Nuclear Physics Research at the High Intensity Gamma-ray Source (HIγS) at TUNL

Calvin R. Howell Duke University and Triangle Universities Nuclear Laboratory (TUNL) December 14, 2015 International Meeting on Laser-Driven Radiation Sources for Nuclear Applications Outline • Basic Research • Applications of Photonuclear Reaction Measurements 1. Nuclear Resonance Fluorescence (NRF) 2. Photofission – real-time detection of neutrons – fission product yields

LDRS – Dec. 2015 1 HIγS: Intracavity Compton-back Scattering

How it works

Example: Ee = 500 MeV è γ = 978 λFEL = 400 nm ħω = 3.11 eV

Eγ = 11.9 MeV

LDRS – Dec, 2015 2 High Intensity Gamma-ray Source (HIγS) Most intense Compton γ-ray source in the world

Features that enable basic and applied research • Wide beam energy range: 1 to 100 MeV • Selectable beam energy spread (by collimation) • High beam intensity on target (>106 γ/s @ ΔE/E = 5%) • >95% beam polarization (linear and circular)

1.2 GeV Storage Ring FEL

Energy resolution by collimation

2500 Eγ =2032 keV

1500 ΔEγ =26 keV

Intensity ΔE/E = 1.3%

500

1950 2000 2050

Eγ (keV)

LDRS – Dec, 2015 3 Studies of Strongly Interacting Matter at HIγS

From 2007 Nuclear Science LRP

GDH Sum Rule Compton Scattering 2H nucleon electric and magnetic polarizabilities 3He nucleon spin polarizabilities

Photo-pion Production

Few-nucleon Systems photodisintegration

Nuclear Structure NRF, (γ,γ’), Compton Scattering (γ,n) reactions, photofission

Nuclear Astrophysics (γ,α), (γ,n) reactions

Milestones (2007 LRP): NS6: collective modes in many-body nuclei HP10: ab initio microscopic studies NA4: 16O(γ,α)12C

LDRS – Dec, 2015 4 HIγS Users (2010-2014) US Collaborang Non-US Collaborang Instuons Instuons Total Collaborating Institutions 23 17 40 at HIGS

American Science and Engineering (AS&E) North Carolina Central University, Durham, NC US Collaborating Institutions Argonne Naonal Laboratory, Argonne, IL Pacific Northwest Naonal Laboratory 43% European Space Agency (ESA) PTB, Braunschweig, Germany 57% Rutgers, The State University of New Jersey, Piscataway, Non-US Collaborating Fakultat fur Physik, LMU Munchen, Garching, Germany New Jersey Institutions Fermi Naonal Accelerator Laboratory, Batavia, IL Temple University Frankfurt Instute for Advanced Studies FIAS, Frankfurt, Germany Thomas Jefferson Naonal Accelerator Facility

George Washington University, Washington, DC Universität zu Köln, Köln, Germany GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany University of California Berkeley

Hebrew University of Jerusalem, Israel University of Conneccut, CT

IKP, TU Darmstadt, Darmstadt, Germany University of Illinois, Urbana-Champaign, Illinois

Instut fur Strahlenphysik, Dresden, Germany University of Kentucky, Lexington, Kentucky

James Madison University University of Lund, Lund, Sweden

Japanese Atomic Energy Agency (JAEA) University of Massachuses, Amherst MA

Kayoto University University of New Hampshire, Durham, NH

Lawrence Berkeley Naonal Laboratory University of Notre Dame

Lawrence Livermore Naonal Laboratory University of Saskatchewan

Los Alamos Naonal Laboratory University of Saskatchewan, Saskatoon, SK, Canada

Naonal Aeronaucs and Space Administraon (NASA) University of Virginia, Charloesville, VA

Naonal Ignion Facility (NIF) Weizmann Instute, Israel NSC Kharkov Instute of Physics and Technology, Kharkov, Ukraine WNSL, Yale University, New Haven, CT

LDRS – Dec, 2015 5 HIγS: Topical groups (collaborators with TUNL faculty)

1. Nuclear Structure and Nuclear Astrophysics: (a) Volker Werner, Yale University (b) Deniz Savran, Univ. Frankfurt and GSI (c) Norbert Pietralla, Univ. Darmstadt Nuclear Structure (d) R. Schwengner, Helmholtz-Zentrum Dresden-Rossendorf and (e) Moshe Gai, Univ. Conn. Nuclear Astrophysics (f) Ernst Rehm, ANL (g) Michael Wiescher, Univ. of Notre Dame (h) Steve Yates, Univ. of Kentucky

2. Compton Scattering: Nucleon and Nuclear Polarizabilities (a) J. Feldman, GWU (b) B. Norum and D. Crabb, UVA (c) D. Hornidge, Mt. Allison Univ., Canada (d) R. Miskimen, U. Mass Low-Energy QCD (nonperturbative QCD) 3. Gerasimov-Drell-Hearn (GDH) Sum Rule (a) B. Norum and D. Crabb, UVA (b) R. Pywell, Univ. of Saskatchewan

LDRS – Dec, 2015 6 Measure 12C(α, γ)16O rate at energies important for evolution of massive star Collaboration 1: M.W. Ahmed (NCCU), M. Gai (U. Conn.) and H.R. Weller (Duke) Technique: CO2 gas target (Optical Time Projection Chamber)

Collaboration 2: E. Rehm (ANL), C. Ugalde (ANL) and A.E. Champagne (UNC) Technique: Superheated liquid bubble chamber

The mass of the iron core at the end nuclear energy generation has a critical influence on the fate of a massive star, i.e., M > 15 Mo core mass > 2.0 Mo è black hole lower mass cores explode easier è neutron stars The mass and size of the final iron core is critically dependent on the 12C(α,γ)16O reaction rate

α + α + α → 12C + γ ; production of 12C during helium burning 12C + α → 16O + γ ; converts 12C to 16O è determines 12C/16O

Need to determine the 12C(α,γ)16O cross section 9 Δσ < 10% at Ecm = 300 keV (0.2 x 10 K)

LDRS – Dec, 2015 7 Unambiguous Identification of the Second 2+ in 12C

Faculty: M.W. Ahmed, H.R. Weller Collaborator: M. Gai (Univ. Connecticut)

Unambiguous Identification of the Second 2+ State in 12C and the Structure of the Hoyle State, Phys. Rev. Lett. 110, 152502 (2013)

Technique: CO2 filled Optical Time Project Chamber (OTPC)

LDRS – Dec, 2015 8 Collective Excitations of Nuclei

M1 E1 Xλ ? E1

p n

P,p,n n CrossSection Sn

1 5 10 20 Ex

(γ,γ)‏ (γ,Xn)‏

Pygmy Dipole Resonance Isovector Giant Quadrupole Resonance

NRF Compton scattering

LDRS – Dec, 2015 9 Nuclear Resonance Fluorescence (NRF): Spin and Parity Determination in Even-Mass Nuclei 0+ à 1(+,-) à 0+ 0+ à 2+ à 0+

138 vertical Ba(γ,γ΄) Eγ = 5.40 MeV 138 * 138Ba Ba

Eγ γ f !

LDRS – Dec, 2015 10 Nuclear Resonance Fluorescence (NRF): Spin and Parity Determination in Even-Mass Nuclei Nuclear Resonance Fluorescence (NRF)

138 Ba(γ,γ΄) Eγ = 5.40 MeV

0+ à 1(+,-) à 0+ 0+ à 2+ à 0+

LDRS – Dec, 2015 11

! The Giant M1 Resonance in 90Zr observed Fine Structure of the Giant M1 via inelastic proton scattering, G. Crawley et Resonance in 90Zr, G. Rusev et al., al., Phys. Lett. B 127, 322 (1983). Phys. Rev. Lett. 110, 022503 (2013).

LDRS – Dec, 2015 12 Precise Determination of the Isovector Giant Quadrupole Resonances S.S.Henshaw et al., PRL 107, 222501 (2011). Experiment Setup

Nuclear Equation of State E(ρ, β) = E(ρ, β = 0) + S(ρ)β2 ρ = ρn + ρp; β = (ρn-ρp)/ρ S(ρ) = E(ρ, β = 1) - E(ρ, β = 0)

( 2 + L ρ − ρ Ksym " ρ − ρ % S(ρ) = *S + s + $ s ' -+.... v 3 18 )* ρs # ρs & ,- 1 ∂2E 3 ∂3E 9 ∂4E S = , L = , K = v 8 ∂β 2 8 ∂ρ∂β 2 sym 8 ∂ρ 2∂β 2 ρs,1 ρs,1 ρs,1

LDRS – Dec, 2015 13 Low-energy QCD at HIγS

χEFT

QCD Nuclei

Measure/determine quantities that can be calculated both by Lattice QCD and χEFT • GDH sum rule on the deuteron (spin-dependent cross section) • Electric and magnetic polarizabilities of the nucleons • Spin dependent polarizabilities of the nucleons

• mu/md via polarized photopion production (test of χPT) • Hadronic weak low-energy parameter in EFT (parity violating measurement of photodisintegration of the deuteron)

LDRS – Dec, 2015 14 GDH (Gerasimov-Drell-Hearn) Sum Rule

Relates the helicity dependence of the photoabsorption cross section of a nucleon/nucleus to its static properties, i.e., magnetic moment, mass and spin: provides opportunities to gain insight about the dynamical response of the internal dof of nucleons to EM impulses over a broad frequency band

σP σA N N 2 target ∞ σ −σ ! e $ I P A d 4 2 2S GDH = ∫ ω = π # & κ γ beam 0 ω " M %

Derived by applying dispersive Baldin sum rule: analysis and assuming: N N • Lorentz invariance 1 ∞ σ −σ α + β = P A dω • Gauge invariance E M 2 2 ∫ 0 2 • Crossing symmetry π ω • Rotational invariance • Causality and • Unitarity Forward spin polarizability: N N 1 ∞ σ −σ γ = − P A dω 0 4π 2 ∫ 0 ω 3

LDRS – Dec, 2015 15 Recent accomplishments and plans for GDH on 2H 2H + γ à n + p

dd dd dd dd ∞∞σσ−−ωωπ σσmax σσ − σσ − PAddωω=+ PA PA d ω + PA d ω ∫∫∫ωω22ωω ωπ ω ∫ ω max ω 0.6 µb Measurements Measurements at Calculated at HIγS LEGS, Mainz, ELSA -14 µb

Measurements at HIγS: W. Tornow et al., Phys. Lett. B 574, 8 (2003). M.A. Blackston et al., Phys. Rev. C78, 034003 (2008) M.W. Ahmed et al., Phys. Rev. C77, 044005 (2008)

LDRS – Dec, 2015 16 Recent measurements and plans for GDH on 3He

G. Laskaris et al., Phys. Rev. Lett. 110, 202501 (2013) G. Laskaris et al., Phys. Rev. C, 89 024002 (2014).

3He + γ à n + p + p (3-body channel) Data taken on 2-body channel; analysis underway 3He + γ à p + d

Future: push to higher energies, up to ~50 MeV

LDRS – Dec, 2015 17 Collective responses of internal structure of nucleons

Focus is on Eγ < 500 MeV !c λ = è λ > 0.4 fm Eγ Most sensitive to the nucleon- (virtual pion cloud) DoF

Pion-cloud physics

Pictures from: J. Arrington, arXiv:1208.4047v1[nucle-ex]

LDRS – Dec, 2015 18 Compton Scattering: Nucleon Polarizabilities

Multipole expansion T = E or M

Scalar polarizabilities

Spin-dependent polarizabilities

R. P. Hildebrandt, H.W. Griesshammer, T.R. Hemmert and B. Pasquini, Eur. Phys. J. A 20, 293 (2004).

LDRS – Dec, 2015 19 Compton Scattering: Nucleon Polarizabilities

Provides insights about: • Freq. response of system • Binding energy of charged constituents • Confinement volume of charged constituents

• Δβn causes a significant uncertainty in calc. mn-mp • βp input to Lamb-shift corr. In µH atoms • Collective response of internal spin dof to em pulse

EFT Extractions – HWG, JAMcG, DRP, GF HWG, JAM, DRP, GF, PPNP, 67 (2012) 841-897 PDG - 2013 JAM, DRP, HWG, EJP, A 49 (2013) 12

Expt. goals: • sum-rule independent meas. of βp • reduce Δβn by ~ factor of 2

R. P. Hildebrandt, H.W. Griesshammer, T.R. Hemmert and B. Pasquini, Eur. Phys. J. A 20, 293 (2004).

LDRS – Dec, 2015 20 Measuring spin polarizabilities

Eγ > 110 MeV Beam and target polarization

LDRS – Dec, 2015 21 HIγS: Nuclear Physics Applications

A. National Nuclear Security • Stockpile Stewardship • Nuclear weapons non-proliferation treaty verification B. Homeland Security • Technologies for screening cargo for special nuclear materials • Development of particle detection technologies C. Energy • Nuclear Fusion – Inertial confinement diagnostics (NIF) – gamma-ray detector R&D (LANL group) D. Medicine and contraband detection • γ-ray beam biopsy, i.e., tissue isotopic assay • Isotopic imaging for medical diagnostics

th TUNL50 – Nov. 7, 22 2015 Active Interrogation Systems σ(γ,γ’) data using Nuclear Resonance Fluorescence (NRF)

Iron (35 cm thick) Lead (20 cm thick)

3.0E-04 = 8 MeV

Light nuclei 2.0E-04

Actinides & Heavy nuclei

1.0E-04 Gamma-ray Transmission Gamma-ray

0.0E+00 0.0 2.0 4.0 6.0 8.0 10.0 Gamma-ray Energy (MeV)

Need to identify J=1 states in actinides that can be photoexcited with

2 < Eγ < 4 MeV

LDRS – Dec, 2015 23 The Challenge of finding low-spin states at Ex > 2 MeV in heavy nuclei

LDRS – Dec, 2015 24 Challenge of finding low-spin states at Ex > 2 MeV (non band states)

240Pu

LDRS – Dec, 2015 25 NRF Measurement Strategy

• Use Bremsstrahlung beam to conduct a search for dipole transitions over a broad γ-ray energy range, e.g.

(2 < Eγ < 4 MeV) • Next use monoenergetic γ-ray beam to make high sensitivity measurements at selected energies based on results obtained with bremsstrahlung beams. Use linear polarization to provide information about the multipolarity of the observed γ-ray transitions.

LDRS – Dec, 2015 26 Detector 1 - Run 330, 334 (5 hr 21 min) Good vs. Accidental RF 200 Good RF

Accidental RF 2566 150 25 78 Tl 25 35 2523

100 254 7 208 26 14 .5

25 04 2494 Counts 50 HIγS: NRF on Radioactive materials 0 240 2450 2500 2550 2600 2650 Target: Pu Energy (keV) Eγ = 2.55 MeV,Detector horizontal 1 RF w/ EnergyHPGe Cut detector Above 1850 (5 keVhrs 21 min) 16 00 14 00 Good RF Cut 12 00 Accidental RF Cut T = 180 ns 10 00 800 600

Counts 400 200 0

800 10 00 12 00 14 0 0 16 0 0 18 0 0 20 0 0 2200 2400 2600 Time (AU) Detector 1 - Run 330, 334 (5 hr 21 min) Good vs. Accidental RF 200 Good RF

Accidental RF 2566 150 25 78 Tl 25 35 2523

100 254 7 208 26 14 .5

25 04 2494 Counts 50

0 2450 2500 2550 2600 2650 Energy (keV) Detector 1 RF w/ Energy Cut Above 1850 keV LDRS – Dec, 2015 16 00 27 14 00 Good RF Cut 12 00 Accidental RF Cut 10 00 800 600

Counts 400 200 0

800 10 00 12 00 14 0 0 16 0 0 18 0 0 20 0 0 2200 2400 2600 Time (AU) 240Pu: Determination of Spin and Parity

Runs 330, 334 (5 hr 21 min) - 24 0Pu @ 2.55 MeV Horizontal and Vertical RF Subtracted 350 Horizontal Vertica l 2578 300 25 6 6 Jπ Energy (keV) 1+/- Ex 250

200 2535

150 25 2 3 2547 2504 2+ Counts 42.8

0+ 0.0 100 2492 240Pu

50

0

2450 2500 2550 2600 2650 Energy (keV)

LDRS – Dec, 2015 28 NRF at excitation energies above the particle separation thresholds, e.g., (γ, α), (γ, n), (γ, p)

1+ 2 E ∞ # & # & 2 x 2J +1 π!c Γ0 n I = σ (E)dE = ⋅% ( Γ1 s0 ∫ γ,γ0 % ( % ( Sn 2J +1 E Γ 4+ 0 $ 0 ' $ γ ' Γ3

Γ = Γ0 +∑Γi Because gN ~ x137 α, expect Γ2 γ0 Γ0 Γ3 >> Γ0, Γ1, Γ2 2+

However, there are exceptions 0+ è Isobaric analog states Let thresholds for (γ, α) and (γ, p) be higher than that for (γ, n)

LDRS – Dec, 2015 29 NRF Measurements on Light Nuclei

Energy Targets Isotopes (MeV) 14 35 NH4Cl, NaCl, N, Cl, 1.7 – 3.1 KNO3 37Cl, 39K natMg metal 24Mg 9.4 – 10.7

natC (graphite) 12C 15.1 – 15.3

LDRS – Dec, 2015 30 Concept for material analysis – Polarized Photofission

• Polarized γ-ray induces fission of target nuclei • Prompt neutrons are detected both parallel and perpendicular to the plane of polarization of the incident γ-ray n det.

LDRS – Dec, 2015 31 Setup for photofission measurements

γ-ray beam

LDRS – Dec, 2015 32 Application of concept

No Neutrons Fission Neutrons Fission + (γ,n) Neutrons

238U Neutrons Eγ (MeV)

5.7 6.2 Fission Threshold (γ,n) Threshold

o Typical energy range Eγ = 5.8 - 7.0 MeV o Only other stable isotopes which can produce neutrons at these energies are 2H and 9Be o The neutron energy detection threshold is 1.5 MeV (all neutrons are fission neutrons)

LDRS – Dec, 2015 33 Example of neutron assembly of fissile vs nonfissile nucleus in Polarized Photofission

LDRS – Dec, 2015 34 Measurements of neutron assembly in polarized photofission

Non-fissile

Fissile

Measurement of prompt neutron polarization asymmetries in photofission of 235,238U, 239Pu, and 232Th, J. M. Mueller et al., Phys. Rev. C 85, 014605 (2012).

LDRS – Dec, 2015 35 Example Publications

A novel method to assay special nuclear materials by measuring prompt neutrons from polarized photofission, J. M. Mueller, M.W. Ahmed and H.R. Weller, Nucl. Instrum. Method A 754, 57 (2014). Europium- and Lithium-Doped Yttrium Oxide Nanocrystals that Provide a Linear Emissive Response with X-ray Radiation Exposure, I. N. Stanton, M. D. Belley, G. Nguyen, A. Rodrigues, Y. Li, D. G. Kirsch, T. T. Yoshizumi, and M. J. Therien, Nanoscale 2014, 6, 5284 - 5288.

Dipole response of 238U to polarized photons below the neutron separation energy, S.L. Hammond, A.S. Adekola, , C.T. Angell, H.J. Karwowski, E. Kwan, G. Rusev, A.P. Tonchev, W. Tornow, C.R. Howell, J.H. Kelley, Phys. Rev. C 85, 044302 (2012). Measurement of prompt neutron polarization asymmetries in photofission of 235,238U, 239Pu, and 232Th, J. M. Mueller et al., Phys. Rev. C 85, 014605 (2012). Discrete Deexcitations in 235U below 3 MeV from Nuclear Resonance Fluorescence, E. Kwan, G. Rusev, A.S. Adekola, S.L. Hammond, C.R. Howell, H.J. Karwowski, J.H. Kelley, R.S. Pedroni, R. Raut, A.P. Tonchev and W. Tornow, Phys. Rev. C 83, 041601(R) (2011). Discovery Low-lying E1 and M1 Strengths in 232Th, A.S. Adekola, H.J. Karwowski, C.T. Angell, S.L. Hammond, C.R. Howell, J.H. Kelley, E. Kwan, R. Raut and A.P. Tonchev, Phys. Rev. C 83, 034615 (2011).

LDRS – Dec, 2015 36 Acknowledgement

Materials provided for this presentation by: Mohammad Ahmed, North Carolina Central University and TUNL Werner Tornow and Henry Weller, Duke University and TUNL

Research presented is in part supported by: • Department of Energy, Office of Nuclear Physics • Department of Energy, National Nuclear Security Administration • Department of Homeland Security, Domestic Nuclear Detection Office

LDRS – Dec, 2015 37 LDRS – Dec, 2015 38