1. 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 A B E Single Particle States; RIB experiments!! Reaction models Practicalities; Inverse Kinematics Results & Perspectives New London NH June 2008 Nuclear Chemistry DExperimental setups C WILTON CATFORD JUNE 2008

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… W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008 WILTON CATFORD JUNE 2008

3. Example of population of single particle state: 21 O 0d 5/2 1s 1/2 0d 3/2 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… 0d 5/2 1s 1/2 energy of level measures this gap J  = 3/2 + 2+2+ x 1/2 + 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 A. SINGLE PARTICLE STATES – EXAMPLE WILTON CATFORD JUNE 2008

4. SINGLE PARTICLE STATES – SPLITTING A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Splitting masks the true SP energy Plot: John Schiffer 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 WILTON CATFORD JUNE 2008

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

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

7. (d, ) p SINGLE PARTICLE STATES A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Population of states in the continuum 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

8. 23 O from USD and Stanoiu PRC 69 (2004) 034312 and Elekes PRL 98 (2007) 102502 25 Ne from TIARA, W.N. Catford et al. Eur. Phys. J. A, 25 S1 251 (2005) Migration of the 3/2+ state creates N=16 from N=20 25 Ne TIARA  USD modified 23,25 O raise further challenges 21 O has similar 3/2+-1/2+ gap (same d5/2 situation) but poses interesting question of mixing (hence recent 20 O(d,p)@SPIRAL) excitation energy (MeV) 4.5 1.5 1.0 0.5 0.0 3.0 2.5 2.0 4.0 3.5 6 8 10 12 atomic number 1d 3/2 1f 7/2 27 Mg 23 O 25 Ne Systematics of the 3/2+ for N=15 isotones (1d 5/2 ) -1 2s 1/2 removing d5/2 protons raises d3/2 and appears to lower the f7/2 20 16 SINGLE PARTICLE STATES – AN ACTUAL EXAMPLE A.B.C.D.E SINGLE PARTICLE STATES 1.2.3.4.5.6.7. Example case in N=15 revealing N=16 WILTON CATFORD JUNE 2008

9. fill g 9/2 hole f 7/2  f 5/2 Serge Franchoo PRC 64(2001)054308 SINGLE PARTICLE STATES – ANOTHER EXAMPLE 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 WILTON CATFORD JUNE 2008

10. A.B.C.D.E REACTION MODEL 1.2.3. Johnson-Soper & ADWA Johnson-Soper Model: an alternative to DWBA that gives a simple prescription for taking into account coherent entangled effects 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 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 spectroscopic factor Hence it depends on the radial wave function and thus the geometry of the assumed potential well or other structure model B. REACTION MODEL FOR (d,p) TRANSFER – the ADWA WILTON CATFORD JUNE 2008

11. A.B.C.D.E REACTION MODEL 1.2.3. Jenny Lee et al validation of ADWA REACTION MODEL FOR (d,p) TRANSFER – the ADWA A CONSISTENT application of ADWA gives 20% agreement with large basis SM 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 Is there a SYSTEMATIC effect as seen in knockout? Results of transfer are consistent but do not yet explore extremes 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 WILTON CATFORD JUNE 2008

12. A.B.C.D.E REACTION MODEL 1.2.3. Other reactions probing single-particle structure 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? 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 ( 9 Be), 3,4 He-induced reactions tail u(r) V(r) WILTON CATFORD JUNE 2008

13. A.B.C.D.E PRACTICALITIES 1.2.3. Transfer at around 10 MeV/A C. USING RADIOACTIVE BEAMS in INVERSE KINEMATICS 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?) WILTON CATFORD JUNE 2008

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

15. A.B.C.D.E PRACTICALITIES 1.2.3. Tackling target thickness limitations 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… But RIBs, as well as being heavy compared to the deuteron target, are: (a)Radioactive (b)Weak Issues arising: (a)Gamma detection useful for improving resolution (b)Active target (TPC) to minimize loss of resolution (c)Need MAXIMUM efficiency for detection Experimental solutions can be classed roughly as: (a)For beams < 10 3 pps ACTIVE TARGET (b)10 3 < beam < 10 6 pps Si BOX in a  -ARRAY (c)For beams > 10 6 pps MANAGE RADIOACTIVITY WILTON CATFORD JUNE 2008

16. 78 Ni(d,p) 79 Ni at 10 A MeV MAYA Now in use at GANIL/SPIRAL TRIUMF ACTAR being designed for future SPIRAL2 A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Active targets: time projection chambers D. SOLUTIONS FOR BEAMS IN RANGE 10 2 to 10 4 pps USING TPC’s WILTON CATFORD JUNE 2008

17. SHARC TIGRESS TRIUMF TIGRESS COLLABORATION York Surrey T-REX MINIBALL REX-ISOLDE MINIBALL COLLABORATION Munich Leuven A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon boxes inside gamma arrays SOLUTIONS FOR BEAMS IN RANGE 10 4 to 10 6 pps USING GAMMAS ORRUBA OAK RIDGE STEVE PAIN WILTON CATFORD JUNE 2008

18. Forward Annular Si 5.6  <  lab < 36  Backward Annular Si 144  <  lab < 168.5  Barrel Si 36  <  lab < 144  Target Changing Mechanism Beam VAMOS A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon for higher beam intensities SOLUTIONS FOR BEAMS IN RANGE 10 6 to 10 9 pps USING GAMMAS WILTON CATFORD JUNE 2008

19. A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES 1.2.3.4.5. Silicon for higher beam intensities SOLUTIONS FOR BEAMS IN RANGE 10 6 to 10 9 pps USING GAMMAS WILTON CATFORD JUNE 2008

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

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

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

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

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

25. A.B.C.D.E. RESULTS AND PERSPECTIVES 1.2.3.4.5. WHAT WE MEASURE – example 25Ne SOME RESULTS and PERSPECTIVES 4030 3330 2030 1680 = 2 = 0 5/2+ 3/2+  = – 1/2+ = 2 = 1 ( = 3) 7/2 – 3/2 – 0.73 0.80 0.15 0.44 0.75 TIARA 1/2+ 3/2+ 5/2+ 3/2+ 5/2+ 9/2+ 7/2+ 5/2+ 0.49 0.10 0.11 0.004 n+ 24 Ne gs USD 0.63 In 25 Ne 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 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 (s 1/2 )   (d 5/2 2 ) 2+ WILTON CATFORD JUNE 2008

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

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 W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008 WILTON CATFORD JUNE 2008