Recent Experimental Results from HELIOS

A new approach to reactions in inverse kinematics

A. H. WuosmaaWestern 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 1/2+

0.00 5/2+

0.33 (0,1)-

0.17 (2,3)-

0.74 5/2+

0.00 1/2+

Evolution of 1s1/2-0d5/2 splitting outside N=8

?? (1,2)-

?? (1,2,3,4)-

17O(Sn=4.14)p(p1/2)2

16N(Sn=2.49)p(p1/2)

15C(Sn=1.22)p(p3/2)4

14B(Sn=0.97)p(p3/2)3

j(p)=j<

attractionj(p)=j<

attractionj(p)=j>

repulsionj(p)=j>

repulsion

J(p),J(n) one j> other j<: attractionJ(p),J(n) both j> or j<: repulsion

=(

0d5/2 neutron has j(n)=j>

(d,p) reaction in different frames

CM frame

Laboratory frame-“normal” kinematics

Laboratory frame-“Inverse” kinematics

qCM

qLAB

qLAB

v0IN OUT

2H

1H

v lab

vlab

z Beam Axis

Cyclotron orbit qBmcycT p2)(

Emitted here

Detected here

We measure: Elab, z, TOF

We deduce:ECM ,qCM

Uniform magnetic field B

The HELIOS approach to inverse kinematics

For a given state

For two states atfixed z

EP(M

eV)

Cos

(qC

M)

Cos

(qC

M)

EP(M

eV)

qLAB (deg) z (m)

1.4 MeV

5 MeV

“Conventional” –measure at fixed qLAB

HELIOS –measure at fixed z

Advantages to the HELIOS approach for (d,p)

dEP/dz=17.5 keV/mm

dEP/dqLAB=175 keV/deg

HELIcal Orbit Spectrometer -HELIOS

2.35 m

0.9 m

X-Y-q positioningstage

BMAX=2.85 T

Laser rangefinder

Silicon ArrayTarget

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

28Si(d,p)29Si commissioning-it works!

0.00

1.272.03

3.07 3.62

4.94

6.19

6.717.79

Excitation energy in 29 Si

6.38

Residual a source background

protons from 28Si+12C

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)

28Si(d,p)29Si Excitation-energy spectrum

Typical resolution ~ 120 keV FWHMBest resolution ~ 80 keV FWHMJ. C. Lighthall et al,

NIMPRA 622, 97 (2010)

16CCore

Valence neutrons

Exotic behavior in 16C?

Study with 15C(d,p)16C No hindrance, andno exotic behavior.

15C(d,p)16C with HELIOS

PRL 105, 132501 (2010)

Proton energy-positioncorrelation

16C Excitation-energy spectrum

(d,p) samples the n(1s1/2) content of

the wave functions for positive-parity states

1.5-2M 15C/s @ 8.2 MeV/u

L=0

L=2

L=0

L=2

15C(d,p)16C results

PRL 105, 132501 (2010)

Shell model – WBPinteraction

Shell model works well – no need for exotica!

Experiment

19O(d,p)20O – further into the sd shell

Proton energy versus position 20O excitation energy

ν(0d5/2)35/2ν(sd)→ν(sd)4 states in 20O

200k-300k 19O/s @ 6.6 MeV/u

C. R. Hoffman et al., PRC 85, 054318 (2012)

What we can learn from 19O(d,p)20O

Angular distributions and neutron vacancies from 19O(d,p)20O

Center-of-mass angle (deg)19O excitation energy (MeV)

Cros

s sec

tion

(mb/

sr)

L=2 L=0+2

Orb

ital v

acan

cy G

+

Solid: L=0; hatched L=2

C. R. Hoffman et al., PRC 85, 054318 (2012)

Broad l=0 and 2 states expectedwith Jπ=(0,1,2,3)-

Sn=0.969

Preliminary excitation-energy spectrum

EX (14B) (MeV)

13B(d,p)14BG<150 keVG~200 keV

Red – 14BBlue – 13B

20-40k 13B/s @15.7 MeV/u

13B(d,p)14B Preliminary ds

/dW

(mb/

sr)

L=0L=2L=0+2

qc.m. (deg)OMPs fit 30 MeV d+12C, p+12,13C elasticscattering at 15 MeV/u

2- 0.0

1- 0.65

3- 1.38

4- 2.08

Shell model withWBT interaction

Experiment

(2-)

G~1

MeV

Preliminary!

L=0L=2

Sn

Preliminary!

136Xe(d,p)137Xe with HELIOS– approaching 132Sn

Proton energyversus position

137Xe excitationenergy

B. P. Kay et al, PRC 84, 024325 (2011)

What we can learn from 136Xe(d,p)137Xe

B. P. Kay et al, PRC 84, 024325 (2011)

136Xe(d,p)137Xe angular distributions and orbital-energy trends near N=82

A variety of measurements• 28Si(d,p)29Si – Aug. 2008 (first commissioning)*• 12B(d,p)13B – March 2009 (RIB commissioning)*• 17O(d,p)18O – Aug. 2009 (unbound states in 18O)• 15C(d,p)16C – Sep. 2009 (exotic behavior in 16C)*• 130,136Xe(d,p)131,137Xe – Nov. 2009 (S.P. states near N=82)*• 86Kr(d,p)87Kr – Feb. 2010 (S.P. states near N=50)• 14C(6Li,d)18O – March 2010, (a-cluster states in 18O:

d not p!)• 19O(d,p)20O – Sep. 2010 (structure of 20O)*• 28Si(d,3He)27Al, 28Si(d,t)27Si – May 2011 (commissioning of

forward-hemisphere configuration)• 13B(d,p)14B – Nov. 2011 (structure of 14B)• 17N(d,p)18N – March 2012 (structure of 18N)

*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: 2M. Alcorta, 2B. B. Back, 2S. I. Baker, 1S. Bedoor, 2P. F. Bertone, 3B. A.

Brown, 2J. A. Clark, 2,4C. M. Deibel, 5P. Fallon, 6S. J. Freeman, 2C. R. Hoffman, 2B. P. Kay, 2,7H. Y. Lee, 1,2J. C. Lighthall, 5A. O. Macchiavelli, 1,2S. T.

Marley, 2K. E. Rehm, 2J. P. Schiffer, 1D. V. Shetty, 8M. Wiedeking

1Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008-5252, USA2Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA

3Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA4Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA

5Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA6Department of Physics, University of Manchester

7LANSCE-NS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA8Lawrence Livermore National Laboratory, Livermore, California 94551, USA

And…The HELIOS CollaborationS. Bedoor, J. C. Lighthall, S. T. Marley, D. Shetty, J. R. Winkelbauer (SULI

student), A. H. WuosmaaWestern 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. FreemanUniversity 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