Recent results on transfer reactions using the MINIBALL/T-REX set-up

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Recent results on transfer reactions using the MINIBALL/T-REX set-up. Thorsten Kröll. Work supported by BMBF (Nr. 06DA9036I and 06MT238), EU (EURONS Nr. 506065), HIC for FAIR, DFG (Excellence Cluster Universe), and the MINIBALL/REX-ISOLDE collaborations. Transfer reactions.
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Recent results on transfer reactions using the MINIBALL/T-REX set-upThorsten KröllWork supported by BMBF (Nr. 06DA9036I and 06MT238), EU (EURONS Nr. 506065), HIC for FAIR,DFG (Excellence Cluster Universe), and the MINIBALL/REX-ISOLDE collaborationsTransfer reactions Spectroscopic tool to study single-particle properties of nuclei
  • selectivity to (1) kinematical matching (e.g. Qopt = 0 for n-transfer)
  • (2) nuclear structure
  • Typical reactions: (d,p), (t,p) …RIBs: inverse kinematicsObservables
  • energies of protons (+ Eg) è(single-particle) level energies
  • angular distributions of protons (+ g-rays) èspin/parity assignments
  • (relative) spectroscopic factors è particle configurations
  • Conceptional limitations
  • only sensitive to nuclear surface
  • phenomenological description (optical pot., DWBA)
  • “meaning” of SF’s?
  • … however, successful tool in nuclear spectroscopy for more than 50 years!!!
  • pg-decaydDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 2Challenges and (open) questions
  • Optical potentials (input for DWBA) for radioactive nuclei are not known
  • elastic scattering of target nuclei
  • extrapolation from stable systems (global description needed)
  • Low beam energy … current limit is 3 MeV/u … and low Q values
  • small proton energies in backward direction
  • smooth angular distributions
  • spectroscopic factors are consistent?
  • è study of 54Fe(d,p)55Fe at different energies M. Mahgoub et al. EPJA 40, 35 (2009)
  • - large spectroscopic factors agree well
  • - small spectroscopic factors can change ... not yet understood
  • Direct transfer reaction or rather fusion-evaporation reaction?
  • evaporationè thermal energy spectra / isotropic angular distribution
  • d(30Mg,31Mg)p @ 2.2 MeV/u ... NO protons from evaporation
  • neutron-rich nuclei: Sn << Spè neutrons will be evaporated
  • (confirmed by Hauser Feshbach calculations)
  • èprotons originate from direct transfer process! M. Pantea, PhD Thesis, TUD (2005)
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 3Overview of experiments done so far …IS491d(78Zn,79Zn)p… talk by R. OrlandiOne- and two-neutrontransfer reactions onneutron-rich isotopesIS454/IS470d(30Mg,31Mg)pt(30Mg,32Mg)pIS469d(66Ni,67Ni)pIS502 (approved)d(28Na,29Na)pIS499t(44Ar,46Ar)pIS430Transfer on 11Be… talk by K. RiisagerLast INTC approvedt(66Ni, 68Ni)pt(72Zn, 74Zn)pDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 4T-REX – Si particle detector arrayT-REX … Si detector array for Transfer experiments at REX-ISOLDECD
  • large solid angle (58% of 4p)
  • position sensitive
  • PID (DE-E): p, d, t, a,
  • … and e- from b-decay (!)
  • Technical details:
  • Barrel: 140 mm DE / 16 resistive strips
  • 1000 mm E / pad
  • Backward CD: 500 mm DE / DSSSD
  • 500 mm E / pad
  • barrelV. Bildstein, K. Wimmer, Th. Kröll, R. Gernhäuser et al. (funded by TU München, KU Leuven, U Edinburgh, CSNSM Orsay, TU Darmstadt)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 5Experimental set-up: T-REX & MINIBALL
  • MINIBALL
  • 24 HPGe
  • 6-fold segmented
  • e ≈ 3% @ 1.3 MeV
  • beambeam… shown is GEANT4 Implementation of set-upDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 631Mg … isotope right on the beachIsland of Inversion again… 35 years after its discovery?C. Thibault et al., Phys. Rev. C 12, 644 (1975)Intruder fp orbitals compete with sd orbitals è breaking of N=20Models describing well 30,32Mg fail to reproduce the 1/2+ spin/parity assignment for the g.s. of 31Mg!?!èafter adaption of a few matrix elements agreement with exp. data for g.s. of 31Mg achievedOur aim:Investigation of single-particlestructure of excited states> 90% intruder configurationV. Bildstein, Dipl. Thesis (Heidelberg, 2005)M. Kowalska et al., EPJA 25, s01, 193 (2005)G. Neyens et al., PRL 94, 022501 (2005)F. Maréchal et al., PRC 72, 044314 (2005)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 7g-rays in coincidence with protons
  • Doppler correction assuming q(31Mg) = 0°
  • 170 keVd(30Mg, 31Mg)p – g-ray spectrum
  • Q00 = 0.18 MeV
  • 30Mg @ 2.86 MeV/u
  • 1- 4 · 104 part/s
  • 1 mg/cm2 deuterated PE
  • populated states not
  • resolved in proton spectrum
  • g-rays needed
  • Analysis by Vinzenz Bildstein(PhD Thesis at TU München)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 8d(30Mg, 30Mg)d – elastic scattering30Mg @ 2.86 MeV/u: elastic scattering èluminosityAll DWBA calculations with FRESCO I. J. Thompson, Comp. Phys. Rep. 7, 167 (1988)Fit to elastic scattering dataExtrapolation of global parameter sets for optical potentialsTotal luminosity: 529 mb-1Analysis by Vinzenz Bildstein(PhD project at TU München)… includes beam contaminations!December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 930Mg – beam composition
  • Analysis of release curves
  • Bragg chamber in beam dump
  • 89% 30Mg11% 30Al<1% others… directly from ISOLDE+ decay productsProton spectra from reactions are NOT affected by 30Al because of different Q valueDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 10!!!Fit to ALL protons (keeping DL=1 contribution fixed) èDL=0 for g.s., DL=2 for 50 keV state, „spectroscopic factors“ S ≈ 0.2731Mg – angular distribution of protons
  • protons in coincidence with 170 keV g-transition
  • analysis using fitted potential parameters
  • DL=1
  • è state has negative parity
  • „spectroscopic factor“
  • S(221 keV) ≈ 0.084
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 11Neutron coupled to 30Mg core … qualitative discussion:30Mg: Beyond Mean Field (BMF)- projection on angular momentum and particle number- configuration mixingè30Mg nearly sphericalTransfer will populate stateswith neutron coupled toprolate configurationsè larger spectroscopic factoror oblate configurationsè smaller spectroscopic factorT. Rodriguez, J. L. Egido; priv. communication (2008)The small SFs indicate that core changes entering the „Island of Inversion“!!!December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 12221 keV:3/2-[321], oblateMixed, mainly 2p3/2DL=1 P[312 3/2]2p3/2g.s.: 1/2+[200], prolateMixed, mainly 2s1/2DL=0 PShape coexistence in 31Mg?221 keV:3/2-[321], prolate1f7/2 orbitalDL=3 ~50 keV: 3/2+[202], prolate1d3/2 orbitalDL=2 PI. Hamamoto, PRC 76, 054319 (2007)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 132n-transferSimilar particle-hole configurations n large overlap of wave functionsèlarge spectroscopic factor for transferShape coexistence at the shore of the island of inversion - the second 0+ in 32MgCoexistence of sphericaland deformed statesMissing part is second 0+ in 32Mg … has not been observed so far !!!normalsd configurations???0+0+2+2+inversionE2E0E2intruderfpconfigurations0+0+30Mg32Mg31MgDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 14Kinematically reconstructed excitation energy in 32Mg
  • Moderate resolution
  • due to kinematics
  • Two states populated:
  • ground state and
  • new state at
  • 1083(33) keV
  • … candidate for the
  • second 0+ state!!!
  • t(30Mg, 32Mg)p – two-neutron transfer
  • 3H loaded Ti foil (40 mg/cm23H, 10 GBq)
  • 30Mg @ 2 MeV/u (to avoid fusion with Ti!!)
  • 4·104 part/s / 150 h beam on target
  • Q00 = -295(20) keV
  • Analysis by Kathrin Wimmer(PhD Thesis at TU München)Phys. Rev. Lett. (in press)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 1532Mg – coincident g-ray spectrum
  • Coincidence with population of 1083 ± 33 keV state
  • Doppler correction assuming q(32Mg)=0°
  • 1058 keVE0(?)E2
  • NO strong 2+ → 0+ transition
  • - no direct population of 2+ state ... protons only from transfer to 0+ states
  • - Eg=172 keV → E(0+) = 1058 keV → 2+ … consistent with 1083 ± 33 keV
  • estimated g-ray yield : 18(3) counts
  • è state decays outside of MINIBALL … rough estimate t > 10 ns
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 16Angular distributions of protons
  • optical model parameters fitted to elastic scattering data,
  • very similar results with exptrapolation from systematics
  • C. M.Perey & F. G. Perey, At. Data Nucl. Data Tab. 17, 1 (1976)
  • almost pure pair transfer, sequential transfer negligible
  • both angular distributions are well described with DL=0 transfer è0+ states
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 1732Mg levels – comparison with theoryPredictions by theory for the excitation energy of the second 0+ state in 32Mg are all considerably higher than the experimental value!E. Caurier et al., Nucl. Phys. A 693, 374 (2001); T. Otsuka et al., Eur. Phys. J. A 20, 69 (2004); R. Rodriguez-Guzmán et al., Nucl. Phys. 709, 201 (2002)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 18Transfer to ground state in 32Mgg.s. occupation numbers using effectiveUSD / SDPF-M interactionsB. H. Wildenthal, Prog. Part. Nucl. Phys. 1, 5 (1984)T. Otsuka et al., Prog. Part. Nucl. Phys. 47, 319 (2001)
  • pure transfer to (f7/2)2 by far to small (radial mismatch)
  • large contribution from (p3/2)2 needed (a > 0.7)
  • … SDPF-M underestimates the np3/2 content in the wave functions
  • … similar to results obtained in neutron knockout from 32,33Mg
  • J. R. Terry et al., Phys. Rev. C 77, 014316 (2008); R. Kanungo et al., Phys. Lett. B 685, 253 (2010)
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 19Transfer to excited 0+ state in 32MgWave function similar to g.s. in 30MgTwo-neutron spectroscopic amplitudesfor pure sd → sd transitions (calculated with USD interaction): a
  • cross section underestimated
  • small (p3/2)2 amplitude (a ≈ 0.3) has to be added
  • … observed also in neutron knockout from 30Mg
  • J. R. Terry et al., Phys. Rev. C 77, 014316 (2008)
  • December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 20Negative parity states predicted by MCSM è … Size of the N=20 gapd(28Na,29Na)p - IS502 … approved
  • 50%/50% mixture normal/intruder in
  • gs wave function (from g factor)
  • Excited states: correspondence
  • exp ó theory not obvious?!?
  • No spin assigments, no configurations
  • 1/2-3/2-, 5/2-7/2-, 9/2-Y. Utsuno et al., PRC 70, 044307 (2004); priv. comm.V. Tripathi et al., PRL 94, 162501 (2005)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 21t(44Ar,46Ar)p – probing N=28Weakening of N=28 closure below 48Ca?è onset of deformation / shape coexistence??? looking for the second 0+Fresh data from October 2010!!!g-rays in coincidence with protonsIdentified protonsTransfer to gs of 46ArAnalysis by Katharina Nowak(PhD project at TU München)Spokesperson/online-analysis: K. WimmerDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 22d(66Ni,67Ni)p – the 68Ni region (N=40)Exists shell closure at N=40?Ex [keV]Ex=3600(250) keVNNDCEg=3619(30) keVEg [keV]Very preliminary… MINIBALL needed to resolve states!Analysis by Jan Diriken(PhD project at KU Leuven)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 23Transfer reactions at HIE-ISOLDEHigher energies at HIE-ISOLDE allow for transfer reactions also with heavy beams!Showcase example: d(132Sn,133Sn)pSeveral LoI‘s for HIE-ISOLDEinvolve nucleon transferreactions with MINIBALL & T-REX:- shell evolution- shape coexistence- pairing correlations ó pair transfer- nuclear astrophysics: (d,p) ó (n,g) capture reactionsUpgrade of T-REX … more flexiblegeometry of Si detectorsSpectrometer planned to identify heavy transfer productsFRESCO calc‘s by K. Wimmer (NSCL, MSU)December 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 24A kind of summary ...
  • One- and two-neutron transfer
  • reactions at REX-ISOLDE …
  • valuable tool to study exotic nuclei
  • Versatile set-up: T-REX & MINIBALL
  • Particle - g-ray coincidences often
  • needed to identify populated states!!!
  • Deuterium und Tritium targets
  • Experiments performed with exotic
  • Be to Zn beams
  • First results published
  • … bright perspectives for transfer
  • reactions at HIE-ISOLDE
  • llllllllllllThank you for your attention!!!!llllllllllllllllllllllllDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 25Announcement: Spettrometer workshopWorkshop onSpectrometer for HIE-ISOLDEMarch 10-11, 2011 at Lund… further informations will be available soonOrganising Committee:Joakim CederkällYorick BlumenfeldThorsten KröllJuha UusitaloDecember 8 - 10, 2010 | ISOLDE Workshop 2010 | Thorsten Kröll | TUD - Institut für Kernphysik | 26
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