Presentation at the 10th RIBLL Collaboration Symposium, Beijing, 2017/1/7

Outline 1. Background 1.1 Decay for proton-rich nuclei 1.2 Astrophysical implications 2. Experiments 2.1 Introduction 2.2 Experimental techniques 2.3 β-decay spectroscopy of 24 Si 2.4 β-decay spectroscopy of 20 Mg 2.5 β-decay spectroscopy of 22 Si 2017-3-2 Page 2/73

1.1 Decay for proton-rich nuclei By now, β-decay mode has been identified in more than 2000 nuclei. 2017-3-2 Page 3/73

1.1 Decay for proton-rich nuclei βp precursors 2017-3-2 Page 4/73

1.1 Decay for proton-rich nuclei β2p precursors 2017-3-2 Page 5/73

1.1 Decay for proton-rich nuclei β3p precursors 2017-3-2 Page 6/73

The stellar nucleosynthesis path under various different conditions. 2017-3-2 Page 7/73

Explosive hydrogen burning scenarios 2017-3-2 Page 8/73

HCNO cycles Explosive hydrogen burning scenarios 2017-3-2 Page 9/73

rp-process HCNO cycles Explosive hydrogen burning scenarios 2017-3-2 Page 10/73

rp-process A key breakout route is via breakout from HCNO HCNO cycles Explosive hydrogen burning scenarios 2017-3-2 Page 11/73

rp-process A key breakout route is via breakout from HCNO HCNO cycles Explosive hydrogen burning scenarios 2017-3-2 Page 12/73

rp-process A key breakout route is via breakout from HCNO HCNO cycles Explosive hydrogen burning scenarios 2017-3-2 Page 13/73

2.1 Introduction In explosive hydrogen burning environments such as novae and X-ray bursts, the 15 O(α, γ) 19 Ne(p,γ) 20 Na reaction sequence is a possible breakout path from the hot CNO cycle into the rp-process. 19 Ne(p,γ) 20 Na For the 19 Ne(p,γ) 20 Na reaction, its stellar reaction rate is expected to be dominated by the low-energy resonant levels in 20 Na. <σν> Reaction rate ωγ (resonance strength) E R (resonance energy) ~455 kev above the S p of 2190 kev in 20 Na 2017-3-2 Page 14/73

2.1 Introduction 20 Ne( 3 He,t) 20 Na 20 Ne(p,n) 20 Na 20 Na 2645 kev 1 + 2017-3-2 Page 15/73

2.1 Introduction 20 Ne( 3 He,t) 20 Na 20 Ne(p,n) 20 Na 20 Na 2645 kev 1 + Theoretical calculations 20 Na 2645 kev 3 + ωγ 16 mev 2017-3-2 Page 16/73

2.1 Introduction 20 Ne( 3 He,t) 20 Na 20 Ne(p,n) 20 Na 20 Na 2645 kev 1 + Theoretical calculations 20 Na 2645 kev 3 + 19 Ne(p,γ) 20 Na 20Na 2645 kev 1 + ωγ 16 mev ωγ 15.2 mev 2017-3-2 Page 17/73

2.1 Introduction Simplified 20 Mg β decay scheme 2017-3-2 Page 18/73

2.1 Introduction Simplified 20 Mg β decay scheme 2017-3-2 Page 19/73

2.1 Introduction?? Simplified 20 Mg β decay scheme 2017-3-2 Page 20/73

2.1 Introduction 20 Ne( 3 He,t) 20 Na 20 Ne(p,n) 20 Na 20 Na 2645 kev 1 + Theoretical calculations 20 Na 2645 kev 3 + 19 Ne(p,γ) 20 Na 20Na 2645 kev 1 + ωγ 16 mev ωγ 15.2 mev 20 Mg β + decay 20 Na 2645 kev (3 + ) 2017-3-2 Page 21/73

2.1 Introduction In explosive hydrogen burning environments such as novae and X-ray bursts, the 15 O(α, γ) 19 Ne(p,γ) 20 Na reaction sequence is a possible breakout path from the hot CNO cycle into the rp-process. 15 O(α,γ) 19 Ne For the 15 O(α,γ) 19 Ne reaction, its stellar reaction rate is expected to be dominated by the low-energy resonant levels in 19 Ne. <σν> Reaction rate ωγ (resonance strength) E R (resonance energy) ~504 kev above the S α of 3529 kev in 19 Ne 2017-3-2 Page 22/73

2.1 Introduction α decay branching ratio (B α ) Independent measurements of the α decay branching ratio have yielded good agreement for the h i g h l y i n g s t a t e s, b u t measurements of the low lying states have been controversial. lifetime (τ) 2017-3-2 Page 23/73

2.1 Introduction Simplified 20 Mg β decay scheme 2017-3-2 Page 24/73

2.1 Introduction Simplified 20 Mg β decay scheme 2017-3-2 Page 25/73

2.1 Introduction??? Simplified 20 Mg β decay scheme 2017-3-2 Page 26/73

2.4 β-decay spectroscopy of 20 Mg It will be a serious challenge to reconstruct the decay scheme and to assign the proton peaks to the right decay branches. A n o t h e r c o m p l i c a t i o n w h e n studying the β decay of 20 Mg is the ~70% branching ratio to bound states in 20 Na. The ground state of 20 Na will decay by β-delayed α emission Decay scheme of 20 Mg 2017-3-2 Page 27/73

2.1 Introduction The property of the 2645 kev state in 20 Na is still controversial even after extensive studies during the last 30 years. The property of the 4033 kev state in 19 Ne is still controversial even after extensive studies during the last 26 years. Besides the measurement of the decay properties of the resonances populated in the β decay, other motivations for studying the β decay of 20 Mg are to measure the β decay strength distribution and investigate the quenching of Gamow-Teller strength in β decay, to test the isobaric multiplet mass equation, and to study the isospin symmetry in comparison with the mirror decay and the mirror nucleus. 2017-3-2 Page 28/73

2.2 Experimental techniques Schematic layout of the detection setup 2017-3-2 Page 29/73

2.3 β-decay spectroscopy of 24 Si Radioactive Ion Beam Line in Lanzhou (RIBLL1) 24 Si β + decay Implantation method βp precursors 2017-3-2 Page 30/73

2.3 β-decay spectroscopy of 24 Si u Under a continuous-beam mode, the isotopes of interest were implanted into two DSSDs. The spectroscopic study of 24 Si was performed with high detection efficiency and low detection threshold. u The detection system of our experiment proved to be a powerful equipment to measure the β-delayed proton decay and further research could be extended to the measurements of more exotic decay modes. 2017-3-2 Page 31/73

2.4 β-decay spectroscopy of 20 Mg Radioactive Ion Beam Line in Lanzhou (RIBLL1) 20 Mg β + decay βp precursors 2017-3-2 Page 32/73

2.4 β-decay spectroscopy of 20 Mg Helium-Jet-Fed On-Line Mass Separator ΔE-E telescopes u establish the position of the IAS in 20 Na u a good test of the validity of the isobaric multiplet mass equation. low statistics high contamination from neighboring nuclei 2017-3-2 Page 33/73

2.4 β-decay spectroscopy of 20 Mg projectile fragmentation pulsed-beam mode impantation method u new proton peaks u more accurate half-life u absolute decay branching ratios u upper limit of 1% 2017-3-2 Page 34/73

2.4 β-decay spectroscopy of 20 Mg projectile fragmentation continuous-beam mode impantation method u new proton peaks u more accurate half-life u absolute decay branching ratios u upper limit of 0.2% 2017-3-2 Page 35/73

2.4 β-decay spectroscopy of 20 Mg projectile fragmentation pulsed-beam mode impantation method proton-γ-ray coincidence u high statistics u entire decay scheme u upper limit of 0.1% u isospin asymmetry u quenching of GT strength 2017-3-2 Page 36/73

2.4 β-decay spectroscopy of 20 Mg fusion evaporation reaction pulsed-beam mode impantation method u high statistics u upper limit of 0.02% u favor a 3 + assignment 2017-3-2 Page 37/73

2.4 β-decay spectroscopy of 20 Mg projectile fragmentation impantation method γ-ray measurements u high statistics u Revalidation of the IMME for the A = 20 quintet 2017-3-2 Page 38/73

2.4 β-decay spectroscopy of 20 Mg Isotope Separation On Line ΔE-E telescopes proton-γ-ray coincidence u new proton peaks u two resonances above the IAS u entire decay scheme 16 O recoils from 20 Na 2017-3-2 Page 39/73

2.4 β-decay spectroscopy of 20 Mg Two-dimensional identification plot of ΔE-TOF 2017-3-2 Page 40/73

2.4 β-decay spectroscopy of 20 Mg Purity of the ions Detector 22 Si (%) 20 Mg (%) ΔE 0.00066 0.127 DSSD1 0.00048 0.090 DSSD2 0.00153 0.281 Two-dimensional identification plot of ΔE-TOF 2017-3-2 Page 41/73

2.4 β-decay spectroscopy of 20 Mg Intensity of the ions Detector 22 Si (pps) 20 Mg (pps) ΔE 0.0031 0.59 DSSD1 0.0020 0.37 DSSD2 0.0015 0.27 Two-dimensional identification plot of ΔE-TOF 2017-3-2 Page 42/73

2.4 β-decay spectroscopy of 20 Mg Comparison of the beam conditions in the present work and the previous experiments 2017-3-2 Page 43/73

2.4 β-decay spectroscopy of 20 Mg β-delayed particle spectra from 20 Mg decay measured by (a) DSSD1 and (b) DSSD2 2017-3-2 Page 44/73

2.4 β-decay spectroscopy of 20 Mg β-delayed particle spectrum from 20 Mg decay measured by the two DSSDs 2017-3-2 Page 45/73

2.4 β-decay spectroscopy of 20 Mg Decay energies of β-delayed protons from 20 Mg decay S. Kubono (kev) J. Görres (kev) A. Piechaczek (kev) J. P. Wallace (kev) M. V. Lund (kev) Present work (kev) p1 847 807(10) 806(2) 797(2) 780(8) 808(13) 885(15) p2 1056(30) ~1050 1071(18) p3 1441(30) 1416(18) p4 1669 1670(10) 1679(15) 1670(10) a 1656(10) 1673(14) p5 1891 1928(16) 1903(5) 1907(3) 1897(17) 2138(6) px 2256(18) p6 2351 2344(25) ~2340 2335(3) 2359(18) p7 2559(45) 2567(4) 2576(20) p8 2865 2884(45) 2768(6) 3081(12) 3320(6) p9 3837(35) 3817(3) 3853(17) p10 3990 4098(19) 4071(30) ~4080 4051(2) 4076(16) p11 4239 4332(16) 4326(30) 4332(16) a 4303(4) 4337(16) 4544(25) 4993(16) 2017-3-2 Page 46/73

2.4 β-decay spectroscopy of 20 Mg Absolute branching ratios for the β-delayed proton decay of 20 Mg Proton S. Kubono (%) J. Görres (%) A. Piechaczek (%) J. P. Wallace (%) Present work (%) p1 9 10.7(5) 11.5(14) 8.6(7) 0.5(1) p2 0.7(1) 0.7(2) p3-0.4(1) p4 5 5.4(5) 4.8(6) 5.6(5) p5 1.1(2) 1.1(1) px 0.3(1) p6 0.3(1)+0.8(1) 0.4(1) p7-0.2(1) p8 - p9 0.2(1)+0.1(1) 0.3(1) p10 0.8 1.3(6) 0.7(1)+0.59(1)+0.3 2(1) 0.9(1) p11 0.7 1.7(6) 1.8(3) 1.0(1) 2017-3-2 Page 47/73

2.4 β-decay spectroscopy of 20 Mg Half-lives of 20 Mg χ 2 /NDF = 1.14 Decay-time spectrum of 20 Mg Literature Year T 1/2 (ms) D. M. Moltz 1979 S. Kubono 1992 114 ± 17 J. Görres 1992 82 ± 4 A. Piechaczek 1995 95 ± 3 J. P. Wallace 2012 ~90 M. V. Lund 2016 91.4 ± 1.0 Present work 2016 90.0 ± 0.6 A. Piechaczek theory 1995 101.8 2017-3-2 Page 48/73

2.4 β-decay spectroscopy of 20 Mg γ-ray spectra from 20 Mg β decay 2017-3-2 Page 49/73

2.4 β-decay spectroscopy of 20 Mg γ-ray spectra in coincidence with p4 from 20 Mg β decay 2017-3-2 Page 50/73

2.4 β-decay spectroscopy of 20 Mg Decay branches and the corresponding initial states in 20 Na and the final states in 19 Ne E * ( 20 Na) kev 19Ne g.s. 238 kev 275 kev 1508 kev 1536 kev 984(3) 2645 2998(13) p1 3863(14) p4 4130(22) p5 p4 4721(18) px 4801(32) p7 p6 p2 5142(18) p3 5595(17) p5 5982(18) px 6318(17) p9 6523(28) p11 p10 p10 2017-3-2 Page 51/73

2.4 β-decay spectroscopy of 20 Mg Decay branching ratios for each decay branch E * ( 20 Na) kev Br (%) 19Ne g.s. 238 kev 275 kev 1508 kev 1536 kev 984(3) 66.9(46) 2645 <0.24(3) <0.24(3) 2998(13) 8.60(64) 8.60(64) 3863(14) 3.67(40) 3.67(40) 4130(22) 2.30(43) 0.38(29) 1.91(31) 4721(18) 1.03(64) 1.03(64) 4801(32) 1.20(34) 0.19(2) 0.38(20) 0.63(27) 5142(18) 0.61(63) 0.61(63) 5595(17) 0.68(30) 0.68(30) 5982(18) 0.67(69) 0.67(69) 6318(17) 1.55(86) 1.55(86) 6523(28) 3.58(57) 1.02(8) 1.92(50) 0.64(26) 2017-3-2 Page 52/73

2.4 β-decay spectroscopy of 20 Mg Excitation energies and decay branching ratios for the states in 20 Na S. Kubono J. Görres A. Piechaczek J. P. Wallace M. V. Lund Present Work E * (kev) br (%) E * (kev) br (%) E * (kev) br (%) E * (kev) br (%) E * (kev) br (%) E * (kev) br (%) 990 85 74(7) 984.25(10) 69.7(12) 983.9(22) 66.9(46) 2637 1 2645 0.2 2645 0.1 2647(3) 0.02 2645 0.24 3046 9 3006(10) 10.7(5) 3001(2) 11.5(14) 2970(8) 10.11(85) 2998(13) 8.6(7) 3075(15) 0.5(1) 3868 5 3869(11) 5.4(5) 3874(15) 4.8(6) 3860(10) 3846(10) 6.59(39) 3863(14) 3.7(4) 4090 4123(16) 2.7(3) 4093(5) 4094(2) 3.21(25) 4130(22) 2.3(5) 4721(18) 1.0(7) 4800 1.9 ~4780 4760(4) 3.16(22) 4801(32) 1.2(4) 5507(10) 1.80(17) 5600 1.5 5604(5) 0.16(6) 5595(17) 0.7(3) 5836(13) 0.97(15) 6266(30) 1.2(1) ~6270 6273(7) 1.93(17) 6318(17) 1.6(9) 6440 1.5 6533(15) 3.0(8) 6521(30) 3.3(4) 6522(16) 6496(3) 4.16(20) 6523(28) 3.6(6) 6770 0.03 6734(25) 0.358(12) 6920 0.01 7440 0.01 7183(16) 0.093(8) 2017-3-2 Page 53/73

2.4 β-decay spectroscopy of 20 Mg Comparison between the excitation energies for the IAS in 20 Na 2017-3-2 Page 55/73

2.4 β-decay spectroscopy of 20 Mg Simplified 20 Mg β decay scheme 2017-3-2 Page 56/73

2.4 β-decay spectroscopy of 20 Mg?? Simplified 20 Mg β decay scheme 2017-3-2 Page 58/73

2.4 β-decay spectroscopy of 20 Mg Comparison of the beam conditions in the present work and the previous experiments Exp. Kubono Görres Piechaczek Wallace Glassman Lund Present Year 1992 1992 1995 2012 2015 2016 2016 Intensity (pps) 10-20 0.7 30-150 ~30 4000 ~60 0.59 Purity (%) 1 65 97.6 10 43 10 0.13 Beam time (h) ~4 a ~14 a ~28 a 53.2 162.3 Total number of 20 Mg 10400 4.5 10 6 3 10 6 >4.3 10 7 7.64 10 6 3.2 10 5 a Estimated from the intensities and the total numbers of 20 Mg. 2017-3-2 Page 59/73

2.4 β-decay spectroscopy of 20 Mg log ft values for the states in 20 Na S. Kubono J. Görres A. Piechaczek J. P. Wallace M. V. Lund Present Work E * (kev) log ft E * (kev) log ft E * (kev) log ft E * (kev) log ft E * (kev) log ft E * (kev) log ft 990 85 74(7) 984.25(10) 3.83(2) 983.9(22) 3.80(4) 2637 1 2645 0.2 2645 6.24 2647(3) 6.9 2645 5.82 3046 9 3006(10) 10.7(5) 3001(2) 4.08(6) 2970(8) 4.10(8) 2998(13) 4.15(4) 3075(15) 5.41(9) 3868 5 3869(11) 5.4(5) 3874(15) 4.17(6) 3860(10) 3846(10) 4.11(6) 3863(14) 4.23(5) 4090 4123(16) 4.33(6) 4093(5) 4094(2) 4.33(8) 4130(22) 4.40(9) 4721(18) 4.5(3) 4800 4.23 ~4780 4760(4) 4.08(7) 4801(32) 4.36(11) 5507(10) 3.99(9) 5600 3.97 5604(5) 5.00(38) 5595(17) 4.24(19) 5836(13) 4.09(15) 6266(30) 3.72(6) ~6270 6273(7) 3.55(9) 6318(17) 3.48(25) 6440 1.5 6533(15) 3.0(8) 6521(30) 3.13(6) 6522(16) 6496(3) 3.09(5) 6523(28) 3.01(8) 6770 5.01 6734(25) 4.00(3) 6920 5.39 7440 4.99 7183(16) 5.14(67) 2017-3-2 Page 60/73

2.4 β-decay spectroscopy of 20 Mg Comparison between the transitions in the mirror β decays of 20 Mg and 20 O Transition log ft Ref. δ 20O 20 F 1057 kev 3.740(6) D. E. Alburger 20Mg 20 Na 984.25(10) kev 3.83(2) A. Piechaczek 0.024(6) 20Mg 20 Na 983.9(22) kev 3.80(4) Present work 0.016(11) 20O 20 F 3488 kev 3.65(6) D. E. Alburger 20Mg 20 Na 3001(2) kev 4.08(6) A. Piechaczek 0.12(3) 20Mg 20 Na 2970(8) kev 4.10(8) M. V. Lund 0.12(3) 20Mg 20 Na 2998(13) kev 4.15(4) Present work 0.14(3) asymmetry parameter 2017-3-2 Page 61/73

2.4 β-decay spectroscopy of 20 Mg u A detection system was specially developed for charged-particle decay studies. u A detailed β-decay spectroscopic study of 20 Mg was performed by a continuousimplantation method. u Improved spectroscopic information including the delayed proton energies, the halflife, the excitation energies, the branching ratios, and the log ft values for the states in 20 Na populated in the β decay of 20 Mg. u The large isospin asymmetry for the mirror decays of 20 Mg and 20 O was also well reproduced. 2017-3-2 Page 62/73

2.4 β-decay spectroscopy of 20 Mg u To clarify the remaining problems about the astrophysically interesting 2645 kev resonance in 20 Na, the 4033 kev resonance in 19 Ne, and construct the decay scheme of 20 Mg completely, a further experiment with higher γ-ray-detection efficiency and improved statistics is highly desirable on the basis of present work. 2017-3-2 Page 63/73

2.5 β-decay spectroscopy of 22 Si Radioactive Ion Beam Line in Lanzhou (RIBLL1) 22 Si β + decay β2p precursors 2017-3-2 Page 64/73

2.5 β-decay spectroscopy of 22 Si u high-quality shell-model calculations u candidate for β-delayed two-proton and three-proton emission u maybe unbound with respect to 2p emission 2017-3-2 Page 65/73

2.5 β-decay spectroscopy of 22 Si u open a way to searching for its exotic decay modes. 2017-3-2 Page 66/73

2.5 β-decay spectroscopy of 22 Si projectile fragmentation pulsed-beam mode impant in the silicon detector and MSGC no γ detector u charged-particle spectra u βp u half-life 2017-3-2 Page 67/73

2.5 β-decay spectroscopy of 22 Si Comparison of the beam conditions in the present work and the previous experiments 2017-3-2 Page 68/73

2.5 β-decay spectroscopy of 22 Si Decay-time spectrum of 22 Si 2017-3-2 Page 69/73

2.5 β-decay spectroscopy of 22 Si β2p β-delayed charged-particle spectrum from 22 Si decay measured by the two DSSDs 2017-3-2 Page 70/73

2.5 β-decay spectroscopy of 22 Si Identification of particles around 5600 kev 2017-3-2 Page 71/73

2.5 β-decay spectroscopy of 22 Si Δ(IAS 22 Al) = Δ( 20 Na)+2*Δ( 1 H)+E 2p Δ( 22 Si) = ΔE C -Δ nh +Δ(IAS 22 Al) S 2p ( 22 Si) = Δ( 20 Mg)+2*Δ( 1 H)-Δ( 22 Si) S 2p ( 22 Si) = -108 (125) kev Partial decay scheme for the decay of 22 Si 2017-3-2 Page 72/73

Acknowledgements Thanks for your attention! 2017-3-2 Page 73/73

3.2 Preliminary Results Total 20 Mg 20 Na 20 Mg background 20 Na 20 Ne Decay-time spectrum of 20 Mg with 20 Na component 2017-3-2 Page 74/73

Appendix 2017-3-2 Page 75/73