 -capture measurements with the Recoil-Separator ERNA Frank Strieder Institut für Physik mit Ionenstrahlen Ruhr-Universität Bochum HRIBF Workshop – Nuclear Measurements for Astrophysics October 23-24, 2006, Oak Ridge, Tennessee

12 C( ,  ) 16 O the Holy Grail of Nuclear Astrophysics e e 3 He( ,  ) 7 Be pp chain

ErEr DANGER OF EXTRAPOLATION ! non resonant process interaction energy E extrapolation or measurements ? direct measurement 0 S(E) LINEAR SCALE S(E)-FACTOR -E r sub-threshold resonance low-energy tail of broad resonance Danger of Extrapolation Important for Experiments Low energy High energy

ERNA - Experimental approach Pro & Cons purification separation A B C n+ detection A  coincidence detection Requirements beam purification 100% transmission for the selected charge state high suppression of the incident beam inverse kinematics (gas target) Advantages low background high detection efficiency measure  tot background free  ray spectra gas target Disadvantages difficult to do commissioning charge state beam intenity ? A different approach: recoil mass separator C

ERNA - Experimental approach projectiles + Recoils p rec = p proj momentum conservation Separation Detection & Identification Recoils projectiles focusing He target  -ray emission  Recoil cone  -Recoil Coincidences Minimum supression factor with  = 10nbarn, n target =1x10 18 at/cm² N proj / N recoils ~ 1x10 14

ERNA - Experimental approachSetup ion source dynamitron tandem accelerator ion beam purification He Gastarget singlet 60° magnet  E-E telescope recoil separation doublet analysing magnet recoil focussing Wien filter magnetic quadrupole multiplets triplet side FC

characteristics:  angular acceptance  32 mrad for 16 O at E lab =3.0 – 15.0 MeV for the total length of the gas target  energy acceptance  10% for 16 O at E lab =3.0 – 15.0 MeV  suppression of incident beam ( )·10 -2 (IC) =>  min < 1 nb  purification of incident beam <  resolution of ion chamber  250·A keV or combination  E-silicon strip detector  layout COSY Infinity (recoils fit in 4” beam tube)  field settings are not calculated, but tuned

Experimental approach: ERNA Gas target Gas pressure profile: 7 Li(  ) 7 Li + energy loss of: 14 N, 12 C, 7 Li

ERNA - Experimental approach Charge State Distributions measured for entire energy range but question about point of origin in the gas target → no equilibrium 4 He gas 12 C beam

ERNA - Experimental approach Setup Solution: a post-target-stripper to the separator ► First test with laser ablated carbon foil: 12 C( 12 C, 8 Be) 16 O ► Final configuration: Ar post-target stripper after the 4 He target 4 He Ar 3 He( ,  ) 7 Be no post-target-stripper – measure all charge states

Angular acceptance along the gas target ERNA - Experimental approach Setup 4 He gas 12 C beam separator central position upstream position beam diameter upstream position (energy acceptance) full angular acceptance  100 % transmission (better 3  ) over the total gas target length and full beam diameter

Angular acceptance along the gas target ERNA - Experimental approach Setup - + Simulation of recoil cone

12 C( ,  ) 16 O: E cm =1.3 MeV  rec = 26 mrad,  E/E = 10.8 %,  ≈ 150 pb ERNA - Experimental approach Angular Acceptance

Angular acceptance along the gas target Energy acceptance Change beam energy transmission  E / E 0 [ % ] experimental calculated ERNA - Experimental approach Setup

ERNA Motivation Helium Burning Main reactions: 3  12 C and 12 C(  ) 16 O Stellar Helium burning: 12 C(  ) 16 O 12 C/ 16 O abundance ratio Subsequent stellar evolution and nucleosynthesis but E 0 ~ 300 keV, very low cross section Accurate measurements at higher energy and extrapolation to E 0 are needed 12 C 4 He 16 O 4 He triple alpha 12 C(  ) 16 O Red Giant

ERNA  E/E Matrix 12 C(  ) 16 O E cm =2.5 MeV Suppression R~8*10 -12

ERNACross Section CurveRESULTS

ERNAastrophysical S FactorRESULTS

12 C( ,  ) 16 O the Holy Grail of Nuclear Astrophysics e e 3 He( ,  ) 7 Be pp chain

Explanation of Stars 1960‘s Davis, Fowler & Bahcall Homestake Experiment solar spy = solar neutrinos Neutrino spectroscopy ? Sun = calibrated source H Hydrogen Burning 4p  4 He e -

ERNA Motivation Neutrino Spectroscopy  (L  ) = 0.4 %  age  ) = 0.4 %  Z/H  ) = 3.3 %  (L  ) = 0.4 %  age  ) = 0.4 %  Z/H  ) = 3.3 %  p-p) = 2 %  3 He+ 3 He) = 6 %  3 He+ 4 He) = 15 %  7 Be+p) = 10 %  p-p) = 2 %  3 He+ 3 He) = 6 %  3 He+ 4 He) = 15 %  7 Be+p) = 10 % Influence of different sources of uncertainties on the neutrino flux

ERNA Motivation Neutrino Spectroscopy Influence of different sources of uncertainties on the neutrino experiment

two types of  rays are used to measure 3 He( ,  ) 7 Be cross section 7 Be 7 Li 3 He+ 4 He 2 1 E cm (MeV) 1.586MeV /2- 7/2- 3/2- 1/2- 3/2- 7/2- 00  478 11  42 9 Capture  -rays:  0,  1,  429 Delayed  - rays: : 7 Be decay:  % 89.48% T ½ =53.3d Q=

Summary for the S 34 (0) values

ERNA Acceptance 3 He( ,  ) 7 Be

ERNA  E/E Spectra 3 He( ,  ) 7 Be E cm =1.8 MeV Inverse kinematics

ERNAastrophysical S FactorRESULTS Preliminary result

 3 He(a,  ) 7 Be -  measurement (free & coincidences)  12 C( ,  ) 16 O -  measurement (jet gas target)  14 N(a,  ) 18 F  d(a,  ) 6 Li ERNA - future plans and other perspectives ERNA – present status  12 C( ,  ) 16 O E cm >1.9 MeV (1.3 MeV)  3 He(a,  ) 7 Be E cm >1.1 MeV (0.6 MeV)