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Recoil Separators for Nuclear Astrophysics studies
Manoel CouderInstitute for Structure and Nuclear Astrophysics
University of Notre Dame
Joint Institute for Nuclear Astrophysics
Outline
• Nuclear astrophysics
• Radiative capture kinematics
• Past, present and future of recoil separator dedicated to radiative capture
• Conclusions
Russbach 2015 2
Radiative Capture Reactions are Presentin Most Stellar Reaction Networks
• From pp-chain to r- and s-process
• Those involving charged particles (p,g) and (a,g) plays crucial role in
– Stellar burning e.g. 12C(a,g)16O, and reactionsequence leading to (and competing with)22Ne(a,n)25Mg
– Explosions in cataclysmic binaries e.g. 30P(p,g)31S
– X-ray burts e.g. 15O(a,g)19Ne (and a lot more inthe rp-process)
– In Supernova, production of 26Al and 44Tiare influenced by (p,g) rates
Part of Nova reaction network
Russbach 2015 3
Published Data
1) Consistent data.
2) Global fit achieved.
Radiatiative capture reaction studies
• Center of mass energies
• (a,g): ~0.01 MeV to ~15 MeV
– (experimentally ~0.3 MeV to …)
• (p,g): ~0.01 MeV to ~4 MeV
– (experimentally ~0.2 MeV to …)
• Direct kinematics
• With stable ions (1H and 4He beams)
– Detection of the gamma’s
– Sometime measurement of theactivity of the produced elements
LUNA underground laboratoryis able to reach lower
Russbach 2015 6
Radiatiative capture reaction studies
• Center of mass energies• (a,g): ~0.01 MeV to ~15 MeV
– (experimentally ~0.3 MeV to …)
• (p,g): ~0.01 MeV to ~4 MeV– (experimentally ~0.2 MeV to …)
• Direct kinematics• With stable ions (1H and 4He beams)
– Detection of the gamma’s– Sometime measurement of the activity of the produced elements
• Inverse kinematics• Radioactive beams• Stable• Recoil detection:
– Coincidence between gamma’s and recoil
LUNA underground laboratoryis able to reach lower
(to improve efficiency and signal to background ratio)
Russbach 2015 7
Radiative capture kinematics
𝑣1 𝑣2a
A
Energy and momentum conservation
In the center of mass frame
B*
p
-p
Radiative capture of a by Aforming B
Russbach 2015 8
Radiative capture kinematics
𝑣1 𝑣2a
A
B*
vg
vB
Velocity
Russbach 2015 9
in the lab
Radiative capture kinematics
𝑣1 𝑣2a
A
B*
Velocity in the lab
Russbach 2015 10
Angular and energy limits
Example
• DISCLAIMER:
– OLD EXAMPLE USING EXPERIMENT PARAMETERS OF AN EXPERIMENT THAT RAN AT NOTRE DAME
– WHILE THE NUMBERS ARE CORRECT THEY ARE NO QUESTIONS REGARDING THE ABILITY TO STUDY THIS SPECIFIC REACTION IN DIRECT KINEMATIC(LENA AND LUNA DID IT!)
Russbach 2015 11
14N(p,g)15O
• proton beam energy: 0.27 to 3.6 MeV
• Ecm: 0.252 to 3.358 MeV
• Q≈7.3MeV
• For ECM=1.65MeV
– ∑Eg ≈7.3+1.65=8.95
– E15O ϵ [0.08,0.15] MeV
Detection of g OK
Detection of 15O KO Since early time of nuclear physics radiative capture are successfully studied with g detection. However, at lower energies or for certain
specific reaction measurement are limited or impossible.Reaction involving radioactive elements are a clear example.
Indirect studies are criticaland provide invaluable data.
Russbach 2015 12
Inverse kinematics
Beam TargetH or He
Recoil*
Recoil
14N(p,g)15O
• Ecm: 0.252 to 3.358 MeV
• 14N beam energy: 3.78 to 54 MeV
• For ECM=1.65MeV Ebeam ≈24.75MeV
– ∑Eg ≈7.3+1.65=8.95
– E15O ϵ [23.59,22.56] MeV
Russbach 2015 13
Inverse kinematics
Beam TargetH or He
Recoil*
Recoil
bbEm
cE
2arctanmax
g
bb
bbrEm
cE
Emppp2
12*
g
g
Maximum angular aperture
Momentum spread
Russbach 2015 14
Principles
projectiles projectiles
target
+recoils
focusingand chargeselection
separation
Detection Identification
recoils
bbEm
cE
2arctanmax
g
Drawings from D. Schürmann
gppp beamrecoil
Velocity/energy selection
Ionization chamberPosition sensitive detectorTime of flight
g detectorHigh efficiencyReduced background forg spectroscopy
Russbach 2015 15
Recoil separator: Basis principle
magnetic dipole
pq
=Br
Momentum filter
electric dipole
- +
2Eq
= Ur
Energy filter
Wien filter
+
-
Velocity filter
v0 = UB
Drawings from D. Schürmann
Charge selection Mass selection
Russbach 2015 16
Recoil separator: Design parameters
• Ratio: DM/M to reject• e.g. 14N(p,g)15O DM/M=1/15
• Angular acceptance• Target effects to be included
• Momentum or energy acceptance
bbEm
cE
2arctanmax
g
bb
bbrEm
cE
Emppp2
12*
g
g
Russbach 2015 17
Some interesting reactions
• 12C(a,g)16O• Holly grail of Nuclear Astrophysics, determine the ratio of 12C/16O after Helium
burning as well as abundance of elements after subsequent evolutionD=±31mrad mrad DE=6.5% (~100pmA)
• 15O(a,g)19Ne• Triggers X-ray burst (escape from b limited hot-CNO) and contribute to determine
their light curveD=±17 mrad DE=3% (~1011 part/s)
• 13N(p,g)14O• first reaction involving radioactive beam, triggered the development of recoil
separators to study radiative capture
• 18O(a,g)22Ne• populate one of the two main ingredient for production of neutron in the s-
processD=±40 mrad DE=7.4%
Russbach 2015 18
19
4He
Det.
Chargeselection
M. Couder Frontiers 2012 20
The beam rejection quality strongly depend on the width of the recoil spot at the mass selection slits
Recoil Beam
18O(a,g)22Ne @ 2. MeV
Mass separation
)|()|()|()|( 001 mxExaxaxxxxmm
EE
Magnification
=0 we want a focus
=0 we want an achromatic focus
)|( mxMM
Spot size is due to magnification
First order spot size
Russbach 2015 21
Transmission requirements
From: PoS(ENAS 6)058
For absolute cross section, full transmission of the selected charge state is needed
Attempt at FMA to study 13C(p,g)14N and 18O(p,g)19F and 18F(p,g)19Nebut limited in transmission Russbach 2015 22
DEDICATED DEVICES
Russbach 2015 23
CTAG CaltechThe availability of post accelerated radioactive beamsopened the door to direct cross section measurements
For example the 13N beam of Louvain-la-Neuve allowedthe study of 13N(p,g) in inverse kinematics
At Caltech, a recoil separator was constructed out ofexisting elements of the accelerator lab to demonstratethe feasibility of a recoil separator
13C(p,g)14N16O(a,g)20Ne12C(a,g)16O
Beam undeflected
Russbach 2015 24
g
ERNA at the DTL, Bochum,
Adapted from a slide of L. Gialanella
European Recoil separator for Nuclear Astrophysics
NABONA in Naples study 7Be(p,g)8BParts moved to Bochum (Germany )Addition of Caltech Wien filter-> ERNADedicated to the study of 12C(a,g)16O
angular acceptance 32 mrad
energy acceptance 10%
For 16O at Elab=3.0 – 15.0 MeVRussbach 2015 25
gas
target
RecoilMass Separator
detector
accelerator
ion sources
ion beam analysis and purification
Radio-chemistry
1
2
ERNA atCIRCE, Caserta
CSSM
Plans:7Be(p,g)8B12C(a,g)16O16O(a,g)20Ne33S(p,g)34Cl14,15N(a,g)18,19FSHE in nature
3MV PelletronHigh intensity stable and radioactive (7,10Be) ion beams(possible 26Al)
Slide of L. Gialanella
Daresbury Recoil Separator DRSORNL - HRIBF
Radioactive beam !
Angular Acceptance: 6.5 msr (+/- 45 mrad horizontal and vertical)A/Q Acceptance: +/- 1.2 %Velocity Acceptance: +/- 2.5 %Energy Acceptance: +/- 5 %A/Q resolution: 1/300A/Q dispersion: 0.1 %/mmOverall Length: 13 m
Rejection ~108-1012
Russbach 2015 27
Radioactive beam !
Two stages
Electrostatic dipolesRejection ~1010-1013
Last news: • 4He(3He,g)7BeWith rejection >1014
• Conditioning ED up to +/-230kV
NIMB 266 (2008) 4171
Russbach 2015 28
Some specs (for a 15O(a,g)19Ne tune):
Optical path length 20.4 m
Acceptance- ang.: (+/-20 horiz. & +/- 25 vert.)- velocity +/- 2 %
Resolving power:200 at first stage600 for second stage
Effective mass resolution:~ 90 after 1st stage,~ 200 after 2nd stage
Russbach 2015 29
PRL 96, 252501 (2006)
Difficult reaction to studyNABONA:
~1995 7Be(p,g)8BDRS:
~2009 17F(p,g)18Ne~1995 7Be(p,g)8B
DRAGON:~2004 21Na(p,g)22Mg~2010 23Mg(p,g)24Al~2006 26gAl(p,g)27Si
Eur. Phys. J. A 7, 303{305 (2000)
Eur. Phys. J. A 42, 457–460 (2009)NIMB 266 (2008) 4171
PRC 81, 045808 (2010)
6 Radioactive beam induced radioactive capture studies in ~17 years !!!
Resonances only …Resonances energies are critical paramters
A lot more induced by stable beamsPossibility to study direct capture
Russbach 2015 30
SEparator for CaptureReaction
SECAR to be installed at ReA3
Radiative capture induced by radioactive beam
Based on design of St. George
JENSA Gas Jet target: up to 1019at/cm2
Acceptance:= ±25mradDE= ±3.1%15<A<65Br<=0.8 Tm
First stage:Resolving power: 750Mass resolution: 520
Second stage:Resolving power: 1330Mass resolution: 775
Design: G.P.A. Berg, M. Couder
Features:Two steps charge state selectionAttention to Wien filter design:• E and B field homogeneity• E/B ratio kept constant with magnetic field
clamps and electrode design.“Clean-up” section – additional momentum analysis
Russbach 2015 31
SECARUpgrade path
Wien filter:Match hardware design to COSYExpectation
Qualitative evaluation of background sources
Russbach 2015 32
Rare Isotopes Science ProjectKorea
Slide from Young Kwan Kwon Russbach 2015 33
Yuri Litvinov talk …
Russbach 2015 34
Measurements with Stable Beams
Russbach 2015 35
From: PoS(ENAS 6)05812C(a,g)16O
Total cross section
Measurements with Stable Beams
Russbach 2015 36
Summary
• Dedicated separator for radiative capture– A tool developed for radioactive beam used successfully for stable and unstable beam– Important tools for direct measurements of astrophysical interests– Rely on direct kinematic measurements, on indirect methods
• For RI beam experiments, need stable beams to commission and tune– Can be used during fast beam operation
• Did not mention target, detection system, diagnostics– They are critical
• ~30 years of separators dedicated for nuclear-astrophysics– Strong interaction between stable and RI Beam community
• New recoil separators are coming
Russbach 2015 37
Thanks !
• ERNA– Lucio Gialanella– Daniel Schürmann
• KUTL separator– Kenshi Sagara
• DRS– Daniel Bardayan
• DRAGON– Dave Hutcheon
• SECAR– Georg Berg
Russbach 2015 38