deple ed silicon (Si) SBD (su ace ba ie de ec o s) om ORTEC wi h ac i e
a eas o 50 mm2. Eigh o hem ha e 15 µm hickness (model ED-35-050-15) (comme cial alue), which a e named by hei se ial
numbe (899–906). The o he eigh ha e 500 µm hickness (Model TB-15-050-500) and a e also named acco ding o hei se ial
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Fig. 2 Se upused o MARS
cha ac e iza ion using he DT4800
emula o
numbe (52–59). Thus, MARS allows one o coupling 8 Si elescopes. These de ec o s, in single o elescope con igu a ions, a e
sui able o cha ged-pa icle iden i ica ion and hei espec i e high- esolu ion spec oscopy. The manu ac u e speci ies esolu ions,
espec i ely, o 35 keV (15 µm) and 15 keV (500 µm), o 241Am alphas (5.486 MeV (85% o in ensi y)) [31,32]. The e iciency o
Si SBD de ec o s, o medium- o high-ene gy pa icles, is commonly assumed o be a uni y ([33] and e e ences he ein). A simple
Mon e Ca lo simula ion pe o med wi h SRIM [34], conside ing he 241Am alpha pa icles, wi h 5.486 MeV, a inciden angle o
0◦, shows ha less han 0.01% a e backsca e ed.
Figu e 1shows MARS elec onic sys em. I combines desk op and VME modules om he CAEN SpA company. I consis s o
wo cha ge sensi i e A1422 p eampli ie s [35], one DT5423 powe dis ibu o [36], h ee V6519P HV powe supply modules [37],
one V1725S digi ize [38] and one V1718 b idge [39]. The V6519P, V1725S and V1718 modules a e connec ed in an 8 slo VME
c a e VME8008B [40]. The V1725S digi ize uns he DPP - PSD (Pulse shape disc imina ion) o DPP - PHA (Pulse heigh analysis),
i mwa e. E en selec ion can be pe o med using a LED (leading edge disc imina o ) o a CFD (cons an ac ion disc imina o ).
The PHA i mwa e allows he digi ize o ob ain an ene gy spec um by applying a apezoidal il e o he inpu pulse and is sui able
o p ocessing pulses wi h long decay imes, such as hose p oduced by alphas and hea y ions in semiconduc o de ec o s [41].
The 16 channels V1725S digi ize is ideal o wo king wi h 16 silicon de ec o s. In pa icula , hei associa ion allows o coupling
8 elescopes, he espec i e coincidence measu emen s and da a acquisi ion. Finally, a PC handles he da a acquisi ion om he
V1725S digi ize by means o CoMPASS (CAEN Mul i-PA ame e Spec oscopy So wa e) [41].
3 MARS cha ac e iza ion
As a p oo -o -concep , p io o i s i s applica ion, MARS has been es ed in a labo a o y en i onmen . Figu e 2schema izes he
i s se up used o cha ac e ize he MARS elec onic sys em. The es pulses we e gene a ed by he 419 ORTEC p ecision pulse
gene a o [42] o he digi al de ec o emula o DT4800 [43]. The DT4800 (Fig. 2) can gene a e andom pulses ha emula e adia ion
sou ces ( o example, a iple alpha sou ce) and de ec o signals, wi h he espec i e ene gy and ime dis ibu ions.
Acco ding o Fig. 2, MARS sys em is di ided in o 8 indi idual elec onic chains (1–8) ela ed o each 8 channels A1422 (13323
and 13324) p eampli ie and 16 da a acquisi ion (DAQ) chains (0–15) ela ed o he V1725S digi ize .
The pulse heigh and ime esponse o he wo p eampli ie s ha e been cha ac e ized using he pulse gene a o . Fo a p ecise
calib a ion p oposal, indi idual ampli ica ion ac o s (F) ha e been de e mined o each A1422 channel. Fo compa ison, he mean
alues o F1.075 (34) and 1.084 (39) we e ob ained, espec i ely, o he modules A1422-13323 and 13324.
Fo bo h A1422 modules, he ise ime is ou
≈13 ns ( o inpu pulses wi h as ise imes in
<15 ns), which is in ag eemen
wi h he da a shee alue ( ou
<25 ns). Fo long inpu pulses ( in
d>1.5 ms), he ou pu decay ime emains cons an a ou
d≈46
µs, which can be compa ed o he da a shee alue ( ou
d50 µs).
The maximum pulse heigh digi ized by MARS is 1.7(1) V. The unce ain y akes in o accoun di e ences ela ed, o example,
o he A1422 ampli ica ion ac o s (F). These ol age alues co espond o ene gies o 19(1) MeV, acco ding o he sensi i i y o
90 mV/MeV o A1422, gi en by he da a shee [35].
Using DT4800 (Fig. 2), we de e mined he ela ion be ween he inpu pulse heigh and he spec um channel. Wi h emula ed
spec a, p ocessed by each o 16 elec onic / acquisi ion chains, we we e able o gua an ee he MARS linea i y. I was u he e i ied
wi h a iple alpha adioac i e sou ce (Sec . 3.1) and du ing he nuclea eac ion expe imen (chap e 4).
We es ima ed he dead ime o he sys em by ansmi ing cons an pulses a di e en equencies. CoMPASS calcula es he dead
ime pe cen age using equa ion (1):
1−O+U+S
I(1)
whe e Ois he numbe o ou pu e en s, Uis he numbe o use -disca ded e en s, Sis he numbe o sa u a ion e en s, and Iis he
numbe o inpu e en s. We obse ed ha inc easing he inpu equency om 102 o 103Hz inc eases he dead ime om 0.2%
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Fig. 3 MARS (le ) coupled o a acuum chambe (in he middle) wi h a iple alpha sou ce, in on o a Si de ec o ( igh ), o s udy he spec al esponse
o he sys em
Table 1 The ene gies and
in ensi ies o he main adioac i e
iple alpha sou ce emissions
Iso ope Ene gy (MeV) In ensi y (%)
233U 4.729 1.6
4.783 13.2
4.824 84.3
239Pu 5.106 11.9
5.144 17.1
5.157 70.8
241Am 5.388 1.7
5.442 13.1
5.486 84.8
The mos ins ense emissions a e
iden i ied in bold
o 1.1%, and inc easing he equency om 103 o 104Hz inc eases he dead ime om 1.2% o 11.6%. Thus, o nuclea eac ion
measu emen s, his p ope y mus be unde con ol o op imizing he coun ing a e.
The DT4800 (in Fig. 2) has also been applied o e i y he esolu ion o di e en emula ed pulse heigh s. Wi h he DT4800,
we emula ed a spec um o a iple alpha sou ce composed o 239Pu (5.15 MeV), 241Am (5.48 MeV) and 244Cm (5.80 MeV). The
esolu ion alues ob ained a y om R0.12% o R0.14%. I allows o esol ing ypical iple alpha peaks, be ween 4 and 6
MeV, o which he main peaks a e sepa a ed by ∼300 keV.
This cha ac e iza ion p ocess was ca ied ou conside ing he maximum numbe o V1725S digi ize acquisi ion channels (214
16384 channels). I should be men ioned ha mos o he alues p esen ed he e go beyond da a shee s, being c ucial o a p ecise
calib a ion, coun ing a e op imiza ion and/o pa icle iden i ica ion p oposals.
3.1 T iple alpha sou ce measu emen s
3.1.1 Labo a o y equipmen and se up
To alida e MARS in a ele an con olled en i onmen , we used he acuum chambe loca ed in he Applied Labo a o y On
Hea y-ions Analysis (ALOHA), a he Depa men o A omic, Molecula and Nuclea Physics o he Uni e si y o Se ille (Fig. 3).
3.1.2 Resolu ion o 500 µmSiSBD
Nex es s aim o de e mine he esolu ion o he hicke (500 µm) de ec o s. Fo his, we used a eal iple alpha sou ce composed
o 233U, 239Pu, and 241Am. The ene gies and in ensi ies o he main alpha emissions a e p esen ed in Table 1.
Figu e 4shows a ypical iple alpha (233U, 239Pu, and 241Am) spec um. Wi h spec a ob ained o all indi idual de ec o s, we
e i ied he linea i y o MARS and s udied he de ec o esolu ion. As expec ed, he main ( iple) alpha peaks, be ween 4 and 6 MeV,
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Fig. 4 Typical iple alpha sou ce
spec um, ela ed o Table 1,
measu ed wi h MARS
sepa a ed by ∼300 keV, a e e y well esol ed. In Fig. 4, he peaks a e sligh ly asymme ic ( o he le ) due o o he decay modes
(see Table 1) wi h lowe yields and lowe ene gies ( om 10 o 100 keV), wi h espec o he main peaks. In Fig. 4, he ull wid h a
hal maximum (FWHM) o he h ee main peaks a e, espec i ely, 32, 39 and 36 keV and he esolu ions R(%) a e 0.67%, 0.74%
and 0.60%.
Fo he sake o compa ison, he PHA pa ame e s we e kep cons an o all chains. Thus, we achie ed esolu ions anging om
0.7% o 2.2%. By indi idually ine- uning he PHA pa ame e s, we we e able o imp o e he esolu ions below 2.0%, ge ing,
on a e age, much close o 1.0%. I is he case o he iple alpha sou ce esul s p esen ed abo e and illus a ed by Fig. 4.These
adjus men s end o dec ease luc ua ions be ween de ec o s and he di e en elec onic/acquisi ion chains. The esolu ion pa e n
alida es MARS o applica ions in nuclea eac ions.
3.1.3 Expe imen al hickness o 15 µmSiSBD
The15µm hick(comme cial alue)o SiSBD ep esen s he echnologicallimi in e mso hickness. This limi implies accen ua ed
hickness a ia ions and he e o e unce ain ies ha mus be quan i ied. The de ec o hickness de e mina ion is manda o y o allow
elescope (E+E) con igu a ion, coincidence measu emen s, as well as he consequen spec oscopy and iden i ica ion o cha ged
pa icles.
The linea s opping powe S o cha ged pa icles in silicon is de ined as he pa icle di e en ial ene gy loss wi hin Si di ided by
he di e en ial pa h leng h:
S−dE
dx(2)
The o al ene gy deposi ed (E) a he pa h leng h can be exp essed by:
E
0
dE
dxdx(3)
whe e ep esen s he Si hickness. The Be he o mula classically desc ibes he speci ic ene gy loss as a unc ion o he agmen
cha ge:
−dE
dx4πe4z2
m0 2NB (4)
whe e
BZln 2m0 2
I−ln1− 2
c2− 2
c2(5)
being he eloci y o he incoming pa icle, ze i s cha ge, N ep esen s he numbe densi y, Zis he a omic numbe o Si (in his
case), m0is he elec on es mass, eis he elec onic cha ge, Iis he a e age exci a ion and ioniza ion po en ial o he Si and cis
he eloci y o ligh in he acuum. Fo non- ela i is ic ( <<c) cha ged pa icles, only he i s e m o B is signi ican [20].
Acco ding o he Be he o mula and he elescope con igu a ion, di e en cha ged pa icles lose di e en amoun s o ene gy
passing h ough he o wa d hinne de ec o . A ypical spec um (E e sus E o al, wi h E o al=E+E) allows o cha ge sepa a ion
and iden i ica ion. In addi ion, he de ec o hickness will de e mine which pa icles s op in he i s ( o wa d) de ec o and which
do no (passing h ough and lea ing he emaining ene gy in he second (backwa d) de ec o ). Thus, hickness de e mina ion is a
key s ep in he cha ac e iza ion o he de ec ion sys em.
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Fig. 5 Typical iple alpha spec a ob ained wi h single and elescope con igu a ions
Table 2 Nominal ( om de ec o s
da a shee ) and measu ed
hicknesses o he hin 15 µm
(comme cial alue) de ec o s
De ec o Nominal hickness (µm) Measu ed hickness (µm)
899 8.0 9.4(4)
900 8.0 11.5(1)
901 14.8 14.2(1)
902 14.6 14.4(3)
903 14.0 13.7(2)
904 14.7 14.5(3)
905 10.4 9.6(2)
906 10.4 10.0(1)
Using he same adioac i e iple alpha sou ce (233U, 239Pu, and 241Am), we de e mined expe imen ally he hicknesses o he
Si de ec o s by measu ing he ene gy deposi ion (E) o he alpha pa icles in a elescope.
The esul s a e p esen ed in Table 2and compa ed o he espec i e nominal hickness alue ob ained om each de ec o da a
shee .
As a p ocedu e, we i s acqui ed a spec um using a single hick (500 µm) Si de ec o (see Fig. 5a on he igh / ed solid line).
Then, we acqui ed coincidence (logic AND) spec a (Fig. 5a) on he le /dashed blue line and Fig. 5b) om a (E+E) elescope.
Fo comple eness and o demons a e he capabili y o he sys em, Fig. 5b shows he 2D spec um.
Figu e 5a shows how he alpha peaks a e shi ed o he le when placing he hin Si de ec o in on o he hick one. In his
case, he shi (E) is, espec i ely, 1.88, 1.79, and 1.72 MeV. As expec ed, acco ding o he Be he o mula, he lowe he inciden
ene gy, he highe he ene gy loss. Measu emen s we e pe o med wi h a collima o wi h 2 mm diame e placed be ween he sou ce
and he de ec o / elescope.
The s opping powe (S) o alpha pa icles, in silicon, was ob ained om SRIM (S opping and ange o ions in ma e ) [34].
Acco ding o equa ion (3), o ob ain he expe imen al hicknesses ( ), he s opping powe (S) is in eg a ed in s eps dx, un il he
measu ed Eis eached. The sum o he s eps p o ides he inal alue o .
In Table 2, he nominal hickness (da a shee o each indi idual de ec o ) anges om 8.0 o 14.8 µm. Acco ding o he man-
u ac u e , he sensi i e dep h (minimum) can a y om 7 o 15 µm. In Table 2, each nominal (absolu e) hickness alue can be
compa ed wi h he expe imen al alue (wi hin i s unce ain y). The mean nominal (absolu e) alue is (11.9±3.0) µm, assuming
he s anda d de ia ion (1σ). I implies a ela i e e o o 25%. The measu ed hickness anges om 9.4 o 14.5 µm. The espec i e
mean alue is (12.2±2.3) µm, assuming he s anda d de ia ion (1σ). I implies a ela i e e o o 19%. These nominal and
measu ed mean hicknesses di e , espec i ely, 21% and 19% om he comme cial alue (15.0 µm).
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Eu . Phys. J. Plus (2025) 140:367 Page 7 o 12 367
Fig. 6 MARS coupled o he 3
MV andem accele a o , a he
CNA, in Se ille (Spain)
Fig. 7 p-EBS spec um o p o ons
beam on C a ge , a 2.50 MeV
and 165.0◦
3.2 Beam es : nuclea eac ion se up
In o de o alida e MARS in an ope a ional en i onmen , a nuclea eac ion expe imen was p oposed. The main goal was o
measu e he 6Li+12C collision a he 3 MV andem accele a o o he CNA (Na ional Accele a o s Cen e ), in Se ille, Spain (Fig. 6).
Fo he cu en s udy, we a e mos in e es ed in he eac ions ha lead o he dissocia ion o 6Li in o i s clus e componen s, 4He+2H.
Fo ins ance, he pu e b eakup o 6Li esul ing on 12C+4He+2H wi h a Q alue −1473.7 keV; deu e on ans e (cap u e) esul ing
on 14N+4He, wi h a Q alue 8798.58 keV, and he 4He ans e (cap u e) esul ing on 16O+2H, wi h a Q alue 5688.18 keV, as a
compe i i e eac ion channel.
The expe imen was ca ied ou in he eac ion chambe o he BNP (Basic Nuclea Physics) line, loca ed a he end o he +30◦
exi o he accele a o .
The ca bon (C) a ge was cha ac e ized in he same acili y by p-EBS (p o on Elas ic Backsca e ing Spec oscopy), using a 2.5
MeV p o on beam and a PIPS (Passi a ed Implan ed Plana Silicon) de ec o se a 165.0◦.
Figu e 7shows he spec um due o 3 di e en a ge componen s: C (12C, 13C) and O (16O). This spec um, simula ed by
SIMNRA [44] (using he na u al iso opic abundance), esul s in he mass densi y o each iso ope: 115(2) µg/cm2 o ca bon (C)
and 1.5(1) µg/cm2 o oxygen (O). Finally, o no maliza ion pu poses, a hin laye (∼14 µg/cm2)o 197Au was e apo a ed on he
a ge .
Figu e 8shows he expe imen al se up inside he eac ion chambe . A double-collima o sys em is ins alled in he en ance o he
eac ion chambe , on he same de ec o s base, jus in on o he a ge . Thus, he beam is aligned and collima ed, which gua an ees
he impac o he beam on he cen e o he a ge . Be o e colliding he 6Li beam wi h he 12C a ge , i was p e iously p ojec ed on a
scin illa o ma e ial (see Fig. 8, on he le ). Thus, he beam was cen e ed on he a ge and i s cu en was op imized. Figu e 8(in he
middle) shows he a ge holde wi h he abo e-men ioned scin illa o and he 12C a ge . The a ge is su ounded by Si de ec o s
(Fig. 8, on he igh ). A simila double-collima o sys em is ins alled in on o each silicon de ec o / elescope. To no malize he
esponse o he de ec ion sys em, elas ic sca e ing o he 6Li on he 197Au (e apo a ed on he 12C a ge ) was measu ed. In he
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367 Page 8 o 12 Eu . Phys. J. Plus (2025) 140:367
Fig. 8 Ta ge holde and de ec ion sys em placed in o he acuum eac ion chambe
ene gy ange, Ru he o d beha io , 1/sin4(θc.m./2), is expec ed o he en i e angula ange. Thus, he geome y o he se up can be
ully checked, and he solid angles a e calcula ed o each de ec o based on hei dis ances o he a ge and labo a o y angles.
4Resul son6Li+12C nuclea eac ions
The i s measu emen was ca ied ou wi h an inciden beam ene gy o Elab 6.00 MeV, which is abo e he Coulomb ba ie
(Vlab
B∼4.5 MeV), o 6Li+12C sys em. Fo his, we used 6Li2+ beam accele a ed by a e minal ol age o VT2.0 MV. The de ec o s
we e moun ed in single and elescope con igu a ions. Following dead ime cons ain s, he in ensi y (cu en ) o he incoming beam
was a ound 20 nA, wi h a maximum coun ing a e o he o de o 1 kHz in he de ec o s, which implies in ∼1.5% dead ime.
Figu e 9shows 6Li+12C nuclea eac ion spec a, measu ed a 6.00 MeV and 35.0◦. This angle was chosen o s a is ical easons.
Figu e 9a shows a one-dimensional (1D) spec um o he 6Li+12C eac ion. He e, se e al nuclea eac ion peaks can be iden i ied.
Mos o he iden i ied peaks a e ela ed o he 12C(6Li,4He)14N∗ eac ion, om which alpha pa icles (4He) a e de ec ed and
comple ely s opped by he single hicke Si de ec o s. One o he peaks iden i ied in he 1D spec um is p oduced by he elas ic
sca e ing o 6Li on 16O (a a ge con aminan , de e mined by p-EBS analysis). Ano he wide peak, cen e ed a ≈3.1 MeV, is
p oduced by he ecoil o 12Cand16O om he a ge . In Fig. 7, we obse e he 16O con aminan ha , in addi ion o he 12C (main
a ge componen ) and acco ding o he simula ions o SIMNRA [44] should (bo h) con ibu e o such a wide peak.
Figu e 9b shows a wo-dimensional (2D) spec um (E+E)o he6Li+12C eac ion, measu ed a 6.00 MeV and 35.0◦. He e,
di e en spo s (a eas) can be iden i ied. Mos o he iden i ied spo s a e (ene gy) co ela ed wi h alpha pa icles coming om he
12C(6Li,4He)14N∗ eac ion.
Figu e 9c shows one-dimensional (1D) spec um o 6Li+12C eac ion, measu ed a 6.00 MeV and 35.0◦( he same as in Fig. 9a).
In addi ion, supe imposed on i , we p esen he p ojec ion o alpha pa icles, obse ed in Fig. 9b, on he o al ene gy (E+E)axis.
Thus, we we e able o ene ge ically co ela e he spo s (a eas) o Fig. 9b wi h iden i ied peaks o Fig. 9a. I is wo h men ioning ha
highe ene gy alphas a e no isible in he 2D spec um because hey deposi a negligible amoun o ene gy in E, which is below
he h eshold.
The e o e, wi h MARS, in single o elescope con igu a ion, we can disc imina e se e al peaks ela ed o he 12C(6Li,4He)14N
nuclea eac ion.
As an example, in he single (1D) spec um o Fig. 9, he esolu ion ob ained om he peak ela ed o he 12C(6Li,4He)14Ng.s.
(alpha pa icles co ela ed wi h he 14N g ound s a e as ou pu eac ion channel) is 2.1%.
Fu he measu emen s ha e been ca ied ou , which allow ob aining exci a ion unc ions o 6Li+12C nuclea eac ions. The
comple e se o measu emen s consis s o 13 bomba ding ene gies: 4.00, 4.50, 5.00, 5.50, 5.75, 6.00, 6.25, 6.50, 6.75, 7.00, 7.25,
7.50, 7.75 MeV; wi h de ec o s moun ed a 8 angles: 35.0, 40.0, 65.0, 70.0, 110.0, 115.0, 140.0, and 145.0◦. Due o collima ion
and he espec i e solid angles, wo consecu i e angles a e compa ible wi hin he angula p ecision (θ±2.5◦). The nuclea e ec s
a e supposed o be p onounced a he ea angles. Figu e 10 shows a 1D spec um ela ed o 6Li+12C eac ions, measu ed a 6.00
MeV, wi h he de ec o a 110.0◦. A qui e simila esolu ion pa e n is obse ed when compa ing he single spec a ob ained a he
o wa d angle (35.0◦) and a he backwa d angle (110.0◦). In bo h cases, he 12C(6Li,4He)14Ng.s.peak is e y well esol ed, wi hou
backg ound. Due o his esolu ion pa e n and o de ec high-ene gy alpha pa icles, measu emen s we e ca ied ou wi h he 8
hicke (500 µm) Si de ec o s, in a single con igu a ion. Thus, we in es iga e he 12C(6Li,4He)14Ng.s. eac ion and i s espec i e
c oss sec ion, as a unc ion o he bomba ding ene gy. Da a we e aken wi h he aim o educing he s a is ical unce ain ies below
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Eu . Phys. J. Plus (2025) 140:367 Page 9 o 12 367
Fig. 9 1D and 2D spec a o he 6Li+12C eac ion measu ed a 6.00 MeV and 35.0◦
5%. Thus, he numbe o coun s (N) ela ed o he 12C(6Li,4He)14Ng.s.peak, o all angles and ene gies, is mainly g ea e han 500
coun s (see, o example, Figs. 9and 10). The s a is ical e o is hen calcula ed as a unc ion o 1/√N, esul ing in he e o ba s
p esen ed in Fig. 11. The e is also an angula unce ain y ela ed o he de ec o s’ posi ion. Howe e , i dec eases wi h he angle o
sca e ing (acco ding o he Ru he o d sca e ing dependence wi h 1/sin4(θc.m./2)), and i is negligible compa ed o he s a is ical
unce ain y a he backwa d angles.
Figu e 11 shows wo exci a ion unc ions ob ained a wo angles (110.0◦and 140.0◦). Fo bo h exci a ion unc ions, we obse e
a con inuous inc ease in he 12C(6Li,4He)14Ng.s. eac ion c oss sec ion, om he bomba ding ene gies a ound he Coulomb ba ie
(Vlab
B∼4.5 MeV). A p onounced inc ease in he eac ion c oss sec ions is obse ed, om ∼6.00 MeV ( e ical dashed line) o
a peak a ∼6.75 MeV. In ac , a a ia ion o one o de o magni ude is obse ed om below he Coulomb ba ie (Vlab
B∼4.5
MeV) o Eop
b∼6.75 MeV. This e ec is be e obse ed a 110.0◦,whe e12C(6Li,4He)14Ng.s.is esol ed o he comple e se o
ene gies. The op imal ene gy (Eop
b), o 6Li dissocia ion, is in good ag eemen wi h ou p edic ion Eop
b≥VB+|Qbu|,whe e,VBis
he Coulomb ba ie o he sys em (Vlab
B∼4.5 MeV); and |Qbu|is he module o he Q- alue o he dissocia ion o 6Li in o i s
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