Recoil Distance Lifetime Measurement of 38 Si and Implementation of - PowerPoint PPT Presentation

Recoil Distance Lifetime Measurement of 38 Si and Implementation of Active Target Technique Mara Grinder Acknowledgements: This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003180

Outline  Physics Background and Motivation for 38 Si  Experimental set up and Method  Preliminary 38 Si Lifetime Data  Discussion of 38 Si Results  Active Target Implementation M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data, Slide 2

Shell Evolution from Mg→Ca  Neutron rich nuclei  Magic Numbers 20 and 28 [1],[2] • Persistent in 40,48 Ca, 34 Si • Absent in 32,40 Mg, 42 Si  Island of inversion [3],[4] • Magicity disappears 2p 3/2 2p 3/2 28 28 28 1f 7/2 1f 7/2 20 20 20 20 1d 3/2 1d 3/2 2s 1/2 2s 1/2 1d 5/2 1d 5/2 Stable Nuclei 8 8 8 8 Proton 1p 1/2 1p 1/2 1p 3/2 Neutron 1p 3/2 2 2 2 2 1s 1/2 1s 1/2 48 Ca 42 Si [1] T. Otsuka et al. Phys. Rev. Lett. 87, 082502 [2] O. Sorlin and M-G Porquet 2014 Phys. Scr. 2013 014003 M. Grinder, October 19, 2018 Joint ICTP-IAEA [3] E. K. Warburton et al. Phys. Rev. C. 41, 1147 (1990) Workshop on Nuclear Structure and Decay Data , Slide 3 [4] B.A. Brown Physics 3,104 (2010)

Shape Evolution Near 38 Si  Si isotopes N=20-28 Potential Energy Surface • Shell evolution • 34 Si is closed shell • No N=28 shell at 42 Si [1]  Triaxial deformation [2]  Cross shell excitations [3] • Between 1f 7/2 and 2p 3/2  Bubble Structure in 34 Si • Persists in neutron rich Si? [1] B. Bastin et al, PRL 99, 022503 (2007) [5] A. Mutschler et al. Nature Physics 13, 152-156 (2017) [2] Y. Utsuka et al. Phys. Rev. C 051301(R)(2012) M. Grinder, October 19, 2018 Joint ICTP-IAEA [3] S. R. Stroberg et al. Phys. Rev. C 91, 041302 (R) (2015) Workshop on Nuclear Structure and Decay Data , Slide 4 [4] T. Otsuka et al. Phys. Rev. Lett. 87, 082502

Collectivity in 38 Si  38 Si • Collective nature • Turning point collectivity • Vibrational → Deformed Vibrational Triaxial Deformed • B(E2) transition strength ( γ =30°) [4] measurement E(4 + )/E(2 + ) 2 2.67 3.3 »Hint at shell configuration B(E2;4 + →2 + ) »Intruder p 3/2 2 1.39 1.43 B(E2;2 + →0 + ) »Information on (4 + 2 ) state Vibrational Limit Rotational Limit Rotational Limit Vibrational Limit [1] R. W. Ibbotson et al, Phys. Rev. Lett. 80, 2081 (1998) [2] F. Nowacki and A. Poves, Phys. Rev. C. 79, 014310 (2009) M. Grinder, October 19, 2018 Joint ICTP-IAEA [3] S. Takeuchi et al. PRL 109, 182501 (2012) Workshop on Nuclear Structure and Decay Data , Slide 5 [4] W. T. Chou et al. Phys. Rev. C 47,157 (1993)

Experimental Setup 38 Si 48 Ca 44,45 Cl http://nscl.msu.edu/public/science/isotope.html Target Degrader  Two Reactions • 44 Cl+ 9 Be→ 38 Si • 45 Cl+ 9 Be→ 38 Si 2 nd Degrader M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 6

S800 Particle Identification 44 Cl Beam Particle Identification 44 Cl +17 38 Si Time of Flight (arb. units ) M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 7

Recoil Distance Method 1mm ≈10ps 2mm Be 0.57mm Ta 0.26mm Ta Target Degrader Degrader  Doppler-shift correction • Each β → peak • Peak height → # decays • Relative height give lifetime information First degrader component  Advantages Counts • Model independent B(E2) measurement Second • 1 ns to 10 ps lifetime range Target degrader component component  Disadvantages • Multiple distance measurements • Reactions in degrader foils Energy (keV) at forward angles M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 8

Target Only Data CM Frame Energy (keV) Population (4 + ) 2382 10 (2) 1308 (15) 2239 1074 4 + 59 (12) 1159 (2) 2 + 31 (6) 1074 1159 1074 (2) 0 + 0 38 Si 1308 [1] K. Steiger et al. Euro Phys J.A (2015) 51:117 M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 9

Three Foil Data Energy (keV) Lifetime (ps) 2382 (4 + ) 1 (4) 1074 1308 (15) 2239 4 + 11 (3) 1159 (2) 1159 2 + 1074 12 (3) 1074 (2) 0 + 0 1308 38 Si [1] K. Steiger et al. Euro Phys J.A (2015) 51:117 M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 10

B(E2) from Preliminary Lifetimes B(E2 ↓) (e 2 fm 4 ) Transition Energy Lifetime Previous Energy B(E2) B(E2 ↓ ) (keV) (ps) Ratio Ratio (e 2 fm 4 ) 2 + →0 + 39 (14) [1] 1074(2) 12 (3) 50 (10) --- --- 4 + →2 + 1159(2) 11 (3) 36 (7) --- 2.08 0.72 (4 + )→2 + 1308(15) 1 (4) >44 --- 2.20 (2 + )→2 + B(M1):>5.2x10 -3 Vibrational Triaxial Deformed ( γ =30°) [2] E(4 + )/E(2 + ) 2 2.67 3.3 B(E2;4 + →2 + ) 2 1.39 1.43 B(E2;2 + →0 + ) * Assuming pure M1 transition [1] R. W. Ibbotson et al, Phys. Rev. Lett. 80, 2081 (1998) [2] W. T. Chou et al, Phys. Rev. C 47,157 (1993) M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 11

Isotopes with B(E2) Ratio less than 1 Extracted from NuDat 2.7 Jun Chen, Private Communication M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 12

Active Target 44 Cl (Beam) D E 38 Si (Product) Z (beam axis)  Track reaction point in target • Better Doppler-shift corrections • Reduce degrader background • Increased sensitivity »Short lifetimes, < a few ps [1] P. Voss et al. Phys. Rev. C 90, 014301 (2014) M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 13

Diamond Active Target  Diamond detector • Radiation hard • 1% energy resolution • 500 μ m thick • 4.5 mm x 4.5 mm • Use in place of target foil  Next Steps • Diamond Detector »Beam test with heavy ions »Characterize M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 14

Summary  For the nuclei in the region around N=20 to 28, there is an evolution of shape and structure due to the change in nuclear shell structure far from stability.  The Si isotopic chain is expected to show a variety of collectivity as predicted by most recent shell model calculations.  The change in collectivity can be seen in B(E2) ratios resulting from deformations due to cross shell excitations.  38 Si is of particular importance as the turning point between vibrational and rotational collective pictures.  Preliminary lifetimes for the first three transitions in 38 Si have been determined.  A diamond active target will be implemented to improve sensitivity of future lifetime measurements. M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 15

Thanks and Questions  Lifetime Group: Hiro Iwasaki, John Ash, Rob Elder, Tea Mijatovic  Collaborators: Nobuyuki Kobayashi, Hye Young Lee, Kenneth Whitmore, Charles Loelius, Jun Chen, Daniel Bazin, Alfred Dewald, Alexandra Gade, Dirk Weisshaar, Peter Bender, Joe Belarge, Eric Lunderberg, Brandon Elman, Brenden Longfellow, Thoryn Haylett, Michael Mathy, Sebastian Heil  NSSC  Questions? Acknowledgements: This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003180 M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 16

[1] T. Otsuka et al. Phys. Rev. Lett. 87 , 082502 (2001) M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 17

Previous Measurements  Coulomb excitation (1998) [1] • E(2 + )=1084 (20) keV, • B(E2↑) of 193 (71) e 2 fm 4  Inelastic proton scattering (2007) [2] • Three gamma peaks in spectrum • Two candidates for the 4 + state  Multinucleon removal (2012) [3] • E(2 + )= 1071 (12), E((4 + ))= 2239 (22), E((4 + ))= 2355 (26) keV  Beta decay (2015) [4] • E(2 + )=1074 (2), E(4 + )=2233 (2) keV • Suggested the lower state as 4 +  No lifetimes measured previously  J π at 2355 keV not confirmed [1] R. W. Ibbotson et al, Phys. Rev. Lett. 80, 2081 (1998) [5] Y. Utsuno et al Prog.Theor.Phys.(Kyoto),Suppl. 196, 304 (2012) [2] C. M. Campbell et al, Phys. Rev. B 4, 652 (2007) M. Grinder, October 19, 2018 Joint ICTP-IAEA [3] S. Takeuchi et al. Phys. Rev. Lett. 109, 182501 (2012) Workshop on Nuclear Structure and Decay Data , Slide 18 [4] K. Steiger et al, Eur. Phys. J. A (2015) 51:117

Target Only Data Lab Frame e + e - 74 Ge(n,n ’) 72 Ge(n,n ’), 27 Al(n,n ’) 72 Ge(n,n ’) 27 Al(n, α ) M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 19

Three Foil Data Ratio Tgt/deg = 1.5 Energy (keV) 1074 2382 (4 + ) 1308 (15) 2239 4 + 1159 (2) 2 + 1074 1074 (2) 0 + 0 38 Si 1159 1308 M. Grinder, October 19, 2018 Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data , Slide 20