Download
proposal of e 107b experiment charge symmetry n.
Skip this Video
Loading SlideShow in 5 Seconds..
Proposal of E-107b experiment: Charge Symmetry in reactions with Exotic Nuclei PowerPoint Presentation
Download Presentation
Proposal of E-107b experiment: Charge Symmetry in reactions with Exotic Nuclei

Proposal of E-107b experiment: Charge Symmetry in reactions with Exotic Nuclei

396 Vues Download Presentation
Télécharger la présentation

Proposal of E-107b experiment: Charge Symmetry in reactions with Exotic Nuclei

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Proposal of E-107b experiment: Charge Symmetry in reactions with Exotic Nuclei Marlete Assunção Departamento de Física - Universidade Federal de São Paulo UNIFESP-campus Diadema massuncao@unifesp.br LIA Meeting, M. Assunção - UNIFESP

  2. OUTLINE • Introduction • Motivations • The Experiment • Procedure of Analysis LIA Meeting, M. Assunção - UNIFESP

  3. INTRODUCTION • The charge symmetryiswellestablishedpropertyofthe nuclear interaction • Effectsof charge symmetry • Spectroscopicpropertiesofmirrornuclei -> coulomb effects are not too important • In levelschemes -> the charge symmetryofstronginteraction is shownifthe coulomb energy • shift is takenintoaccount LIA Meeting, M. Assunção - UNIFESP

  4. INTRODUCTION • Effectsof charge symmetry in collisions • No easywayofseparatingthecontributionofthe Coulomb force • Collisionsbetweennucleonsand light nuclei -> sometimesledtocontroversy*ref1 • In transferreactions • The charge symmetryiswelltestedbyBarshay-TemmerTheorem*ref 2 • -> consideringthat: • (1) thecollindingnucleihave zero isospinsand • (2) theexitchannelconsistsofthepairofmirrornuclei • -> Studiescanbeperformedbycollidingstablenuclei*ref 3 ref 1: Tilley et al., NPA54,1 (1992) ref 2: Temmer et al.. Proceeding of the Internacional Course on Fundamentals in Nuclear Theory, Trieste, 1966 ref 3: Oertzen et al., PL28B, 482 (1969) LIA Meeting, M. Assunção - UNIFESP

  5. INTRODUCTION Radioactive nuclear beams -> study mirror elastic collisions involving heavy ions • Mirror elastic collisions involving heavy ions • The charge symmetry must introduce some relationship between these reactions -> there is no simple way to relate its cross sections • The complexity of the interpretation of cross sections increases considerably with the increase of A • In collision process below the Coulomb barrier • The Coulomb force which dominates the collision process is much stronger than for very light systems • In collision process above the Coulomb barrier • The existence of many open channels (threshold energy is also sensitive to the effects of the Coulomb force) can hide the manifestation of charge symmetry LIA Meeting, M. Assunção - UNIFESP

  6. MOTIVATIONS TO INVESTIGATE THE CHARGE SYMMETRY • First Experiment using the Mirror elastic Collision (E. Liénard et al. PRC52 (1995) • Mirror System: 13C+12C and 13N+12C • Goal: to study the dependence of parity resulting from similar masses of the target and the projectile • The Liénard´s conclusions: point to the study of other mirrors systems involving heavy ions • Principal motivation to measure the mirror elastic collision involving exotic nuclei • The core-core interaction involving an exotic nuclei is expected to be sensitive to specific properties, for example, to the size of the radius. • Exotic Nuclei Radius is very large due to the low binding energy -> breakup channels play an important role, and can affect the optical potential through an additional polarization potential -> as breakup channels are different in mirror systems is expected that the charge symmetry will be broken LIA Meeting, M. Assunção - UNIFESP

  7. CHARGE SYMMETRY EXPERIMENT • The Experiment • Mirror System: 7Li+24Mg and7Be+24Mg • Reaction Energy (lab): close andabovethecoulombbarrier 22MeV ) • RIBRAS - RadioactiveIonBeam in BRAZIL • -> PrimaryBeams : Pelletron Accelerator, IFUSP-São Paulo, Brazil • Energy PrimaryBeam (6Li): ~28 MeV • ProductionReaction (7Be): 6Li(7LiF, 7Be) • 7Be production rate: ~105pps • 7Li (stable) Beam: Pelletron Accelerator • Target: 24Mg (99,9% enriched) ofthe 1mg/cm2 • -> Backing: 12C (~15mg/cm2) • Normalization: 197Au (~4mg/cm2) • Detectors System: 4 telescope (DE-E Si detectors) • -> Thicknesses of 20 and 1000 μm • Angular range: 15o to 120o Top view of the telescopes on the turntable inside of the secondary chamber (courtesy KCCPires) LIA Meeting, M. Assunção - UNIFESP

  8. RIBRAS (Radioactive Ion Beam in Brazil) Primary Beam from Pelletron Accelerator LABORATÓRIO DE FÍSICA NUCLEAR PELLETRON-LINAC INSTITUTO DE FÍSICA DA UNIVERSIDADE DE SÃO PAULO • RIBRAS consists of two superconducting solenoids and three scattering chambers -> Maximum central magnetic field: 6.5T LIA Meeting, M. Assunção - UNIFESP

  9. SCATTERING CHAMBER Measurements: 2 energies at close and above of Coulomb barrier • Primary Beams Elab(6Li3+ ) = ~28MeV Elab(7Li3+)= ~25MeV Primary Beam Primary Target Faraday Cup • Angular acceptance of 2◦- 6◦ in the entrance and 1.5◦ − 3.5◦ at the exit of the solenoid. Primary Chamber • The 7Bebeam will produced by the 6Li(7Li,7Be) reaction and focused by the first solenoid onto the secondary target. • On the 24Mg target Elab(7Li3+ )=Elab(7Be3+ )=~21.8MeV Intensity = 200-300 nAe Secondary Chamber LIA Meeting, M. Assunção - UNIFESP

  10. PROCEDURE OF ANALYSIS The charge symmetry is observed from the potential calculations for mirror systems measurements. If the charge symmetry is confirmed, then (1) the nuclear potential will be the same for 7Li+24Mg and 7Be+24Mg (2) Coulomb contributions (different for mirror systems) should be observed ref 4. SPP: L.C. Chamon et al., PRC 66 (2002) 014610. • This experiment is our first in a series of measurements for understanding the mechanisms involved in mirror elastic scattering • The idea is to performed potential calculations considering all contributions to confirm this hypothesis LIA Meeting, M. Assunção - UNIFESP

  11. COLLABORATORS (at moment) P. Descouvemont ULB- Brussel V. Guimarães – IFUSP-Brazil M. S. Hussein – IEA/USP – Brazil RIBRAS collaboration Orsay collaboration F. De Oliveira - Ganil LIA Meeting, M. Assunção - UNIFESP

  12. LIA Meeting, M. Assunção - UNIFESP