Presolar Grains Bulk of material in the solar system is a mixture from a large number of stellar source---mixing in interstellar medium or during solar system formation Some primitive meteorites contain dust grains which show isotopic abundances with order-of-magnitude deviation from mean solar abundances—presolar star dust “Each grain is essentially a frozen piece of a single star that ended its life before the formation of the solar system.” Seen as nanodiamonds, graphite, carbides, Si3N4, corundum, spinel, … Stellar source? Compare ratios of isotopic ratios

Presolar Grains SiC grain Spinel grain (MgAl2O4) Graphite grain 100-nm slice of graphite grain, TiC cluster in circle HST of planetary nebula NGC6751 X-ray image SN Cas A

Isotopic Ratios Most dust grains originate in AGB or Red Giant stars A few SiC grains have low 12C/13C ratios and 30Si enrichment—possible origin in ONe novae x

Condensates from a ONe Nova

Nova Model of Josė,Coc & Hernanz [Astroph.J. 560(2001)897] Abundances depend on amount of mixing, whether CO or ONe white dwarf, mass of white dwarf Elements in Si to Ca region require high-mass (1.35Msun) ONe nova 30P(p,γ)31S a key reaction, determining abundance of 30Si and beyond Hauser-Feshbach statistical model used to estimate 30P(p,γ)31S rate, but it is questionable whether level density is high enough Calculated 30Si abundance in nova ejecta drops 30x if capture rate is increased to 100x H-F rate, increases 5x if capture rate decreased 100x Calculated 30Si/ 28Si ratios much higher than seen in presolar grains → mixing with solar-composition dust ?

Nuclear Reaction Network Si to Ca

JCH abundances for low/nominal/high 30P(p,γ) rates

Excited states in 31S and 31P

Capture Reaction Rates Reaction strength Stellar rate Yield per beam particle

ωγ for 1 ct/hr vs Beam Intensity, Eres

The Experiment at DRAGON Q-value = 6.133 MeV → max. recoil angle 10 mrad at 0.25 MeV/u Max. TOF kinematic spread +/-30ns → probability of accidental coinc is 3x10-5 at BGO trigger rate 500 Hz ∆E≈15 keV/u at cell pressure 6 Torr 30Si contaminant in beam? - normalization for beam-on-target - accidental background - resonances? → DSSSD+β det’r? MCP+I.C.? Scan all energies 500 keV/u → low as beam intensity allows Beam production target/ion source ??? TiC+FEBIAD? Oxide+ECR? Sulfide+ECR? …