Ness LUNA II facility. INFN underground Gran Sasso Laboratories. P. Corvisiero INFN - Italy

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1 Ness 2002 LUNA II facility INFN underground Gran Sasso Laboratories P. Corvisiero INFN - Italy

2 the pp chain p + p d + e ν e e d + p 3 3 He He + γγ 84.7 % 13.8 % 3 3 He He He He α + 2p 3 2p 3 He He He He 7 7 Be Be + γγ % 0.02 % Be+e Be+e Li Li + γ γ +ν 7 Be +ν e Be + p 8 8 B+γ B+γ e 7 7 Li Li + p α α + α 8 8 B B 2α 2α + e + + ν e e 4p 4 He + 2e + + 2ν e MeV

3 Tunnel & gamow T sun k E MB 1.3keV Exponential drop of cross section in the energy range of the sun The Gamow Peak: Energy window in which non resonant reactions take place in stellar environment. Examples: E c /kev E 0 /kev σ (E 0 )/barn E min /kev 3 He( 3 He,2p) 4 He He(α,γ) 7 Be N(p,γ) 15 O

4 The astrophysical S-factor σ(e) = S(E) exp(-2πη) /E S(E) = E σ(e) exp(2πη)? 2πη = Z 1 Z 2 (µ/e) 0.5

5 Reaction rates inside the sun: Luminosity Q-value reaction rates L = MeV/s Q=26.73 MeV L R = Q = s -1 in the Lab: ε ~ 10 % I P ~ ma τ ~ µg/cm 2 pb < σ < nb R lab = σ ε I p τ N av /A??? event/month < R lab < event/day signal rate background rate cosmic ray flux at the sea level cm -2 s -1 on a 10 cm 2 detector 2000 events/day!!!

6 Shower on LNGS Background reduction in LNGS (shielding 4000 m w.e.) Cosmic shower Radiation Muons Neutrons Photons LNGS/surface Gran Sasso underground halls

7 Luna goal LUNA the first worldwide underground accelerator facility goal: technique: Provide a direct measurement of the most relevant fusion reactions of astrophysical interest taking advantage of the very low background of Gran Sasso underground Laboratories

8 LUNA site LUNA underground Laboratories LUNA 50kV LUNA 400kV

9 Luna 50 kv LUNA facility LUNA1 50 kv accelerator En. range: 3 50 kev En. stability: < 10-4 current intensity: µa windowless gas target mbar 3 He( 3 He,2p) 4 He D(p,γ) 3 He Gamow peak fully explored D( 3 He,p) 4 He electron screening

10 Foto 50 kv

11 Luna 400 kv LUNA2 400 kv accelerator En. range: kev current intensity: µa Two different beam lines (2003) for solid and/or mbar gas target En. calibrated to < 0.3 kev at E p = kev Capture γ-rays from 12 C(p,γ) 13 N reaction; Resonances: 23 Na(p,γ) 24 Mg (E p = kev) 26 Mg(p,γ) 27 Al (E p = kev) 25 Mg(p,γ) 26 Al (E p = kev) Present and future activity: 14 N(p,γ) 15 O 4 He( 3 He,γ) 7 Be in progress scheduled in 2004

12 LUNA phase 2LUNA II foto New 400 kv accelerator

13 U max = kv LUNA 400 kv at LNGS: I LUNA II max = 650 µa Foto = 0.07 kev E max allowed beams : protons, alphas

14 detectors Detectors 50x50 mm 2 Si detectors (1 mm thick) 50x50 mm 2 E- E Sitelescopes 3 He( 3 He,2p) 4 He D( 3 He,p) 4 He BGO 28cmx8cm 4π D(p,γ) 3 He 14 N(p,γ) 15 O four high eff. HpGe (140%, 120%, 2x100%) 14 N(p,γ) 15 O 4 He( 3 He,γ) 7 Be

15 30 10 BGO detector BGO Channels seeds Energy / kev 14 N(p,γ) 15 O Simulation Channels 12.5 days Background Spectrum Measured Underground E>5.5 MeV: 4.4 cts/mev/day Energy / kev

16 BGO & gastarget Bgo BGO and gas target and gas target pumping stages target calorimeter beam

17 background Silicon array: Background Less than 4*10-2 counts per day in ROI BGO: See spectrum HpGe: See spectrum

18 BGO spectrum numebr of events above E = 5 MeV: < 4 counts/mev/day Excellent for reactions with a Q-value > 5 MeV total Energy (MeV)

19 HpGe spectrum K 214 Bi 208 Tl LNGS background HpGe 120 % t meas = 3.5 days above E = 5 MeV: < counts/kev/day

20 P + N14 LUNA results 3 He( 3 He,2p) 4 He D(p,γ) 3 He 14 N(p, γ) 15 O

21 He3 + He3 Lowest energy: 2cts/month Lowest cross section: 0.02 pbarn Background < 4*10-2 cts/d in ROI

22 P + d test D(p,γ) 3 He The second reaction mesured below the Gamow peak Test for: detector, gas target, electronics Detector: BGO ( r int =3 cm, r ext =10 cm, L=28cm) Target: Gas target (p= 1 mbar, L targ = 10 cm) Eγ: 5.5 MeV `

23 P + d previous D(p,γ) 3 He: Physics case important reaction in protostars cosmogenic d is present in the gas cloud Griffiths et al 1963 Schmid et al 1997 no p+p bottleneck time evolution is governed by the S 1 2 factor Existing data are inconsistent

24 D(p,g) P + d 10 kev D(p,γ) 3 He LUNA data E cm = 10 kev

25 P + d 6 kev D(p,γ) 3 He below the Gamow peak E cm = 6 kev σ = 0.01 pbarn Viviani et al. PRC61 (2000)

26 CNO cycle p,γ 12 C 13 N p,α β - 14 N(p,γ) 15 O Bottle neck of CNO cycle 15 N 13 C 15 O β + p,γ p,γ 14 N Determination of CNO neutrino fluxes Slowest reaction

27 P+ 14 N and g.c.age P + N14 glob. clusters 14 N(p,γ) 15 O Chronometer of The Universe age S 14,1 /5 S 14,1 x5 Standard CF88

28 P + N14 Exc st 14 N(p,γ) 15 O E p = 250 kev Q = 41.2 C t = 20 h I =570 µa E target = 45 kev

29 P + N kev 14 N(p,γ) 15 O E p = 250 kev Q = 41.2 C t = 20 h I =570 µa E target = 45 kev

30 P + N14 g.s. 14 N(p,γ) 15 O E p = 250 kev Q = 41.2 C t = 20 h I =570 µa (p,γ 0 ) direct capture to g.s. E target = 45 kev

31 P + N14 Exc st 14 N(p,γ) 15 O E p = 250 kev Q = 41.2 C t = 20 h I =570 µa (p,γ x ) capture to exc. states 5.18 E target = 45 kev

32 P + N kev 14 N(p,γ) 15 O Direct capture ground state transition in the 14 N(p,γ) 15 O reaction at a c.m. energy of 200 kev.

33 P + N1 4 rate 14 N(p,γ) 15 O Counting rate: p=1 mbar; η=50%; I beam= 250 µa back 1σ E beam (kev)