Скачать презентацию Portuguese groups at ISOLDE — CERN Ulrich Wahl Скачать презентацию Portuguese groups at ISOLDE — CERN Ulrich Wahl

bbb834167bee2281aff3bd45a9e86a77.ppt

  • Количество слайдов: 11

Portuguese groups at ISOLDE - CERN Ulrich Wahl Instituto Tecnológico e Nuclear (ITN) Sacavém Portuguese groups at ISOLDE - CERN Ulrich Wahl Instituto Tecnológico e Nuclear (ITN) Sacavém Centro de Física Nuclear da Universidade de Lisboa (CFNUL) ØISOLDE and Nuclear Solid State Physics ØPortuguese experiments at ISOLDE: history, people, collaborations ØExamples: - position-sensitive electron detector development - emission channeling lattice location of Fe in Si - PAC investigation of O and F in High-Tc Hg-1201 ØConclusions amd outlook

The ISOLDE on-line isotope separator Available beams: ~ 600 isotopes of ~ 70 elements The ISOLDE on-line isotope separator Available beams: ~ 600 isotopes of ~ 70 elements mass separation target and ion source 60 ke. V acceleration 1 Ge. V protons radioactive ion beams

Experiments involving Portuguese groups: typically around 10 -12 shifts per year i. e. ~3% Experiments involving Portuguese groups: typically around 10 -12 shifts per year i. e. ~3% of ISOLDE availability Solid State Physics 22% Particle and Astro-Physics 13% ISOLDE Experiments 2003 Biology/Medicine 5% Atomic Physics 15% Weak Interaction and Nuclear Physics 46% 37 Experiments 300 Users 96 Institutes 22 Countries 375 8 h-shifts of radioactive beams

Portuguese groups: emission channeling (EC) perturbed angular correlation (PAC) Experimental techniques used with radioactive Portuguese groups: emission channeling (EC) perturbed angular correlation (PAC) Experimental techniques used with radioactive isotopes at ISOLDE

History of e--g PAC and EC at ISOLDE-CERN 1986 e-g PAC at ISOLDE 1994 History of e--g PAC and EC at ISOLDE-CERN 1986 e-g PAC at ISOLDE 1994 Test of new PAC probes IS-P 66 IS 01/13 spokesperson J. C. Soares e--g PAC spokesperson J. G. Correia 197 m. Hg, 73 Ge, 127 Cs, 80 Br 1997 ~2006 IS 360 Studies of high-Tc superconductors with radioactive isotopes 1998 ~2006 IS 368 Lattice location of transition metals and rare earths in semiconductors 2000 ~2005 IS 390 Studies of colossal magnetoresistive oxides with radioactive isotopes 2001 New improved electron emission channeling pad detectors and spokesperson J. G. Correia (ITN & CFNUL) spokesperson U. Wahl (ITN & CFNUL, then IKS Leuven) spokesperson V. Amaral (U Aveiro) development of self-triggering front-end electronics Cooperation agreement between ITN, CFNUL and CERN EP-ATT Group (now: PH-TA 1)

Network of groups involved KU Leuven (Belgium) Prof. André Vantomme 2 Ph. D students: Network of groups involved KU Leuven (Belgium) Prof. André Vantomme 2 Ph. D students: Bart De Vries LEUVEN Stefan Decoster Univ. of Kwazulu Natal (South Africa) Prof. Krish Bharuth-Ram University of Göttingen (Germany) Prof. Hans Hofsäss (future collaboration) CFNUL Lisbon ITN Sacavém Prof. José C. Soares Dr. J. Guilherme Correia Prof. Manuel. R. Silva Dr. Ulrich Wahl 2 Ph. D students: Dr. Heinz Haas (retired) Elisabete Rita Ana C. Marques 1 Diploma student: Sonia Dias University of Porto University of Aveiro Prof. Vitor Amaral Dr. Mario S. Reis 1 Ph. D student: Armandina Lopes 1 Diploma student: João C. Amaral Prof. J. Pedro Araújo 1 Masters student: Tania Mendonça CERN Dr. Peter Weilhammer (detector development)

Funding: mainly from national sources KU Leuven (Belgium) Fund for Scientific Research - Flanders Funding: mainly from national sources KU Leuven (Belgium) Fund for Scientific Research - Flanders (dedicated project on emission channeling) CFNUL Lisbon ITN Sacavém Portuguese Foundation for Science & Technology (dedicated CERN project on PAC & emission channeling) University of Porto Univ. of Kwazulu Natal (South Africa) University of Aveiro University of Göttingen (Germany) Federal Ministry of Education and Research (dedicated project on emission channeling) Portuguese Foundation for Science & Technology (dedicated CERN project on magnetic oxides) CERN

Position-sensitive Si pad detectors for Emission Channeling Collaboration: ITN, CFNUL & CERN PH-TA 1 Position-sensitive Si pad detectors for Emission Channeling Collaboration: ITN, CFNUL & CERN PH-TA 1 group Future detectors: pads self-triggering Þ 5 ke. V trigger Þ 10 k. Hz readout 73 As in Zn. O Cooled 2 o C low electron energy [0001] [-1102] Arsenic occupies multiple sites in Zn. O

Lattice site changes of implanted 59 Fe in Si as-implanted: annealed at T=300°C: annealed Lattice site changes of implanted 59 Fe in Si as-implanted: annealed at T=300°C: annealed at T=800°C: mainly displaced substitutional Fe mainly tetrahedral interstitial Fe mainly ideal substitutional Fe Fe is gettered by at least two types of vacancy-like defects Following release to interstitial state re-gettering occurs at a different gettering center on ideal substitutional sites U. Wahl et al. , accepted by Phys. Rev. B al. ,

Oxygen & Fluorine Configurations in Hg 1201 (High-Tc) Ra di oa ct i ve Oxygen & Fluorine Configurations in Hg 1201 (High-Tc) Ra di oa ct i ve PAC h ~ 0. 20 Experiment EFG Simulations 100 io n C s PA 50 0 0 2500 w(Mrad/s) 5000 h ~ 0. 0 100 PA C 50 Electric Field Gradient dopant configuration fingerprint Hg. Ba 2 Cu. O 4+ d Tc > 92 K 0 0 2500 5000 w(Mrad/s) J. G. Correia et al. , submited to Phys. Rev. B al. ,

Conclusions and outlook: Currently and near future (till ~2006): Ø IS 368: Lattice location Conclusions and outlook: Currently and near future (till ~2006): Ø IS 368: Lattice location in semiconductors, e. g. Si, Ge, Si. Ge, diamond, III-V, nitrides, II-VI, Zn. O… electrical doping, transition metals, rare earths, diluted magnetic semiconductors Ø IS 360: PAC in High-Tc superconductors Ø IS 390: Magnetism in manganites (CMR) After 2006: New emission channeling proposal(s) applying… Ø new position-sensitive detectors (self-triggering pad, CCD) Þ - on-line experiments with short-lived isotopes - low energy electron emitters (Auger electrons? ) a new variety of elements (e. g. Mg, Co, Ni, Zn, Ge) will be available for emission channeling