1. The scientific program for the first five years of LUNA-MV
High current H+ (1 mA), 4He+ , 12C+ (150 μA) and 12C++ (100 eμA) beams in the energy range: (7) MeV deep
From hydrogen burning to helium and carbon burning
Carlo Broggini
INFN-Padova
Nucleosynthesis: from p-p chain, CNO, NeNa and MgAl cycles to the region beyond Fe
Stellar evolution: from Main Sequence stars to thermonuclear supernovae and core collapse supernovae

2. 14N(p,g)15O
278
7556
1/2 +
The bottleneck reaction of
the CNO cycle already studied
by LUNA ( )
7297
7276
7/2 +
14N+p
13C
(p,g)
14N
15O b+
(p,a)
12C
13N
15N
6859
5/2 +
-21
6793
3/2 +
“High” energy: solid target + HpGe,
excellent energy resolution but small
efficiency. Study of the 5 different
radiative captures.
- 504
6176
3/2 -
5241
5/2 +
2) Low energy: gas target + BGO,
bad energy resolution but excellent
efficiency. Study of the total
cross section. s(70 keV)=200 fb,
11 events/day
5183
1/2 +
(p,g)
16O
Measurement with a clover detector
in the energy region above the
259 keV resonance
15O
1/2 -
LUNA: St(0)=1.57±0.13 keV b
Sgs(0)=0.20±0.05 keV b
Adelberger et al : St(0)=1.66±0.12 keV b
Sgs(0)=0.27±0.05 keV b
Q. Li et al. 2016, study over a wide energy
region of 6.79 MeV and g.s. transitions: Sgs(0)=0.42± keV b
It is mandatory to have a low background measurement over a wide energy region

3. cno = LF(S1,14,C+Ncore) The solar abundance problem
new spectroscopic determination of the solar photosphere, in
particular C, N and O: 30-40% lower than before
SSM predictions disagree with heliosysmology results
Physical conditions in the solar core are determined
by pp-chain, in particular the temperature profile,
CNO luminosity ~1%
cno = LF(S1,14,C+Ncore)
probe of the (C+N) abundance
in the Sun core
Borexino: cno< 7.7*108 cm-2s-1
From A.Serenelli, Topical Issue on
underground nuclear astrophysics and
solar neutrinos EPJA 52(2016):
Intrinsic error on the (C+N) determination of 11%, 2.6% from heavy element settling
and 10.6% from nuclear cross sections (S17 and S114, ~7.5% each).
CNO neutrino flux with 10% uncertainty C+N abundance in the Sun core
with ~15% uncertainty

4. 14N(p, g)15O @LUNA MV: day zero experiment to verify accelerator
and solid target set-up + to reduce the error on S114
Set-up: several gamma ray detectors (if necessary, there is space for
an array).
Expected beam time: ~6 months

5. 12C+ 12C the trigger of Carbon burning
* The lower stellar mass bound Mup for the Carbon ignition:
C-O white dwarf (+Nova or thermonuclear supernova) or
massive O-Ne WD or core collapse supernova (+neutron star or
black hole)
* Protons and alpha injection for nucleosynthesis in massive stars
Coulomb barrier: EC= 6.7 MeV
12C+12C 20Ne + a Q=4.62 MeV
12C+12C 23Na + p Q=2.24 MeV
12C+12C 24Mg + g Q=13.93 MeV negligible
12C+12C 23Mg + n Q=-2.62 MeV endothermic
12C+12C 16O + 2a Q=-0.12 MeV three particles
12C+12C 16O + 8Be Q=-0.21 MeV higher Coulomb barrier

6. 12C+12C 20Ne + ai + gi 12C+12C 23Na + pi + gi
Energy (CM) region of interest:
MeV
explosive C-burning from
0.7 MeV
Relevant energy range in stars
12C+12C 20Ne + ai + gi
12C+12C 23Na + pi + gi
Eg = 440 keV
Detection: particles (Silicon
detectors, ΔE-E telescopes,
ionization chambers)
and gammas (from the first
excited state, Ge detectors)
Eg = 1634 keV
Main advantage deep
gamma
ray suppression in a shielded
detector (~5 orders of
magnitude)

7. Beam induced bck: 1H and 2H in the target
T. Spillane et al., Phys Rev Lett. 98 (2007)
Several resonances spaced by keV, typical width G≈10 keV
With a shielded Ge detector bck of 52 cpd keV and 1 cpd keV
Minimum energy 1955 for the proton channel
(bck limited) and 1605 keV for the alpha channel (time limited). All this with 1mm thick carbon target, 5 keV spacing and 30% stat. error)
Expected beam time: ~2.5 years
Beam induced bck: 1H and 2H in the target
Gamma detection: 2H(12C,p1 γ)13C
and 1H(12C,γ )13N
Particle detection (at backward
angles): 2H(12C,2H)12C + 12C(d,p)13C
Heating at high temperature
is able to reduce the contamination D
educe

8. The neutrons for the s-process: nucleosynthesis of half of all elements heavier than Fe (e.g. W, Pd, La, Nd)
Two components were identified and connected to stellar sites:
Main s-process ~90<A<210
Weak s-process A<~90
TP-AGB stars
massive stars > 10 M⊙
shell He-burning He-flash
T9 ~ 0.1 K ≤ T9 ~ 0.4 K
cm cm-3
13C(a,n)16O 22Ne(a,n)25Mg
core He-burning shell C-burning
3-3.5·108 K ~109 K
106 cm cm-3
22Ne(a,n)25Mg
13C(a,n)
22Ne(a,n)

9. 13C(a,n)16O large statistical uncertainties at low energies
Energy region of interest: keV (T = 90 · 106 K)
[MeV]
c.m. E
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1 S [ M e V b ] 1 2 3 4 5 6 10
Davids1968
Bair1973
Kellogg1989
Drotleff1993
Harrissopulos2005
Heil2008
fits/theory
Hale1987
Kubono2003
large statistical uncertainties at low energies
large scatter in absolute values (normalization problem)
unknown systematic uncertainties
uncertainties in detection efficiencies
contribution from sub-threshold state (E=6.356 MeV in 17O)
contribution from electron screening
LUNA400 range
No data at low energy because of high neutron background in surface laboratories.
Extrapolations differ by a factor ~4 (10% accuracy and precision would be required).

10. Direct Kinematics
energy range Ecm = 210 – 300 keV (Ebeam ~ 275 – 400 keV) at LUNA-400
energy range Ecm = 240 – 1060 keV (Ebeam ~ 0.3 – 1.4 MeV) at LUNA-MV
4He beam
13CH4 gas target (drawbacks: limit on the density, possible molecule cracking)
P = 1 mbar
L = 10 cm
13C-enriched solid target (drawbacks: degradation and possible carbon deposition)
density 2· at/cm2
(electron gun evaporation, implantation on Au/ Ta, synthetic diamonds……)
atoms/cm2
beam induced background (α,n) reactions on target impurities or along the beam line
( 10B, 11B, 17O, 18O)
neutron energy range: En = 2 – 3.5 MeV
Inverse Kinematics (different systematics)
13C beam (only possible at LUNA-MV)
4He gas target
P = 1 mbar
L = 10 cm
beam induced background: 13C reaction on 2H, 6Li, 7Li, 10B, 11B, 16O, 19F
neutron energy range: En = 2 – 5 MeV
atoms/cm2

11. Both solid target and gas target solutions are tested @ LNL and LNGS: R&D+first measurement @LUNA400
Reaction rate with enriched 13C target (99%)
and Ia = 200 μA
Elab
[keV]
Ecm
Rate
[neutr/h]
Nt = 1018 at/cm2
1200
918
2 105
1000
764
4 106
800
612
2 107
400
306
339
375
287
103
350
268 28
300
229
1.3
275
210
0.2
250
191
0.02
Ia = 1 mA
Lower beam current at high energy to reduce the neutron production (maximum
acceptable rate: 2000 neutrons/s).
≈ 1-2 months beam time with bck = 0
Work in progress to optimize the neutron detector efficiency for the 3He proportional counters inside a polyethylene cube

12. 3He tubes in two concentric ring: r1 inner radius, r2 outer radius
Polyethylene cube of L ~ 40 cm
18 stainless tubes (1 inch diameter,
25 or 40 cm long, P = 10 atm)
Expected 2 MeV › 30% r1 r2
A different neutron detector might be developed for LUNA-MV in addition to
3He counters: panels of 6Li loaded plastic scintillator surrounding a polyethylene-graphyte moderator

13. 22Ne(a,n)25Mg Eth= 0.57 MeV - Very complex level scheme of 26Mg
- The lowest well studied resonance at Eα=832 keV dominates the rate
- The influence of a possible resonance at 635 keV has been ruled out because of parity conservation
Only upper limits at: 570<Eα<800 keV (~10 pb), the energy region of interest for AGB stars. Extrapolations may be affected by unknown resonances
@T9 < 0.18 the competing reaction 22Ne(α,γ)26Mg (Q=10.6 MeV) should become dominant (400 kV accelerator).
For the 22Ne windowless
gas target + 3He counters inside moderator.
To fully exploit LNGS low background we need:
shielded detector, selected tubes, pulse shape
discrimination, remove 11B (because of
11B(a,n)14N)… to reach the level of ~10 n/day.

14. 14N(p,g)15O: the bottleneck reaction of the CNO cycle in connection
Scientific program of LUNA-MV (first run January 2019) ˃ 10 years mainly devoted to the study of helium and carbon burning
First 5 years:
14N(p,g)15O: the bottleneck reaction of the CNO cycle in connection
with the solar abundance problem
12C + 12C: the trigger of carbon burning in star, White Dwarf (+Nova or thermonuclear SN) or O-Ne WD or core collapse SN (+neutron star or black hole)
Sources of the neutrons responsible for the S-process: 50% of the elements beyond Iron (neutron capture followed by beta decay):
13C(a,n)16O: isotopes with A≥90 during helium burning shell in low mass AGB stars (4 solar masses)
22Ne(a,n)25Mg: isotopes with A‹90 during He burning in high mass AGB stars and during He and C burning in massive stars
12C(a,g)16O: the flagship reaction of the next 5 year plan

16. 1400 m of dolomite rock, CaMg(CO3)2, (~3800 m w.e.)
1979 proposed by A. Zichichi , 1989 MACRO experiment ON
1400 m of dolomite rock, CaMg(CO3)2, (~3800 m w.e.)
Surf.: m2, Vol.: m3, Ventilation: 1 vol / 3.5 hours (Rn in air Bq m-3)
Muon flux: 1.1 m-2h-1, 6 orders of magnitude reduction
Neutron flux, mainly from (,n): cm-2s-1 (0-1 keV), cm-2s-1 (> 1 keV), 3 orders of magnitude reduction
Gamma rays: only 1 order of magnitude reduction, but with thick shield about 5 orders of magnitude in the region of natural radioactivity and 4-5 orders above 3.2 MeV without any shield
Alpha particles: factor ~15 below 3 MeV (shielded Si detector)

17. ≥ 1 month
≥ 308 day
- Terminal voltage Ripple (Rms): V

18. Underground accelerators
Bck.
Acceler.
Beam intensity
Program
Expected start
Notes
LUNA
LNGS
LUNA 400
~300 mA
13C(a,n) et al.,
2017
Solid + gas target
JUNA
~ 2 OoM better
400 kV – ECR
10 mA !
25Mg(p,g)
13C(a,n)
12C(a,g)
Mid 2016
2019
Gas target + 3He tubes in liq. Scint.
CASPAR
~ LUNA
Old 1 MV
150 mA
14N(p,g) ?
22Ne(a,n) ?
Gas target + 3He tubes
LUNA MV
3.5 MV + ECR
1 mA
14N(p,g)
12C + 12C