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Spokesperson: Marialuisa Aliotta School of Physics - University of Edinburgh

34 Ar( a ,p) 37 K reaction in type I X-ray bursts: time-reversed approach and resonant elastic scattering investigation. Spokesperson: Marialuisa Aliotta School of Physics - University of Edinburgh Scottish Universities Physics Alliance. presented by: David Jenkins. CERN INTC – October 2012.

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Spokesperson: Marialuisa Aliotta School of Physics - University of Edinburgh

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  1. 34Ar(a,p)37K reaction in type I X-ray bursts:time-reversed approach and resonant elastic scattering investigation Spokesperson: Marialuisa Aliotta School of Physics - University of Edinburgh Scottish Universities Physics Alliance presented by: David Jenkins CERN INTC – October 2012

  2. the astrophysical case Relevance to type-I XRBs • (a,p) reactions on 22Mg, 26Si, 30S, 34Arcould provide waiting points in reaction flow • 30S(a,p)33Cl ,34Ar(a,p)37Kreaction rates • responsible for double-peak structure • inbolometric luminosity • direct link with observation Current information • no experimental data available • reaction rate calculations based on Hauser-Feshbach statistical approach • limited accuracy, more so for 0+ + 0+ channel • single resonances may dominate reaction rate Fisker et al. ApJ 608 (2004) L61

  3. Proposed investigations: • 34Ar(a,p)37K cross-section by time-reversal approach • compound states in 38Ca by resonant elastic scattering

  4. EG EG X(a,p)Y Q-value little information available Y(p,a)X compound the methodology time-reversed approach: X(a,p)Y  Y(p,a)X detailed-balance theorem saX calculated using statistical approach spY derived from detailed-balance theorem direct approach: spin-less particles  only natural parity states can be populated indirect approach: no selectivity However! kinematic selection on transitions between ground states  ensure only natural parity states have been populated Requirement: first excited state in X above ~ 1MeV

  5. the case for 34Ar(a,p)37K relevant temperature: T = 1-2 x109 K Gamow peak: E = 1.5-4.0 MeV energy in 38Ca: Ex = 8.6-10.1 MeV (all energies in MeV) Gamow region Ecm = 3.2 – 3.8 Ecm = 4.8 – 5.4 8.595 2.09 26 known states 1.380 a + 34Ar 1.371 Q = 1.559 p + 37K Q = 6.107 • experimental requirements: • 37K beam at HIE-ISOLDE (~ 4.9-5.5MeV/u) • CH2 targets (inverse kinematics) • exclusive measurements 38Ca

  6. kinematics curves 37K(p,a)34Ar kinematics at Ebeam = 204 MeV angular range covered by CD-PAD detector angular range covered by S2 detector 34Ar recoils 4He ejectiles inverse kinematics  forward focussed reaction products particle identification by DE/E and total energy reconstruction

  7. CH2 target S2 detector: alpha particles CD-PAD: heavy ions 34Ar, 37K LEDA: RBS on Au spot W: protons (alphas) LEDA S2 W1-W2-W3 CD-PAD 100 mm target beam 80 mm 250 mm 350 mm Experimental setup aim 1): measure coincident yield for 34Ar+alpha particle identification by DE-E technique (thin target measurements) 37K beam I ~ 3x105 pps E ~ 5.5 – 4.9 MeV/u aim 2): measure resonant elastic proton scattering (thick target measurement)

  8. scattering chamber provided by Edinburgh or use CERN one if available NOTE: Same approach used successfully for 18Ne(a,p)21Na time-reversal measurement @TRIUMF [see PRL 108 (2012) 242701]

  9. beam time request 37K(p,)34Ar measurement 27 shifts • Np = 3x105 pps • NT ~ 4.3x1019 protons cm-2(think CH2 target; dx = 500 mg/cm2) • total cross-sections s (HF formalism; ground state-to-ground state transitions only) • isotropic distribution in centre-of-mass system • total detection efficiency h = 50% 37K(p,p)37K measurement 3 shifts assumptions: • Np = 3x105 pps at Ebeam = 204 MeV (5.5 MeV/u) • NT ~ 8x1020 protons cm-2(thick CH2 target to stop beam; dx = 100 mm) calibration + tuning + energy changes 3 shifts Total beam-time request: 30 + 3 shifts

  10. M. Aliotta1, T. Davinson1, A. Murphy1, G. Lotay1, P.J. Woods1 S. Bishop2, R. Kruecken2,3, T. Faestermann2, R. Gernhaeuser2, A. Parikh4 B. Fulton5, D. Jenkins5, A.M. Laird5 J. Cederkall6 1 University of Edinburgh 2 Physik Department E12, Technische Universität München 3 TRIUMF 4 Universitat Politècnica de Catalunya 5 University of York 6 CERN

  11. the model X-Ray Bursts semi-detached binary system: Neutron star+ less evolved star • thermonuclear runaway on surface of accreting neutron star • explosive ignition of H and/or He • emission of strong X-rays • if matter transfer continues process may repeat T ~ 109 K  ~ 106 g cm-3 (,p) and (p,) reactions on proton-rich nuclei nucleosynthesis up to A ~ 80-100 mass region

  12. Hot CNO 3a reactiona+a+a12C the reaction network nucleosynthesis path: breakout from Hot CNO, onset of rp-process 14O(a,p)17F(p,g)18Ne18Ne(a,p)21Na(p,g)22Mg 22Mg(a,p)25Al(p,g)26Si 26Si(a,p)29P(p,g)30S 30S(a,p)33Cl(p,g)34Ar 34Ar(a,p)37K… …and so on break-out from HCNO ap-process

  13. observational features type I X-ray bursts luminosity curve • 1038 - 1039 erg/s • fast rise time (1-10 s) • duration (~10-100 s) • recurrence intervals (several hours) periodicity J. V. Paradijs et al. Sp. Sci. Rev., 62 (1993) 223 Sztajno et al ApJ 299 (1985) 487-495

  14. double-peak structures bursts from 4U/MXB 1636-53 burst from 4U 1608-52 Szatjano et al. ApJ 299 (1985) 487-495 Penninx et al. A&A 208 (1989) 146-152 origin of double-peak structures still controversial

  15. possible explanations • impeded heat transfer between burning zones • localised burning regions • multiple release of thermonuclear energy • radius expansion when burst luminosity exceed Eddington limit • waiting-point impedance(s) in reaction flow potential waiting points: 22Mg, 26Si, 30S, and 34Ar Fisker et al. ApJ 608 (2004) L61-L64 Fig. 1.—Targets with (p, g) Q-values of ≤0.0, 0.0–0.5, 0.5–2.5, 2.5–3.5, 3.5–5.5, and 5.5–8.0 in increasing levels of gray. Stable nuclei are colored black. The reaction flow rates during the burst peak temperature are shown with solid lines. The thickness indicates the strength of the reaction flow with the exception of isotopes in (p, g)-(g, p) equilibrium, which are shown in thick lines although the net flow is close to zero. The reaction paths that circumvent the waiting points are indicated with dashed arrows.

  16. 34Ar(a,p)37K statistical approach generally applicable if: D    E0 spacing between levels (here: 1/32 MeV-1) Gamow region width (here: 0.97 MeV) average resonance width (here: ~Gp 5-20 keV) Hauser-Feshbach cross section Rauscher & Thielemann, At. Data. Nucl. Data Tables 79 (2001) 47 statistical approach typically uncertain by factor 10

  17. 37K(p,a)34Ar time-reversal cross section Hauser-Feshbach cross section ground-state to ground-state Ecm inv = Ecm dir + Q Q = 1.559 MeV Rauscher & Thielemann, At. Data. Nucl. Data Tables 79 (2001) 47

  18. LEDA S2 W1-W2-W3 W1-W2 100 mm target beam catcher 80 mm 250 mm 350 mm experimental approach and setup arrays of Si detectors LEDA (500mm) q = 23o – 55o RBS for beam normalisation S2 DE-E (40+650mm) q = 8o – 24o alphas from (p,a) channel CD-PAD (35+1500mm) q = 1.5o – 6.5o heavy ions (34Ar, 37K) W1+W2+W3 (2500mm) q = ±6o protons from resonant scattering alternative arrangement W1+W2 (20+500mm) q = ±4o heavy ion detection efficiency ~ 100%

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