Nuclear Astrophysics and Exotics

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Artemis Spyrou

Michigan State University

Artemis Spyrou, Belfast 2017, 1 Overview

Lecture 1: Intro to Nuclear Astrophysics - reactions Lecture 2: How to measure cross sections + activity Lecture 3: Nuclear structure for astrophysics Lecture 4: Exotic phenomena close to the drip lines

Artemis Spyrou, Belfast 2017, 2 Abundances

From M. Wiescher, JINA web Artemis Spyrou, Belfast 2017, 3 Nucleosynthesis paths

56Fe

Stellar burning

pp chain N Artemis Spyrou, Belfast 2017, 4 Paths beyond Iron

Artemis Spyrou, Belfast 2017, 5 Nuclear Astrophysics Connections

Numerical approximaons

Astrophysical Nuclear Input condions

Stellar modeling

• Solar system abundances • Stellar observaons – Abundances Compare to • Meteoric samples Observaons • Light output / Energy producon • Time scales

Artemis Spyrou, Belfast 2017, 6 Nuclear input: What do we need? o Basic nuclear properties • Mass

• Binding energy

• Half life • Level structure

• Angular • Nuclear radius/shape Momentum

Artemis Spyrou, Belfast 2017, 7 Nuclear Input νp-process • Close to proton drip line • Masses, T1/2 mostly known • Most important (p,n) reactions

rp-process r-process • Close to proton drip line 56Fe • Masses, T1/2 mostly known • Far from stability • Proton capture reactions • Most properties not known • Masses • T1/2 • Pn Burning • Neutron captures p-process • Nuclear reactions • Resonance properties • Close to stability i-process • Masses, T1/2 known s-process • Between s and r • γ-induced reaction rates • Along stability • Mass, T1/2 known • Most properties known • Missing neutron captures • Missing neutron captures

Artemis Spyrou, Belfast 2017, 8 Nuclear Reactions in Stars

Main focus on capture reactions

Artemis Spyrou, Belfast 2017, 9 Y X

r = NX NYυσ(υ)

∞ r N N f(υ)σ(υ)υdυ f (υ) = X Y ∫ 0

r: reaction rate

Nx, Ny: number of particles υ:velocity r ∞ σ(υ): reaction cross section at υ συ = = f(υ)σ (υ)υdυ N N ∫ f(υ): velocity distribution X Y 0 <συ>: reaction rate per particle pair

Rolfs and Rodney, “Cauldrons in the cosmos” Artemis Spyrou, Belfast 2017, 10 Maxwell – Boltzmann distribution

2 ⎛ mυ ⎞ 0.5 3/ 2 ⎜ ⎟ ⎜ − ⎟ 2 ⎛ m ⎞ ⎝ 2kT ⎠ f(υ) = 4πυ ⎜ ⎟ e 0.4 (E)

2πkT φ ⎝ ⎠ 0.3

0.2

Distribution Distribution 0.1 3/ 2 ⎛ E ⎞ ⎜ − ⎟ 2 ⎛ 1 ⎞ 1/ 2 kT φ(E) = ⎜ ⎟ E e⎝ ⎠ 0.0 π ⎝ kT ⎠ 0kT 2kT 4kT 6kT 8kT 10kT 12kT 14kT Energy E

1/2 ! E $ ! 8 $ 1 ∞ #− & (E)Ee" kT %dE συ = # & 3/2 ∫ σ "πµ % (kT) 0

Rolfs and Rodney, “Cauldrons in the cosmos” Artemis Spyrou, Belfast 2017, 11 Tunnel Effect – S-factor

2 Coulomb barrier ψ (Rn ) P = 2

ψ (Rc ) projecle Tunneling probability -> R n Rc Distance r increasing with energy Potenal V(r)

Nuclear radius Artemis Spyrou, Belfast 2017, 12 Cross section has two components: 1. Interaction between particles (pure nuclear) 2. The Coulomb force

Astrophysical S-factor 1 (−2πη) σ (E) = e S(E) Contains all the pure nuclear E properties

Z Z e2 η: Sommerfeld parameter η = 1 2 !υ

Rolfs and Rodney, “Cauldrons in the cosmos” Artemis Spyrou, Belfast 2017, 12 Astrophysical region S-factor σ(Ε) Coulomb Barrier Log Scale Cross Section

Extrapolation The dangers of extrapolation S(E) factor Linear Scale Energy E

Artemis Spyrou, Belfast 2017, 13 Gamow Window Maxwell – Boltzmann distribuon Tunneling probability ⎛ E ⎞ # & ∝ exp⎜− ⎟ EC ⎝ kT ⎠ ∝ exp%− ( $ E ' Gamow peak

ΔE0 Relative probability

E0 Energy

Artemis Spyrou, Belfast 2017, 14 Gamow Window • Charged particles Burning: T= 0.01 – 0.1 GK o (p,γ): Ep= 0.02 – 0.2MeV Standard approximation o (α,γ): Eα= 0.05 -0.5 MeV p process: T= 1.8 – 3.3 GK 2 2 2 1/3 E0 = 0.12204(Z1 Z2 µT9 ) o (p,γ): Ep= 1 – 5 MeV [in MeV] o (α,γ): Eα= 4 -12 MeV E 0.237(Z 2Z 2 T 5 )1/6 Δ 0 = 1 2 µ 9 rp process: T= 1.1 – 1.3 GK o (p,γ): E = 0.8 – 2 MeV ΔE p Window: E + 0 νp process: T= 1.5 – 3.0 GK 0 2 o (p,γ): Ep= 1 – 4 MeV • Neutrons No Coulomb barrier, angular momentum 1 s process: T~ 0.3GK Eeff = 0.172T9 (ℓ + ) 2 o (n,γ): En= 25 - 75 keV [in MeV] i process: T= 0.1-0.3GK 1 o (n,γ): Ep= 10 – 75 MeV ΔEeff = 0.194T9 ℓ + 2 r process: T= 0.1 – 2.0 GK ΔEeff Window: E + o (n,γ): Ep= 10 – 500 keV eff 2

Rauscher, PRC 81 (2010) 045807 Kadonis.org : Gamow Calculator Artemis Spyrou, Belfast 2017, 15 Nuclear input: What do we need? o Nuclear reactions/Astrophysical reaction rates * a A B B Radiative capture reactions Incoming channel + → → +γ

Resonant Statistical Direct

A A A Q Q Q B B B

Artemis Spyrou, Belfast 2017, 16 o Example: 24Mg(p,γ)25Al

Marialuisa Aliotta, University of Edinburgh 11th Euro Summer School on Exotic Beams Artemis Spyrou, Belfast 2017, 17 Nuclear input: What do we need? o Nuclear reactions/Astrophysical reaction rates a + A → B* → B +γ Prompt Outgoing channel

or other particle channels (Competing channels) n γ B-1n Delayed A Q β B n Τ1/2 γ C-1n C

Artemis Spyrou, Belfast 2017, 18 Experiment Accelerator Facilities

Artemis Spyrou, Belfast 2017, 19 Facilities Stable beam facilities (Intro Physics) • Van de Graaﬀ (single-ended or tandem) • Cyclotrons • LINACS

Artemis Spyrou, Belfast 2017, 20 Basic Components

Analyzing magnet

Accelerator Ion sources

Beam Lines

5MV tandem accelerator @ Institute of Nuclear Physics, “Demokritos”, Athens, Greece Artemis Spyrou, Belfast 2017, 21 Radioactive Beams • Fragmentaon: NSCL/FRIB, GSI/FAIR, RIKEN, … Target Fast RIB Stable beam Fragmentaon Separaon • Isotope Separaon On-Line (ISOL): TRIUMF, SPIRAL, ISOLDE, … Target Extracon Stable beam RIB

Separaon Reacceleraon • Fission source: CARIBU/ANL Fission source Separaon Acceleraon RIB Extracon • Low energy reacons: ANL, FSU, Texas A&M, Notre Dame, … Target Low energy RIB Stable beam Reacon Separaon? Artemis Spyrou, Belfast 2017, 22 NSCL@MSU • Naonal Superconducng Cyclotron Laboratory

“Stopped beam area”

Gas Stopper ReAccelerator Facility

K500 Cyclotron S800 Spectrograph

A1900 Fragment Separator K1200 Cyclotron

Artemis Spyrou, Belfast 2017, 23 Coupled Cyclotron Facility

Example: 86Kr → 78Ni K500 ion sources

coupling 86Kr14+, line 12 MeV/u K1200 A1900 focal plane

Δp/p = 5% producon transmission stripping 86Kr34+, target foil of 65% of the 140 MeV/u produced 78Ni wedge

fragment yield aer target fragment yield aer wedge fragment yield at focal plane

Artemis Spyrou, Belfast 2017, 24 Neutron Facilities Time-of-Flight: e.g. nTOF@CERN, LANSCE@ Los Alamos, IRMM@Geel, Belgium, etc • High energy protons on heavy target, broad energy distribuon, pulsed beam.

Reacon-based, quasi-monoenergec: Any low energy facility 2 2 3 • Reacons: H( H,n) He – Q= 3.3 MeV - En= 2.5 MeV 3 2 4 H( H,n) He – Q= 17.6 MeV - En = 14.1 MeV 7 7 Li(p,n) Be – Q= - 1.64 MeV – En=? – How can you get 25 keV? …

Artemis Spyrou, Belfast 2017, 25 In the Laboratory

Number of reactions • Yield of reaction: Y = Number of beam particles

Yield of reaction N • Cross section: σ = = R Number of target particles Nb ⋅ NT

To measure a cross section you need three things:

1. Number of target particles (NT) !!!

2. Number of beam particles (Nb) !!!

3. Number of reactions (NR) !!!

Artemis Spyrou, Belfast 2017, 26 Number of target particles 1 • Rutherford backscattering

92 ΔΕ0 Mo target

0 Mo Ed = 1.35 MeV

- ΔΕ experiment 0 0 Ε Ε Beam simulation ο 170 Ε1 Ε1-ΔΕ Al backing 1 Si detector # events

ΔΕ # events 1 Energy (keV) Ε -ΔΕ Ε Ε 1 1 1 o Simulation with SIMNRA o Known detector geometry N : Avogadro number N Aξ A o Known cross section NT = A: Atomic mass A ξ: target thickness in g/cm2 o Free parameter: target thickness/composition

Artemis Spyrou, Belfast 2017, 27 Tools 1 Si surface barrier detector – Semi-conductor

hp://nsspi.tamu.edu/nssep/courses/basic-radiaon-detecon/ semiconductor-detectors/introducon/introducon Artemis Spyrou, Belfast 2017, 28 Number of target particles 1 • X-ray Fluorescence (XRF)

M L K M L K

X-ray detector # events

Energy (keV) Artemis Spyrou, Belfast 2017, 29 Tools 1 SiLi detector – Semi-conductor X-ray tube

• Cooling • Addition of Li helps remove impurities

hp://nau.edu/cefns/labs/electron-microprobe/glg-510-class-notes/ detecon-of-signals/ hp://www.schoolphysics.co.uk/age16-19/Medical%20physics/text/ X_rays/index.html Artemis Spyrou, Belfast 2017, 30 Number of target particles 1 • Particle energy loss ΔΕ0 0 - ΔΕ 0 0

Ε α α Ε source source Si detector Si detector # events

Ε Ε0-ΔΕ0 Ε0

o Many other techniques like resonance measurement, use of spectrometer or recoil separator, use a reaction, etc o If radioactive sample: activity from decay

Artemis Spyrou, Belfast 2017, 31 In the Laboratory

Number of reactions • Yield of reaction: Y = Number of beam particles

Yield of reaction N • Cross section: σ = = R Number of target particles Nb ⋅ NT

To measure a cross section you need three things:

1. Number of target particles (NT) !!!

2. Number of beam particles (Nb) !!!

3. Number of reactions (NR) !!!

Artemis Spyrou, Belfast 2017, 32 Number of beam particles 2 • High beam intensities: measure deposited charge

Collimator 1 Collimator 2

Target beam detector

A Ammeter/ Current integrator e.g. 1H+ beam: each beam particle deposits 1.6 x 10-19 Cb (e- charge) 84Kr27+ beam: each beam particle deposits 27 x 1.6 x 10-19 Cb

Artemis Spyrou, Belfast 2017, 33 Number of beam particles 2 • High beam intensities: measure deposited charge

Collimator 1 Collimator 2

- Target e e- beam detector - - e - e e- e

A Ammeter/ Current integrator

Artemis Spyrou, Belfast 2017, 34 Number of beam particles 2 • High beam intensities: measure deposited charge

Collimator 1 Collimator 2

- Target e- - e e- beam e detector - - e- e- e - e e- e- e e-

A Ammeter/ Current integrator +- Beam: positive charge +1e + +-+- Measurement 1: +1e +- Measurement 2: +2e = false +- +- +- How do we ﬁx it?

Artemis Spyrou, Belfast 2017, 35 Number of beam particles 2 • Low beam intensities: measure each particle in detector 1. In beam detector upstream to measure continuously 2. In beam detector upstream to insert every so often 3. Scattering detector upstream 4. Detector looking at target scattering 5. Detector downstream after target 6. Activation (especially for neutrons) 3 1,2 Si Si Target Si beam Ion chamber

Plastic scint. Si Si MCP 4 Si Diamond Fission detector

Artemis Spyrou, Belfast 2017, 36 Overview

Artemis Spyrou, Belfast 2017, 37 In the Laboratory

Number of reactions • Yield of reaction: Y = Number of beam particles

Yield of reaction N • Cross section: σ = = R Number of target particles Nb ⋅ NT

To measure a cross section you need three things:

1. Number of target particles (NT) !!!

2. Number of beam particles (Nb) !!!

3. Number of reactions (NR) !!!

Artemis Spyrou, Belfast 2017, 38 Regular kinematics 3

n, p, α - beam heavy nucleus (target)

Facilies: Stable beam (ATOMKI, Athens, Notre Dame, Cologne, Florida State, nTOF, Los Alamos, Karlsruhe, etc) Equipment: Gamma-ray detectors, X-ray detectors, charged parcle detectors Techniques: Acvaon, Angular distribuon, Summing Advantages: •High intensity stable beams •Well developed techniques Disadvantages • Not applicable for all targets, in parcular radioacve nuclei

Artemis Spyrou, Belfast 2017, 39 Activation 3

o Irradiate for time according to Pb half life HPGe o Monitor beam intensity ≈ 55% o After irradiation move sample to low background area, HPGe o Detect β-delayed γ-rays Target

T. Sauter and F. Kappeler, Phys. Rev. C 55, 3127 (1997). Artemis Spyrou, Belfast 2017, 40 Tools 3

High Purity Ge detectors inside shielding

Artemis Spyrou, Belfast 2017, 41 Angular Distributions 3

±15o Entry state

Ecm

HPGe (ε =100%) BGO o In beam γ-ray detection Q o Measure at many angles o High resolution system (HPGe) o Create angular distributions o Extract reaction yield B o Extract cross sections e.g. Galanopoulos, et al, PRC 67 (2003) 015801 Artemis Spyrou, Belfast 2017, 42 Tools 3 ±15o

HPGe (ε =100%) BGO

Artemis Spyrou, Belfast 2017, 43 Angular Distributions 3

60000 14000 634 keV 55000 527 keV 12000 50000

10000 45000 W(ϑ) = A0 (1+ a2P2 (cos40000 ϑ) + a4P4 (cos8000 ϑ)) 35000 6000

30000 400070000 20 40 60 80 100 120 140 20 40 60 80 100 120 140 80000 Fit719 with keV Legendre 65000Polynomial924 keV

60000 70000

55000

60000 50000

A 45000 0 50000

4000018000 20 40 60 80 100 120 140 20 40 60 80 100 120 140 40000 1089 keV 16000 1160 keV 14000 35000

12000

30000 10000

25000 8000

6000 20000 4000

1500012000 2000 20 40 60 80 100 120 140 20 40 60 80 100 120 140 11000 1310 keV 25000 10000 1454 keV A 9000 20000 8000 j

7000 15000 σT = 6000 A0 10000 5000∑ 4000 N ξ 5000 ⋅ 3000 j A 20 40 60 80 100 120 140 20 40 60 80 100 120 140

e.g. Galanopoulos, et al, PRC 67 (2003) 015801 Artemis Spyrou, Belfast 2017, 44 Summing Technique 3 Entry E es = E cm + Q γ state 1,0 Small size detector γ2,1 γ

2,0 γ2 Compton

Counts γ 1 γ Ecm 0 γ0 γ γ 1 2 γ 2 4 calorimeter Σ

γ2,1 γ2,0

1 Counts Q γ1,0

g.s. 0 Photon Energy Target o In beam γ-ray detection o Sum all energy in a cascade o Need very high eﬃciency detector o Need highly enriched samples o Eﬃciency dependence on the γ-multiplicity o Simple analysis

Spyrou et. al. PRC 76 (2007) 015802 Simon et. al. NIMA 703 (2013) 16 Artemis Spyrou, Belfast 2017, 45 Tools 3

NaI

12”x12” HECTOR @Notre Dame 4π@Bochum

SuN@MSU

Spyrou et. al. PRC 76 (2007) 015802 Simon et. al. NIMA 703 (2013) 16 Artemis Spyrou, Belfast 2017, 46

800 90 91 700 Zr(p,g) Nb 600 sum peak 500 400 19F(p,ag)16O 300 200 Summing Technique 3 100 (a) 0 92 93 2614 keV Zr(p,g) Nb

Counts / 15 keV 2000 sum peak

1500 19 16 F(p,ag) O

1000 92Mo(α,γ)96Ru 500 12000 (b) Eα = 11 MeV 10000 Eα = 10.6 MeV 0 Eα = 10.2 MeV 2 4 6 8 10 E = 9.8 MeV 8000 α Eg (MeV) 6000

4000 Yield mC /

2000

0 10000 11000 12000 E (keV) γ Spyrou et. al. PRC 76 (2007) 015802 Simon et. al. NIMA 703 (2013) 16 Artemis Spyrou, Belfast 2017, 47 Summing Technique 3 Eﬃciency depends on energy AND γ multiplicity

I Reactions = SumPeak ε

Spyrou et. al. PRC 76 (2007) 015802 Simon et. al. NIMA 703 (2013) 16 Artemis Spyrou, Belfast 2017, 48 Comparison – Stable Beam Acvaon technique - Oﬀ line

Low energy γ-rays Small size HPGe Natural targets Suitable half-life

Angular Distribuons – In beam Decay scheme informaon High volume HPGe detector Time-consuming data collecon and analysis

Angle integrated measurements – In beam High eﬃciency Simple analysis procedure Limited spectroscopic informaon Artemis Spyrou, Belfast 2017, 49 Inverse kinematics 3

ü recoil separators ü ring measurements heavy beam ü γ-summing heavy recoil ü acvaon/implantaon Light target (H, He) Radioacve Beam Facilies: TRIUMF, MSU, GSI, GANIL, CERN, ANL? Equipment: Dragon, SECAR, Storage ring, SuN, LISE, …

TRIUMF MSU GANIL

GSI

Artemis Spyrou, Belfast 2017, 50 Recoil separators 3 o Many diﬀerent separators in operation or under construction o Main use: rejection of incoming beam while selecting recoils o Gamma rays around target in coincidence with recoils o Very clean measurements DRAGON @ TRIUMF SECAR @ MSU

St. George @ Notre Dame

Artemis Spyrou, Belfast 2017, 51 Storage rings 3 96Ru(p,γ)97Rh

Mei, et. al. PRC 92 (2015) 035803 Artemis Spyrou, Belfast 2017, 52 Summing in inverse kinematics 3 Isolang Flange MCP Detector (ND) Beam

• Hydrogen gas target S.J. Quinn, et al., Nucl. Instr. Meth. A 57, 62 (2014) • Heavy beam • Doppler shift Artemis Spyrou, Belfast 2017, 53 Let’s put it all together!!!! You learned: • How to measure the number of target nuclei • How to measure the number of beam particles • How to measure the number of reactions that occurred

Yield of reaction N • Cross section: σ = = R Number of target particles Nb ⋅ NT

Artemis Spyrou, Belfast 2017, 54 p process example: 74Ge(p,γ)75As

Rapp et al. AJ 653 (2006) 474 Artemis Spyrou, Belfast 2017, 55 p process example: 74Ge(p,γ)75As Two measurements: Angular Distributions + Summing

Post-Processing Code NucNet Tools Brad Meyer, Clemson University

S. J. Quinn, A. Simon, A.S., et al., Phys. Rev. C 88, 011603 (R) (2013). A. Sauerwein, et al, Phys. Rev. C, 86, 035802 (2012) Artemis Spyrou, Belfast 2017, 56 (n,γ) cross sections

Direct measurements: A lot of measurements along the valley of stability Best resource: KADONIS library: http://www.kadonis.org/

Artemis Spyrou, Belfast 2017, 57 s process example: 63Ni(n,γ)64Ni Observaonally conﬁrmed: Asymptoc giant branch (AGB) stars Classic s process Weak s process

N Artemis Spyrou, Belfast 2017, 58 s process example: 63Ni(n,γ)64Ni “The 63Ni sample was produced about 30 years ago by breeding a highly enriched 62Ni sample in the ILL high ﬂux reactor at Grenoble.”

• nTOF facility @ CERN • Use resonance parameters to calculate Maxwellian Averaged Cross Section (MACS) • New MACS is a factor of 2 higher than previous estimate • 64Ni increased by 20% • 63Cu decreased by 15% • 63Cu/65Cu ratio changes

C. Lederer, et. al. (nTOF collaboration) PRC 89 (2014) 025810, PRL 110 (2013) 022501 Artemis Spyrou, Belfast 2017, 59 Overview

Artemis Spyrou, Belfast 2017, 60 Indirect Measurements

Artemis Spyrou, Belfast 2017, 61 Nova contribution to Galactic 26Al?

Nova Cygni 1992 (in 1994) NASA, ESA, HST

Last nuclear-physics uncertainty is 25Al(p,γ)26Si rate

Data from COMPTEL & INTEGRAL-SPI (MPE Garching / Roland Diehl)

Artemis Spyrou, Belfast 2017, 62 25Al(p,γ)26Si resonance GeDSSD SeGA

26P(β+γ)26Si

Measured g branch for ﬁrst time to determine 3+ strength: up to 30% of Galactic 26Al produced in novae.

M. B. Bennett et al., Phys. Rev. Lett. 111, 232503 (2013) Artemis Spyrou, Belfast 2017, 63 The trouble with neutron capture

o Regular kinemacs • Measuring Neutron Capture reactions on short-lived nuclei is neutron beam heavy nucleus at best challenging (target) • Need indirect techniques • Surrogate technique (d,p)-(n,γ) • Measure NLD, γSF • Can also be applied to (p,γ) – why? o Inverse kinemacs

heavy beam o Colliding beams ? heavy recoil heavy beam neutron beam Neutron target

Artemis Spyrou, Belfast 2017, 64 Surrogate technique (n,γ) • Formation of compound nucleus (CN) independent of its decay • Form same CN as (n,γ) via (d,p) (A-1, Z) • Study its decay • Inform the models γ • Applicable in regular and inverse kinematics • Applicable a few steps from stability

Validation: 95Mo(n,γ)96Mo Significant progress during the last couple of years

A. Ratkiewicz, J. Cizewski, EPJ Web of Conferences 92 (2015) 02012 Artemis Spyrou, Belfast 2017, 65 Calculate (n,γ) Cross Section Hauser – Feshbach (n,γ) • Nuclear Level Density Constant T+Fermi gas, back-shied Fermi

gas, superﬂuid, microscopic Level density (A-1, Z) • γ-ray strength funcon Generalized Lorentzian, Brink-Axel, γ various tables

• Opcal model potenal Phenomenological, Semi-microscopic

(A, Z) γ-strength funcon

OMP 95Sr(n,γ)96Sr

ALL TALYS

Artemis Spyrou, Belfast 2017, 66 Traditional Oslo method Ø Use reacon to populate the compound nucleus of interest Ø Measure excitaon energy and γ-ray energy Ø Extract level density and γ-ray strength funcon (external normalizaons) Ø Calculate “semi-experimental” (n, γ) cross secon Ø Excellent agreement with measured (n, γ) reacon cross secons

Excitaon energy

P(Eγ , Ex ) ~ ρ(Ex − Eγ )T (Eγ ) Gamma energy (MeV) Unfolding Normalization Iterative subtraction T.G. Tornyi, M. Guttormsen,et al., PRC2014 Artemis Spyrou, Belfast 2017, 67 Example Oslo method

L. Crespo-Campo, et. al. PRC 94 (2016) 044321 Artemis Spyrou, Belfast 2017, 68 β-Oslo β- (n,γ) (A, Z-1)

SuN @ MSU (A-1, Z) γ

(A, Z)

• Populate the compound nucleus via β-decay (large Q-value far from stability) • Spin selectivity – correct for it • Extract level density and γ-ray strength function • Advantage: Can reach (n,γ) reactions with beam intensity down to 1 pps.

Spyrou, Liddick, Larsen, Guttormsen, et al, PRL2014 Artemis Spyrou, Belfast 2017, 69 Example β-Oslo R. Surman, et al., , AIP Advances 4, 041008 (2014)

69Ni(n,γ)70Ni 69 70 BRUSLIB 7 Ni(n,γ) Ni rate 10 JINA REACLIB

) Oslo matrix for central segments final

-1 70 70 10000 Co-> matrixCo70_finalNi Entries 49194 Mean x 1458 mol 9000 Q = 12.3 MeV -1 6 β Mean y 4908

s 10 3 8000 RMS x 1311 Sn =7.3 MeV RMS y 1969

) S7000n (cm 〉 v

σ 6000 〈 keV

A 5

10 ( N

x 5000 E 4000 69 70 Ni Ni 3000 β- 10-1 1 (n,γ) 2000 T (109 K) 70 1000 Co 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Qβ = 12.3 MeV Eγ (keV) Artemis Spyrou, Belfast 2017, 70 Nuclear Structure

Artemis Spyrou, Belfast 2017, 71 s/r-process paths and abundances

Sneden, C., Cowan, J. J., & Gallino, R., Ann. Rev. Ast. Ap. 46 (2008) 241.

Cowan and Thielemann, Physics Today, 2004 Artemis Spyrou, Belfast 2017, 72 Mass measurements • Strong connection between nuclear mass (binding energy) and shell closures • Two-neutron separation energies – example N=20

N=28

Artemis Spyrou, Belfast 2017, 73 Impact of mass to astrophysics r-process abundances

X-ray burst Luminosity

M. Mumpower, et. al. Prog. Nucl. Part. Phys. 86 (2016) 86. M. del Santo et al., Physics Letters B 738, 453 (2014). Artemis Spyrou, Belfast 2017, 74 Mass measurements •Time-of-Flight ( ToF) • Multi-reﬂection ToF (MR ToF) • Penning Traps (PT) • Storage Rings – Schottky (SR-Sch) • Storage Ring – Isochronous Mass Spectrometry (SR – IMS)

Z. Meisel, PhD thesis, MSU 2015 Artemis Spyrou, Belfast 2017, 75 Penning Trap • Triple motion in penning trap • Used for measuring the mass of nuclei with very large accuracy • Conﬁning particles in electric and magnetic ﬁelds

• Canadian Penning Trap @ANL • LEBIT @ MSU • ISOLTRAP @ ISOLDE, CERN • TITAN @ TRIUMF • JYFLTRAP@Jyvaskula • SHIPTRAP@GSI m g

101Sr TITAN 72Br LEBIT

R. Klawitter, et. al. Phys. Rev. C 93 (2016) 045807 A. Valverde, et. al. Phys. Rev. C 91 (2015) 037301 Artemis Spyrou, Belfast 2017, 76 Example results: Penning Trap

• Canadian Penning Trap @ANL • Collaboration ANL + Notre Dame • Impact on r-process calculations

N = N = 50 82

Z = 50

RECENT

J. A. Clark and G. Savard, Int. J. Mass Spectrom. 349-350, 81 (2013). Artemis Spyrou, Belfast 2017, 77 Time-of-Flight • Naonal Superconducng Cyclotron Laboratory @ MSU

S800 Spectrograph

K500 Cyclotron

A1900 Fragment Separator K1200 Cyclotron

Z. Meisel, S. George, et. al. Prys. Rev. Lett. 114 (2015) 022501 Artemis Spyrou, Belfast 2017, 78 Storage Rings

www.gsi.de Artemis Spyrou, Belfast 2017, 79 MR-ToF

Diﬀerent types of MR-ToF

W. Plaβ et. al., Intern. J. of Mass Spectrom. 349 (2013) 134 Artemis Spyrou, Belfast 2017, 80 β decay properties

• Half life T1/2 • β-delayed neutron emission probability Pn • β-decay intensity

n γ B-1n Delayed A Q β B n Τ1/2 γ C-1n C

Artemis Spyrou, Belfast 2017, 81 Half life • Impact of half-lives on r-process

M. Mumpower, et. al. Prog. Nucl. Part. Phys. 86 (2016) 86. Artemis Spyrou, Belfast 2017, 82 Half life • RIKEN recently completed a major upgrade • Higher beam rates than other facilities • Systematics of T1/2 • Impact on r process

without

with

G. Lorusso, et. al. Phys. Rev. Lett. 114 (2015) 192501 Artemis Spyrou, Belfast 2017, 83 High resolution • Mentioned that nuclear structure understanding is important for all astrophysical processes • Many ways to study nuclear structure • β decay is typically the ﬁrst view of a nucleus (low beam intensity) • High resolution measurements for the low lying level scheme

GRIFFIN @ TRIUMF SeGA + BCS @ MSU

Artemis Spyrou, Belfast 2017, 84 Evolution of Nuclear Structure

Shell model N=51

HPGe Clovers @ ORNL

S. Padget, et. al. Phys. Rev. C 82 (2010) 064314 Artemis Spyrou, Belfast 2017, 85 Why measure β-decay intensity? • Model constraints for better input in r-process calculations (Cannot measure everything - we need to rely on model predictions) • Nuclear structure information

Ø T 1/2 sensitive to nuclear shape Ø Can get same T1/2 for diﬀerent shapes Ø β-decay strength: sensitive constraint 76Sr β-decay

•Lucrecia @ CERN

E. Nacher, et al., Phys. Rev. Lett. 92 (2004) 232501. Artemis Spyrou, Belfast 2017, 86 Total Absorption Spectroscopy β- (A, Z-1)

John Milton’s "Paradise Lost

(A, Z) Small size – low eﬃciency detector Large size - high eﬃciency detector

Iγ(in) Iβ γ beam Iβ= Iγ(out) - Iγ(in)

Iγ(out)

Ex= Eγ1 + Eγ2 + Eγ3 + Eγ4 + ... J.C. Hardy et al., Phys. Lett. B 71 (1977) 307. Artemis Spyrou, Belfast 2017, 87 The Pandemonium in Action 76Ga β decay TAS - SuN NNDC

Total Absorption Spectrum

101 101Zr 101Nb * + e- + 40 Zr 61 →β 41 decay 60 νe 102 Q = 5717 keV β

1 experiment TAS - SuN Normalized Counts / 12 keV NNDC simulation 10-1 1000 2000 3000 4000 5000 6000 Energy (keV)

A. Dombos, et. al. PRC93 (2016) 064317 Artemis Spyrou, Belfast 2017, 88 r-process example: 70Co β-decay Intensity

SuN @ MSU

16’’

45 mm

Double Sided Si Strip Detector For ion and β detection

A. Spyrou, S.N. Liddick, et al. Phys. Rev. Lett. 117 (2016) 142701 Artemis Spyrou, Belfast 2017, 89 Importance of Pn values with bdne hot wind without bdne

cold wind

ns merger r-process simulation results with and without β-delayed neutron emission

R. Surman, et. al. JPS Conf. Proc. 6 (2015) 010010 Artemis Spyrou, Belfast 2017, 90 Measuring Pn values • Integrated measurement - 3He counters (3Hen, NERO, BRIKEN) • Time of ﬂight – energy information (VANDLE, LENDA, DESCANT) • New technique – Paul trap (@ ANL) VANDLE @ ORNL DESCANT @ TRIUMF

NERO @ MSU

M. Madurga, et. al. Phys. Rev. Lett. 117 (2016) 092502 Artemis Spyrou, Belfast 2017, 91 Paul trap

• Surround ion trap (Paul trap) with plasc scinllators (to detect β’s) and MCPs (to detect decay recoils) • Beta-delayed neutron decay measured without detecng neutron

N. Scielzo, et. al., Nucl. Data Sheets 120 (2014) 70 Artemis Spyrou, Belfast 2017, 92 Example: Recent Pn measurements

• Installed at RIKEN Nishina Center in Wako/ Japan • 148 3He-ﬁlled neutron counters from Germany, Japan, Spain, USA and 2 HPGe clovers (Oak Ridge) • Implantation detector AIDA (Edinburg, Daresbury) • First parasitic experiment – more to come 2017-2019 N=50

BRIKEN N=50

N=50 • Goal: Measure >100 of the most Z exoc neutron-rich isotopes presently accessible • More recent results – Ask Iris J

A/Q Artemis Spyrou, Belfast 2017, 93 Summary for Nuclear Astrophysics We covered A LOT of material but we didn’t cover EVERYTHING. Here’s what we didn’t cover: • Isomers • Charge Exchange Reactions • (p,n) reactions for νp process • (α,n) reactions for neutron-star crusts • Equation of State experiments • Fission • Photon beam • …

Artemis Spyrou, Belfast 2017, 94 Overview

Artemis Spyrou, Belfast 2017, 95 Reaching the limits

Proton halos High Z Diproton decay Superheavies Location of drip line

Island of stability

Neutron halos Neutron skins Dineutron decay Structure changes neutrons, N New radioactivity Location of drip line

Artemis Spyrou, Belfast 2017, 96 Structure Evolution

Artemis Spyrou, Belfast 2017, 97 Nuclear Binding

2 2 2 Binding energy: B(N, Z) = ZM H c + NM nc − M(N, Z)c

http://www.bbc.co.uk/bitesize/higher/physics/radiation/nuclear_reactions/revision/2/ Artemis Spyrou, Belfast 2017, 98 Nucleon separation energies

Neutron Separation Energy: Sn = B(N, Z)− B(N −1, Z)

Two neutron Separation Energy: S2n = B(N, Z)− B(N − 2, Z) Proton Separation Energy: Sp = B(N, Z)− B(N, Z −1)

Two proton Separation Energy: S2 p = B(N, Z)− B(N, Z − 2)

Kankainen, et. al. J. Phys. G: Nucl. Part. Phys. 39 (2012) 093101 Artemis Spyrou, Belfast 2017, 99 Neutron separation energies

6 4 2 0

-2 Neutron Neutron Separation energy dripline 9Be 10Be 11Be 12Be 13Be 14Be 15Be 16Be

Neutron unbound Kankainen, et. al. J. Phys. G: Nucl. Part. Phys. 39 (2012) 093101 Artemis Spyrou, Belfast 2017, 100 Neutron dripline

31Ne︎

Z=8 N=20

“Dripline: The limit of the nuclear Z=2 landscape where additional protons or neutrons can no longer be kept in the nucleus, they literally drip out” B. Jonson N=8 N=2 Artemis Spyrou, Belfast 2017, 101 How to measure structure evolution

• Nuclear existence • Mass measurements • γ-ray spectroscopy – excitation energies • Neutron spectroscopy – unbound states • Reaction cross sections • β-decay properties • …

Artemis Spyrou, Belfast 2017, 102 Isotope Discovery National Superconducting Cyclotron Laboratory Michigan State University, US

“Stopped beam area”

Gas Stopper ReAccelerator Facility

K500 Cyclotron

S800 Spectrograph Loss Energy

A1900 Fragment Separator K1200 Cyclotron Corrected ToF

MSU • 3 events of 40Mg in 7.6 days • 23 events of 42Al • 1 event 43Al

RIKEN • About 1000 per day!!! RIKEN, RIBF, Japan Baumann, et. al. Nature 449 (2007) 1022 Artemis Spyrou, Belfast 2017, 103 γ-ray spectroscopy • Yesterday we talked about γ-spectroscopy following β-decay • Today we will focus on reactions • The goal is the same: Study the evolution of single-particle levels • Reminder: Shell model

What can we learn? • Location of levels • Cross section of reaction • Life time of levels • Angular distribution – multipolarity • Occupation of levels

Artemis Spyrou, Belfast 2017, 104 γ-ray spectroscopy

26Ne 24O Ζ = 10 Ν= 16 Ζ = 8 Ν= 16 1d3/2

1d3/2 2s1/2 2s1/2 1d5/2 1d5/2

1p1/2 1p1/2 1p3/2 1p3/2

1s1/2 1s1/2

Many diﬀerent ways to populate a state: • Excitation (Coulomb, inelastic) Important note: • Nucleon transfer Some reactions are very selective so • Knockout the structure of the initial nucleus • Fusion evaporation matters. • Charge exchange • …

C. Hoffman, et al. Phys. Lett. B, 2009 Artemis Spyrou, Belfast 2017, 105 Selective population 26 Ne 26Mg 27Mg 28Mg 29Mg 30Mg Ζ = 10 Ν= 16

1d3/2 25Na 26Na 27Na 28Na 29Na 2s1/2 1d5/2 26Ne 24Ne 25Ne 26Ne 27Ne 28Ne 1p1/2 Ζ = 10 Ν= 16 1p3/2 1d3/2 23F 24F 25F 26F 27F 2s1/2 1s1/2 1d5/2 27 25Ne 1p1/2 Na 1p3/2 Ζ = 11 Ν= 16 Ζ = 10 Ν= 15 1d3/2 1d3/2 1s1/2 2s1/2 2s1/2 1d5/2 1d5/2

1p1/2 1p1/2 1p3/2 1p3/2

1s1/2 1s1/2

Artemis Spyrou, Belfast 2017, 106 Tools

DALI2 @ RIKEN TIGRESS@TRIUMF

Artemis Spyrou, Belfast 2017, 107 Example – Island of Inversion C. Thibault et al. Phys. Rev. C 12 (1975) 646 31,32 • Local increase to S2n for Na (masses) • N=20 shell closure would lead to decrease

C. Detraz et al. Phys. Rev. C 19 (1979) 164 • Low lying 2+ state in 32Mg (β-decay) • N=20 shell closure would lead to a high-lying 2+

T. Motobayashi et al. Phys. Lett. B 346 (1995) 9 • 32Mg deformed (Coulomb excitation) • N=20 shell closure would mean spherical shape

1f7/2 1f7/2 A. Gade et al. Phys. Lett. B 346 (1995) 9 • 36 Ν= 20 Ν= 20 Mg strong inverted component (2p knockout) • N=20 shell closure would mean 1d3/2 1d3/2 2s1/2 2s1/2 1d5/2 1d5/2 And many more…

1p1/2 1p1/2 1p3/2 1p3/2 Intruder conﬁgurations in the ground state of Z=10-12 and N=20-22 nuclei 1s1/2 1s1/2

E. Warburton et. al. Phys. Rev. C 41 (1990) 1147 Artemis Spyrou, Belfast 2017, 108 Neutron separation energies

6 4 2 0

-2 Neutron Neutron Separation energy dripline 9Be 10Be 11Be 12Be 13Be 14Be 15Be 16Be

Neutron unbound Kankainen, et. al. J. Phys. G: Nucl. Part. Phys. 39 (2012) 093101 Artemis Spyrou, Belfast 2017, 109 Neutron spectroscopy • The same reactions can be used to populate neutron-unbound states • Detect neutron and remaining fragment • Invariant mass analysis to extract the excitation energy

15 14 15 m( Be) = m( Be)+ m(n)− Sn ( Be)

If Sn>0: bound If Sn<0 unbound Invariant mass analysis

2 2 Ed = M f + M n + (2E f En − p f pn cosθopen ) − M f − M n

f: Fragment n: Neutron

Artemis Spyrou, Belfast 2017, 110 Example: 26O – bound or unbound unbound • 26O predictions for 30 years • Calculations vary: from bound by 5 MeV to unbound by 4 MeV bound

Artemis Spyrou, Belfast 2017, 111 26O: Experiment@MSU

MoNA/Sweeper setup

n 24O n

Artemis Spyrou, Belfast 2017, 112 Example: 26O – bound or unbound @MSU 26O unbound by <200 keV

@RIKEN 26O unbound by <100 keV

Y. Kondo, et. al., Phys. Rev. Lett. 116 (2016) 102503

@GSI 26O unbound by <50 keV C. Caesar, et. al., Phys. Rev. C 88 (2013) 034313

E. Lunderberg, et. al., Phys. Rev. Lett. 108 (2012) 142503 Artemis Spyrou, Belfast 2017, 113 Halo Nuclei

31Ne

Z=8 N=20

Z=2 N=14 N=16

1n - halo N=8 N=2

Bauman-Spyrou-Thoennessen, Rep. Prog. Phys. 75 (2012) 036301 Artemis Spyrou, Belfast 2017, 114 Halo Nuclei Borromean nuclei

31Ne

Z=8 N=20

Z=2 N=14 N=16 P. Mueller, PRL2007 2n - halo 1n - halo N=8 N=2

Bauman-Spyrou-Thoennessen, Rep. Prog. Phys. 75 (2012) 036301 Artemis Spyrou, Belfast 2017, 115 Halo Nuclei 2p - halo

31Ne 1p - halo Z=8 N=20

Z=2 N=14 N=16

2n - halo 1n - halo N=8 N=2

Bauman-Spyrou-Thoennessen, Rep. Prog. Phys. 75 (2012) 036301 Artemis Spyrou, Belfast 2017, 116 Halo Nuclei Discovery Tanihata et al., Phys. Rev. Lett. 55, 2676 (1985), Phys. Lett. B 160, 380 (1985). Experiment: Very large interaction cross section for some light nuclei – large radius

Hansen and Jonson, Europhys. Lett. B 4, 409 (1987). Theory: Explain the matter radius experiments: Introduced term „halo”

Characteristics of halo nuclei • Very low binding energy of the last nucleon(s) • Large interaction cross section • Narrow momentum distribution of the fragments in breakup reactions.

Artemis Spyrou, Belfast 2017, 117 Example: 31Ne halo

• Large cross section of 31Ne Coulob excitation • Low angular momentum of valence neutron • Weak binding of last neutron • 31Ne inside the island of inversion @RIKEN

Nakamura et. al. Phys. Rev. Lett. 103 (2009) 262501 Artemis Spyrou, Belfast 2017, 118 2p radioactivity • 2p radioactivity predicted by Goldansky Nucl. Phys. 19 (1960) 482 • Single proton emission suppressed - Simultaneous emission of two protons • Experimentally observed: 45Fe, 19Mg, 48Ni, 54Zn

First observation: 45Fe Pfutzner, et. al. Eur. Phys. J. A 14 (2002) 279 – Submitted May 17 Giovinazzo, et. al. Phys. Rev. Lett. 89 (2002) 102501 – Submitted May 21

44Mn+p

p 2p 45Fe

43Cr+2p

Artemis Spyrou, Belfast 2017, 119 2p radioactivity Interesting detection approach: optical Time Projection Chamber 45Fe @ NSCL

Diproton observation hard to observe due to coulomb barrier

Miernik et. al. Phys. Rev. Lett. 99 (2007) 192501 Artemis Spyrou, Belfast 2017, 120 Di-neutron decay: 16Be

n 1 16Be 15Be+n n2 14Be+2n

n2 n1 16Be 14Be+2n

Spyrou et. al. Phys. Rev. Lett. 108 (2012) 102501 Artemis Spyrou, Belfast 2017, 121 Di-neutron decay: 16Be

4.0 Shell model

3.5 1/2+ 3.0 + + + 2 3/2 ,5/2 2.5 15 Be 16 Be 22Ne 2.0 + gy (MeV) 2 17B 1.5 Ener 1.0 + 16Be 0 MoNA @ MSU 0.5 14Be 2n 0.0 0+ 14Be 15Be 16Be

Spyrou et. al. Phys. Rev. Lett. 108 (2012) 102501 Artemis Spyrou, Belfast 2017, 122 Di-neutron decay: 16Be Sequential 3-body Dineutron

15 Be 16 Be 22Ne E(n1+n2) θ(n1+n2)

17B

16Be

14Be 2n

• First observation of di-neutron decay • Interpretation still under debate § Di-neutron in 16Be? § Initial state: pairing of neutrons in 17B (2n halo)? § Final state interaction?

Spyrou et. al. Phys. Rev. Lett. 108 (2012) 102501 Artemis Spyrou, Belfast 2017, 123 Summary

Proton halos High Z Diproton decay Superheavies Location of drip line

Island of stability

Neutron halos Neutron skins Dineutron decay Structure changes neutrons, N New radioactivity Location of drip line

Artemis Spyrou, Belfast 2017, 124