1. β decay of 69 Kr and 73 Sr and the rp process Bertram Blank CEN Bordeaux-Gradignan

2. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Motivation 69 Kr – rp-Process Drip-Line Nucleus 69 Br Measurement of the 69 Br ground state. Constraints on the 68 Se rp-process “waiting point”. 73 Sr – rp-Process Drip-Line Nucleus 73 Rb Measurement of the 73 Rb ground state. Constraints on the 72 Kr rp-process “waiting point”.

3. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Br and the rp process The rapid proton, or rp process, is thought to mainly occur during Type I X-ray bursts (timescale of ~10-100 s). Burst properties and nucleosynthesis of heavy nuclei is significantly influenced by “waiting-point” nuclei. T 1/2 ( 68 Se)=35.5s and 69 Br is proton unbound. How strongly can the 68 Se waiting point be bypassed via 2p captures? 2p-capture rate depends exponentially on S p. ⇒ Need spectroscopy beyond the drip line. A. Rogers, ANL

4. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Previous measurements Non-observation: Upper limit on the 69 Br lifetime estimated from 78 Kr fragmentation cross sections  T 1/2 <100 ns  S p < -450 keV (Blank et al., 1995)  T 1/2 <24 ns  S p < -500 keV (Pfaff et al., 1996) Indirect: High-precision penning trap mass measurements of 68 Se and 69 Se + CDE (Coulomb Displacement Energy)  S p = -636 105 keV (Brown et al., 2002; Schury et al., 2007; Savory et al., 2009) Direct: Kinematic reconstruction of the 69 Br proton decay  S p = -785 +35 -40 keV (A.M. Rogers et al., 2011) P. Schury et. al A. M. Rogers et al.

5. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Populating 69 Br via 69 Kr β decay Method: Populate the 69 Br g.s. in the β decay of 69 Kr and look at β-p correlations Monoenergetic protons. Clean and selective technique. Problem: Decay to the Isobaric Analog State is favored over the g.s. -- X.J. Xu et al. Phys. Rev C 55, R533 (1997) However, a few percent of the decay flux may go to the g.s.

6. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Setup Fragmentation of 78 Kr primary beam. E=70 MeV/A Intensity ~ 3-4 eμA. Utilized the LISE3 spectrometer with an Al (100μm) degrader and a Wien filter. CSS1 CSS2 LISE3 DSSSD MCP EXOGAM Clovers Implant-decay experiment using β-p and β- γ event tagging. ToF from RF and MCP's. Si detector for energy loss of heavy ions. Heavy ions are implanted into a 16x16 strip DSSD (3 mm pitch, 500 μm thick). γ 's are measured using four germanium clover detectors. ΔE E ToF LISE Target: nat Ni 200 mg/cm 2 CENBG, GANIL, ANL

7. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Identified 211 69 Kr implantation events →87 69 Kr/day. Clean PID based on redundant identification parameters. Fragmentation of 78 Kr primary beam. E=70 MeV/A Intensity ~ 3-4 eμA. Utilized the LISE3 spectrometer with an Al (100μm) degrader and the Wien filter. Setup

8. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Measurements of known half-lives Known T 1/2 ( 62 Ga) = 116.12 (23) ms. Negligible additional decay components. Known T 1/2 ( 67 Se) = 136 (12) ms So far there is good agreement with most easily measured half-lives.

9. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 65 Se β decay preliminary results Batchelder et al (Phys. Rev. C 47, 2038 1996) identified a single proton group at 3.55 (0.03) MeV. We also observe a proton peak at an energy of 3.51 MeV.

10. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Kr β decay preliminary results

11. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Kr β decay preliminary results Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T 1/2 =32 (10) ms. Also claimed to observe a single proton group at 4.07 (0.05) MeV. X. J. Xu et al, Phys. Rev. C 533, 1997

12. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Kr β decay proton spectrum Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T 1/2 =32 (10) ms. Also claimed to observe a single proton group at 4.07 (0.05) MeV. We observe proton decays to excited states. However, IAS is observed at E=2.97 MeV. We do not observe 69 Br ground- state proton decays.

13. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Kr β decay preliminary results Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T 1/2 =32 (10) ms. Also claimed to observe a single proton group at 4.07 (0.05) MeV. We observe proton decays to excited states. However, IAS is observed at E=2.97 MeV. We do not observe 69 Br ground- state proton decays.

14. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Level Scheme

15. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 69 Kr 73 Sr 73 Rb 72 Kr 69 Br 68 Se Measurement aims: Study of decay of 73 Sr to 73 Rb and 72 Kr Study of decay of 69 Kr to 69 Br and 68 Se Known Properties: 73 Sr decay: - Proton line at 3.75(4) MeV assumed to be IAS (Batchelder et al., PRC48 (1993) 2593) 73 Rb: - half-life T 1/2 < 30ns (Janas et al., PRL82 (1999) 295)

16. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Production: 92 Mo fragmentation at the FRS at 500 MeV/u, 4g/cm2, 9 Be target, 5e9pps expected rates: 73 Sr: 250 per day 69 Kr: 200 per day in same setting  5-7 days experiment  Factor of 5 more statistics than at GANIL for 69 Kr  First data for 73 Sr decay (beyond IAS) setup: DSSSD setup Gamma-ray detection B. Fernandez-Dominguez et al.

17. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011

18. Bertram BlankPRESPEC meeting, Brighton, 12-13 January 2011 Correlation method For any given implant there are uncorrelated decay events that follow implantation. One of the events will be a true correlation while the others are false/uncorrelated. SPATIAL CORRELATION: Requirement that the implant and decay occurs in the same DSSD pixel. TIME CORRELATION: Requirement that the decay occurs within an adjustable time correlation window. False correlations add to a randomly distributed continuous background.