Recent Experimental Results from HELIOS A new approach to reactions in inverse kinematics A. H. Wuosmaa Western Michigan University

Why still study nucleon transfer? Renewed emphasis on transfer reactions with RIBS: – Properties of nuclei far from stability, esp. near “closed” shells (spins, parities, spectroscopic factors, s.p. energies, residual interactions) – Importance of the tensor interaction – Test/tune new shell-model interactions Broader applications: – e.g. astrophysics, stewardship (“surrogates” for capture reactions) Life is much more difficult with inverse kinematics and radioactive beams

0.87 1/ / (0,1) (2,3) / /2 + Evolution of 1s 1/2 -0d 5/2 splitting outside N=8 ?? (1,2) - ?? (1,2,3,4) - 17 O(S n =4.14)  (p 1/2 ) 2 16 N(S n =2.49)  (p 1/2 ) 15 C(S n =1.22)  (p 3/2 ) 4 14 B(S n =0.97)  (p 3/2 ) 3 j(p)=j < attraction j(p)=j < attraction j(p)=j > repulsion j(p)=j > repulsion J(p),J(n) one j > other j < : attraction J(p),J(n) both j > or j < : repulsion 0d 5/2 neutron has j(n)=j >

(d,p) reaction in different frames CM frame Laboratory frame- “normal” kinematics Laboratory frame- “Inverse” kinematics  CM  LAB v0v0 IN OUT 2H2H 1H1H v lab

z Beam Axis Cyclotron orbit Emitted here Detected here We measure: E lab, z, TOF We deduce: E CM,  CM Uniform magnetic field B The HELIOS approach to inverse kinematics For a given state For two states at fixed z

E P (MeV) Cos(  CM ) E P (MeV)  LAB (deg) z (m) 1.4 MeV 5 MeV “Conventional” – measure at fixed  LAB HELIOS – measure at fixed z Advantages to the HELIOS approach for (d,p) dE P /dz=17.5 keV/mm dE P /d  LAB =175 keV/deg

HELIcal Orbit Spectrometer -HELIOS 2.35 m 0.9 m X-Y-  positioning stage B MAX =2.85 T Laser rangefinder Silicon Array Target Beam J.P. Schiffer, RIA equipment workshop 1999, AHW et al, NIMPRA 580, 1290 (2007) J. C. Lighthall et al, NIMPRA 622, 97 (2010)

Spectrometer completed in August 2008

28 Si(d,p) 29 Si commissioning-it works! Excitation energy in 29 Si 6.38 Residual  source background protons from 28 Si+ 12 C J. C. Lighthall et al, NIMPRA 622, 97 (2010) T(ns) A/q=1, 1 turn A/q=1, 2 turns (A/q=2, 1 turn)

28 Si(d,p) 29 Si Excitation-energy spectrum Typical resolution ~ 120 keV FWHM Best resolution ~ 80 keV FWHM J. C. Lighthall et al, NIMPRA 622, 97 (2010)

16 C Core Valence neutrons Exotic behavior in 16 C? Study with 15 C(d,p) 16 C No hindrance, and no exotic behavior.

15 C(d,p) 16 C with HELIOS PRL 105, (2010) Proton energy-position correlation 16 C Excitation-energy spectrum (d,p) samples the (1s 1/2 ) content of the wave functions for positive-parity states 1.5-2M MeV/u

L=0 L=2 L=0 L=2 15 C(d,p) 16 C results PRL 105, (2010) Shell model – WBP interaction Shell model works well – no need for exotica! Experiment

19 O(d,p) 20 O – further into the sd shell Proton energy versus position 20 O excitation energy ν(0d 5/2 ) 3 5/2  ν(sd)→ν(sd) 4 states in 20 O 200k-300k MeV/u C. R. Hoffman et al., PRC 85, (2012)

What we can learn from 19 O(d,p) 20 O Angular distributions and neutron vacancies from 19 O(d,p) 20 O Center-of-mass angle (deg) 19 O excitation energy (MeV) Cross section (mb/sr) L=2L=2L=0+2L=0+2 Orbital vacancy G + Solid: L=0; hatched L=2 C. R. Hoffman et al., PRC 85, (2012)

Broad l=0 and 2 states expected with J π =(0,1,2,3) - S n =0.969 Preliminary excitation-energy spectrum E X ( 14 B) (MeV) 13 B(d,p) 14 B  <150 keV  ~200 keV Red – 14 B Blue – 13 B 20-40k 13 MeV/u

13 B(d,p) 14 B Preliminary d  /d  (mb/sr) L=0 L=2 L=0+2  c.m. (deg) OMPs fit 30 MeV d+ 12 C, p+ 12,13 C elastic scattering at 15 MeV/u Shell model with WBT interaction Experiment (2-)  ~1MeV L=0 L=2 SnSn

136 Xe(d,p) 137 Xe with HELIOS– approaching 132 Sn Proton energy versus position 137 Xe excitation energy B. P. Kay et al, PRC 84, (2011)

What we can learn from 136 Xe(d,p) 137 Xe B. P. Kay et al, PRC 84, (2011) 136 Xe(d,p) 137 Xe angular distributions and orbital-energy trends near N=82

A variety of measurements 28 Si(d,p) 29 Si – Aug (first commissioning)* 12 B(d,p) 13 B – March 2009 (RIB commissioning)* 17 O(d,p) 18 O – Aug (unbound states in 18 O) 15 C(d,p) 16 C – Sep (exotic behavior in 16 C)* 130,136 Xe(d,p) 131,137 Xe – Nov (S.P. states near N=82)* 86 Kr(d,p) 87 Kr – Feb (S.P. states near N=50) 14 C( 6 Li,d) 18 O – March 2010, (  -cluster states in 18 O: d not p!) 19 O(d,p) 20 O – Sep (structure of 20 O)* 28 Si(d, 3 He) 27 Al, 28 Si(d,t) 27 Si – May 2011 (commissioning of forward-hemisphere configuration) 13 B(d,p) 14 B – Nov (structure of 14 B) 17 N(d,p) 18 N – March 2012 (structure of 18 N) *Published or In Press

Summary HELIOS provides a new approach to studying reactions in inverse kinematics Alleviates problems with light particle identification and gives improved excitation- energy resolution and straightforward determination of CM quantities Can obtain data with quality approaching that of normal-kinematics measurements The method can be applied to a variety of other inverse-kinematic reactions in addition to (d,p) Other examples are being considered at HIE- ISOLDE, SPIRAL2, ReA3/FRIB

Many thanks to: 2 M. Alcorta, 2 B. B. Back, 2 S. I. Baker, 1 S. Bedoor, 2 P. F. Bertone, 3 B. A. Brown, 2 J. A. Clark, 2,4 C. M. Deibel, 5 P. Fallon, 6 S. J. Freeman, 2 C. R. Hoffman, 2 B. P. Kay, 2,7 H. Y. Lee, 1,2 J. C. Lighthall, 5 A. O. Macchiavelli, 1,2 S. T. Marley, 2 K. E. Rehm, 2 J. P. Schiffer, 1 D. V. Shetty, 8 M. Wiedeking 1 Department of Physics, Western Michigan University, Kalamazoo, Michigan , USA 2 Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 3 Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA 4 Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA 5 Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 6 Department of Physics, University of Manchester 7 LANSCE-NS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 8 Lawrence Livermore National Laboratory, Livermore, California 94551, USA

And… The HELIOS Collaboration S. Bedoor, J. C. Lighthall, S. T. Marley, D. Shetty, J. R. Winkelbauer (SULI student), A. H. Wuosmaa Western Michigan University B. B. Back, S. Baker, C. M. Deibel, C. R. Hoffman, B. Kay, H. Y. Lee, C. J. Lister, P. Mueller, K.E. Rehm, J. P. Schiffer, K. Teh, A. Vann (SULI student) Argonne National Laboratory S. J. Freeman University of Manchester Work supported by the U. S. Department of Energy, Office of Nuclear Physics, under contract numbers DE-FG02-04ER41320 (WMU) and DE-AC02-06CH11357 (ANL) Also, special thanks to: N. Antler, Z. Grelewicz, S. Heimsath, J. Rohrer, J. Snyder