Beta Decay – General Principles - PowerPoint Presentation

1. Beta Decay – General PrinciplesPaul ManticaLecture 1Euroschool for Exotic BeamsLeuven, Belgium - 2009

2. Beta Decay of Exotic Nuclei:Science OpportunitiesGamow-Teller strength in N~Z nuclei to 100SnPersistence of shell gaps in extreme neutron-rich nuclei (60Ca, 128Pd)r-process waiting point nuclei along N=82 (124Mo, 123Nb, …) and N=126 (195Tm, 194Er …)E(4+)/E(2+) and phase transitions away from stability (122Pd, 90Ge, 148Xe, …) and others …Beta decay properties of unstable nuclei far from stability can provide valuable insight into nuclear shell structure and nuclear deformation changes toward the drip lines.Precise beta-decay half-lives, end point energies, and branching ratios to unbound states are crucial nuclear physics input parameters for network calculations of the astrophysical rapid neutron capture process.The selective method of beta decay, in combination with spectroscopic measurements of gamma-rays and neutrons, will open new opportunities to study, for example:

3. Beta Decay of Exotic Nuclei:Application of Fast BeamsSignificant progress has been made in the measurement of beta-decay properties of exotic nuclei, attributed directly to particle-detection techniques employed with fast beams.Advantage of fast beams:Can correlate implantations and decays event-by-event ID of decay parentsuitable for cocktail beams crucial for systematic investigationsreduction in background and increased sensitivity half-life: few per day beta-neutron: few per hour beta-gamma: few per minute

4. Beta Decay of Exotic Nuclei:Reach Across the Nuclear ChartFirst 2+ energies Beta decay half-livesMajor advance in characterizing the systematic variation of E(2+) and E(4+)/E(2+) with increasing neutron numberAll waiting points along N=82 and many along N=126 will be established

5. Beta Decay of Exotic Nuclei:Experimental Needs and ObservablesNeeds:Fast beams via fragmentation or fissionHighly-segmented implantation detectorOverall implantation rate < 500 s-1 high resolution separator Digital readout (dedicated electronics)Ancillary detectors electrons, neutrons, photons, etc.Floor space: 3 m x 3 m x 3 mObservables:Half-livesQ values (masses) Absolute branching ratios Excited states in daughter nuclei Microsecond isomersexcited states in parentBCSSeGANERO

6. Types of Beta DecayNeutron numberProton number204Pb204Tl204Bib- decayEC/b+ decayb- decayEC decayb+ decay

7. Beta Decay Observablesb–ggggb–b–nT1/2QbPnT1/2gisomeric gamma raysdelayed gamma raysabsolute beta branchingisomer half-livesbeta half-livesdelayed neutron branchingBeta endpoint energy

8. Beta Decay EnergeticsMass = f1(A)Z2+f2(A)Z+f3(A)-d204Pb204Tl204BiA=204 Mass Chain

9. Beta Decay Endpoint Energyb- decayEC decayb+ decay

10. Beta Energy SpectrumEnergy spectrum is for the positron is continuous up to the endpoint energyDecay energy is shared between the electron and the neutrino ~1/3 Eb(max)

11. Radioactive Decay KineticsRadioactive decay and growth as the form of a first order rate lawNt=Noe-ltNo is the initial number of nucleiNt is the number of nuclei at time te is a mathematical constant 2.7182818284l is the decay constantThe characteristic rate of a radioactive decay is conveniently given in terms of the half lifet1/2=ln 2/l  0.693/lThe half life is the average time required to reduce the initial number of nuclei by a factor of 2

12. Radioactive Decay Curve

13. Decay Rates for Beta Emission:EnergeticsThere are a wide range of beta decay half lifes:IsotopeDecay Energy (E0)Half life40K210.044 MeV4.00 x 1016 s50K3114.2 MeV4.27 x 10-1 sIn general, large decay energies are associated with very short beta-decay half-livesRate is proportional to Decay Energy (E0) and Proton Number (Z)

14. Decay Rates for Beta EmissionInitial and Final StatesIsotopeDecay Energy (E0)Half life32Si180.221 MeV4.73 x 109 s66Ni380.20 MeV1.96 x 105 sBeta transition strength is expressed as a product of the energy factor times the half-life (log f0t values).However, beta-decay half-lives also depend strongly on the properties of the initial and final states involved in the decay

15. Allowed Beta Decay Allowed transitions come in two types: Fermi (D=0) and Gamow-Teller (D= 1).Relative orientation of angular momentum vectors for the emitted neutrino and fast electron Log fot is an expression of the transition strength that considers the energy of decay (fo value) and the time for decay (t), where t is the partial half-life for the decay. log fot = log fo + log tlog t is the logarithm of the partial half-life of the beta decayt = [t1/2]/branch (in seconds)DJ=0 Dp=nolog ft ~ 3.5DJ=0,1 Dp=nolog ft ~ 4-7Superallowed Fermi DecayAllowed Decayp=(-1)parity

16. Gross Beta Decay TheoryGross b decay results overestimate the half-lives of the most neutron-rich isotopesb-decay rate to low-energy states in daughter underestimatedTachibana et al., Prog. Theor. Phys. 84, 641 (1990)Pfeiffer, Kratz and Möller, Prog. Nucl. Energy 41, 39 (2002)T1/2  a  (Qb - C)-ba = 2740 sb = 4.5Qb = b endpoint energyC = cutoff energy (pairing gap in daughter)Sb(E) is the beta-strength functionf is the Fermi functionR is the nuclear radiusQb is the endpoint energyEi is the energy of the final state

17. Gross Theory vs. ExperimentNote that:Fermi function is dominated by the phase space factor (Qb-Ei)5The average error increases as T1/2 increasesInclusion of first forbidden decay (ff) improves average error for longer T1/2 valuesUncertainty in masses far from stability does not dramatically impact T1/2, since relative error does not increase rapidly (Qb is large) Möller et al., PRC 67, 055802 (2003)

18. Beta Decay – Execution at Fast Beam FacilitiesPaul ManticaLecture 2Euroschool for Exotic BeamsLeuven, Belgium - 2009

19. National Superconducting Cyclotron Laboratory30 Faculty19 Experimental 7 Theory4 Accelerator Physics60 Graduate Students50 Undergraduate Students700 member Users GroupSelected to design and establish Facility for Rare Isotope Beams (FRIB)ChemistryBiochemistryLaw schoolNSCL… a world leader in rare isotope research and education

20. NSCL Coupled Cyclotron Facility

21. Projectile FragmentationFast-moving projectile is abraded, resulting projectile-like fragment travels with a velocity similar to initial projectileProduce many isotopes below the initial projectile A and Z, both stable and radioactiveSeparation does not depend on the chemical properties of the isotopes TOFDE 78Kr Fragmentation @ 70 MeV/AEach fragment can be uniquely identified using time-of-flight, energy-loss, and magnetic rigidity

22. Rare Isotope Beam ProductionK1200K500A1900Primary stable atoms are ionized in an ECR source and injected into the accelerating system composed of the coupled K500 and K1200 superconducting cyclotronsThe fast, stable beam is then impinged on a target at the object of the A1900 separator

23. Rare Isotope Beam SelectionMorrissey et al., NIM B 204, 90 (2003)K500K1200A1900ECR ion sourcestargetwedgefocal planeThe A1900 Fragment Separator is used to select the rare isotope of interest from unwanted fragmentation productsDp/p = 5% maxBr = 6.0 Tm max8 msr solid angle35 m in lengthProduction of 78Ni from 140 MeV/A 86Kr

24. NSCL Beta Counting System (BCS)Implantation detector: 1 each MSL type BB1-1000 4 cm x 4 cm active area 1 mm thick 40 1-mm strips in x and yCalorimeter: 6 each MSL type W 5 cm active area 1 mm thick 16 strips in one dimensionPINSPlaner GeBackplatePrisciandaro et al., NIM A 505, 140 (2003)

25. Heavy Charged ParticlesPrimary interaction is via the electromagnetic interaction between the positive charge of the heavy ion and the negative charge of the orbital electrons within the detection medium. The maximum energy that can be transferred is 4Eme/mWhere m and E are the particle mass and energy, respectively, and me is the electron mass. Since me is much smaller than the incoming particle mass, the energy transfer is small. primary particle loses its energy over MANY interactions produce many excited atoms or ion pairs in the detector material

26. Stopping PowerThe linear stopping power for charged particles is given as Through the Bethe formula, the linear stopping power is a function of the atomic number of the stopping material (Z) and the ion charge (q) and velocity (b=v/c) of the incident particle Distance of penetration-dE dxRange can be obtained by integrating the energy loss rate along the path of the ion:

27. Range of Projectile Fragments in SiliconStopping power scales with ion mass, charge and energy:Scaling can be extended to range calculations:http://www.physics.nist.gov/PhysRefData/Star/Text/ASTAR.html

28. Practical Calculation:Range of 78Ni in SiliconThe range of 100 MeV/A 78Ni in Si can be scaled from the range of 100 MeV/A alpha particles.

29. Fast Electrons vs. Heavy IonsFast electrons lose energy at a lower rate and follow a more torturous path through absorbing materials. This can be attributed to the low ion charge (z = 1) and low mass of the electron. Fast electrons can also lose energy through radiative processes S  (1/v)2 NZ (electronic) S  NEZ2 (radiative)Therefore the radiative loses are most important for high energy electrons where the absorbing material has a large atomic number.

30. Range of Fast Electrons in Siliconhttp://physics.nist.gov/PhysRefData/Star/Text/ESTAR.htmlThe range of a 10 MeV beta particle in Si is 5.8 g/cm2r(Si) = 2.33 g/cm3Therefore, the amount of Si required to fully stop a 10 MeV beta particle is ~ 2.5 cm!

31. Signal Processing for Heavy Ions and Betas in a Single Silicon DetectorChallenge: beta DE ~ 100’s of keV beam E ~ 1’s of GeVCPA16 dual gain preamp from MultiChannel Systems: 16 channels, 50W input impedance, 2V output, ~350 ns rise time.Low gain: High gain:0.03 V/pC 2.0 V/pCoutput to ADCs output to Pico Systems 16 ch shaper

32. BCS ElectronicsPIDVME ReadoutCAMAC ShapersNIM TriggerPIDDigitizationConventional BCS Electronics: Block DiagramXIA PIXE-16Digitized waveform: short-lived proton decay of 145TmGrzywacz NIMB 204, 649 (2003)660 channels commissioned and in use with SeGA

33. Bulk Activity MeasurementsImplant activity into a stopper material for time timplant.Cease implantation and observe decay for time tdecay.If necessary, introduce a “clean” stopper material and repeat.For deposit of a single isotope:A0For exampleshown:timplant = tdecay =4t1/2A=Nl

34. Time Correlation of Implantations and Charged-Particle DecaysCorrelations between an implantation event and subsequent b-decay events are done based on position and timeInformation regarding the particle ID is carried over to a correlated decay event, therefore, b decays are unambiguously identifiedBoth prompt and delayed g rays can also be unambiguously assignedDecay curves are generated from the difference in absolute times between and implantation and correlated decay eventThe high pixel density of the DSSD and low implantation rates (less than 200 ions/second) are essential to reduce probabilities for incorrect correlationsAzq+bImplantationDecayAbsolute timePosition (x,y)Energy loss and time of flightFragment total kinetic energyGate the g-array ADCs for 20 msAbsolute timePosition (x,y)Energy of outgoing particleGate the g-array ADCs for 20 ms

35. Bateman EquationsThe Bateman equations provide a means for analyzing a chain of many successive radioactive decays.Special assumption: At t=0, only parent is present.

36. Consecutive First-Order DecaysFor nuclei far from stability, the typical condition is that This condition is the non-equilibrium case for radioactive decay, and, for a three-generation decay, the number of grand-daughter nuclei will eventually equal the initial number of parent nuclei (assuming the daughter and grand-daughter are not produced directly)parentdaughtergrand-daughter

37. Low Counting Statistics and the Likelihood FunctionPereira et al., PRC 79, 035806 (2009)1 decay observed:2 decays observed: 10 scenarios →3 decays observed: 20 scenarios →constantBackgroundDecay FunctionsEfficiency

38. Background and Maximum LikelihoodBackground rate was determined uniquely for each 100Sn decay by considering the entire time-lapsed history of implantations into the DSSDThe simulation below shows the close matching between simulated and observed decay rate.Determination of the 100Sn half-life came from maximizing the likelihood function, considering also those implantation events that were not correlated with a decaySince N0 depends on l1 itself, an iterative process is used to maximize the function

39. Beta Decay – Neutron-Deficient NucleiPaul ManticaLecture 3Euroschool for Exotic BeamsLeuven, Belgium - 2009

40. Demonstrated burst conditions [1] T=1.5-2 GK r ~ 106 g/cm3 lb ~ 0.6 s-1 lp ~ 10,000 s-1rp-Process NucleosynthesisReactions of rp-processFeeding from (a,p)-processSchatz et al., NPA 688, 150c (2001)Parameters: b-decay rates (a,g),(p, g) rates MassesTermination point

41. Challenges with Neutron-Deficient NucleiSelected Fragment: Mo-84Projectile: 124Xe48+ at 140 MeV/ATarget: 9Be, 305 mg/cm2Acceptance: 1%Wedge: 27Al, 180 mg/cm2Rate in pps/pnA from LISE++Not only is the production of 84Mo overwhelmed by peak production of lighter isotones, but the low-momentum tails of the more prolifically produced, near stable isotopes also dominate the total yield, even with use of a wedge degrader.N=40424442Mo8283848586870.080.441Nb8182838485864340Zr80818283848537339Y7980818283846040038Sr787980818283500100037Rb77787980818220001000

42. RF Fragment SeparatorThe RF Fragment Separator was commissioned at NSCL in April 2007. The first beta-decay campaign to study neutron-deficient nuclei was initiated October 2007.Beam PacketsOperating principle:Beam species that have similar Br differ in TOF.

43. 84Mo Production and RFFS PerformanceV = 0 kVY slits = 50 mmIbeam = 0.8 pnA83 s-1 over DSSDV = 47 kVY slits = 10 mmIbeam = 10 pnA0.5 s-1 over DSSDV=0 kVV=47 kVRejection84Mo1*183Nb1516182Zr8040281Zr2010280Y1302000.679Sr4000854778Rb187000.44670077Kr135000.34500076Br1150157774Se1980540073As7006301.1All83**0.5**180beam0.8 pnA 10 pnA* Rates relative to 84Mo, 5×10-4 pps/pnA** particles/s-pnAPID are normalized to same number of 80Y implantations

44. Half-life of 84Mo84Mo is a waiting point along the rp-process. The re-measured half-life was found to be more than 1s shorter than the previous value, accelerating mass processing along the rp-process pathway. Previous T1/2 = 3.7 (+1.0, -0.8) sHalf-lives of even-even N=Z nuclei compared with theoryDecay curve for 84MoT1/2 = 2.2±0.2 sStoker et al., PRC 79, 015803 (2009)

45. Correlated 84Mo DecaysMaximum likelihood analysis requires extraction of correlated beta decays.Correlations were defined for 84Mo by limiting the time window for correlations to less than 20 s after an implantation.In addition, beta decays that occurred in the same pixel as the implantation, or any of the four nearest-neighbor pixels, were considered.Three generations of decays were taken into account to generate the likelihood function. The log t between a given 84Mo implantation and the subsequent one, two, and three beta correlations are shown to the right. The half-life value from the maximum likelihood analysis was consistent with that extracted from the decay curve fit.

46. Impact of the Shorter Half-Life of 84MoThe order of magnitude uncertainty in the final 84Sr abundance has been reduced to less than a factor of 2 with the new half-life.A=84 abundancesSchatz et al., Phys. Rep. 294, 167 (1998)Previous uncertainty bounded by divergent theoretical T1/2 predictions(0.8 s lower bound; 6.0 s upper bound)

47. Delayed Proton EmissionFor nuclei with Z > N, the proton drip line is located where the proton separation energy equals zeroSpNeutron-deficient nuclei near the proton drip line typically have large QEC values, and beta decay can directly populate proton unbound states.The “delayed” protons will be emitted with the apparent half-life of the beta decay.

48. Statistical Treatment of Delayed Proton EmissionWhen the level density of the proton unbound states in the daughter is smaller than the resolution of the particle detector, the individual protons cannot be distinguished. A statistical treatment of the proton spectrum can then be applied.Need GT matrix element <s>, level densities r, and transmission coefficient for proton decay TℓHuang et al., PRC 59, 2402 (1999)

49. Delayed Protons from 81Zr DecayDelayed gamma raysDelayed protons

50. Termination of the rp ProcessKnown ground state alpha emitters among the neutron-deficient Te isotopes result in the theoretical termination of the rp process with the Sn-Sb-Te cycle.Decay data in the vicinity of the doubly-magic nucleus 100Sn is critical to the characterization of the nuclear structure effects in this region of the nuclear chart.Sn-Sb-Te cycle. The solid lines indicate reaction flows of more than 10%. Schatz et al., PRL 86 3471 (2001)

51. Gamow-Teller Beta Decay of 100SnBrown and Rykaczewski, PRC 50, R2270 (1994)Simple shell model calculation would predict GT decay to a single pg9/2-1ng7/2+1 state in 100In with B(GT) = 17.82p-2h admixtures in both the 100Sn initial and the 100In final states will fragment the B(GT), but most of the strength is still expected to reside within the Qb windowThe calculation to the right considers such mutliparticle-multihole admixtures. The lowest 1+ state in 100In is predominantly 1p1h, but the B(GT) is reduced by a factor of 4. Extraction of B(GT) for 100Sn requires accurate determination of T1/2 and branching ratios to final states in 100In100Sn → 100In

52. Beta Decay of 102SnKarny et al., EPJ A 25, s01, 135 (2005)Faestermann et al., EPJ A 15, 185 (2002)2800 102Sn nucleiT1/2 = 3.8(2) s; QEC = 5.76(14) MeVBoth high resolution and calorimetric g-ray detection

53. B(GT) Hindrance Factors102Sn: B(GT) = 4.2(9)Hindrance Factor hh(102Sn) = 3.7Karny et al., EPJ A 25, s01, 135 (2005)

54. What is Known About 100Sn?ProductionGANIL [Lewitowicz et al., PLB 322, 20 (1994)]112Sn at 63 MeV∙A onto a 144 mg/cm2 Ni target11 events attributed to 100Sn48+ in 44 hours cross section for 100Sn ≥ 120 pbGSI [Schneider et al., ZPA 348, 241 (1994)]124Xe at 1095 GeV∙A onto a 6 g/cm2 Be target9 events attributed to 100Sn50+ in 277 hours cross section for 100Sn ~11 pbDecayGSI [Summerer et al., NPA 616, 341c (1997)]6 events followed by subsequent b decayT1/2 = 0.94 (+0.54, -0.27) sQb = 7.2 (+0.8, -0.5) MeVB(GT) = 11.3 (+6.5, -8.3) assuming all decay to a single 1+ state in 100InGANILGSI100Sn100Sn

55. Radio Frequency Fragment SeparatorRadio Frequency Fragment Separator (RFFS)NSF MRI PHY-05-209301.5-m long RF cavity, Vmax=100 kVFirst campaign in Fall 2008Beam rejection factor of >200 for 100SnPurification of neutron-deficient beams by time-of-flight

56. Production of 100SnBazin et al., PRL 101, 252501 (2008)Only the third time 100Sn was ever produced and studied.Production rate of 100Sn and other N=Z nuclei was below EPAX predictionsCountssexpt (pb)sEPAX (pb)Ratio97Cd1.14(1) x 1053900(700)65001.7(3)99In3.02(9) x 104900(200)10001.1(3)101Sn3.6(3) x 103100(30)1001.0(4)96Cd274(24)5.5(14)17031(+10, -6)98In216(21)3.8(12)4111(+5, -3)100Sn14(5)0.25(15)6.626(+40, -10)Primary beam dose of 6.7 x 1016 112Sn ions over 11.5 days

57. Half-life of 100Sn, 98In, 96CdThe half-lives of the ground states of heavy N=Z nuclei were deduced by event-by-event decay correlation measurements and analyzed based on a maximum likelihood probability function. The new values are:96Cd: 1.3 (+0.24, -0.21) s98In: 0.047 (13) s100Sn: 0.55 (+0.70, -0.31) sComparison with theoryLog(time) curvesBazin et al., PRL 101, 252501 (2008)

58. Ground State of 101SnGround state spin and parity of 101Sn up for debate 7/2+ from Darby et al. [next presentation] a decay fine structure 5/2+ from Seweryniak et al., PRL 99, 022504 (2007). g-ray correlated with protons from 101Sn decay N=51 isotonesZ=50 isotopes

59. 101Sn Beta-Delayed Proton DecayKavatsyuk et al., EPJ A 31, 319 (2007)Lorusso et al., PoS (NiC-X) 172 (2008)The b-delayed proton spectrum from 101Sn is strongly influenced by the angular momentum of the ground stateFactor of 4 improvement in statistics over previous measurement. Shape of spectrum more consistent with the model-dependent statistical treatment assuming 5/2+ ground state spin and parity

60. Other NSCL bp Results Delayed proton emission observed for first time in 98,99In and 96CdApproved experiments to study bp and other decay modes in much lighter, neutron-deficient nuclei

61. Fermi Beta Decays along N=ZFaestermann et al., EPJ A 15 185 (2002)All N=Z odd, odd nuclei above A=75 have very short (< 100 ms) b-decay half-livesSeveral of these nuclides have two b-decaying statesShort half-lives indicative of superallowed Fermi 0+  0+ b decaysOpen questions: Do the states with short b half-lives correspond to the ground states of the parents?Are there b-decaying isomers in 82Nb and 86Tc?What is the ground-state to ground-state branching ratio for the short-lived b decays? Isomer and b-delayed g-ray spectroscopy on odd-odd, N=Z nuclides with A > 80.RatepnA·sTotal in 96 hE(2+) in daughter (keV)eg(%)Counts in 2+ 0+ peak*82Nb0.2645,000407111,00086Tc0.0610,0005669180* Assumes 0.5% branching to non-analog states.

62. Beta Decay – Neutron-Rich NucleiPaul ManticaLecture 4Euroschool for Exotic BeamsLeuven, Belgium - 2009

63. Delayed Neutron EmissionFor nuclei with N > Z, the neutron drip line is located where the neutron separation energy equals zeroNeutron-rich nuclei near the proton drip line typically have large Qb- values, and beta decay can directly populate neutron unbound states.The “delayed” neutrons will be emitted with the apparent half-life of the beta decay.Parallels delayed proton emission…

64. Tensor Interaction andMonopole Shift of Single-Particle OrbitalsOtsuka et al., PRL 95, 232502 (2005)j> =  + 1/2j< =  – 1/2Attractive: In general:Radial wavefunctions must be similarLarge  and ´ enhance tensor monopole effect pg9/2–ng7/2323456pg9/2 fillspf7/2 fillspf7/2–nf5/2Repulsive:

65. Sn Region of the Nuclear ChartSnSbN=50N=82Z=50d3/2h11/2s1/2g7/2d5/2d3/2h11/2s1/2g7/2d5/2protonsneutrons5664667882N Z 

66. Proton Single-Particle Energy Shift in 51Sb Isotopesproton g7/2 orbital “moves” relative to proton d5/2 when neutron h11/2 orbital is occupied

67. Attractive Monopole Interaction4050g9/2protonsneutronsp1/2f5/2p3/250d5/2g7/2h11/2s1/2d3/2g9/2d5/2g7/2h11/2s1/2d3/2Proton-neutron interaction is strongest when the orbitals they occupy strongly overlap. This overlap is maximum when n ~ p. The attractive nature of the monopole interaction may lead to a re-arrangement of the single-particle orbitals.In 51Sb, a change in the proton single-particle states is observed upon filling of the h11/2 neutron orbital.

68. Shell Model Calculations with the GXPF1 Effective InteractionHonma et al., PRC 65, 061301(R) (2002)Removal of protons from f7/2 orbital produces significant energy gap between nf5/2 and np1/2 orbitals at Ti (Z=22) and Ca (Z=20)Two questions to be addressed:Is there evidence for an N=34 subshell closure in Ca?How are the neutron spe’s evolving with changing proton number?Ca (Z=20)Ti (Z=22)

69. E(2+) and Shell Closures[MeV]20285082126The excitation energy of the first excited 2+ state in even-even nuclei can provide initial insight into the degree of nuclear collectivity

70. Nuclear Shapes within a Major Shell66Dyvibrationaldeformedsingle-particle

71. Systematic Variation of 66Dy 2+ and 4+ states3.3 for rigid rotor2+4+66Dy

72. Systematic Variation of E(2+) pf7/2 fillspf7/2 fillsExcited states in 54Ca34 have remained elusive!

73. Production of Neutron-Rich Ca IsotopesBr1,2 = 4.3867 TmBr3,4 = 4.1339 TmTarget 352 mg/cm2 Be16 hoursBr1,2 = 4.4030 TmBr3,4 = 4.1339 TmTarget 352 mg/cm2 Be167 hoursPrimary beam: 76Ge 130 MeV/nucleonMomentum Acceptance: 5%300 mg/cm2 Al wedge at I2 position

74. Decay Curves for 53-56CaMantica et al., PRC 77, 014313 (2008)212690314148

75. 53-56Ca T1/2 Comparison to TheoryGross TheoryShell ModelHonma et al., PRC 69, 034335 (2004)N=32No discrimination between theoretical treatments at N=34(No N=32,34 gaps)(N=32,34 gaps)

76. Segmented Germanium Array (SeGA)16-detector SeGA arrangement – 24 cm i.d.Warm FETsResolution < 3.5 keV at 1.3 MeVStopped beam experimentsMueller et al., NIM A 466, 492(2003)

77. 54Ca54Sc54Ti247100214950+1+(3)+4+2+0+(pf7/2)1(nf5/2)1(np1/2)254Ca Beta-Delayed Gamma RaysT1/2 = 86±7 msQb = 10.33±0.79 MeV (sys.)Delayed gamma raysDecay curve gated on delayed gamma rays

78. Beta-Decay Branching RatiosAbsolute intensities for gamma-ray transitions are obtained from the following:Number of parent nuclei correlated with beta decayNumber of detected gamma raysGamma array peak efficiency curveFor the 247-keV transition in 54CaNo = 136Ng = 23eg = 14%Ig(abs) ~ 100%Direct feeding to the ground state determined from missing absolute gamma-ray intensity.In the case of the decay of 54Ca, the apparent beta feeding all proceeds through the excited state at 247 keV.log fot = log fo + log tpartialEb(max) = Qb – Ex = 10.33 MeV -0.28 MeV = 10.05 MeVtpartial = t1/2/branch = 0.086 s/1.0 = 0.086 shttp://www.nndc.bnl.gov/logft/log fot = 4.25±0.18

79. Pandemonium EffectHardy et al., PLB 71, 307 (1977)The word “apparent” was purposefully used in the description of the beta feeding following the decay of 54Ca. Note that the Qb value is more than 10 MeV. There is the likelihood of the presence of higher-energy with intensities below detection threshold. These unobserved transitions will impact the calculated branching ratios.Gierliket al., NPA 724, 313 (2003)509 discrete g raysQEC = 8.91 MeVOnly Ig > 1% shown4.2 MeV

80. Delayed Neutrons Can Help…Neutron-rich nuclei will have Qb values that fall above Sn in the daugher nucleus. Therefore, detection of neutrons with high efficiency can offset the impact of unobserved gamma rays on calculated beta branches. 54Ca54Sc2470+1+(3)+T1/2 = 86±7 msQb = 10.33±0.79 MeV (sys.)Sn = 4.6±0.5 MeVneutronsdiscrete gamma raysSimultaneous neutron and gamma measurements are not straightforward, as both demand high solid angle coverage, but require different active media for efficient detection.

81. r-Process Elemental AbundancesNuclear properties (e.g. mass) determine r-process yieldsPredicted r-process yields do not match observationsNeed masses, half-lives, and neutron branchingsNucleosynthetic process in Type II supernovae(?) or neutron star mergers(?)Rapid neutron captures on seed nuclei followed by b- decaysPath on neutron-rich side of stabilityK.-L. Kratz ISOLDE Workshop, CERN, Geneva, Dec. 15 - 17, 2003 N=82N=126

82. r-process nucleiTime of flight (m/q)Energy loss in Si (Z)77Ni78Ni75Co74Co73CoMSU – Mainz – LANL – Maryland – Notre DameNeutron-Rich Ni and Co Isotopestime (ms)Time between arrival and decays:MLHResult for half-life: 110 +100-60 msCompare to theoretical estimate used:470 ms

83. Neutron Emission Ratio Observer (NERO)NERO consists of 44 BF3 and 16 3He proportional counters.11.2 cm13.6 cm19.2 cm24.8 cmCadmiumShieldingPolyethylene ModeratorBF3 Proportional Counters3He Proportional CountersBCSNERO efficiency ~45% to 1 MeVLorusso et al., PoS (NIC-IX), 243 (2006)

84. QRPA Moeller et al. 1997QRPA Moeller et al. 2003CQRPA Borzov 2005 OXBASH Lisetzky et al.This workPrevious workPn and T1/2 for Neutron-Rich Cu and Ni

85. 120Rh75 Beta-Delayed NeutronsMontes et al., PRC 73, 035801 (2006) Small neutron branching observed for 120Rh decay not consistent with macroscopic models that include an ad-hoc quenching of the N=82 shell closurePn  5.4%Can use combination of T1/2 and Pn to isolate ground state deformation

86. Pn Determined from Gamma RaysThe delayed gamma-ray spectra from 55Sc and 56Sc have “identical” transitions with energies 592 and 1204 keV: Provides evidence for delayed neutron emission following decay of 56Sc.The absolute gamma ray intensities can be used to deduce Pn; however, this will be a lower limit, since the calculation only considers neutron transitions that populate excited states in the A-1 daughter.

87. 56Sc has two β-decaying states: a short-lived, low-spin state and a longer-lived high spin states. 56Sc also has a microsecond isomer that decays by several prompt gamma rays.Complicated Decays: 56Sc

88. Beta Decay – Future @ FRIBPaul ManticaLecture 4Euroschool for Exotic BeamsLeuven, Belgium - 2009

89. Facility for Rare Isotope Beams(FRIB)MSU selected to design and establish FRIB at the present NSCL site

90. FRIB Location on the MSU Campus

91. Scientific Goals of FRIB Drive SpecificationsFRIB with 400 kW for all beams and minimum energy of 200 MeV/u will have beam rates for some isotopes up to 100 times higher than other facilitiesFor example: FRIB intensity will allow the key benchmark nuclei 54Ca (reaccelerated beams) and 60Ca (fast beams) to be studied

92. Experimental AreasA full suite of experimental equipment will be available for fast, stopped and reaccelerated beamsNew equipmentStopped beam area (LASERS)ISLA Recoil SeparatorSolenoid spectrometerActive Target TPC