Report on Nuclear Spectroscopy at JYFL

Transcription

1 Report on on Report Nuclear Spectroscopy Spectroscopy Nuclear at JYFL JYFL at

2 In-beam & Decay Spectroscopy (Daresbury, Liverpool, Manchester, Paisley, Surrey, York) Collinear Laser Spectroscopy (Birmingham, Manchester) Physics Highlights

3 The GREAT Focal-Plane Spectrometer for γ-ray, e - -, β -, p- and α- particle detection 2 x 60mm x 40mm DSSD (4800 pixels) 28 x 40mm x 40mm PIN Diodes 24 x 12 Segmented Planar Ge Compton-Suppressed Segmented Ge Clover Position-Sensitive MWPC UK Investment

4 TDR : Total Data Readout Triggerless Data Acquisition System Rates up to 850 khz without deadtime 380 channels timestamped data 10 ns resolution Time-of-Day clock with 32 day rollover Flexible + Easily Scalable UK Investment

5 In-beam gamma-ray spectroscopy JUROGAM ~ EUROGAM 1 (Daresbury) 43 EUROGAM Phase 1 Ge detectors + BGO shields Eff. at 1.3 MeV 4% At JYFL: 39 EoC pool + 10 UK-France pool Ge detectors 30 EoC shields + 15 UK-F shields Successor of JUROSPHERE Eff. 1.5 %

6 Complete Spectroscopy Jurogam Array RITU gas filled recoil separator Approx 1 μs Q1 D Q2 MWPC Q3 PIN Diodes DSSD Planar GREAT Ge (prompt) Recoil Δt Ge (delayed) Recoil Δt

7 RDT Instrumentation at JYFL GREAT Focal plane spectrometer RITU Gas-filled recoil separator Transmission % JUROGAM TDR Total Data Readout Triggerless data acquisition system with 10 ns time stamping

8 The Recoil Decay Tagging Technique Counts γ Counts Recoil - γ 176 Pt Yrast Band Energy (kev) Energy (kev) JUROGAM+RITU+GREAT experiment at JYFL α Recoil - γ J.Simpson, R. Julin et al., Counts Correlate radiation detected at the target position with characteristic decays at the focal plane Energy (kev) 176 Hg Yrast Band

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10 170 Pt Proton Drip Line? The Z 82 Region Z= Re 163 Re Pb Tl Hg Au Pt Ir Os Re W Ta Hf Lu Yb N=82 Stable N=104 Nuclei Proton emitter Alpha emitter Beta emitter New Isotope

11 Physics Programme in W-Os- Pt Region 169 Os Joss et al., Phys. Rev. C66 (2002) Pt Joss et al., Phys. Rev. C, in press. 167,168 Os Joss et al., Nucl. Phys. A689 (2001) Pt Back et al., E. Phys. J A17 (2003) ,166 Os Appelbe et al., Phys. Rev. C66 (2002) ,172 Pt Cederwall et al., Phys. Lett. B443 (1998) ,166 Os King et al., Phys. Rev. C62 (2000) ,170 Pt King et al., Phys. Lett. B443 (1998) Os Joss et al., Phys. Rev. C66 (2002) Hg Melarangi et al., Phys. Rev. C68 (2003) R. 167 Re Joss et al., Phys. Rev. C68 (2003) Re Lagergren et al., submitted to Phys. Rev. C. 159 Ta, 160 W Keenan et al., Phys. Rev. C63 (2001)

12 In-beam spectroscopy programme SHE- nuclei near 254 No (Z=102) Shape-coexistence in the light Pb region Competing structures in W Pt region approaching the proton drip line Isomer spectroscopy of light (A 140) Eu Hf nuclei Towards light Z 50 nuclei Studies of light neutron-rich nuclei by deep inelastic collisions (tagging). NEW: β tagging of odd-odd N = Z nuclei

13 JUROGAM Campaigns Campaign 1 4/ /2003 : 9 months 14 experiments Campaign 2 4/2004-6/ /2004-3/2005 : 9 months 13+1 experiments Campaign 3 9/2005 9/2006 : 12 months 13 experiments Expt. No Title Spokeperson(s) Expt. No Title Spokeperson(s) JR01 JR01 JR04 JR05 JR07 JR09 JR11 JR12 JR12 JR13 JR16 Search for triple shape coexistence in 190 Po A recoil-gated plunger lifetime measurement of 188 Pb with JUROGAM and the RITU separator Recoil-decay tagging employing the alphadecaying nuclei produced in deep inelastic reactions Rotational band structures in the odd-z transfermium 251 Md nucleus studied by prompt gamma spectroscopy The structure of K-isomers at the proton drip-line: 140 Dy Yrast structre of the neutron-deficient nucleus 170 Pt Alpha-decay tagging of 106 Te and 107 Te Search for spherical, deformed oblate and isomeric states in 184 Pb Nuclear structure of the extremely neutron deficient nuclides 161 Re and 162 Os A.N. Andreyev A. Dewald J. Uusitalo A. Chatillon P.T. Greenlees R.-D.Herzberg D.M. Cullen D.T. Joss B. Cederwall R. Wadsworth R.D. Page R. Julin K. Lagergren D.T. Joss JR19 In-beam gamma-spectroscopy study of 254 No M. Leino JR21 JR23 JR25 Identification of excited states in the first proton-unbound N=77 isotone 146 Tm using recoil-isomer and proton-decay tagging Spectroscopy 223 Pa (Z=91): A step towards octupole deformation studies of high-z nuclei Gamma-ray spectroscopy of 192 Po with JuroGam C. Scholey B.J.P.Gall P. Rahkila JR26 Search for an oblate band in 186 Pb J. Pakarinen Expt. No JR02 Title Gamma-ray spectroscopy of the very neutron-deficient nucleus 188 Po Spokeperson(s) P.T. Greenlees S. Juutinen A.N. Andreyev JR18 Ground state and excited bands in 250 Fm R.-D. Herzberg JR24 JR27 JR29 JR30 JR31 JR32 JR33 JR34 JR35 A plunger lifetime measurement of lowlying yrast states in 194 Po Spectroscopy of the deformed groundstate proton emitter 113 Cs Spectroscopy of 176 Hg: shape coexistence at the extremes High-spin states in the N=84 isotones 156 Hf, 157 Ta and 158 W In-beam gamma-spectroscopy study of 253 No Detailed spectroscopy of 191Bi A recoil-decay tagged plunger lifetime measurement for the yrast levels of 186 Pb In-beam gamma-ray spectroscopy of the transfermium nucleus 255 Lr Identification of excited states in the proton unbound nucleus 166 Ir T. Grahn J.F. Smith J. Simpson R. Julin D.T. Joss J. Uusitalo R.-D. Herzberg P. Reiter S. Juutinen T. Grahn A. Dewald P.T. Greenlees R.-D. Herzberg Ch. Theisen C. Scholey JR10 Proof-of-principle for recoil-beta tagging D. Jenkins JR15 Gamma-ray spectroscopy of 195 At H. Kettunen JR36 JR37 JR39 Recoil-decay tagging of exotic light neutron-rich (N<28,Z<18) nuclei employing the alpha-decaying nuclei J. Uusitalo produced in deep-inelastic reactions Shape co-existence in very neutron-deficient 189 Bi Identification of excited states in the deformed proton emitter 117 La using recoil-decay tagging with JUROGAM, GREAT and RITU S. Juutinen Y. Le Coz J.F. Smith JR40 RDDS lifetime measurements of yrast states in 180,182 Hg T. Grahn JR41 JR42 JR43 JR44 JR45 JR46 Coulex-plunger lifetime measurements with Xe beams and test of inverse kinematics for future coulex-plunger experiments Search for deformed excitations in 185 Pb Commissioning of the second multi-wire proportional counter for GREAT S. Harissopulis A.N. Andreyev D.M. Cullen D.M. Cullen Search for N=82 shell quenching for neutron-rich nuclei X. Liang In-beam gamma-ray spectroscopy of heavy elements: 256 Rf Gamma spectroscopy of 256 No using a radioactive 238 U target P.T. Greenlees R.-D. Herzberg Ch.Tiesen B. Gall B. Gall R.-D. Herzberg Ch. Teisen P.T. Greenlees JR47 Alpha-decay tagging spectroscopy of 110 Xe B. Cederwall JR48 Structure of high-k states in 254 No R.-D. Herzberg P.T. Greenlees JR50 The changing structure of the light Re isotopes: Recoildecay tagging of the neutron-deficient nucleus 163 Re D.T. Joss JR51 Search for magnetic rotation and superdeformation in Po A. Wilson JR52 JR53 Identification of low-lying T=0,1 states in the N=Z nucleus 78 Y Investigation of K-isomerism in 250 Fm S.N.S. Bondili R. Wadsworth P.T. Greenlees R.-D. Herzberg JR55 Ground state band of 248Fm R.-D. Herzberg JR56 JR58 Probing the onset of collectively in 196 Po by means of RDDS lifetime measurements Evolution of single-particle states near the N=82 shell gap; spectroscopy of 168 Pt and neighbouring isotopes T. Grahn M. Boden Gomez JR59 Recoil-Decay Tagging spectroscopy of Au B. Cederwall JR60 Decay studies of the isomers in the proton emitter 151 Lu and its daughter nucleus 150 Yb Z. Liu

14 Spectroscopy of very neutron deficient and heavy nuclei + Can be produced via fusion evaporation with stable-ion beams and stable targets + Short-living alpha or proton emitters tagging methods - Cross-sections sections down to 1 nb - Only levels near the yrast line populated

15 Superheavy Nuclei Produced in asymmetric cold-fusion reaction X( 48 Ca,2n)Y ideal for RITU Only one reaction channel open Total compound cross-section down to 50 mb I beam up to 30pnA on a 0.5mg/cm 2 target in in-beam runs Fission dominates: : 1 I beam limited by the Ge rate Very low focal-plane rate Enables long t 1/2 α tagging

16 Motivation Odd Z 251 Md, 255 Lr Odd N 253 No Darmstadtium Even Z Shell-Correction Energies 252 No 254 No 250 Fm 248 Fm Future: 256 Rf -7 MeV -6 MeV -5 MeV -4 MeV -3 MeV R. Smolanczuk et al., Phys. Rev. C 52, 1872(1995) R. Smolanczuk and A. Sobiczewski, Proc. XV Nucl. Phys. Div. Conf., Singapore (1995), p. 313 S. Hofmann, Nucl. Phys. News Intl

17 What determines stability? Number of protons sea of instability peak of Sn peak of Pb peak of Th,U island of spherical SHE strait of radioactivity Magic Numbers Neutrons Protons 20 peak of Ca 20, 50, 20, 50 82, ,??? Number of neutrons

18 In-beam Data

19 Single Particle States Protons 9/2+[624] Neutrons

20 254 No SACRED + RITU data No 254 No-recoil gated in-beam conversion electrons from 208 Pb( 48 Ca,2n) 254 No Discrete lines + M1 continuum M1 P.A. Butler at al. PRL 89 (2002)

21 SAGE : 2007 Simultaneous Gamma & Conversion electron studies

22 Triple - shape coexistence In Pb isotopes Close to the proton drip-line

23 Shape coexistence near the Z=82 shell closure E (ħ ω) GROUND STATE (Weakly Deformed) A phenomenon where nuclear configurations at similar excitation energies are built on very different deformations. ε2 INTRUDER (Well Deformed) Shape coexistence is expected to occur in transitional regions between weakly and strongly deformed ground states

24 Three low-lying lying 0 + states in 186 Pb observed in the α- decay of 190 Po Where is the OBLATE band? 0p-0h 2p-2h 4p-4h SPHERICAL OBLATE PROLATE A. Andreyev et al. Nature 405 (2000) 430

25 Pb Prolate 4p-4h Oblate 2p-2h Even-mass Pb isotopes level systematics 186 Pb Spherical 0p-0h

26 RDT experiment for 186 Pb with JUROGAM+RITU+GREAT 106 Pd( 83 Kr,3n) 186 Pb 186 Pb THE PROLATE BAND A NEW BAND

27 PROLATE OCTUPOLE OBLATE GAMMA 186 Pb

28 Kinematic moment of inertia 186Pb OBLATE 188Pb OBLATE Pb PROLATE Po OBLATE

29 Differential-Plunger Plunger-Lifetime measurements by using RDT for intruder bands in very neutron deficient 186,188 Pb and 194 Po Differential plunger inside JUROGAM 114 Cd( 83 Kr,3n) 194 Po 186 Pb Prolate 4p-4h Oblate 4p-4h 194 Po 188 Pb

30 Proton Emitting Nuclei α decay proton decay β decay m isomeric state g ground state Ir 165 Ir 166 Ir m g 167 Ir m g Z = Re 160 Re 161 Re m g 162 Re m g 163 Re m g Ta 156 Ta m g 157 Ta m 1 m 2 g 158 Ta m 1 m 2 g 159 Ta m g 160 Ta m g

31 RDT of the proton emitter 161 Re Spectroscopy of Proton Emitters b α = 92 % b p = 8 % b p = 100 %

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33 K. Lagergren et al., Submitted to Physical Review C.

34 Experimental details 58 Ni Cd 164 Os 300MeV Planar Ge 159 Re, p4n 160 Re, p3n Clover Ge 106 Cd 1.1mg/cm 2 & Avg I B ~ 7 pna

35 Searching for proton emitters Counts (10 5 ) per 2keV Escaped α particles 152 Er 153 Tm 156m Lu 156m Hf E (kev)

36 162 Os Re 4 Re proton emission DT Joss, RD Page, IG Darby, J Simpson et al., 159 Re Counts per 2keV W T 1/2 = 21μs Counts E (kev) E p = 1805 kev Δt (μs) 162 Os

37 Re Isomeric πh 11/2 state Partial half life (secs) h 11/ Re proton decay Q value (MeV) s 1/2 d 3/2 -

38 LISA : 2007

39 Medium-heavy and light nuclei Produced in symmetric fusion-evaporation reactions Difficulties with a gas-filled separator (separation of scattered beam) No fission large number of fusion ev. reaction channels σ 1mb High recoil rate focal-plane - ~ 1kHz/1pnA on a 0.5mg/cm 2 target Limited possibilities for short-t 1/2 p- or α- tagging Need mass-selectivity vacuum recoil-separator β- tagging!?

40 Recoil- β tagging: Proof-of-principle experiment: Access to excited state structure of N=Z superallowed β -emitters DG Jenkins, R Wadsworth, A Steer et al E β vs. E β 40 Ca( 36 Ar,pn) 74 Rb Z=N=37 In-beam γ

41 The New JYFL vacuum mode separator JYFL new What - Configuration kind of research work can be done QQQEDMD were RITU separator is not feasible -Horizontal magnification Vertical magnification Probing the N Z line up to 112 Ba M/Q dispersion 8.1 mm/% - decay spectroscopy (proton and α-particle decay) at the 100 Sn region - First order resolving power, mm rp-process beam spot -Solid - angle proton-neutron acceptance pairing interaction 10 msr - Energy - mirror acceptance nucleifor central mass and - study angle of isospin symmetry +20 % - breaking 15 % - M/Q acceptance - superdeformation and ± 7 hyperdeformation % (N Z 40)

42 GREAT The next step BEAMS TARGET ARRAY DAQ RITU / NEW SEPARATOR

43 JUROGAM II : 2008 Efficient and versatile spectrometer

44 Digital electronics

45 Focal Plane Upgrades

46 Modified 2 MWPC Setup

47 Summary Highly successful, productive and continuing UK involvement in JYFL. Internationally leading/competitive science programmes. Major new spectrometer developments; SAGE, LISA, Vacuum mode separator. Development of new techniques; Beta tagging, tagged plunger measurements. New cyclotron, beam developments and digital electronics.