44Ti and core collapse - University of Edinburghamurphy/44Ti_files/PAC-MurphyLOI-lite.pdf ·...

GANIL EEC March 11th 201016 Nov 2006 ERAWAST, PSI 1

Alex Murphy

Nuclear astrophysics http://www.ph.ed.ac.uk/nuclear/Dark Matter http://hepwww.rl.ac.uk/ukdmc/ukdmc.html/

44Ti and core collapse supernovae

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Core Collapse Supernovae

Supernovae are… Some of the most powerful explosions in the Cosmos Some of the most scrutinised objects in the Universe Responsible for production of many heavy elements Responsible for shaping our local distribution of stars

Until recently there was consensus on the basic mechanism The best simulations still don’t reliably explode Neutrino driven or acoustic mode mechanism?

Extremely complex Need a good diagnostic

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The Neutrino Mechanism

Massive star (>8–10 M) Stellar evolution onion-skin-like structure At maximum of BE/A, thermal support lost Collapse Huge flux of neutrinos “re-energises” explosion Neutrino driven wind – an excellent candidate site for the r-process

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Acoustic mechanism

Self-consistent simulations of neutrino driven mechanism do not produces a robust explosion

New mechanism: Burrows et al. (ApJ 640 (April 2006) 878-890)

In-fall of matter on to the core induces strong gravity waves

These set up acoustic oscillations a few hundred milliseconds after core collapse.

Oscillations couple efficiently with the outer core/overlying material,

Intense sound waves radiated. Appears to lead to robust explosion

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Importance of 44Ti

44Ti that is ejected will become a γ-ray emitter τ=60 yrs, Eγ=1.157 MeV ‘Easily’ observable INTEGRAL & other missions

Also Meteoritic data Enrichment of 44Ca in type X presolar grains

A grain from the Murchison Meteorite

Integral

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44Ti production as a diagnostic

Amount ejected sensitively depends on location of the ‘mass cut’ Material that ‘falls back’ is not

available for detection 44Ti yield a sensitive

diagnostic of the explosion mechanism

Thus, very useful for models to make comparisons against

Timmes et al. (1996)

Wilson. (1985)

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Which reactions are important?

44Ti abundance determined by only a few key reactions:(L.S. The et al. ApJ 504 (1998) 500)

40Ca(α,γ) 44Ti(α,γ) 44Ti(α,p) 45V(p,γ) Triple α

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Key Reactions

40Ca(α,γ) Recent from Nassar et al. (PRL 96 (2006) 041102) Results from Vockenhuber et al. (PRC 76 (2007) 035801)

Triple−α Ubiquitous; not the focus here

44Ti(α,p) Sonzogni et al. PRL 84 (2000) 1651: Measured above

Gamow window 44Ti(α,γ)

No relevant data 45V(p,γ)46Cr

Interesting, no relevant data

DONE!

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44Ti(α,p): Sonzogni data

Note: Astrophysical region is ~1-4 MeV Need to be able to access cross sections to ~0.1 mb Accuracy of SMOKER reduces at lower energies

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The ERAWAST Project

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• “Exotic Radionuclei from Accelerator Waste”

• Nuclear Astrophysics, geophysics, medicine, industry, etc etc...

• 3.5 MBq presently available (~2x10^17 ions)

• Factor 10 increase shortly (summer, maybe autumn, new PDRA at PSI, working on this, with Astrophysics as main driver)

Implant Ti in to sputter source pill or otherwise bleed in to ion source

Impinge accelerated beam on to 4He gas cell / Windowless gas target

Could consider making 44Ti target

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Reclaiming of 44Ti

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Direct measurement of the 44Ti(a,p) at astrophysically relevant energies

Bleed 44Ti into a stable ion source doped sputter pill?

Inverse kinematics Helium target LEDA silicon array

Cross section ~0.1 mb Require Elab 36-60 MeV

Degrader Intensity: ~2x106 pps for 10 days

~2x1012 ions delivered to targetc.f. ~2 x 1018 ions available

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Investigation of 45V(p, γ )46Cr reaction rate

• Simplest method: 45V(p,p) – resonant elastic scattering- 45V beam, thick CH2 target

• Useful (necessary) precursor to direct 45V(p,γ)46Cr• He & Murphy PRC 75 068801 (2007)- Suggests proton widths are very narrow- No similar studies- Could be a surprise? - 5 x 10^5 pps requires only 1 day running

• Indirect possibilities- 45V(3He,d), 45V(4He,t): angular distributions and

DWBA: (but Jiang et al, Phys.Rev. C 80, 044613 (2009))- What about 45V(d,n)?: Needs a neutron wall

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A new neutron time-of-flight wall? ZEPLIN-III Veto detector 1052kg plastic scintillator in 52 sections. Fully instrumented, available in ~ 12 months time. May need funds to pay for transport etc.

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Purpose of this LoI…

There is an exciting science case for investigating reactions that determine 44Ti production in supernovae 44Ti(a,p) (main interest here) 45V(p,g)

Reclaimed 44Ti is available Need low energy acceleration and delivery (only ~1 ug is available!) Need to address possible contamination issues

Neutron time-of-flight wall could be available Would facilitate (d,n) study of states in 46Cr Could be a long term installation

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Thank you