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SATURN HST/ IR 1998, TETHYS VOYAGER2 1981, URANUS HST/ IR 1986

What can we learn from transfer, and how is best to do it?. Wilton Catford University of Surrey. WILTON CATFORD JUNE 2008. A. Single Particle States; RIB experiments!!. B. Reaction models. C. Practicalities; Inverse Kinematics. Nuclear Chemistry. D. Experimental setups.

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SATURN HST/ IR 1998, TETHYS VOYAGER2 1981, URANUS HST/ IR 1986

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  1. What can we learn from transfer, and how is best to do it? Wilton Catford University of Surrey WILTON CATFORD JUNE 2008 A Single Particle States; RIB experiments!! B Reaction models C Practicalities; Inverse Kinematics Nuclear Chemistry D Experimental setups New London NH June 2008 E Results & Perspectives SATURN HST/ IR 1998, TETHYS VOYAGER2 1981, URANUS HST/ IR 1986

  2. Approach: To highlight the questions that have to be addressed in doing this work That is: As we embark on the new enterprise of working with radioactive beams… How do we do it? the choices for the experimental setup… why different experiments/teams will make different choices How do we interpret the measurements? what exactly are we measuring and why (and how well)? Philosophy: … this is the Gordon, so… Not a traditional review, but a snapshot of thoughts in progress… … an open discussion… WILTON CATFORD JUNE 2008 W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008

  3. 1s 1/2 0d 5/2 A. SINGLE PARTICLE STATES – EXAMPLE Example of population of single particle state: 21O WILTON CATFORD JUNE 2008 0d 3/2 energy of level measures this gap 1s 1/2 Jp = 3/2+ 0d 5/2 The mean field has orbitals, many of which are filled. We probe the energies of the orbitals by transferring a nucleon This nucleon enters a vacant orbital In principle, we know the orbital wavefunction and the reaction theory But not all nuclear excited states are single particle states… x 1/2+ Jp = 3/2+ 2+ We measure how the two 3/2+ states share the SP strength when they mix A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Pure and Mixed States

  4. SINGLE PARTICLE STATES – SPLITTING WILTON CATFORD JUNE 2008 If we want to measure the SPE, splitting due to level mixing means that all components must be found, to measure the true single particle energy Plot: John Schiffer A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Splitting masks the true SP energy

  5. SINGLE PARTICLE STATES Changes – tensor force, p-n Residual interactions move the mean field levels Magic numbers “migrate”, changing stability, reactions, collectivity… WILTON CATFORD JUNE 2008 Similarly… proton filling affects neutron orbitals A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Motivation – monopole migration

  6. SINGLE PARTICLE STATES (d, ) p WILTON CATFORD JUNE 2008 Probing the changed orbitals and their energies… A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Population in an exotic nucleus

  7. SINGLE PARTICLE STATES (d, ) p As we approach the dripline, we also have to worry about the meaning and theoretical methods for probing resonant orbitals in the continuum… WILTON CATFORD JUNE 2008 A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Population of states in the continuum

  8. Systematics of the 3/2+ for N=15 isotones 4.5 4.0 3.5 3.0 27Mg 23O 25Ne 2.5 2.0 1f7/2 1.5 1.0 excitation energy (MeV) 0.5 0.0 (1d5/2)-1 6 1d3/2 2s1/2 8 10 12 atomic number 16 16 20 SINGLE PARTICLE STATES – AN ACTUAL EXAMPLE WILTON CATFORD JUNE 2008 removing d5/2 protons raises d3/2 and appears to lower the f7/2 Migration of the 3/2+ state creates N=16 from N=20 25Ne TIARA  USD modified 23,25O raise further challenges 21O has similar 3/2+-1/2+ gap (same d5/2 situation) but poses interesting question of mixing (hence recent 20O(d,p)@SPIRAL) • 23O from USD and Stanoiu PRC 69 (2004) 034312 and ElekesPRL 98 (2007) 102502 • 25Ne from TIARA, W.N. Catford et al.Eur. Phys. J. A, 25 S1 251 (2005) A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Example case in N=15 revealing N=16

  9. SINGLE PARTICLE STATES – ANOTHER EXAMPLE WILTON CATFORD JUNE 2008 Serge Franchoo PRC 64(2001)054308 fill g9/2 p f5/2 hole f7/2 A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Example fp protons Z=28 to 40 for n-rich

  10. Spectroscopic Factor Shell Model: overlap of  (N+1)  with  (N) core  n ( j) Reaction: the observed yield is not just proportional to this, because the overlap integral has a radial-dependent weighting or sampling overlap integral Hence it depends on the radial wave function and thus the geometry of the assumed potential well or other structure model spectroscopic factor B. REACTION MODEL FOR (d,p) TRANSFER – the ADWA • Johnson-Soper Model: an alternative to DWBA that gives a simple prescription for taking into account coherent entangledeffects of deuteron break-up on (d,p) reactions [1,2] • does not use deuteron optical potential – uses nucleon-nucleus optical potentials only • formulated in terms of adiabatic approximation, which is sufficient but not necessary [3] • uses parameters (overlap functions, spectroscopic factors, ANC’s) just as in DWBA • [1] Johnson and Soper, PRC 1 (1970) 976 • [2] Harvey and Johnson, PRC 3 (1971) 636; Wales and Johnson, NPA 274 (1976) 168 • [3] Johnson and Tandy NPA 235 (1974) 56; Laid, Tostevin and Johnson, PRC 48 (1993) 1307 WILTON CATFORD JUNE 2008 A.B.C.D.E REACTION MODEL 1.2.3. Johnson-Soper & ADWA

  11. Valence nucleon orbital from Hartree-Fock, not just standard W-S geometry Jenny Lee, Jeff Tostevin, Alex Brown et al. Lee et al PRC 73 (2006) 044608 Kramer et al for (d,3He) NPA 679 (2001) 267 Is there a SYSTEMATIC effect as seen in knockout? Results of transfer are consistent but do not yet explore extremes REACTION MODEL FOR (d,p) TRANSFER – the ADWA A CONSISTENT application of ADWA gives 20% agreement with large basis SM WILTON CATFORD JUNE 2008 80 spectroscopic factors Z = 3 to 24 Jenny Lee et al. Tsang et al PRL 5 (2005) 222501 Lee et al PRC 75 (2007) 064320 Delaunay at al PRC 72 (2005) 014610 A.B.C.D.E REACTION MODEL 1.2.3. Jenny Lee et al validation of ADWA

  12. tail u(r) V(r) REACTION MODEL FOR (d,p) TRANSFER Given what we have seen, is transfer the BEST way to isolate and study single particle structure and its evolution in exotic nuclei? WILTON CATFORD JUNE 2008 Transfer – decades of (positive) experience Removal – high cross section, similar outputs, requires full orbitals (e,e’p) – a bit ambitious for general RIB application (p,p’p) – more practical than (e,e’p) for RIB now, does have problems Complementary to (d,p) …to be validated with (d,t) YES Also: Heavy Ion transfer (9Be), 3,4He-induced reactions A.B.C.D.E REACTION MODEL 1.2.3. Other reactions probing single-particle structure

  13. C. USING RADIOACTIVE BEAMS in INVERSE KINEMATICS WILTON CATFORD JUNE 2008 Single nucleon transfer will preferentially populate the states in the real exotic nucleus that have a dominant single particle character. Angular distributions allow angular momenta and (with gammas) spins to be measured. Also, spectroscopic factors to compare with theory. Around 10A MeV/A is a useful energy as the shapes are very distinctive for angular momentum and the theory is tractable. Calculated differential cross sections show that 10 MeV/A is good (best?) A.B.C.D.E PRACTICALITIES 1.2.3. Transfer at around 10 MeV/A

  14. USING RADIOACTIVE BEAMS in INVERSE KINEMATICS (d,t) (d,d) WILTON CATFORD JUNE 2008 (d,p) f = 1/2 for (p,d), 2/3 for (d,t) q@ 1 + Q tot / (E/A) beam A.B.C.D.E PRACTICALITIES 1.2.3. Inverse kinematics

  15. But RIBs, as well as being heavy compared to the deuteron target, are: • Radioactive • Weak • Issues arising: • Gamma detection useful for improving resolution • Active target (TPC) to minimize loss of resolution • Need MAXIMUM efficiency for detection • Experimental solutions can be classed roughly as: • For beams < 103 pps ACTIVE TARGET • 103 < beam < 106 pps Si BOX in a g-ARRAY • For beams > 106 pps MANAGE RADIOACTIVITY ISSUES ARISING FROM TARGET THICKNESS LIMITATIONS It turns out that the target thickness is a real limitation on the energy resolution… Several hundred keV is implicit, when tens would be required, So the targets should be as thin as possible… WILTON CATFORD JUNE 2008 A.B.C.D.E PRACTICALITIES 1.2.3.Tackling target thickness limitations

  16. D. SOLUTIONS FOR BEAMS IN RANGE 102 to 104 pps USING TPC’s MAYA Now in use at GANIL/SPIRAL TRIUMF WILTON CATFORD JUNE 2008 ACTAR being designed for future SPIRAL2 78Ni(d,p)79Ni at 10 A MeV A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Active targets: time projection chambers

  17. SOLUTIONS FOR BEAMS IN RANGE 104 to 106 pps USING GAMMAS SHARC TIGRESS TRIUMF TIGRESS COLLABORATION York Surrey WILTON CATFORD JUNE 2008 T-REX MINIBALL REX-ISOLDE MINIBALL COLLABORATION Munich Leuven ORRUBA OAK RIDGE A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon boxes inside gamma arrays STEVE PAIN

  18. SOLUTIONS FOR BEAMS IN RANGE 106 to 109 pps USING GAMMAS Target Changing Mechanism Barrel Si 36 < lab < 144  WILTON CATFORD JUNE 2008 Beam VAMOS Forward Annular Si 5.6 < lab < 36  Backward Annular Si 144 < lab < 168.5  A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon for higher beam intensities

  19. SOLUTIONS FOR BEAMS IN RANGE 106 to 109 pps USING GAMMAS WILTON CATFORD JUNE 2008 A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon for higher beam intensities

  20. NOVEL SOLENOID FOR 4p DETECTION to DECOMPRESS KINEMATICS WILTON CATFORD JUNE 2008 Actual solenoid – from MRI Trajectories for 132Sn(d,p) at 8 MeV/A HELIOS: Wuosmaa, Schiffer et al. avoids this compression A.B.C.D.E COMPLEMENTARY APPROACHES 1.2.3.4.5. Solenoidal devices

  21. FROZEN TARGETS and not detecting the LIGHT PARTICLE A. Obertelli et al., Phys. Lett. B633, 33 (2006). WILTON CATFORD JUNE 2008 Also: Elekes et al PRL 98 (2007) 102502 22O(d,p) to n-unbound 23O SP states And helium: Especially (a,3He) etc. at RIKEN A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5.Frozen targets

  22. 5/2+ 7/2+ 9/2+ 0.004 5/2+ 0.11 3/2+ 5/2+ 0.10 3/2+ 0.49 n+24Negs 1/2+ 0.63 USD E. SOME RESULTS and PERSPECTIVES ( = 3) 4030 0.73 7/2 – WILTON CATFORD JUNE 2008 p = – 3330 0.75 3/2 –  = 1  = 2 0.44 2030 3/2+ 1680 0.15 5/2+  = 2 In 25Ne we used gamma-gamma coincidences to distinguish spins and go beyond orbital AM  = 0 0.80 1/2+ TIARA A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5. Gamma rays as an aid to identification

  23. SOME RESULTS and PERSPECTIVES TIARA/MUST2 campaign at GANIL 2007 Surrey, Liverpool Orsay, Saclay, GANIL SPIRAL: 20O and 26Ne beams… N=16, 28 GANIL: 34Si, other frag beams… N=20, 28 WILTON CATFORD JUNE 2008 JEFF THOMAS f 7/2 SPIRAL beam 26Ne (pure) 2300 pps A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5. Recent TIARA+MUST2 campaign

  24. Geant4 simulation 3000 ? 1410 Sn Ex elastic On-Line data 885 765 ? transfer 0 SOME RESULTS and PERSPECTIVES Geant4 simulation beam + n WILTON CATFORD JUNE 2008 On-Line data beam-like at 0° Several x 100 counts “beam” proton from (d,p) Energy Lab angle A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5. On-Line results from SPIRAL + TIARA + MUST2

  25. 5/2+ 7/2+ 9/2+ 0.004 5/2+ 0.11 3/2+ 5/2+ 0.10 3/2+ 0.49 n+24Negs 1/2+ 0.63 USD SOME RESULTS and PERSPECTIVES ( = 3) 4030 In 25Ne the 3/2+ state was far from a pure SP state due to other couplings at higher energies, but it was clear enough in its ID and could be used to compare with its SM partner to improve the USD interaction 0.73 7/2 – WILTON CATFORD JUNE 2008 p = – 3330 0.75 3/2 –  = 1  = 2 0.44 2030 3/2+ 1680 0.15 5/2+  = 2 It is not always necessary to map the full SP strength which may be very much split and with radioactive beams it may not often be possible Includes also n(s1/2)  p(d5/22)2+  = 0 0.80 1/2+ TIARA A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5. WHAT WE MEASURE – example 25Ne

  26. GRAPA GAMMA RAY AND PARTICLE ARRAY SOME RESULTS and PERSPECTIVES WILTON CATFORD JUNE 2008 “… WORK IN PROGRESS” A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5.GRAPA and GASPARD

  27. What do we measure and Why? And Where (on the Segre chart)? Single particle states (in amongst, mixed with, other states) Migration of magic numbers – “monopole migration”, implications What is the best way to measure these things – choice of reaction Classic transfer Removal reactions (sometimes called knockout) Knockout reactions (such as (p,p'p) or (e,e'p) So, what do we really measure? What should we measure? SPE? Full strength? How reliable is what we measure? What radioactive beams do we need? How good do they have to be? Speed? Purity? Focussing? Timing? So how do we do it? the choices for the experimental setup… Si arrays (TIARA, MUST/2, ORRUBA, SHARC), Solenoid, Active targets Ways in which it helps to know your gammas How do we interpret the measurements? ADWA. DWBA. Form factor. Unbound states. Weighted SPE vs SM comparison WILTON CATFORD JUNE 2008 W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008

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