SATURN HST/ IR 1998, TETHYS VOYAGER2 1981, URANUS HST/ IR 1986

What can we learn from transfer, and how is best to do it?

Wilton CatfordUniversity of Surrey

A

B

E

Single Particle States;RIB experiments!!

Reaction models

Practicalities;Inverse Kinematics

Results & Perspectives

New London NH June 2008

Nuclear Chemistry

D Experimental setups

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Approach:

To highlight the questions that have to be addressed in doing this work

That is:

As we embark on the new enterprise of working with radioactive beams…

How do we do it? the choices for the experimental setup…

why different experiments/teams will make different choices

How do we interpret the measurements?

what exactly are we measuring and why (and how well)?

Philosophy: … this is the Gordon, so…

Not a traditional review, but a snapshot of thoughts in progress…

… an open discussion…

W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008

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Example of population of single particle state: 21O

0d 5/21s 1/2

0d 3/2

The mean field has orbitals, many of which are filled.We probe the energies of the orbitals by transferring a nucleonThis nucleon enters a vacant orbitalIn principle, we know the orbital wavefunction and the reaction theory

But not all nuclear excited states are single particle states…

0d 5/21s 1/2

energy of level measures this gap

J = 3/2+

J = 3/2+

2+

x 1/2+

We measure how the two 3/2+ statesshare the SP strength when they mixA.B.C.D.E SINGLE PARTICLE STATES

1.2.3.4.5.6.7. Pure and Mixed States

A. SINGLE PARTICLE STATES – EXAMPLE

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SINGLE PARTICLE STATES – SPLITTING

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Splitting masks the true SP energy

Plot: John Schiffer

If we want to measure the SPE,splitting due to level mixingmeans that all componentsmust be found, to measure the true single particle energy

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SINGLE PARTICLE STATES

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Motivation – monopole migration

Changes – tensor force, p-n

Residual interactions move themean field levels

Magic numbers “migrate”,changing stability, reactions, collectivity…

Similarly…

proton filling affectsneutron orbitals

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(d, )pSINGLE PARTICLE STATES

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Population in an exotic nucleus

Probing the changedorbitals and their energies…

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(d, )pSINGLE PARTICLE STATES

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Population of states in the continuum

As we approach the dripline, we alsohave to worry about the meaningand theoretical methods for probingresonant orbitals in the continuum…

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• 23O from USD and Stanoiu PRC 69 (2004) 034312 and Elekes PRL 98 (2007) 102502• 25Ne from TIARA, W.N. Catford et al. Eur. Phys. J. A, 25 S1 251 (2005)

Migration of the 3/2+ state creates N=16 from N=20

25Ne TIARA USD modified

23,25O raise further challenges

21O has similar 3/2+-1/2+ gap (same d5/2 situation) but poses interesting question of mixing (hence recent 20O(d,p)@SPIRAL)

exci

tatio

n e

nerg

y (M

eV

) 4.5

1.5

1.0

0.5

0.0

3.0

2.5

2.0

4.0

3.5

6 8 10 12

atomic number

1d3/2

1f7/2

27Mg23O 25Ne

Systematics of the 3/2+ for N=15 isotones

(1d5/2)-1

2s1/2

removing d5/2 protons raises d3/2and appears to lower the f7/2

20

1616

SINGLE PARTICLE STATES – AN ACTUAL EXAMPLE

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Example case in N=15 revealing N=16

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fillg9/2

hole f7/2

f5/2

Serge Franchoo PRC 64(2001)054308

SINGLE PARTICLE STATES – ANOTHER EXAMPLE

A.B.C.D.E SINGLE PARTICLE STATES1.2.3.4.5.6.7. Example fp protons Z=28 to 40 for n-rich

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A.B.C.D.E REACTION MODEL1.2.3. Johnson-Soper & ADWA

Johnson-Soper Model: an alternative to DWBA that gives a simple prescription for taking into account coherent entangled effects of deuteron break-up on (d,p) reactions [1,2]• does not use deuteron optical potential – uses nucleon-nucleus optical potentials only• formulated in terms of adiabatic approximation, which is sufficient but not necessary [3]• uses parameters (overlap functions, spectroscopic factors, ANC’s) just as in DWBA[1] Johnson and Soper, PRC 1 (1970) 976[2] Harvey and Johnson, PRC 3 (1971) 636; Wales and Johnson, NPA 274 (1976) 168[3] Johnson and Tandy NPA 235 (1974) 56; Laid, Tostevin and Johnson, PRC 48 (1993) 1307

Spectroscopic FactorShell Model: overlap of (N+1) with (N) core n ( j)Reaction: the observed yield is not just proportional to this, because the overlap integral has a radial-dependent weighting or sampling

overlap integral

spectroscopic factor

Hence it depends on theradial wave function andthus the geometry of theassumed potential well orother structure model

B. REACTION MODEL FOR (d,p) TRANSFER – the ADWA

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A.B.C.D.E REACTION MODEL1.2.3. Jenny Lee et al validation of ADWA

REACTION MODEL FOR (d,p) TRANSFER – the ADWA

A CONSISTENT application of ADWA gives 20% agreement with large basis SM

80 spectroscopic factorsZ = 3 to 24Jenny Lee et al.

Tsang et alPRL 5 (2005) 222501

Lee et alPRC 75 (2007) 064320

Delaunay at alPRC 72 (2005) 014610

Is there a SYSTEMATIC effectas seen in knockout?

Results of transfer are consistentbut do not yet explore extremes

Valence nucleon orbitalfrom Hartree-Fock, not juststandard W-S geometryJenny Lee, Jeff Tostevin,Alex Brown et al.

Lee et alPRC 73 (2006) 044608

Kramer et al for (d,3He)NPA 679 (2001) 267

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A.B.C.D.E REACTION MODEL1.2.3. Other reactions probing single-particle structure

REACTION MODEL FOR (d,p) TRANSFER

Given what we have seen, is transfer the BEST way to isolate and studysingle particle structure and its evolution in exotic nuclei?

Transfer – decades of (positive) experience

Removal – high cross section, similar outputs, requires full orbitals

(e,e’p) – a bit ambitious for general RIB application

(p,p’p) – more practical than (e,e’p) for RIB now, does have problems

Complementary to (d,p)…to be validated with (d,t)

YESAlso: Heavy Ion transfer (9Be),3,4He-induced reactions

tailu(r)

V(r)

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A.B.C.D.E PRACTICALITIES1.2.3. Transfer at around 10 MeV/A

C. USING RADIOACTIVE BEAMS in INVERSE KINEMATICS

Single nucleon transfer will preferentially populate the states in the real exotic nucleus that have a dominant single particle character.

Angular distributions allow angular momenta and (with gammas) spins to be measured. Also, spectroscopic factors to compare with theory.

Around 10A MeV/A is a useful energy as the shapes are very distinctive for angular momentumand the theory is tractable.

Calculated differential cross sections show that 10 MeV/A is good (best?)

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A.B.C.D.E PRACTICALITIES1.2.3. Inverse kinematics

USING RADIOACTIVE BEAMS in INVERSE KINEMATICS

f = 1/2 for (p,d), 2/3 for (d,t)q 1 + Q tot / (E/A) beam

(d,t) (d,d)

(d,p)

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A.B.C.D.E PRACTICALITIES1.2.3. Tackling target thickness limitations

ISSUES ARISING FROM TARGET THICKNESS LIMITATIONS

It turns out that the target thickness is a real limitation on the energy resolution…

Several hundred keV is implicit, when tens would be required,So the targets should be as thin as possible…

But RIBs, as well as being heavy compared to the deuteron target, are:(a) Radioactive(b) Weak

Issues arising:(a) Gamma detection useful for improving resolution(b) Active target (TPC) to minimize loss of resolution(c) Need MAXIMUM efficiency for detection

Experimental solutions can be classed roughly as:(a) For beams < 103 pps ACTIVE TARGET(b) 103 < beam < 106 pps Si BOX in a -ARRAY(c) For beams > 106 pps MANAGE RADIOACTIVITY

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78Ni(d,p)79Ni at 10 A MeV

MAYANow in use atGANIL/SPIRALTRIUMF

ACTARbeing designedfor futureSPIRAL2

A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES1.2.3.4.5. Active targets: time projection chambers

D. SOLUTIONS FOR BEAMS IN RANGE 102 to 104 pps USING TPC’s

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SHARCTIGRESSTRIUMF

TIGRESSCOLLABORATION

YorkSurrey

T-REXMINIBALLREX-ISOLDE

MINIBALLCOLLABORATION

MunichLeuven

A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES1.2.3.4.5. Silicon boxes inside gamma arrays

SOLUTIONS FOR BEAMS IN RANGE 104 to 106 pps USING GAMMAS

ORRUBA OAK RIDGESTEVE PAIN

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Forward Annular Si5.6 < lab < 36

Backward Annular Si144 < lab < 168.5

Barrel Si36 < lab < 144

Target Changing Mechanism

BeamVAMOS

A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES1.2.3.4.5. Silicon for higher beam intensities

SOLUTIONS FOR BEAMS IN RANGE 106 to 109 pps USING GAMMAS

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A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES1.2.3.4.5. Silicon for higher beam intensities

SOLUTIONS FOR BEAMS IN RANGE 106 to 109 pps USING GAMMAS

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Trajectories for 132Sn(d,p) at 8 MeV/AHELIOS: Wuosmaa, Schiffer et al.

avoids thiscompression

Actual solenoid – from MRI

A.B.C.D.E COMPLEMENTARY APPROACHES1.2.3.4.5. Solenoidal devices

NOVEL SOLENOID FOR 4 DETECTION to DECOMPRESS KINEMATICS

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A.B.C.D.E COMPLEMENTARY EXPERIMENTAL APPROACHES1.2.3.4.5. Frozen targets

FROZEN TARGETS and not detecting the LIGHT PARTICLE

A. Obertelli et al., Phys. Lett. B633, 33 (2006).

Also:Elekes et al PRL 98 (2007) 10250222O(d,p) to n-unbound 23O SP states

And helium:Especially (,3He) etc. at RIKEN

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A.B.C.D.E. RESULTS AND PERSPECTIVES1.2.3.4.5. Gamma rays as an aid to identification

4030

3330

2030

1680

= 2

= 0

5/2+

3/2+

= –

1/2+

= 2

= 1

( = 3)

7/2 –

3/2 –

0.73

0.80

0.15

0.44

0.75

TIARA

1/2+

3/2+

5/2+

3/2+

5/2+

9/2+

7/2+

5/2+

0.49

0.10

0.11

0.004

n+24Negs

USD

0.63

E. SOME RESULTS and PERSPECTIVES

In 25Ne we used gamma-gamma coincidencesto distinguish spinsand go beyond orbital AM

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TIARA/MUST2 campaign at GANIL 2007Surrey, LiverpoolOrsay, Saclay, GANIL

SPIRAL: 20O and 26Ne beams… N=16, 28GANIL: 34Si, other frag beams… N=20, 28

A.B.C.D.E. RESULTS AND PERSPECTIVES1.2.3.4.5. Recent TIARA+MUST2 campaign

SOME RESULTS and PERSPECTIVES

f 7/2

SPIRAL beam

26Ne (pure) 2300 pps

JEFF THOMAS

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?

A.B.C.D.E. RESULTS AND PERSPECTIVES1.2.3.4.5. On-Line results from SPIRAL + TIARA + MUST2

SOME RESULTS and PERSPECTIVES

Lab angle

Energy proton from(d,p)

beam-like at 0°

Geant4simulation

On-Linedata

Ex

0

765885

1410Sn

?

Several x 100counts

On-Linedata

Geant4simulation

elastic

transfer

3000

beam+ n

“beam”

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A.B.C.D.E. RESULTS AND PERSPECTIVES1.2.3.4.5. WHAT WE MEASURE – example 25Ne

SOME RESULTS and PERSPECTIVES

4030

3330

2030

1680

= 2

= 0

5/2+

3/2+

= –

1/2+

= 2

= 1

( = 3)

7/2 –

3/2 –

0.73

0.80

0.15

0.44

0.75

TIARA

1/2+

3/2+

5/2+

3/2+

5/2+

9/2+

7/2+

5/2+

0.49

0.10

0.11

0.004

n+24Negs

USD

0.63

In 25Ne the 3/2+ state wasfar from a pure SP statedue to other couplings athigher energies, but it wasclear enough in its ID andcould be used to comparewith its SM partner to improvethe USD interaction

It is not always necessaryto map the full SP strengthwhich may be very much splitandwith radioactive beamsit may not often be possible

Includes also (s1/2) (d5/2

2)2+

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A.B.C.D.E. RESULTS AND PERSPECTIVES1.2.3.4.5. GRAPA and GASPARD

SOME RESULTS and PERSPECTIVES

GRAPAGAMMA RAY AND PARTICLE ARRAY

“… WORK IN PROGRESS”

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What do we measure and Why? And Where (on the Segre chart)?Single particle states (in amongst, mixed with, other states)Migration of magic numbers – “monopole migration”, implications

What is the best way to measure these things – choice of reactionClassic transferRemoval reactions (sometimes called knockout)Knockout reactions (such as (p,p'p) or (e,e'p)So, what do we really measure?What should we measure? SPE? Full strength?How reliable is what we measure?

What radioactive beams do we need?How good do they have to be? Speed? Purity? Focussing? Timing?

So how do we do it? the choices for the experimental setup…Si arrays (TIARA, MUST/2, ORRUBA, SHARC), Solenoid, Active targetsWays in which it helps to know your gammas

How do we interpret the measurements?ADWA. DWBA. Form factor. Unbound states. Weighted SPE vs SM comparison

W.N. CATFORD TRANSFER: WHAT DO WE MEASURE & HOW IS BEST TO DO IT? 16 June 2008

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