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

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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

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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

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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)

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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

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Radiative capture kinematics

𝑣1 𝑣2a

A

B*

vg

vB

Velocity

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in the lab

Radiative capture kinematics

𝑣1 𝑣2a

A

B*

Velocity in the lab

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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!)

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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.

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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

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Inverse kinematics

Beam TargetH or He

Recoil*

Recoil

bbEm

cE

2arctanmax

g

bb

bbrEm

cE

Emppp2

12*

g

g

Maximum angular aperture

Momentum spread

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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

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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

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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

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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%

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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

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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

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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

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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

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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

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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

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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

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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

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SECARUpgrade path

Wien filter:Match hardware design to COSYExpectation

Qualitative evaluation of background sources

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Rare Isotopes Science ProjectKorea

Slide from Young Kwan Kwon Russbach 2015 33

Yuri Litvinov talk …

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Measurements with Stable Beams

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From: PoS(ENAS 6)05812C(a,g)16O

Total cross section

Measurements with Stable Beams

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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

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Thanks !

• ERNA– Lucio Gialanella– Daniel Schürmann

• KUTL separator– Kenshi Sagara

• DRS– Daniel Bardayan

• DRAGON– Dave Hutcheon

• SECAR– Georg Berg

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