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Results from the first tests with the SPEDE spectrometer

Philippos Papadakis

ISOLDE Workshop and Users Meeting 2014

UNIVERSITY OF JYVÄSKYLÄ

Motivation

Shape coexistence:

A. Andreyev et al., Nature (London) 405, 430 (2000).

Octupole collectivity:

L.P. Gaffney et al., Nature (London) 497, 199 (2013).

186Pb

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Approved proposals Proposals

– P. Butler, D.T. Joss, M. Scheck et al.,

IS552 - Measurements of octupole collectivity in Rn and Ra nuclei using Coulomb excitation – J. Pakarinen et al.,

IS556 - Probing intruder configurations in 186,188Pb using Coulomb excitation – K. Wrzosek-Lipska, D.T. Joss, D. Jenkins, J. Pakarinen et al.,

IS563 - Coulomb excitation of 182-184Hg: Shape coexistence in the neutron-deficient lead region – P.A. Butler, D.T. Joss et al.,

IS475 - Measurements of octupole collectivity in odd-mass Rn and Ra nuclei using Coulomb excitation

LOIs:– P. Butler et al.,

Measurements of octupole collectivity in odd-mass Rn, Fr and Ra isotopes – N. Warr et al.,

Shape studies in the neutron rich N ~ 60 region – P. Van Duppen D.T. Joss, D.G. Jenkins, J. Pakarinen et al.,

Shape coexistence in the neutron-deficient region around Z=82 studied via Coulomb excitation and few-nucleon transfer reactions

– D. Jenkins et al.,

Shape changes and proton-neutron pairing around the N=Z line

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Miniball array

CD detector

Target

e-

γ-ray

SPEDE concept

Silicon detector

Beam

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From concept to design

Si-detector

Absorberfoil Target CD-detector

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From design to reality

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SPEDE in Miniball

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δ electron suppression

Low energy electrons produced when beam and target particles collide

Detector at backwards angle HV on target Absorber foil between target and detector RIBs - Lower beam intensity

β-decay background supressed through coincidences with scattered particles

U. Bechthold et al., Phys. Rev. Lett 79, 2034 (1997)

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Absorber foil

Covers detector surface Hole for the beam Different materials and

thicknesses tested (Aluminium, Aluminised Mylar, Mylar).

Al 30μmAl Mylar 12μmAl 30μmAl Mylar 12μm

~10keV FWHM @ 320keV~7.5keV FWHM @ 320keV~6keV FWHM @ 320keV

No foil

Energy loss of electrons through Al foilEnergy loss of electrons through Al Mylar foil

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Biased target

Bias on in-beam target up to 5kV Other targets floating or at

ground potential

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Detector design

24 segments

48segments

24 segments

48segments

Geant4 simulationBeam: 188Pb @ 2.82 MeV/u, Target: 112Cd,  2 mg/cm2

J. Konki et al., EPJ Web of Conferences 63, 01019 (2013).

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Detector design – simulated efficiency

Courtesy of D. Cox.

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Silicon detector and PCB layout

24 segments, 500μm thick.

Copper cooling block

Cooled to -15C

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In-beam tests

Investigate:– If the concept works– Performance of SPEDE– δ-electron suppression

Cocktail beam: 20Ne, 40Ar, and 60Ni Beam intensity and time profile similar to HIE-ISOLDE

100μs 100μs

1ms or 10ms

Beam intensity up to 50E6pps:Count rate per channel ~20kHz

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In-beam tests

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174Yb Coulex test

40Ar on 174Yb Ebeam 4.1MeV/u, Ibeam ~40E6pps Aluminised Mylar foil Tests with no high-voltage and 5kV on target

174Yb

Conversion electrons for the 176.7keV transition:K: 115.3keVL: 166.1keV

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High-voltage On/Off

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X ray and δ electron pile-up signal

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Commissioning

Commissioning– 197Au at 4.1 MeV/u on 112Cd Coulex experiment– Well known level scheme– Highly converted transitions– Reaction kinematics close to our MINIBALL Coulex

programme

197Au

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Project time line

2013 2014 2015

Mechanical design

Electronic tests

Proposals to INTC

Development at JYFL

In-beam tests at JYFL

Commissioning at JYFL

HIE-ISOLDE stage 1

SPEDE campaign

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Summary

Possibility to measure γ-rays and conversion electrons simultaneously in-beam @ HIE-ISOLDE

First in-beam tests @ JYFL completed Concept works More in-beam tests and commissioning @ JYFL in 2015 Ready for in-beam use at HIE-ISOLDE second half of 2015 For more information:

– https://www.jyu.fi/fysiikka/en/research/accelerator/nucspec/spede/– P. Papadakis et al., JPS Conference Proceedings, article in press

(An introduction to SPEDE)– J. Konki et al., EPJ Web of Conferences 63, 01019 (2013)

(Simulations)

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Collaboration

University of Jyvaskyla, Finland J. Pakarinen, P. Papadakis, P.T. Greenlees, J. Konki, P. Rahkila, K. Ranttila, V.P. Saarela

University of Liverpool, United Kingdom P.A. Butler, D.M. Cox, R.-D. Herzberg, G.G. O’Neill, J. Thornhill, D. Wells

University of York, United Kingdom P. Davies, D.G. Jenkins

Katholieke Universiteit Leuven, Belgium M. Huyse, P. Van Duppen