ithemba LABS RIB project: Some thoughts on Nuclear Astro R Neveling, ithemba LABS

Transcription

1

2 ithemba LABS RIB project: Some thoughts on Nuclear Astro R Neveling, ithemba LABS

3 RIB at itl: a phased approach R Neveling, ithemba LABS

4 Bridging the gap Extended period before we have post-accelerated RIB We must be able to show we have a plan for the big increase in beamtime we will have (cannot give away beam to Isotopes any more) Doubling in beamtime (at least) What to do with that time? Who will use it? (manpower)

5 Planned maintenance: 3429 MW Unplanned outages: MW Monday 26 January 2015, 17:25 Other constraints?

6 Unplanned Capacity Loss Factor Other constraints?

7 Unplanned Capacity Loss Factor Other constraints? Medupi: original unit 1 (of 6) synchronization date: 2010,2011,2012? 2015? Kusile: original unit 1 (of 6) synchronization date: 2011,2012,2013? 2017?

8 Bridging the gap Stable beam period may be longer than anticipated We must be able to show we have a plan for the big increase in beamtime we will have (cannot give away beam to Isotopes any more) Doubling in beamtime (at least) What to do with that time? Who will use it? (manpower)

9 Bridging the gap m en t Stable beam period may be longer than anticipated Doubling in beamtime (at least) What to do with that time? Who will use it? (manpower) S up pl y C ha in an ag e M We must be able to show we have a plan for the big increase in beamtime we will have (cannot give away beam to Isotopes any more)

10 High energy resolution 0 measurements AIM: High energy resolution ( 100 kev FWHM) dispersion matching required Low background clean and stable beams, X&Y focal plane detection Medium energy particles p,d,t, (Ebeam MeV/A) Three successful setups: IUCF, USA (p,p'), 160 MeV, 35 kev Grand RCNP, Japan (3He,t), 420 MeV, 21 kev (p,p'), 295 MeV, 20 kev (p,t), 98 MeV, 13 kev PRC (2007) NIM A 605 (2009) 326 PRC (2009) PRC75 (2007) KVI, The Netherlands (d,2he), 172 MeV, 100 kev PRC75 (2007) / NPA (2004)

11 High energy resolution 0 measurements AIM: High energy resolution ( 100 kev FWHM) dispersion matching required Low background clean and stable beams, X&Y focal plane detection Medium energy particles p,d,t, (Ebeam MeV/A) Three successful setups: IUCF, USA (p,p'), 160 MeV, 35 kev Grand RCNP, Japan (3He,t), 420 MeV, 21 kev (p,p'), 295 MeV, 20 kev (p,t), 98 MeV, 13 kev PRC (2007) NIM A 605 (2009) 326 PRC (2009) PRC75 (2007) Facility decommissioned (1999) Now also at: KVI, The Netherlands (d,2he), 172 MeV, 100 kev PRC75 (2007) / NPA (2004) ithemba LABS (p,p') & (α,α'), 200 MeV (p,t), 100, 200 MeV

12 The K600 at 0 : a special instrument ITL-TUD-WITS-UCT project, made possible by: Financial assistance: German DFG, SA NRF Technical assistance: RCNP, TUD, U Notre Dame

13 The K600 at 0 : a special instrument Extended periods of beamtime great for zero degree experiments ITL-TUD-WITS-UCT project, made possible by: Financial assistance: German DFG, SA NRF Technical assistance: RCNP, TUD, U Notre Dame

14 Build on our strengths Structure studies (clusters, GDR, GMR...) Astrophysics studies (spectroscopic info & reaction rates) 0 0

15 Catherine Deibel, Argonne

16 What do we want to do? With ample stable beam: afford the luxury of reactions such as (4He,6He) (3He,6He) (4He,8He) (3He,8He) T1/2=801 ms T1/2=119 ms Reaction forward peaked: zero degrees, or 4 mode small cross-section (nb) 1 count/h (50nA, 1mg.cm2) spectroscopic info allows reaction rate calcs

17 8 (α, He) 22 Na produced in Ne novae (30% of observed novae, O-Ne-Mg dwarfs) 22 Ne β+ decays; followed by MeV γ How strongly enriched is 22Mg? Processes to deplete it?...not enough 22Na seen compared to models Al(p,γ) Si spectroscopic info needed

18 8 (α, He) 28 Si(α,8He)24Si 23 Al(p,γ)24Si PRL 79 (1997) 3845 IUCF, 177 MeV beam, 0-3

19 8 (α, He) 28 Si(α,8He)24Si PRC 15 (1977) 2028

20 Georg Berg

21 Georg Berg

22 The K600 at 0 : unique opportunities + NEP funded

23 What can we do? Structure studies (clusters, GDR, GMR...) Astrophysics studies (BR, particle width) α0 p0 α1 p1 p2 E (decay particle) p3... Ex

24 The K600 at 0 : unique opportunities + + THE FUTURE

25 The K600 at 0 : unique opportunities + + THE FUTURE BR & particle widths PDR & E1 strength

26 What do we want to do? Philip Adsley

27 With RIB: what can be done? Philip Adsley

28

29 20 Search for 5α cluster state in Ne Candidates for 5 -cluster Hoyle-analogue state requires closer look Measure ( 0,1+16Ogs,6.05), branching ratios Inelastic scattering at 0 : Excites natural parity states Best angle to excite 0+ Future? Aim for complete decay measurement, 4 decay...? ultimately require -array JJ van Zyl, Research proposal, ithemba LABS PAC - 24 Oct 2013

30 20 Search for 5α cluster state in Ne Candidates for 5 -cluster Hoyle-analogue state requires closer look Measure ( 0,1+16Ogs,6.05), branching ratios Inelastic scattering at 0 : Excites natural parity states Best angle to excite 0+ Future? Aim for complete decay measurement, 4 decay...? ultimately require -array JJ van Zyl, Research proposal, ithemba LABS PAC - 24 Oct 2013

31 Astrophysics: 15O -capture

32 What do we want to do? With ample stable beam: can afford the luxury of reactions such as (4He,6He) (3He,6He) (4He,8He) measure states allows reaction rate calcs

33 What is the αp-process? Series of (α,p) and (p,γ ) reactions, following the break out from the HCNO cycles at very high temperatures > 0.8 GK. It bypasses the slower rp-process, a series of (p, γ ) and β+ decays that occurs a lower temperatures. At sufficiently high temperatures the αp-process can occur in the atmosphere of a neutron star that is accreted from a binary companion star and can be observes as X-ray bursts (see Light Curves) measured in satellite bases γ - detectors. Explosive X-ray bursts last from a few to 1000 seconds and can have time structures like the double peaks seen in the figure. More precise αp-rate calculations may help to understand such observations. The αp-process ends in the A region, owing to the Coulomb barrier. The rp-process continues to higher masses.

34 Astrophysics: 15O -capture

35 Astrophysics: 15O -capture 4033-keV (L=1) state: with Γα = Bα Γtot Bα = 2.9± from: F(3He,t)19Ne*(,α)15O 19 Difficult: 8 t-α events; background = 35 Γtot = Γγ 1/τ with τ = 11(+4)(-3) fs from: γ-ray Doppler-shift lineshape [2] Γα = 17±13 μev Sensitivity to modeling and reaction rates presently not disentangled Further clarification of reaction rate necessary.

36 Astrophysics: 15O -capture 4033-keV (L=1) state: Known to have 5 particle-2 hole structure [1] Strongly populated in the 21Ne(p,t)19Ne reaction, see plot from Ref. [1]. Use this reaction to maximise yield to the 4033-keV state Ground state of 21Ne is 3/2+ so populate the 4033-keV state with an L=0 reaction peaked at 0 Kinematics of (p,t) such that 19Ne recoil is boosted backwards in lab frame Silicon array at backward angles to detect coincident alpha-particles Low branching ratio: 2 coincident events per shift + other alpha-induced reactions where the compound can be accessed via (p,t): 14 O(α,p)17F, 18Ne(α,p)21Na etc. Oxygen-15 alpha capture PR227, Adsley, Diget, Neveling, et al. [1] Fortune et al. Phys. Rev. C 18, (1978) [2] Ugalde et al. Phys. Rev. C (2007)

37 The Pygmy Dipole Resonance Savran et al. S. Goriely, Physics Letters B 436 (1998) 10

38 PDR studies at KVI Slide by Janis Endres

39 PDR studies at KVI PDR splitting (Endres et al. PRL 105 (2010) ) α-particles more sensitive to surface neutron oscillations low-lying 1- states represent isoscalar neutron-skin oscillation higher-lying 1- states belong to tail of isovector GDR

40 Particle-gamma coincidence at itl 1368 kev HAGAR Transition to: gs Mg 1368 kev α threshold : MeV Ne 1634 kev HAGAR results: 220 kev (FWHM) resolution

41 detection 7-9 December 2012: K600 + Two Clovers + HAGAR Scattering chamber: 524mm diameter Sliding seal configuration HAGAR: ~30 years old NaI(Tl) single crystal (Bicron) 356 mm long, 238 mm diam Outer shell of BC408 (outer diam 486 mm) High energy Anticoincidence GAmma Ray spectrometer Clovers: 50mm x 70mm HPGe

42 Selectivity at 0 12 C (0+) (2-) (2+) 2+ 2-

43 Collaborations P Jones, J. Mira, M Wiedeking, JL Conradie, D Fourie JJ van Zyl, F Nemulodi, P Papka, C Swartz H Fujita. Y Fujita, A Tamii, R Fearick, SM Perez N Orce G Berg M Freer, Tz Kokalova, C Wheldon D Jenkins, C Diget W Catford J Carter, I Usman, E Sideras Haddad, L Donaldson, M Jingo, O Kureba P von Neuman Cosel, A Richter, D Savran, A Zilges

44 BigByte efficiency