Mass measurements for nuclear astrophysics

Transcription

1 Mass measurements for nuclear astrophysics Lecture 1: introductory physics and methods David Lunney Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM IN2P3 / CNRS) Université de Paris Sud, Orsay Joint Institute for Nuclear Astrophysics Special School on Nuclear Mass Models Argonne National Laboratory - May 8-16, 2007

2 I. General concepts binding energy; the mass unit; resolution; precision; accuracy II. III. IV. Physics motivation a nuclear structure shells, deformation, pairing, halos (the mass scale) b weak interaction superallowed beta decay and the CKM matrix c astrophysics stellar nucleosynthesis Production of radionuclides methods of FIFS (fragmentation) et ISOL; (ion manipulation using traps and gas cells) Mass measurement techniques i. indirect methods reactions et decays ii. direct methods time of flight (SPEG et CSS2 au GANIL; ESR isochronous mode at GSI); revolution (cyclotron) frequency (ESR Schottky mode; ISOLTRAP and MISTRAL at ISOLDE) V. Comparisons of the different methods VI. VII. The atomic mass evaluation (demonstration of the program NUCLEUS) Mass models and comparisons; chaos on the mass surface? VIII. A look into the future IX. Conclusions

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4 Some introductory remarks on history High resolution mass spectrographs F.W.Aston (~1920 s): 212 isotopes discovered Packing fraction A. Eddington (~1920) Stellar combustion E = mc 2 How the sun shines, J. Bahcall

5 the atomic mass Z m p + N m n ( + Z m e ) BINDING ENERGY nuclear structure (shells, shapes, halos) nuclear astrophysics (decay mode, reaction)

6 stable isotopes s-process path r-process path β decay path known masses Pt Ir Os Re W Ta Hf Lu Yb Tm Er Au Hg Tl Pb p-isotope s-isotope r-isotope Bi Po one / two β -delayed neutron decay β decay neutron number 126 Stellar Nucleosynthesis (A 200) At

7 rapid proton-capture (rp) process N=Z Y77 Y78 Y79 Y80 Y81 Y82 Y83 Y84 Y85 Z = Rb71 Sr73 Rb72 Sr74 Rb73 Sr75 Rb74 Sr76 Rb75 Sr77 Rb76 Sr78 Rb77 Sr79 Rb78 Sr80 Rb79 Sr81 Rb80 Sr82 Rb81 Sr83 Rb82 Sr84 P Rb83 37 Kr69 NASA/CXC/SSC/J. Keohane et al. 36 Br67 Br68 Kr70 Br69 Kr71 Br70 Kr72 Br71 Kr73 Br72 Kr74 Br73 Kr75 Br74 Kr76 Br75 Kr77 Br76 Kr78 P Br77 Kr79 Br78 Kr80 Br79 Kr81 Br80 Kr82 Br As63 Se65 As64 Se66 As65 Se67 As66 Se68 As67 Se69 As68 Se70 As69 Se71 As70 Se72 As71 Se73 As72 Se74 P As73 Se75 As74 Se76 Se77 Se78 As75 As76 As77 Se79 As78 Se80 As79 Ge62 Ge63 Ge64 Ge65 Ge66 Ge67 Ge68 Ge69 Ge70 Ge71 Ge72 Ge73 Ge74 Ge75 Ge76 Ge77 Ge78 possible rp - process main path (H. Schatz et al. Phys. Rep. 294 (1998) 167) possible waiting points mass excess not yet measured (AME95) ISOLTRAP measurements before 2000

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9 -55 Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr MASS EXCESS (MeV) sec mins hours days stable Z,N= 42,58 41,59 40,60 39, (A = 100 isobars)

10 S n (MeV) Nucleon pairing N Li Be B C N O F Ne Na Mg Al Si 10-5

11 nuclear structure from the mass surface shell opening and magic number migration

12 nuclear structure from the mass surface shell opening and magic number migration

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14 S Singer SIRIUS Science CLRC ISBN

15 one-neutron separation energy (MeV) measured masses exp95 TF94 FRDM95 DZ97 SM98 KUTY00 HF S n N (Z = 12) two-neutron separation energy (MeV) measured masses exp95 TF94 FRDM95 DZ97 SM98 KUTY00 HF S 2n N (Z = 12)

16 drip line phenomena - small binding energies

17 Superlarge nuclides 11 Li Simple, illustrative approach (Hansen and Jonson, 1987) ρ = h/(2μs 2n ) 1/2 For 3-body models: S 2n is input parameter two-neutron halo Borromean system

18 J.R. Nix and P. Moeller, LA-UR (1997) Superheavy Elements

19 S n (MeV) Nucleon pairing N Li Be B C N O F Ne Na Mg Al Si 10-5

20 pairing energy Δ Δ (3) N ( 80 Hg) (4) ( N) = ( 1) 2 N ( N) = ISOLTRAP data S. Schwarz et al., Nuc. Phy. A (2000) Δ n ground state [ B( N 1) + B( N + 1) 2 B( N) ] (3) (3) [ Δ ( N) + Δ ( N 1) ] δ<r 2 > (fm 2 ) δ<r 2 > ground state Δ n (MeV) -0.6 δ<r 2 > isomeric state (J. Bonn et al., 1972) A ( 80 Hg)...very high precision needed

21 Hancock bldg (344 m high) Pairing gap: 1 MeV Shell gap of 132 Sn ~ 6 MeV Binding Energy of 132 Sn ~ 1 GeV Earth s radius: 6000 km

22 mass measurements: what you want - what you need 10 5 shells astrophysics relative precision metrology weak interaction pairing halos stable short-lived exotic

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24 Motivation from fundamental physics metrology: the kilogram: 28 Si atomic mass standard and other fundamental constants (what if they vary with time?!)

25 What does a relative uncertainty of 10-8 mean? weight (empty): kg contact lenses?

26 mass measurements: what you want - what you need 10 5 shells astrophysics relative precision metrology weak interaction pairing halos stable short-lived exotic

27 Production (and separation) techniques for exotic nuclides Isotope Separation On-Line (ISOL) Fragmentation In-Flight Separation (FIFS) GeVprotons MeV heavy ions neutrons / electrons driver GeV/u heavy ions ionizer Diffusion: release time and chemistry g/cm 2 target mg/cm 2 separator Straggling: phase space kev GeV good beam quality (charge-breeding) post-acceleration short lived / unbound deceleration or stopping

28 worldwide radioactive ion beam facilities ISAC BEARS ANL HRIBF NSCL SIRIUS SISSI SPIRAL ISOLDE JYFL EXCYT Dubna DRIBS ARENAS FRS ISOL SHIP MAFF BAEI Lanzhou RIBF JHP ISOL thick-target facilities in-flight separation facilities MASS MEASUREMENTS (NEAR) FUTURE

29 Techniques Indirect (energy) Direct (mass spectrometry) PRODUCTION SCHEME reactions: A(a,b)B Q = M A + M a -M b -M B decays: A B + α Q α = M Β M Α time of flight: TOF = (m/q) (L/Bρ ) cyclotron frequency: f c = qb/m FIFS (MeV) ISOL (kev) better sensitivity better precision

30 m q = Bρ v Mass separator -spectroscope -spectrograph -spectrometer d Dispersion Mass Resolution D = d m/δm R = m/δm = d/δx m/δm R = π Δa D / 4ε Δx high resolution necessary but not sufficient for high precision

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32 postaccelerator separator target cyclotron magnet

33 accurate precise...but not precise...but not accurate high precision necessary but not sufficient for high accuracy

34 Mass measurements by reactions missing mass from reaction A(a,b)B intensity particle background (contaminants) resonances of nuclide B bound states of nuclide B ground state M B = M A + M a M b Q decay energy of B (calibrated) Yu. Penionzchevich, Hyp. Int. 132 (2001) 265 invariant mass from B b + x M B = { M x2 + M b 2 +2E x lab E b lab primary beam (radioactive) B x b detector spectrometer 2P x lab P b lab } 1/2 10 Li, 13 Be, 18 Na Somewhat limited but imperative for unbound

35 masses of unbound nuclides using MAYA at GANIL SPEG Q31 Q35 26 F (d, 3 He) 25 O reaction Q33 D3P Q26 D4P Q25 radioactive beam MAYA MAYA Z Y Z X Y X C.-E. Demonchy Ph.D. (2003)

36 Mass measurements by Beta decay: Q β = M parent M daughter P(p) dp = G 2 M if 2 2π 3 h 7 c 3 p 2 (E 0 -E) 2 F(Z,E) detected Betas E 0? E Kurie Plot: [P(p) / p 2 F(Z,E)] 1/2 vs. E Instrumentation effects (response function) Kurie E 0 Decay Branching (detailed spectroscopy) E Kurie E 0? γ E

37 Mass measurements by alpha and proton decay C.N. Davids et al., Hyp. Int. 132 (2001) 133

38 reactions and decays (so-called indirect techniques) Reactions: masses of unbound nuclides 15 F: W. A. Peters et al., PRC (2003) 11 N: V. Guimarães et al., PRC (2003) 25 O: W. Mittig et al., (2004) Decay studies: masses byproducts (Q-values) Z = 114/116: Oganessian et al., PRC (2004) 135 Tb p decay: P.J. Woods et al., PRC (2004) 130 Eu p decay: C.N. Davids et al., PRC (2004) 233 Am α decay: M. Sakama et al., PRC (2004) 265 Bh α decay: Z.G. Gan et al., EPJA (2004) 130 Cd β decay: I. Dillmann et al., PRL (2003) Mass values for the most exotic species

39 UW-PTMS SPEG CSS2 (GANIL) FSU- TRAP (MIT) SMILE- TRAP (MSI) ESR-FRS (GSI) ISOLTRAP (CERN) MISTRAL (CERN)

40 mass measurement programs at GANIL CSS1 SPEG time-of-flight + magnetic rigidity m = q Bρ T /L Resolving power: 10 4 extremely sensitive S 2n [MeV] B. Jurado, H. Savajols et al., PLB (2007) Ca Ar Cl S P S i 2002 ( 48 Ca) N SPEG

41 F. Sarazin et al., 1999 SPEG resolving ~ 5000 sensitivity ~ 0.01 /s

42 SPEG 2007 SPEG 2000 AME# 2000 mass difference (k Ne 33Na 36Mg 39Al 41Si 43P 45S 46Cl -2000

43 K500 TOF start TOF stop S800 K1200 A1900 transfer hall 10m B ρ meas. de [a.u.] 86 Kr primary beam M. Matoš (CGS-12, Notre Dame) AIP Conf. Proc. 819 (2006) 164 A. Estrade (NiC-IX, CERN) Proceedings of Science (2006) ΔTOF[ns] Ge Ga Zn Cu Ni Co Fe Mn Cr V Ti Sr Ca K Ar Cl S

44 mass measurement programs at GANIL CSS2 time-of-flight: phase difference with acceleration (longer flight path) CSS1 CSS2 M.B. Gomez Hornillos, M. Chartier et al. (soon)

45 mass measurement programs at GANIL CIME (SPIRAL) time-of-flight: variable RF acceleration (longer flight path) M.-B. Gomes Hornillos et al., J. Phy. G 31 (2005) S1869

46 Multiple-Reflection TOF-MS MCP-Detector Ion Source Reflector 1 Reflector 2 mass measurement accuracy (~ ppm) short measurement durations (< 1 ms) Casares, Geissel, Plass, Scheidenberger, Wollnik et al. (Proc. 48th ASMS Conf. Mass Spectrom. Allied Topics, Long Beach, CA, 2000)

47 mass measurement programs at GSI Experimental Storage Ring: Δm/m = γ t2 Δf/f + (γ t2 γ 2 ) Δv/v Schottky Mode very precise but cooling slow Isochronous Mode very fast but not so precise

48 mass measurement programs at GSI Experimental Storage Ring: stripped, H- and He-like ions

49 Nuclear Physics in Storage Rings Mass Measurements and Decay Studies in the ESR Reaction studies in the ESR Yuri A. Litvinov Arbeitstreffen Kernphysik, Schleching 22 February 2007 Mass matters!

50 SMS 4 particles with different m/q time

51 SMS Sin(ω 1 ) Sin(ω 2 ) Fast Fourier Transform Sin(ω time 3 ) ω 4 ω 3 ω 2 ω 1 Sin(ω 4 )

52 Broad-band Schottky Frequency Spectra

53 electrons ions Electron cooling of fast ion beams (CRYRING at MSI, Stockholm)

54 IMS: Time-of-Flight Spectra Nuclei with half-lives as short as 20 microseconds are accessible About 13% in mass-over-charge range Kr Br Se particles As 40 Zn Cu Rb Na Al Ne Mg Cl As P Si Fe Ni Ar Se S Ca Cu Co Mn Cr V Ti Sc Ca K Ge Ge Sc Ga Zn Ga V Ti Zn Cu Cr Mn Ni Fe Co Br m Revolution time / ns M. Hausmann et al., Hyperfine Interactions 132 (2001) 291

55 Measured Mass Surface Masses of more than 1100 Nuclides were measured Mass accuracy: SMS up to IMS ~ Results: ~ 350 new masses In addition more than 300 improved mass values

56 Present Knowledge of Atomic Masses stable nuclei nuclides with known masses G.Audi et al., Nucl. Phys. A729 (2003) 3 measured nuclides with at FRS-ESR known masses (published) G.Audi et al., Nucl. Phys. A595 (1995) 409 measured at FRS-ESR (in analysis) observed nuclei observed nuclei r-process path

57 Yu. Litvinov, Ph.D. (2003): ~ 600 species in the ring 466 masses measured (117 calibration masses) 139 masses from links 200 improved masses 75 new mass values Yu. Novikov et al., Nucl Phys A (2002) Yu. Litvinov et al., (2005) IMS J. Stadlmann (Ph.D) and Phys. Lett. B (2004) IMS 2002 M. Matos, Ph.D (2004) mass is input parameter for halo models SMS 2002 E. Kaza, Ph.D (2004)

58 A new binding energy for the 11 Li halo Wouters88 (TOFI) Kobayashi91 (reaction) MISTRAL Li S 2n (kev) Young93 (reaction) AME Thibault75 (mass spec.) % higher than currently used to adjust models... C. Bachelet, Ph.D. thesis (2004)

59 Quadrupole Doublet MISTRAL COLETTE Paul trap Reference Source ISOLDE Beam m Alburger 78 * MISTRAL 2005 Detector Mass Excess (kev) Be (T 1/2 = 21 ms) * D.E. Alburger et al. Phys. Rev. C 18, 2727 (1978)

60 10 m ISOL- TRAP MISTRAL GPS REX-ISOLDE proton beam 1 GeV HRS ISOLDE CERN, Geneva

61 The mass spectrometer ISOLTRAP hyperbolic Penning trap: precision mass measurement 2 cm 1 m cylindrical Penning trap: isobar separation & cooling 20 cm continuous 60 kev ISOLDE beam low energy bunches Gas-filled RF-Paul trap: universal beam collector

62 Penning Trap U r B z ω c = qb/2πm ω z SHM mass independent ωc = ω + + ω in a quadrupole field

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64 Techniques Indirect Direct (mass spectrometry) PRODUCTION SCHEME reactions: A(a,b)B Q = M A + M a -M b -M B decays: A B + α Q α = M Β M Α time of flight: SPEG/CSS2, GANIL ESR, GSI cyclotron frequency: ISOLTRAP, ISOLDE MISTRAL, ISOLDE FIFS (MeV) gas cell RFQ ISOL (kev) better sensitivity better precision the best of both worlds CPT at ANL

65 Canadian Penning Trap (CPT) facility at ANL

66 TITAN (TRIUMF) CPT (ANL) LEBIT (NSCL) (RIKENRING) JYFLTRAP SMILETRAP (MSI) ISOLTRAP (CERN) SHIPTRAP (GSI) MATS (FAIR) MAFFTRAP or what ISOLTRAP hath wrought

67 JYFLTRAP at the IGISOL facility in Jyväskylä trap cooler mass separator ion guide ISOLDE elements JYFLTRAP masses from IGISOL: V. Kolhinen, NIMB (2004) & Ph.D. S. Rinta-Antila et al., PRC (2004) A. Jokinen, ENAM04 (2004)

68 SHIPTRAP facility at GSI ISOL facility for transuranium nuclides 92 Mo ( 58 Ni,xpyn) 147 Ho new masses for 147 Ho, 147,148 Er ( 10 6 ) (M. Bloch et al., ENAM04) Ana Martin!

69 Low Energy Beam & Ion Trap (LEBIT) facility at NSCL/MSU G. Bollen EMIS/ENAM proceedings

70 Let s pause and catch our breath How do all these (different?) programs compare? Are they really different? Are they complementary? (no one facility has enough beam time or students to analyze the data!)

71 comparison of current (direct) mass measurement programs SPEG ESR MISTRAL ISOLTRAP resolution precision sensitivity 10-1 /s /s 10 2 /s half-life 1 μs 10 s 1 ms 50 ms applicability forte Achilles heel A < 70 exotic species μs-isomers universal life-times calibration universal (ISOLDE) short T ½ & accuracy sys. error universal (ISOLDE) highest accuracy meas. time future better timing CIME isochronous mode μs cooler ICR detection

72 10-4 SPEG relative uncertainty ESR SMS 1995 ESR SMS 1997 ISOLTRAP ESR IMS CSS2 MISTRAL relative isobaric distance from stability Reviews of Modern Physics, 75 (2003) 1021

73 10-4 relative uncertainty ESR SMS CPT ISOLTRAP CSS2 ESR IMS SPEG MISTRAL relative isobaric distance from stability ENAM04 Proc., Eur. Phys. J. A, 25 (2005) 3

74 relative uncertainty (CSS2) (ESR SMS) ISOLTRAP LEBIT CPT (ESR IMS) ORNL JYFLTRAP SHIPTRAP SPEG MISTRAL relative isobaric distance from stability Proc. Nuclei in the Cosmos IX, PoS (2006)?

75 10-4 Performance of the various methods relative uncertainty CSS2 ESR SMS CPT ISOLTRAP JYFL COOL ESR IMS SPEG MISTRAL half life (seconds) See: Lunney, Pearson & Thibault, Rev. Mod. Phys. 75 (2003) 1021

76 10-4 neutron-rich proton-rich relative uncertainty (ESR IMS) (CSS2) (ESR SMS) JYFLTRAP SHIPTRAP ISOLTRAP CPT ORNL SPEG MISTRAL LEBIT (left) neutron- (right) proton-separation energy (MeV)

77 stable indirect GANIL SPEG CSS2 GSI ESR-SMS ESR-IMS SHIPTRAP proton dripline (FRDM95) Z ISOLDE MISTRAL ISOLTRAP neutron dripline (FRDM95) 20 0 Other Penning traps CPT (ANL) LEBIT (MSU) JYFLTRAP N

78 I. General concepts binding energy; the mass unit; resolution; precision; accuracy II. III. IV. Physics motivation a nuclear structure shells, deformation, pairing, halos (the mass scale) b weak interaction superallowed beta decay and the CKM matrix c astrophysics stellar nucleosynthesis Production of radionuclides methods of FIFS (fragmentation) et ISOL; (ion manipulation using traps and gas cells) Mass measurement techniques i. indirect methods reactions et decays ii. direct methods time of flight (SPEG et CSS2 au GANIL; ESR isochronous mode at GSI); revolution (cyclotron) frequency (ESR Schottky mode; ISOLTRAP and MISTRAL at ISOLDE) V. Comparisons of the different methods VI. VII. The atomic mass evaluation (demonstration of the program NUCLEUS) Mass models and comparisons; chaos on the mass surface? VIII. A look into the future IX. Conclusions