Recent Experimental Results from HELIOS
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Transcript of Recent Experimental Results from HELIOS
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