isomeric beams
DESCRIPTION
ISOMERIC BEAMS. Phil Walker – University of Surrey. Shell-model isomers in the 208 Pb region Stopped isomeric beams: τ < 1 ms Stopped isomeric beams: τ > 1 ms Fast isomeric beams: purification Fast isomeric beams: reactions. 212 Po = 208 Pb + α. 2911 keV, (18+) τ = 65 s , α decay. - PowerPoint PPT PresentationTRANSCRIPT
ISOMERIC BEAMS
• Shell-model isomers in the 208Pb region
• Stopped isomeric beams: τ < 1 ms
• Stopped isomeric beams: τ > 1 ms
• Fast isomeric beams: purification
• Fast isomeric beams: reactions
Phil Walker – University of Surrey
212Po = 208Pb + α
2911 keV, (18+) τ = 65 s, α decay
ground state, 0+, 430 ns, α decay
wait for one second: isomer purity = 100 %
E > 1MeV, τ > 1 ms isomers
Walker and Dracoulis, Nature 399 (1999) 35
high-spin isomer chart
a Phil Walker special
long-lived, high-spin isomers
Walker and Dracoulis, Hyp. Int. 135 (2001) 83
hafnium (Z=72) isomers
Walker and Dracoulis, Hyp. Int. 135 (2001) 83
178Hf 188Hfexpt.
calc.
Super-FRS yields215Ra
215Ra
Stuchbery et al.Nucl. Phys. A641 (1998) 401
τ = 800 ns, 43/2-, 3.8 MeV
407 keV γ-ray
from 206Pb(13C,4n)
215Ra γ-ray spectrum
from 238U fragmentation
Z. Podolyak, private communication
217Ac level scheme
from (HI,xn) reactionsDecman et al., Nucl Phys. A436 (1985) 311
29/2+, T1/2 = 740ns217Ac
217Ac γ-ray spectrumZ. Podolyak, private communication
from 238U fragmentation
208Pb region
many μs isomersexpected
212Po, 18+, 65s
215Ra, 43/2-, 800ns
217Ac, 29/2+, 1μs
Summary217Ac: 1μs isomer purified by flight time through FRS (factor of 15 in 300 ns) good for RISING fast beam opportunity for (i) γ-gated Coulex (ii) knockout reactions …… and knockout to other isomers: RISING stopped beam
212Po: 65s isomer 100 % purified by flight time in ESR
N~126, Z<82: many new μs isomers expected good for RISING stopped beam test N=126 shell-gap stability approach r-process path ….