Reaction Studies

1
Reaction Studies UK Experimental Programmes at
GANIL and SPIRAL Wilton Catford University of
Surrey In UK Surrey, Birmingham, Liverpool,
Daresbury, Paisley

• Outline
• Halo and structure studies with knockout
  reactions (N8 breaking)
• Cluster breakup reactions
• Knockout spectroscopy measuring p// with EXOGAM
  for gamma-rays
• Using SPIRAL beams with TIARA to study (d,p)
  transfer (N16/20)
• More recent collaboration emerging TIARA/MUST2
  first experiments
• Outlook for SPIRAL2 era

2
Letters of Intent 2006, 19 LoIs, 595
physicists, 34 countries
UK involvement 9 institutions, in 11 LoI, 32
academics, 7 spokespersons
By project/group

• DESIR (Low energy area) Manchester, Daresbury,
  Surrey
• S3 super separator-spectrometer Liverpool, York
• Fusion reactions Surrey
• Fusion-transfer tunnelling Daresbury
• High Res Gamma-Ray Spectroscopy York, Daresbury,
  Surrey, Liverpool,
• Manchester, Paisley
• PARIS (High energy gammas) York, Surrey
• Astrophysics Surrey, Daresbury, Liverpool,
  Paisley
• GASPARD (reaction spectroscopy) Daresbury,
  Surrey, Liverpool, Paisley
• ACTAR (active target) Liverpool, Daresbury,
  Surrey, Birmingham,
• Edinburgh, York
• FAZIA (reaction dynamics) Daresbury

NB collaboration building is still in progress,
so lists may be incomplete
3
Letters of Intent 2006, 19 LoIs, 595
physicists, 34 countries
UK involvement 9 institutions, in 11 LoI, 32
academics, 7 spokespersons
By group/project

• Birmingham ACTAR
• Daresbury Fusion-transfer, High-Res Gamma
  (SIMPSON), Astro,
• GASPARD (LEMMON), ACTAR, Reaction Dynamics
• Edinburgh ACTAR
• Liverpool S3, High-Res Gamma, Astro, GASPARD,
  ACTAR (CHARTIER)
• Manchester DESIR (CAMPBELL), High-Res Gamma
• Open GASPARD
• Paisley High-Res Gamma, Astro, GASPARD
• Surrey (theory) Fusion, High-Res Gamma, PARIS,
  Astro, GASPARD
• Surrey (exp) DESIR, High-Res Gamma, PARIS,
  Astro, GASPARD
• York S3, High-Res Gamma (WADSWORTH, BENTLEY),
• PARIS (JENKINS), ACTAR

NB collaboration building is still in progress,
so lists may be incomplete
4
As one of the 34 ESFRI approved new physics
facilities in Europe, SPIRAL2 is eligible for
funds to build the user community and formalities.
Strict guidelines control the maximum amount of
technical work that can be included (lt50) and
the grant size. Submitted for 2 May deadline.
FP7 ESFRI Preparatory Phase Build
management/collaborations, 24 mths
UK involvement Some technical support,
Management of ALL meetings
Work Pack Brief Title Coordinator Cost/EU-request
1 Management GANIL 1307/1292 k 23
2 Coordination UK (Surrey) 1227/1227 k 22
3 Legal GANIL 197/197 k 4
4 Finance GANIL 119/119 k 2
5 Technical Poland (COPIN) 4014/1241 k 22
6 Linac INFN 1520/550 k 10
7 Target/beam INFN 1852/546 k 10
8 Infrastructure GANIL 621/280 k 5
9 Agreement CEA/CNRS 93/93 k 2
TOTAL 10949/5545 k 100
NB the fraction request/cost is defined by the
nature of the work package
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Spectroscopy of Molecular and Halo States
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4n ?
8
12Be
? n
X
X
11Be
X
1/2?
1/2
5/2
UNBOUND
ground
bound
n 10Be
9
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N8 shell gap vanishes in 12Be
12Be
neutron removal from 12Be beam
E(rel) for 10Be n
Coulex also
Steven PAIN, WNC et al
11
LISE2000
ECLAN
CHARISSA
at
12
DEMON
19C ? 18Cn 11Be (p,d) 10Be nucleon transfer
12Be ? 6He 6He 10Be ? 6He 4He 16C ? 10Be
6He 14Be ? 13Be ? 12Ben 12Be ? 11Be ?
10Ben 17C ? 16B ? 15Bn 14Be ? 10Be 4n ?
13
4-body BRUNNIAN nucleus e.g. ONLY 10C
10C vs 10Be
a-a-p-p
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N Z
0d 5/2 is full, neutrons enter 1s 1/2
For very neutron-rich nuclei, the neutrons to
some extent favour 1s 1/2 over 0d 5/2
N 2 Z
Cocktail beam of two dozen species single
neutron removal dominates - a single spectrometer
setting used - compare to large-basis shell model
E. Sauvan, N.A. Orr, F. Carstoiu et al., Physics
Letters B491 (2000) 1 and Phys Rev C70 (2004)
014305
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Knockout reactions beam production.

• Knockout reactions use intermediate energy
  secondary beams gt 50 MeV / nucleon.
• Cocktail beam of neutron rich nuclei produced
  using SISSI at GANIL.

• 36S primary beam incident
• on a 450mg/cm2 12C target.
• Cocktail beam is produced
• and subject to selection in the
• alpha spectrometer.
• Secondary cocktail beam sent
• to the SPEG room.

16
The gamma ray array EXOGAM and NaI.

• Forward and backward angle germanium clovers.
• NaI detectors at 90 for increased efficiency.

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How a knockout experiment is carried out
somewhat simplified!
Gas Ionisation Chamber Plastic Scintillator
(?E-E)
Drift Chambers
SPEG magnetic spectrometer (With central B?
2.68Tm Setting.)
26Ne beam directed off focal plane.
Energy loss in target is small ?v 0
One neutron knockout from 26Ne -gt 25Ne involves a
4 reduction in A.
After the reaction target 26Ne un-reacted beam
B? 2.8Tm 25Ne from 1 neutron knockout.
12C (180mg/cm2)
Before the reaction target 26Ne Beam with B?
2.8Tm
Z remains constant.
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Schematic experimental setup an overview of the
focal plane detection.
Gas Ionisation Chamber Plastic Scintillator
(?E-E)
Drift Chambers
SPEG magnetic spectrometer

• Drift chambers reconstruct focal plane
• position and momentum distributions.

Germanium gamma detection at forward and backward
angles.

• Gas ionisation chamber filled with 400mb
• isobutane. Gives energy loss information
• related by Bethe-Bloch equation.

12C (180mg/cm2)

• Plastic scintillator stops all charged
  particles.
• Allow for ?E-E particle identification.

NaI perpendicular to beam.
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SINGLE PARTICLE STATES
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
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Beam of 24Ne (d,pg) N16 replaces broken N20
Schematic of the TIARA setup. A beam of 105 pps
of 24Ne at 10.5A MeV was provided from SPIRAL,
limited to 8p mm.mrad to give a beam spot size of
1.5-2.0 mm. The target was 1.0 mg/cm2 of (CD2) n
plastic. The TIARA array covered 90 of 4p with
active silicon.
W.N. Catford et al., Eur. Phys. J. A25, Suppl. 1,
245 (2005).
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Target Changing Mechanism
Barrel Si 36? lt ?lab lt 144 ?
Beam
VAMOS
Forward Annular Si 5.6? lt ?lab lt 36 ?
Backward Annular Si 144? lt ?lab lt 168.5 ?
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Outer barrel is new for this 2007 campaign
annular array visible near 180
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Beam of 24Ne (d,pg) N16 replaces broken N20
Measured energy-angle curves showing the
population of various excited states in different
reaction channels, measured simultaneously with
TIARA. The different channels were selected
according to the identified particle in VAMOS,
and are compared with Geant simulations.
W.N. Catford et al., Eur. Phys. J. A25, Suppl. 1,
245 (2005).
24
Simultaneously measuring the elastic
scattering gives an internal absolute calibration
for the cross section
25
Geant simulation first interaction point for
E(gamma) 2.05 MeV
opposite
adjacent
26
Detailed Géant4 Simulations
4030
Entry at 4.0 MeV
3330
? 2
2030
1680
? 0
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Fits with resolution that depends on reaction
angle
counts
excitation
149 (lab)
133 (lab)
109 (lab)
101 (lab)
117 (lab)
125 (lab)
158 (lab)
164 (lab)
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Adiabatic Model calculation for 24Ne(d,p)25Neg.s.
Various optical potentials were assessed and
checked for consistency
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Adiabatic Model calculations for 24Ne(d,p)25Ne
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Beam of 24Ne (d,pg) N16 replaces broken N20
Left Coincident gamma ray spectra from
24Ne(d,pg)25Ne. Spectra (a) and (b) are gated
according to the indicated regions of excitation
energy in 25Ne as plotted in the inset, derived
using the measured proton energies and angles.
The two prominent gamma peaks are shown by
gamma-gamma gating in (c) and (d) to be in
cascade. Right Levels identified in 25Ne and the
measured spectroscopic factors, highlighting the
failure of the conventional USD shell model
interaction for the raised 3/2 level.
W.N. Catford et al., Eur. Phys. J. A25, Suppl. 1,
245 (2005).
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E. SOME RESULTS and PERSPECTIVES
(? 3)
4030
7/2
0.73
p
3330
3/2
0.75
? 1
? 2
2030
3/2
0.44
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
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TIARA
E522s/E445aS
Experiments at GANIL/SPIRAL Aug-Dec 2007, 20O
and 26Ne and 36S (d,p) etc.
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SOME RESULTS and PERSPECTIVES
TIARA/MUST2 campaign at GANIL 2007 Surrey,
Liverpool Orsay, Saclay, GANIL SPIRAL 20O and
26Ne beams N16, 28 GANIL 34Si, other frag
beams N20, 28
JEFF THOMAS
f 7/2
SPIRAL beam
26Ne (pure) 2300 pps
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GEANT 4 SIMULATIONS
MUST2
Barrel
Hyball
EXOGAM
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SOME RESULTS and PERSPECTIVES
Geant4 simulation
beam n
On-Line data
beam-like at 0
Several x 100 counts
beam
proton from (d,p)
Energy
Lab angle
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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
7/2
0.73
p
3330
3/2
0.75
? 1
? 2
2030
3/2
0.44
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
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FUTURE DEVELOPMENTS
WORK IN PROGRESS
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J. S. Thomas, N. L. Achouri2, H. Al Falou2, N. I.
Ashwood3, D. Beaumel4, Y. Blumenfeld4, S. M.
Brown1, W. N. Catford1, R. Chapman5, M.
Chartier6, N. Curtis3, G. de France7, F.
Delaunay7, N. de Séréville4, B.
Fernández-Domínguez6, C. Force7, S. Franchoo4,
J. Guillot4, P. Haigh3, F. Hammache4, M.
Labiche8, V. Lapoux9, A. Leprince2, R. C.
Lemmon8, F. Maréchal4, B. Martin9, X. Mougeot9,
B. Mouginot4, L. Nalpas9, A. Navin7, N. A. Orr2,
N. P. Patterson1, B. Pietras6, E. C. Pollacco9,
A. Ramus4, M. Rejmund7, J-A. Scarpaci4, O.
Sorlin7, J. Stefan4, and G. L. Wilson1
1University of Surrey, 2LPC-Caen, 3University of
Birmingham, 4IPN Orsay, 5University of the West
of Scotland, 6University of Liverpool, 7GANIL,
8STFC Daresbury Laboratory, 9SPhN-CEA Saclay
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Reaction Studies Wilton Catford University of
Surrey In UK Surrey, Birmingham, Liverpool,
Daresbury, Paisley

• Collaborations
• Charissa and TIARA are at cutting edge in their
  fields
• Further experiments approved for TIARA and MUST2
  together
• GASPARD project at SPIRAL2 is natural successor
  to TIARA/MUST

• Outlook
• Transfer work needs 8 - 30 MeV/A and SPIRAL2 is
  well matched
• SPIRAL2 beams suited to resonant reactions (for
  clusters) in TPC
• Involvement/synergy with other ISOL facilities
  can be exploited
• (small but perhaps increasingly coherent
  reactions community in UK)
• Links also with R3B and EXL at NUSTAR at FAIR