E408S: The structure of 212Po
from 8He reactions on 208Pb
Phil Walker, University of Surrey
photo from Wilton Catford (2004)
NIM article
2002 data
NB: 3 full-size Clovers + 1 small Clover, not close packed,
2 bad crystals; overall efficiency = 3.4% at 662 keV
~2 days of ~105 /s 8He: 208Pb(8He,4n)212Po
singles
γ-rays: singles, doubles, triples
doubles
triples
2004: high-power target tests
peak current: 17 μA of 75 MeV/u 13C6+, i.e. 2.8 kW
~8x105 s-1 8He
average over 5 days ~2x105 s-1 8He
2004
data article
JPG
NB: 4 full-size Clovers, close packed,
overall efficiency = 13.5% at 662 keV
~4 days of ~2x105 /s 8He: 208Pb(8He,4n)212Po
improvement for γ-γ: 2x2х(13.5/3.4)2 = 60
1
st
1
and
nd
2
223 keV gate
2002 data
223 keV gate
2
2004 data
Garnsworthy et al., J. Phys. G31 (2005) s1851
212Po
adding to: Poletti et al.,
Nucl. Phys. A473 (1987) 595
212Po
levels
partial scheme
868 keV gate
981 He
singles
8
singles
223
212Po
405
Energy
beam detector problems: (i) too much beam scattering
(ii) too low efficiency
beamline
2.5m
target
beam
detector
~35μg/cm2
singles time spectra
time spectra
without T
ref
with Tref
~40 ns
Outcomes:
1. New transitions assigned to 212Po.
2. Beam timing not yet realised.
“the day will come when thou shalt see with
thine own eyes what an honourable thing
it is to wander in the pursuit of this calling”
Don Quixote, Cervantes, 1605
cleaning up heavy-ion,xn spectra
thick target: no charged-particle reaction products
90 ns between beam pulses (cf. ~20 ns time resolution)
10 μs between beam particles, for 105 8He per second
beam-particle detection is needed (or neutrons)