abc In-beam gamma-ray spectroscopy of 36,38 Mg Pieter Doornenbal - - PowerPoint PPT Presentation

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abc In-beam gamma-ray spectroscopy of 36,38 Mg Pieter Doornenbal - - PowerPoint PPT Presentation

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abc In-beam gamma-ray spectroscopy of 36,38 Mg Pieter Doornenbal Outline Motivation The Island of Inversion Experimental Setup The Island of Inversion Results Present experimental

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abc

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In-beam gamma-ray spectroscopy of 36,38Mg

Pieter Doornenbal ピーター ドルネンバル

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Outline

The “Island of Inversion” Experimental Setup Results Summary and Outlook PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 3

  • Motivation

✦ The “Island of Inversion” ✦ Present experimental status

  • Experimental setup

✦ RIB selection and identification with BigRIPS/ZDS ✦ Gamma-ray detection with DALI2

  • Results

✦ E(4+

1 ) and E(2+ 1 ) in 36,38Mg

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The “Island of Inversion”

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 4

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Nuclear Chart

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 5

28 Ni 50 Sn 82 Pb 2 8 20 28 50 82 126 162 184

number of neutrons number of protons

stable isotopes (300) known isotopes (3000) isotopes estimated to exist (6000)

Island of Inversion

  • Neutron-rich Ne, Na, Mg iso-

topes near N = 20

  • Vanishing N = 20 shell closure
  • Rapid changes in nuclear struc-

ture

  • 48Ca beam at 345 MeV/u
  • High intensity > 100pnA
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The “Island of Inversion”

The “Island of Inversion” ❖ Nuclear Chart ❖ Shell Structure Signatures Experimental Setup Results Summary and Outlook PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 6

  • 30Si

31Si 32Si 33Si 34Si 35Si 36Si 37Si 38Si 29Al 30Al 31Al 32Al 33Al 34Al 35Al 36Al 37Al 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne 33Ne 34Ne 25F 26F 27F 28F 29F 30F 31F 32F 33F

N = 16 N = 18 N = 20 N = 22 N = 24 Z = 10 Z = 12 Z = 14

228(41) 350(50) 215(10) 270(14) 270(16) 113(33) ? 413(29) 84(33) ? 631(126) 190(60) ? ? 190(70) 2018 1473 2235 1310 1482 1942 792(4) 885 3328 722(9) 670 1399 ? 660(6) 1084 ? 4020 5280 ? (1789) (5220) (2235) 2322 ? ? (2120) ? ? ? ? ? 2.7 2.4 ? (1.2) (2.7) (2.8) 2.6 (1.0) ? (3.2) ? ? ? ? ( 5

2 +) 5 2 + 5 2 +

1+ ( 3

2 +)

1+

3 2 +

3+

3 2 +

( 5

2 +) 3 2 +

( 3

2 , 5 2 )+

?? ( 3

2 +)

2+

1 2 (+)

1+ ( 3

2 +)

( 5

2 +) 3 2 +

( 3

2 )+

??

? 2 ?

(3, 4)−

? 2 ?

??

? 2 ? ? 2 ?

( 3

2 )+ ? 2 ?

??

? 2 ?

?? ( 7

2 −)

?? ( 7

2 −) ? 2 ? ? 2 ? ? 2 ?

even-even

B(E2↑) E(2+

1 )

E(4+

1 ) E(4+

1 )

E(2+

1 )

PD, H. Scheit et al., PRL 103, 032501 (2009)

  • A. Gade et al., PRC 83, 044305 (2011)
  • A. Gade et al., PRL 99, 072502 (2007)

38Mg

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SLIDE 7

Experimental Shell Structure Signatures

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 7

500 1000 1500 2000 2500 3000 3500 14 16 18 20 22 24 26 E(21

+) (keV)

Neutron number Z=16 (S) Z=14 (Si) Z=12 (Mg) Z=10 (Ne)

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Experimental Setup

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 8

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BigRIPS Overview

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 9

Production Target

Big RIKEN Projectile Fragment Separator

  • Two stage separator

✦ 1st: separation ✦ 2nd: identification, further separation

  • Large acceptance (80 mr, 100 mr, 6 %)

✦ projectile fragmentation ✦ in-flight fission of U

Bρmax = 9 Tm L ∼ 77m P/∆P ∼ 1300(1st) 3300(2nd)

first stage second stage

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ZeroDegree Spectrometer

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 10

2nd BigRIPS stage

0◦ Spectrometer ZeroDegree

  • particle ID after secondary target
  • fragment momentum distribution
  • various modes of operation

mode p/∆p ∆p

  • Ang. Accep.

Large Accep. 1240 ±3% ±45 mrad(V) ±30 mrad(H) High res.(achrom) 2120 ±3% ±20 mrad(V) ±30 mrad(H) Dispersive 4130 ±2% ±20 mrad(V) ±30 mrad(H)

secondary target

∼ 3 m between Q-poles

  • DALI2 array, 186

NaI(Tl)

  • GRAPE HPGe array
  • Ebeam ∼ 100 − 250

MeV/u

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SLIDE 11

DALI2

The “Island of Inversion” Experimental Setup ❖ BigRIPS Overview ❖ ZeroDegree ❖ DALI2 Results Summary and Outlook PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 11

  • 186 NaI(Tl) detectors
  • ϑ coverage 11◦ to 165◦
  • ∆E/E ≈10(11) % (FWHM) at 100(250) MeV/u
  • ≈ 20% FEP efficiency at 1 MeV
  • Thick targets, 2.54 g/cm2 C, 2.13 g/cm2 CH2, 3.37

g/cm2 Pb

  • S. Takeuchi et al., RIKEN Pr. Rep. 36, 148 (2003)
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Results

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 12

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PID in Front of Secondary Target

The “Island of Inversion” Experimental Setup Results ❖ PID ❖ PID Behind Target ❖ Level Structure in Mg Summary and Outlook PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 13

Mass to Charge Ratio A/Q 2.8 2.85 2.9 2.95 3 3.05 Charge Q 12 13 14 15 16 1 10

2

10

3

10

Si

40

Al

39

  • ∆E − Bρ−TOF method

✦ Z ∝ ∆E ∆Z = 0.33 (FWHM) ✦ A/Q ∝ TOF ∆A = 0.08 (FWHM)

  • 40Si: 3000/s

E ≈ 230 MeV/u

  • 39Al: 100/s

E ≈ 215 MeV/u

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PID Behind Target and γ-ray Spectra

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 14

Mass to Charge Ratio A/Q 2.9 3 3.1 3.2 3.3 Charge Q 10 11 12 13 14

  • 1

10 1 10

PID after F8

  • 48Ca, 70 pnA primary beam
  • C(40Si,38Mg*), C(39Al,38Mg*)
  • 40Si: 3000 pps, 230 MeV/u
  • F8 target: nat.C, 2.54 g/cm2
  • E(2+

1 ) at 660(10) keV

  • Total data taking: 14.7 hours

5 10 15 20 500 1000 1500 2000 2500 Eγ (keV) Counts / 20 keV

C(39Al,38Mg*) (2+

1)

0+

g.s.

5 10 15 20 Counts / 20 keV

C(40Si,38Mg*) (2+

1)

0+

g.s.

4+

1 ?

Doppler corrected γ-ray energy

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SLIDE 15

Level Structure of Neutron-Rich Magnesium Isotopes

The “Island of Inversion” Experimental Setup Results ❖ PID ❖ PID Behind Target ❖ Level Structure in Mg Summary and Outlook PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 15

1 2 3 Ex (MeV) A=32 34 36 38

0+ 0+ 0+ 0+ 2+ 2+ 2+ (2+) (4+) (4+) (4+) (4+)

1 2 3 Ex (MeV) A=32 34 36 38

0+ 0+ 0+ 0+ 2+ 2+ 2+ (2+) (4+) (4+) (4+) (4+)

Utsuno Caurier Nowacki

  • E(4+

1 )/ E(2+ 1 ) ≈ 3.1 for A = 34 − 38

  • Y. Utsuno et al., PRL 60, 04315 (1999)
  • E. Caurier et al., NPA 693, 374 (2001)

F . Nowacki and A. Poves, PRC 79, 014310 (2009)

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Summary and Outlook

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 16

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Summary and Outlook

The “Island of Inversion” Experimental Setup Results Summary and Outlook ❖ Summary ❖ Collaboration PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 17

  • Found new excited states in 18 nuclei within 2.5 days of

beam time

  • E(2+

1 ) of 38Mg at low energy

  • E(4+

1 )/ E(2+ 1 ) ≈ 3.1 for 34-38Mg

  • Preliminary results, analysis ongoing
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Collaboration

The “Island of Inversion” Experimental Setup Results Summary and Outlook ❖ Summary ❖ Collaboration PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 18

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THE END

PD, In-beam gamma-ray spectroscopy of 36,38Mg ARIS Conference, May 30th – June 3rd, 2011 – 19