Bentley et al - Istanbul May 7th 2010 1

Letter of Intent: AGATA@GSI

Letter of Intent:

Isospin Symmetry and Transition Rates in Isobaric Multiplets

M.A.Bentley, R.Wadsworth et al (Univ.York)

D.Rudolph et al (Lund)

A.M.Bruce et al (Brighton)

P.Reiter et al (Koln)

S.Lenzi et al (Padova)

G.deAngelis, E.Sahin et al (INFN)

A.Obertelli et al (CEA Saclay)

M.Labiche, J.Simpson (STFC Daresbury Lab.)

+ PRESPEC TEAM (GSI)

Bentley et al - Istanbul May 7th 2010 2

AIMS

Topic: Isospin dependence of B(E2) strengths in T=1 triplets...

Aims:

• To test a direct prediction (largely untested) of isospin formalism: dependence of B(E2) with Tz for IAS transitions

• To search for isospin mixing effects at the ~ few % level

• Examine precision lifetime measurements of T=1 2+ to 0+ transtions in T=1 Triplet

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IS IV

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LINEAR DEPENDENCE of ME with Tz

PRESPEC Meeting: S363 Report 3

et al...

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Effect of Isospin Mixing

Effect of isospin mixing on B(E2) strengths in T=1 triplets...??

• Proximity of T=1 and T=0 states in odd-odd N=Z system

• T=0 admixtures possible in both 0+ and 2+ states

• Introduces isovector components in B(E2) in N=Z odd-odd (Tz=0)

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AIMS

• Perform high-precision RELATIVE measurement of B(E2) in T=1 TRIPLET

• Use identical method for B(E2) measurement

• Use identical population method for states of interest

• Try to eliminate direct/side feeding

• Use identical experimental conditions

• PERFORM in same EXPERIMENT

TWO POSSIBLE CASES...

• A=46 T=1 triplet

• A=62 T=1 triplet

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A=46 Isobaric Triplet

46Cr - P.J.Garrett et al Phys. Rev. Lett. 87(2001)132502

B(E2)’s known only at ± 20% level

T1/2 = 8-9 ps

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46CrStack of 3 gold foils (~500 mg/cm2) separated by ~1mm

(Sort of) differential plunger

Designed for specific case/lifetime

Key points:

2+ states all populated directly by Coulex

Lifetime determined from lineshape alone

Can use 2,3,4 foils...

Could use Koln plunger...

Proposed Method

Preliminary Simulation

15.9 degrees

36.0 degrees

• Performed for “Euroball” RISING

• Assumes 2% energy resolution

• 10,000 counts in triple-peak

• 2x750mg/cm2 + 1x500mg/cm2

• 1mm gap

• 915 keV transition in 46V

• 150Mev/u

±20% in B(E2)

RATES

• Make 46Cr, 46V and 46Ti from fragmentation of 78Kr or 58Ni primary beam

• Assume 1x1010 pps 78Kr, 4g/cm2 primary Be target

• Assume FRS transmission efficiency of 20% (LISE)

• 3% efficiency in a ring with 2% energy resolution

• 450mb Coulex cross section (measured)

• 50kHz secondary beam limit

• 2000 mg/cm2 Au in total...

GIVES: 1.5kHz 46Cr → 25,000 counts in line-shape in 3 days

50kHz 46V → 100,000 counts in line-shape in 1 day

50kHz 46Ti → 100,000 counts in line-shape in 1 day

D.Rudolph et al

N=Z N=Z+2

A=62 Isobaric Triplet

A=62 Isobaric Triplet

D.Rudolph et al

• 62Ge: 2+ state only tentatively assigned – needs confirmation

• 62Ga: 2+ state only tentatively assigned – needs confirmation

• 62Ge: 2+ state is non-YRAST – Coulex ideal to populate state

Key points:

• Isospin-mixing predicted to increase with Z2

• Confirmation of 2+ states in 62Ga and 62Ge

• Shorter half-life (~3 ps)

• Not as high-statistics as A=46, but larger effect?

RATES

• Make 62Ge, 62Ga and 62Zn from fragmentation of 78Kr primary beam

• Assume 1x1010 pps 78Kr, 4g/cm2 primary Be target

• Assume FRS transmission efficiency of 20% (LISE)

• 3% efficiency in a ring with 2% energy resolution

• 450mb Coulex cross section (assumed same as A=46)

• 50kHz secondary beam limit

• 2000 mg/cm2 Au in total...

GET: 1.5kHz 62Ge → 1,000 counts in line-shape in 3 days

50kHz 62Ga → >100,000 counts in line-shape in 1 day

50kHz 62Zn → >100,000 counts in line-shape in 1 day

UNIQUENESS?

Key Points:

1.Technique requires high-energy / high β

• Allows thick targets, large gaps, short lifetimes

• Gives more pronounced line-shape

2.Position-resolution of AGATA benefits technique (improves line-shape, allows for definition of effective “rings”)

BOTH give major advantage over MSU capability (for example)