β decay of 69 Kr and 73 Sr and the rp process Bertram Blank CEN Bordeaux-Gradignan
β decay of 69Kr and 73Srand the rp process
Bertram BlankCEN Bordeaux-Gradignan
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
MotivationMotivation
69Kr – rp-Process Drip-Line Nucleus 69Br Measurement of the 69Br ground state. Constraints on the 68Se rp-process “waiting point”.
73Sr – rp-Process Drip-Line Nucleus 73Rb Measurement of the 73Rb ground state. Constraints on the 72Kr rp-process “waiting point”.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6969Br and the Br and the rprp process process The rapid proton, or rp process, is thought to mainly occur during Type I
X-ray bursts (timescale of ~10-100 s). Burst properties and nucleosynthesis of heavy nuclei is significantly
influenced by “waiting-point” nuclei.
T1/2(68Se)=35.5s and
69Br is proton unbound. How strongly can the
68Se waiting point be bypassed via 2p captures?
2p-capture rate depends exponentially on Sp.
⇒Need spectroscopy beyond the drip line.
A. Rogers, ANL
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Previous measurementsPrevious measurements
Non-observation: Upper limit on the 69Br lifetime estimated from 78Kr fragmentation cross sections
T1/2<100 ns Sp < -450 keV (Blank et al., 1995)
T1/2<24 ns Sp < -500 keV (Pfaff et al., 1996) Indirect: High-precision penning trap mass measurements of 68Se and 69Se + CDE
(Coulomb Displacement Energy) Sp= -636 105 keV
(Brown et al., 2002; Schury et al., 2007; Savory et al., 2009)
Direct: Kinematic reconstruction of the 69Br proton decay Sp = -785+35-40 keV
(A.M. Rogers et al., 2011)
P. Schury et. alA. M. Rogers et al.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Populating Populating 6969Br via Br via 6969Kr β decay Kr β decay Method: Populate the 69Br g.s. in
the β decay of 69Kr and look at β-p correlations
Monoenergetic protons. Clean and selective technique.
Problem: Decay to the Isobaric Analog State is favored over the g.s. -- X.J. Xu et al. Phys. Rev C 55, R533 (1997)
However, a few percent of the decay flux may go to the g.s.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
SetupSetup Fragmentation of 78Kr
primary beam. E=70 MeV/A
Intensity ~ 3-4 eμA. Utilized the LISE3
spectrometer with an Al (100μm) degrader and a Wien filter.
CSS1CSS2
LISE3
DSSSD
MCP
EXOGAMClovers
Implant-decay experiment using β-p and β-γ event tagging.
ToF from RF and MCP's.Si detector for energy loss of heavy ions.Heavy ions are implanted into a 16x16
strip DSSD (3 mm pitch, 500 μm thick).γ's are measured using four germanium
clover detectors. ΔE
E
ToF
LISE Target: natNi 200 mg/cm2
CENBG, GANIL, ANL
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Identified 211 69Kr implantation events →87 69Kr/day.
Clean PID based on redundant identification parameters.
Fragmentation of 78Kr primary beam.
E=70 MeV/A Intensity ~ 3-4 eμA.
Utilized the LISE3 spectrometer with an Al (100μm) degrader and the Wien filter.
SetupSetup
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Measurements of known half-livesMeasurements of known half-lives
Known T1/2(62Ga) = 116.12 (23) ms.
Negligible additional decay components.
Known T1/2(67Se) = 136 (12) ms
So far there is good agreement with most easily measured half-lives.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6565Se β decay preliminary resultsSe β decay preliminary results
Batchelder et al (Phys. Rev. C 47, 2038 1996) identified a single proton group at 3.55 (0.03) MeV.
We also observe a proton peak at an energy of 3.51 MeV.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6969Kr β decay preliminary resultsKr β decay preliminary results
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6969Kr β decay preliminary resultsKr β decay preliminary results
Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T1/2=32 (10) ms.
Also claimed to observe a single proton group at 4.07 (0.05) MeV.
X. J. Xu et al, Phys. Rev. C 533, 1997
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6969Kr β decay proton spectrumKr β decay proton spectrum
Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T1/2=32 (10) ms.
Also claimed to observe a single proton group at 4.07 (0.05) MeV.
We observe proton decays to excited states.
However, IAS is observed at E=2.97 MeV.
We do not observe 69Br ground-state proton decays.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
6969Kr β decay preliminary resultsKr β decay preliminary results
Half-life previously measured by X.J. Xu et al, Phys. Rev. C R533, 1997 of T1/2=32 (10) ms.
Also claimed to observe a single proton group at 4.07 (0.05) MeV.
We observe proton decays to excited states.
However, IAS is observed at E=2.97 MeV.
We do not observe 69Br ground-state proton decays.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Level SchemeLevel Scheme
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
69Kr
73Sr
73Rb
72Kr
69Br
68Se
Measurement aims:Measurement aims:Study of decay of 73Sr to 73Rb and 72Kr
Study of decay of 69Kr to 69Br and 68Se
Known Properties:
73Sr decay:
- Proton line at 3.75(4) MeV
assumed to be IAS
(Batchelder et al.,
PRC48 (1993) 2593) 73Rb:
- half-life T1/2 < 30ns
(Janas et al., PRL82 (1999) 295)
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Production:Production:92Mo fragmentation at the FRS at 500 MeV/u, 4g/cm2, 9Be target, 5e9pps
expected rates: 73Sr: 250 per day
69Kr: 200 per day
in same setting
5-7 days experiment
Factor of 5 more statistics
than at GANIL for 69Kr
First data for 73Sr decay
(beyond IAS)
setup: DSSSD setup
Gamma-ray detection
B. Fernandez-Dominguez et al.
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Bertram Blank PRESPEC meeting, Brighton, 12-13 January 2011
Correlation methodCorrelation method For any given implant there
are uncorrelated decay events that follow implantation.
One of the events will be a true correlation while the others are false/uncorrelated.
SPATIAL CORRELATION: Requirement that the implant and decay occurs in the same DSSD pixel.
TIME CORRELATION: Requirement that the decay occurs within an adjustable time correlation window.
False correlations add to a randomly distributed continuous background.