Novae Reaction Rates and Measurements

Transcription

1 Nova Cygni Nova T Pyxidis Novae Reaction Rates and Measurements Measuring Nuclear Reaction Rates One Step at a Time Shawn Bishop, TUM Erice School,

2 Talk Outline Astrophysics Primer Experimental nuclear astrophysics The novae phenomenon Reaction Rates & Measurements Facilities at MLL Mapping Explosive Rates: Q3D Spectrometer Doppler Lifetime Station Search for Supernova Signal in the Fossil Record Intersection of astrophysics, nuclear physics techniques, geophysics & microbiology Summary Erice School,

3 We are star-stuff. -- Carl Sagan ASTROPHYSICS PRIMER Erice School,

4 Red Giant Companion WD Transfer of H+He-rich (or solar-like) material Erice School,

5 ONe-Nova Burning Cycles 34 Ar 35 Ar 36 Ar 25 Al 33 Cl 34 Cl 35 Cl 22 Mg 23 Mg 24 Mg 32 S 33 S 34 S 21 Na 22 Na 23 Na 20 Ne 21 Ne 22 Ne Y Erice School,

6 Main Sequence Companion or AGB A. Iyudin et al. COMPTEL Observation WD Transfer of H+He-rich (or solar-like) material Erice School,

7 A Recent Surprise from Nova Cas Technische Universität München Erice School,

8 Directionality Temporal Spectral Erice School,

9 Q = 78 kev Q p What happens here? 34 Ar 5.56% T 1/2 =32min T 1/2 =1.5s 34 Cl 94.44% Isomeric Bypass 845ms 298ms 2.5s 1.18s 4.14s 2.6s Q p All Roads lead to Rome at 32 S 2.5min T 1/2 =32min T 1/2 =1.5s 34 Cl Isomeric Feeding, 42% = MeV S 34 9

10 A Thermonuclear Thermometer. Erice School,

11 34m Cl: A Thermonuclear Thermometer 3 + isomeric state gives rise to 2.12 MeV -line ¼ 42% per decay Connected directly to ground by M3 transition (45.6% of the time) Radiation field can also connect isomeric state to ground state by induced transitions into higher states If this is large enough, lifetime will be reduced from 32 min. System of coupled differential equations has been solved 13.7 ps 9.1 ps 5.2 ps 32 min 2.2 s Whoa huge lifetime reduction! Exp t S.M % 0 34 S * 34 Cl 34 S Coc et al., PRC61 (1999) Erice School,

12 Some Key Nuclear Reactions 34m Cl is a last chance -emitter for novae nucleosynthesis Bypassed: 33 Cl(p, ) 34 Ar Produced: 33 S(p, ) 34m Cl Destroyed: 34m Cl(p, ) 35 Ar Excited states need to be mapped out Energy, width, branching ratio, spin Equipment and Instruments Q3D spectrometer 95% hpge detector (Canberra) Si-detector charged particle telescopes (Micron UK) Erice School,

13 Gamow Window Technische Universität München What Needs to be Measured to Determine the Rates Rates in explosive h-burning dominated by resonant proton-capture into excited states Properties of these states uniquely determine explosive X(p, )Y reaction rates Nuclear properties required: Spin Excitation energy Lifetime Proton and/or partial decay-widths Goal: Build facilities at MLL to accomplish these J p X(p, )Y Q-value Y E x Erice School,

14 X(p, )Y Resonant Reaction Rate -value X(p, )Y Y resonance strength µ - reduced mass J i,j p,j X Spins of: resonance state/ projectile/ target T temperature E i energy of state relative to Q Γ p, Γ γ partial width of p- / γ- decay B p = Γ p / Γ branching ratio Key quantity Erice School,

15 Measuring Astrophysical Rates one Step at a Time FACILITIES Erice School,

16 MLL Overview 14 MV Terminal voltage Pulsed beam 200 ns between pulses Pulse width ~ 1 ns Cesium sputtering ion source Negative ion beams No Nobel gas ion beams (except 3,4 He) Isobaric separation at bending magnet Erice School,

17 Accelerator Laboratory: Overview AMS Q3D Doppler Shift Lifetime Station Erice School,

18 Extracting exp(-e i /kt) MAPPING EXPLOSIVE REACTION RATES: THE Q3D Erice School,

19 Q3D High Resolution Spectrograph at TUM Momentum resolution: J p E x X(p, )Y Q-value Used to search for, and study, excited states of nuclei by populating those states using one-step transfer reactions: X( 3 He,t)Y, as an example Y Position of triton along Focal Plane is a measure of the excitation energy. 19

20 Erice School,

21 A Relevant Example: to the 34 Cl -ray Emitter: 33 S(p, ) 34 Cl 34 Cl excited states populated by 33 S(p, ) can -decay into 34m Cl 845ms 298ms 2.5s 1.18s 2.6s 4.14s 2.5min 21

22 S( 3 He,t) 34 Cl, E He = 25 MeV, q = 15 E x ( 34 Cl) Parikh et al. PRC (2009) Erice School,

23 Extracting B p MAPPING EXPLOSIVE REACTION RATES: THE Q3D Erice School,

24 Transfer reaction populates astrophysical state Product Y * will either: gamma-decay proton-decay Decay cone for -decay is small Detection of Y with Q3D, reconstruct kinematics, determine fraction of -decays Decay cone for proton decay large Detect X and p together with Si, determine proton decay fraction Transfer reaction in inverse kinematics J p X(p, )Y Q-value Y E x X + p Beam Y* Q3D Y + Si Detector Erice School,

25 Extracting the ħ/t term DOPPLER LIFETIME STATION Erice School,

26 Si Detectors Target Foil hpge Detector Y 27

27 Measurement of the Doppler shifted gamma yields velocity distribution of nucleus at instant of decay. Decay probability in : Fraction of N total nuclei that decay with velocity in [ (t) cos f, (t + dt) cos f]: Erice School,

28 Velocity distribution formed by an ensemble of N decaying particles: E.K.Warburten et al. Phys. Rev. 160, (1967) Erice School,

29 Target ladder/target Collimator Copper cold trap LN 2 Feedthrough R = 7 cm Silicon DE-E telescope Slider assembly Target ladder Stepper Motor Erice School, 2010 Turbo Pump 30

30 Target Chamber Innards Installation on MLL Beamline Target Ladder Collimator Holder DE-E Si Telescope Erice School,

31 Doppler Shift Station: Target Chamber 14 cm Erice School,

32 Commissioning (two weeks ago) Chose the 32 S( 3 He,a) 31 S reaction 1 st and 2 nd excited states previously observed Lifetimes known Energy spacing large Gammas easily distinguishable Alpha particles well-separated kinematically 32 S beam energy: 80 MeV Target: Au foil, 15 micron thick 1 st 0.5 micron implanted with 3 He at FZD Analysis presently underway Erice School,

33 Particle ID Plot (Uncalibrated) Technische Universität München E a t p D Elastic 3 He DE Erice School,

34 Si-Detector (x,y) Hit Pattern (Raw and Uncalibrated) Y Erice School, X

35 Looking into the Past ACCELERATOR MASS SPECTROMETRY Erice School,

36 Accelerator Mass Spectroscopy at TUM magnetic rigidity in a gas-filled magnet 37

37 150 My BP The dead don t talk, but perhaps they have left us a message BIOGENIC RECORD OF A SUPERNOVA? Erice School,

38 Miocene extinction event ~2-3 My ago Characterized by drop in molluscs and gastropods in Florida, Western Atlantic ocean, Antarctica Possible reasons: C. Fitoussi et al, PRL 101 (2008) T ~ 2.8 Myr ago Glacation & Climate cooling Rising of Panama isthmus Cosmic event partial marine food chain failure Erice School,

39 Ocean Drill Core Samples Technische Universität München Erice School,

40 Fe Concentration in Drill Core Fe concentration: w = sample mass (~ 5 g) m s = <sample magnetic moment>(~ 6 Am 2 ) m rs = saturation magnetization (92 Am 2 /kg) Primary Fe minerals: Dispersed magnetite: Intact M-somes: Erice School,

41 Estimate of 60 Fe in the Magnetofossils Technische Universität München Atom flux of iron from bacteria growth and sedimentation rate: Atom flux of 60 Fe: PRL (2004) ] ; f 60 = 3.8 x 10 8 atom/cm 2 [Knie et al., Ratio of fluxes gives atom ratios: t ~ 500 kyr Amount of drill core: grams; approx. 2 4 mg magnetite Erice School,

42 Earth: A SN Yield Detector D Particle Flux of isotope i at radius D without decay: Cross sectional area of Earth intercepting SN debris: This debris deposited on Earth uniformly, over an area of: Number of atoms i deposited in uniform layer on Earth s surface (now include decay) after a time T since SN occurred: Ratio of any two radio-nuclides: Independent of unknown distance D! 43

43 The Problem of AMS Detection Beyond Iron Technische Universität München Iron-group abundance peak order drop in abundance from Fe-group Erice School,

44 Could These be the Result of Microbial Activity? External ferrihydrite (rust) Distinct internal Fe-rich minerals Banded Iron Formation Erice School,

45 Summary Astrophysics program at TUM underway Technische Universität München Objective: Properties of nuclear states for nova Status of program Q3D spectrograph for measuring/searching out excited states Doppler lifetime station commissioning underway Arrival of neutron detector in July to extend Doppler station to transfer reaction channels with neutron ejectiles Try to utilize pulsed-beam feature of MLL Tandem Another PhD student required (know any candidates?) Supernova search in microfossils Initial phases of project underway (another PhD project) Manuscript presently under peer review: Icarus Erice School,

46 EXTRA SLIDES Erice School,

47 Erice School,

48 Bacteria and Archean Nuclear Reactors Connected to when bacterial life evolved to cope with increasingly richer O 2 atmosphere Ca. 3 Gyr before present Erosion carries UO 2 to into shallow basins Photosynthesis of newly evolving bacteria produces O 2 in shallow water, bringing U 6+ into purely dissolved form in water column Water motion/currents carry U 6+ out of O 2 - rich water Redox boundary changes U 6+ U 4+ U 4+ is precipitated out of solution at the oxicanoxic boundary Highly concentrated in small zone Possible source of natural nuclear reactor Look for depletions in 235 U Erice School,

49 If Companion is AGB 36 S is s-process: not nova AGB Star: 36 Cl(n,p) 36 S 34 S in nova from 34 Cl decay Sulfur measurements should be target of grains Ar Cl S 35 Erice School,