Photodisintegration Reactions for the Synthesis of the P-Nuclei

PHOTODISINTEGRATION REACTIONS FOR THE SYNTHESIS OF THE P-NUCLEI

Eleni Vagena Bio in a nutshell

2004 - απόφοιτος του τμήματος Φυσικής του Α.Π.Θ

2007 - απόφοιτος μεταπτυχιακού διπλώματος «Ραδιοηλεκτρολογίας» Α.Π.Θ.

2016 - κάτοχος διδακτορικού διπλώματος στη Πυρηνική Φυσική με τίτλο «Μελέτη ιοντιζουσών ακτινοβολιών σε χώρους επιταχυντών» • Διεξαγωγή πειραμάτων με τη μέθοδο της ενεργοποίησης υλικών για τη μελέτη του φάσματος των νετρονίων στο μικτό n-γ πεδίο των ιατρικών επιταχυντών. 2014-2015 – υπότροφος Ι.Κ.Υ- CERN-HERMES για ερευνητική εργασία στην ISOLDE- CERN • Προσομοιώσεις με χρήση του GEANT4 ανιχνευτικών συστημάτων καθώς και νετρονιακές μελέτες στο χώρο του facility. 2016 – επισκέπτης ερευνητής στο LAPP- Annecy, France για συμμετοχή στο πρόγραμμα: • Muon tomography based on MicroMegas detectors 2015-2016 – υπότροφος διακρατικής συμφωνίας μεταξύ Ελλάδας-Σερβίας για διεξαγωγή έρευνας με θέμα (Παν. Novi Sad): • Νετρονιακή μελέτη σε χώρους ιατρικών επιταχυντών 2016-2017 – υποτροφίας ΙΚΥ-Siemens για μεταδιδακτορική έρευνα με θέμα (A.Π.Θ): • Χρήση Ιατρικών Επιταχυντών στη μελέτη Πυρηνικών Αντιδράσεων-εφαρμογή στην Πυρηνική Αστροφυσική. 2011-2016 – Συμμετοχή σε ερευνητικές δραστηριότητες του Εργαστηρίου Πυρηνικής Φυσικής κ Φυσικής Υψηλών Ενεργειών, ΑΠΘ. (π.χ Μετρήσεις Ραδιενέργειας Περιβάλλοντος The Astrophysical Journal Supplement Series,201:26(16pp),2012August Rauscher

90 1 90 1

80 0.9 80 0.9 0.8 0.8 70 70 0.7 0.7 60 0.6 60 0.6 50 0.5 50 0.5

40 0.4 40 0.4 proton number proton number 0.3 g.s. contribution 0.3 g.s. contribution 30 30 0.2 0.2 20 0.1 20 0.1 10 0 10 0 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 neutron number neutron number FigureThe 3. AstrophysicalGround-state contribution Journal SupplementX to stellar (γ Series, n) rates,201:26(16pp),2012August at 1.5 GK. Figure 6. Ground-state contribution X to stellar (α, γ )ratesat1.5GK. Rauscher (A color version of this ﬁgure is available in the online journal.) (A color version of this ﬁgure is available in the online journal.) 90 1 90 1 90 1 80 0.9 90 80 1 0.9 0.9 80 0.8 0.9 0.8 70 0.8 80 70 70 0.7 0.8 0.7 60 0.7 70 60 0.6 0.7 0.6 Why (γ,x) reaction cross-sections are important for nuclear astrophysics? 60 0.6 50 0.5 60 50 0.6 0.5 50 0.5 40 0.4 50 40 0.5 0.4 proton number proton number

0.4 g.s. contribution g.s. contribution 35 neutron deficient isotopes (p-nuclei) are produced through ( 40 γ,n), ( 0.3 γ,p), (γ,a) reactions (T9=2-3 K) 0.3

proton number 0.4 30 g.s. contribution 40 30

0.3 proton number • low isotopic abundances in comparison to s 30 - and r- isotopes (below 1%) 0.2 0.3 0.2g.s. contribution 20 0.2 30 20 0.1 0.2 0.1 • 20 0.1 Abundance information of the p-nuclei is available from chemical analysis of meteoritic data. 10 0 20 10 0.1 0 10 0 20 40 60 80 100 120 140 160 180 0200 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100neutron 120 number140 160 180 200 10 neutron number 0 0 20 40 60 80 100 120 140 160 180 200 neutron number Figure 3. Ground-state contribution X to stellar (γ, n) rates at 1.5 GK. Figure 6. Ground-stateneutron contribution number X to stellar (α, γ )ratesat1.5GK. Figure 4. Ground-state(A color version contribution of this figureX to stellaris available (p, γ )ratesat1.5GK. in the online journal.) (A color version of this figure is available in the online journal.) Why photoactivation experiments in the Lab? Figure 7. Ground-state contribution X to stellar (γ, α)ratesat1.5GK. The Astrophysical Journal Supplement Series,201:26(16pp),2012August (A color version of this figure is available in the online journal.)Rauscher 90 1 (A color version of this figure is available in the online journal.) 90 1 90 90 1 1 90 1 80 0.9 80 0.9 80 0.9 0.9 0.9 80 0.8 As for the 80 dependence of the rates on certain widths, a few 0.8 70 0.8 0.8 cases can be distinguished regarding the ratio of widths in0.8 70 70 70 0.7 70 0.7 0.7 Equation (8). 60 0.7 0.7 60 60 0.6 60 0.6 60 0.6 0.6 1. The fraction foremost depends on the smallest width ap- 0.6 50 0.5 F 50 0.5 50 50 0.5 0.5 pearing 50 in the numerator when the value of the denominator 0.5 0.4 0.4 40 0.4 is dominated by the larger width in the numerator. This is

proton number 0.4 40 40 0.4 g.s. contribution 40

proton number proton number 40

frequentlyproton number the case as the denominator contains the sum of

g.s. contribution g.s. contribution 0.3 proton number g.s. contribution 0.3 30 0.3 0.3 g.s. contribution all channels including the ones appearing in the numerator. 0.3 30 30 30 0.2 30 0.2 0.2 In this case the denominator cancels with the larger width 20 0.2 0.2 20 20 0.1 and the 20 smaller width remains. Its energy dependence then 0.1 20 0.1 0.1 0.1 10 0 determines the energy dependence of the cross-section. The 10 0 10 10 0 20 40 60 80 100 120 140 160 180 0 0200 rate and 10 cross-section will then be completely insensitive to0 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100neutron 120 number140 160 180 200 changes in the larger width (as long as it does not become neutron number neutronneutron number number neutron number Figure 4. Ground-state contribution X to stellar (p, γ )ratesat1.5GK. comparable to or smaller than the other width in the numer- Figure 3. Ground-state contribution X to stellar (γ, n) rates at 1.5 GK. Figure 6. Ground-state contribution X to stellar (α, γ )ratesat1.5GK. Figure 7. Ground-state contribution X to stellar (γ, α)ratesat1.5GK. Figure 5. Ground-state(A color version contribution of this figureX to stellaris available (γ, p) in rates the onlineat 1.5 GK. journal.) ator) and any change in the smaller width will transfer fully (A color version of( thisγ figure, n) is available in the online journal.) (A color(A color version version of this of figurethis(γ figure is, availablep) is available in the in online the online journal.) journal.) to the cross-section(A color version and of this rate.( figureγ, isa available) in the online journal.) 90 1 90 1 2. When the denominator is not dominated by either of the two comparatively 90 narrow as it depends on the width of the1 Gamow 0.9 widths appearing in the numerator, it is irrelevant whether • For γ-induced reaction the 0.9 g.s contribution is almost zero 80 As for the dependence of the rates on certain widths, a few 80 peak at the given temperature and the effective cross-section is they are equal or of different magnitudes. The cross-section 80 0.9 0.8 casesT. Rauscher, can be distinguishedApJSS regarding201 the ratio(2012) 26 of widths in • Larger contribution from excited states in the stellar plasma (T 0.8 integrated over 70 this range. It is even narrower for neutron=1.5) chan- and rate will be sensitive to a change in any of the widths, 70 0.89 0.7 eitherEquation one in (8 the). numerator and athirdwidthdominatingthe 0.7 nels 70 where the relevant energy range is given by the width of 60 denominator. A change in the denominator, however, will 60 the Maxwell–Boltzmann distribution. 0.7 0.6 1. The fraction foremost depends on the smallest width ap- 0.6 60 F BUT! The knowledge of the cross-section of ( 50 γ,x) reactions gives information for the inverse 0.6 0.5 pearing in the numerator when the value of the denominator 50 0.5 6 is dominated by the larger width in the numerator. This is 50 0.5 0.4 0.4 40 frequently the case as the denominator contains the sum of 40 proton number g.s. contribution

proton number neutron capture reaction by using detailed balance 0.4 g.s. contribution 40 0.3 all channels including the ones appearing in the numerator.

0.3 proton number

30 g.s. contribution 30 0.3 0.2 In this case the denominator cancels with the larger width 0.2 30 20 and the smaller width remains. Its energy dependence then 20 0.2 0.1 0.1 20 determines the energy dependence of the cross-section. The 10 0.1 0 rate and cross-section will then be completely insensitive to 10 0 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 10 0 changes in the larger width (as long as it does not become 0 20 40 60 80 100 neutron120 140 number 160 180 200 neutron number comparable to or smaller than the other width in the numer- Figure 5. Ground-stateneutron number contribution X to stellar (γ, p) rates at 1.5 GK. ator) and any change in the smaller width will transfer fully Figure 4. Ground-state contribution X to stellar (p, γ )ratesat1.5GK. Figure 7. Ground-state(A color contribution version of thisX to figure stellar is (availableγ, α)ratesat1.5GK. in the online journal.) to the cross-section and rate. (A color version of this figure is available in the online journal.) (A color version of this figure is available in the online journal.) 2. When the denominator is not dominated by either of the two 90 1 comparatively narrow as it depends on the width of the Gamow widths appearing in the numerator, it is irrelevant whether they are equal or of different magnitudes. The cross-section 0.9 peak at the given temperature and the effective cross-section is 80 As for theintegrated dependence over this of the range. rates It ison even certain narrower widths, for a neutron few chan- and rate will be sensitive to a change in any of the widths, 0.8 cases can be distinguished regarding the ratio of widths in either one in the numerator and athirdwidthdominatingthe 70 nels where the relevant energy range is given by the width of 0.7 Equation (the8). Maxwell–Boltzmann distribution. denominator. A change in the denominator, however, will 60 0.6 1. The fraction foremost depends on the smallest width ap- F 6 50 0.5 pearing in the numerator when the value of the denominator is dominated by the larger width in the numerator. This is 40 0.4 frequently the case as the denominator contains the sum of proton number 0.3 g.s. contribution all channels including the ones appearing in the numerator. 30 0.2 In this case the denominator cancels with the larger width 20 and the smaller width remains. Its energy dependence then 0.1 determines the energy dependence of the cross-section. The 10 0 rate and cross-section will then be completely insensitive to 0 20 40 60 80 100 120 140 160 180 200 changes in the larger width (as long as it does not become neutron number comparable to or smaller than the other width in the numer- Figure 5. Ground-state contribution X to stellar (γ, p) rates at 1.5 GK. ator) and any change in the smaller width will transfer fully (A color version of this figure is available in the online journal.) to the cross-section and rate. 2. When the denominator is not dominated by either of the two comparatively narrow as it depends on the width of the Gamow widths appearing in the numerator, it is irrelevant whether peak at the given temperature and the effective cross-section is they are equal or of different magnitudes. The cross-section integrated over this range. It is even narrower for neutron chan- and rate will be sensitive to a change in any of the widths, nels where the relevant energy range is given by the width of either one in the numerator and athirdwidthdominatingthe the Maxwell–Boltzmann distribution. denominator. A change in the denominator, however, will

6 Photoactivation experiments

(Ee-<20 MeV) in large-scale facilities

• ELSA electron linac of CEA/DAM in Arpajon, France e.g 85Rb(γ,n), C. Plaisir et al., Eur. Phys. J. A 48 (2012) 68 • ELBE bremsstrahlung facility at FZ Dresden-Rossendorf

e.g 92Mo(γ,n), 144Sm(γ,n), C.Nair et al., J. Phys. G35 (2008) • S-DALINAC superconducting Darmstadt electron linear accelerator Darmstadt High Intensity Photon Setup (DHIPS) e.g 170Yb(γ,n), J. Glorius et al., • TERAS Tsukuba Electron Ring for Acceleration and Storage, National Institute of Advanced Industrial Science and Technology (AIST), Japan e.g 76,78 Se(γ,n) , F. Kitatani et.al., J of Nuclear Sci and Tech 48 (2011) Photoactivation at a medical LINAC ELEKTA SL

Why photoactivation experiments using a medical Linac?

v The derived photon intensity is comparable to widely used photon sources v extremely stable operation

v15 MV Medical e-Linear Accelerator vIrradiated targets vCalibration Set: Au, As, Ir, Mn, Sn, Se, Ni vEr, Dy, Yb Photoactivation at a medical LINAC

Calibration Set Simulated photon spectrum-GEANT4

2.5e+10 ] 1 2.0e+10 − s . 1 −

MeV 1.5e+10 . 2 − cm

1.0e+10

5.0e+09 Photon Flux [ph.

0.0e+00 02468101214 Eγ [MeV] Different materials monitor the photon flux in different energy intervals from the threshold energy Φ(Ε) is calculated with GEANT4 of each reaction used up to the end-point energy of the photon beam. E. Vagena et.al, Rad. Phys. Chem. 120 (2016) 89 New Method for the determination of the experimental (γ,n) reaction cross section

Er p-nuclei 162Er (γ, n)

σeff = 87 (±14) mb E = 9.2-14 MeV

E. Vagena and S. Stoulos, Nuclear Physics A 957 (2017) New Method for the determination of the experimental (γ,n) reaction cross section

Dy nuclei

156 168 Dy (γ, n) σeff =144 (±44) mb Yb (γ, n) σeff = 106 (±26) mb 158 170 Dy (γ, n) σeff = 168 (±42) mb Yb (γ, n) σeff = 117 (±22) mb 160 176 Dy (γ, n) σeff = 152 (±41) mb Yb (γ, n) σeff = 123 (±16) mb

E. Vagena and S.Stoulos Eur. Phys. J. A 957 (2017) E. Vagena and S.Stoulos, Phys. Rev. C (under review) Experimental photo-disintegration cross section of p-nuclei Published data: 162Er, 156,158Dy, 168Yb Data under progress: 74Se, 106,108Cd, 112,114Sn

138La No experimental data for the: 96Ru(γ,n)95Ru 98Ru(γ,n)97Ru 102Pd(γ,n)101Pd 152Gd(γ,n) 151Gd Theoretical photo-disintegration cross section

q Brink-Axel (Standard Lorentzian SLO) (default) (B-A) q Kopecky-Uhl (Generalized Lorentzian GLO) (K-U) q Goriely’s hybrid model (similar with the GLO) (H-F) q Hartree-Fock (H-F-B) q Hartree-Fock-Bogolyubov (Gor)

n Fermi-gas model (T constant) (default) n Back-shifted Fermi- gas model nuclear level densities n Generalized Superfluid model n Hartree-Fock-Bogolyubov + Goriely’s or Hilaire’s combinatorial tables

The difference between these models < 5% The (γ, n) cross section is less sensitive to the nuclear level density [since n channel dominates over p and a channel] The (γ, n) cross-sections were calculated using the default level density

Key quantity: γ-ray strength function Theoretical photo-disintegration cross section even-even Possible explanation for the differences occurring in even-even nuclei: Neutron-to-proton ratio • 58Ni: n/p ≅ 1 -> K-U and Goriely (GLO model) • 112Sn: n/p = 1.3 -> H-F model • 74Se: n/p = 1.3 -> H-F-B model To test the validity of the above assumption the several even-even nuclei are tested.

• 40Ca: n/p = 1-> K-U and Goriely • 56Fe: n/p = 1.1-> K-U and Goriely • 94Mo: n/p = 1.3 -> H-F and/or H-F-B • 82Se: n/p = 1.4 -> almost all models Odd-Even 197Au, 191Ir, 75As, 55Mn • 154Sm: n/p = 1.4 -> almost all models 110 = follow the Brink-Axel SLO model • Pd: n/p 1.4 -> almost all models (Default) Theoretical photo-disintegration cross section for p-nuclei of the RRE (TALYS) TALYS Experiment n/p K-U B-A H-F H-F-B Gor

162 Er (γ,n) σeff = 87 (±14) mb 1.4 89 – 96 – 185 – 128 - 73

156 Dy (γ,n) σeff =144 (±44) mb 1.4 143 – 141 – 191 – 169 - 119

158 Dy (γ,n) σeff = 168 (±42) mb 1.4 146 – 152 – 201 – 178 - 124

168 Yb (γ,n) σeff = 106 (±26) mb 1.4 100 – 109 – 139 – 123 - 83

K-U and B-A γ-ray strength model describes well the heavy Rare Earth Elements (γ,n) reaction in the GDR energy region) Theoretical photo-disintegration cross section (TALYS)

For neutron-deficient isotopes higher cross sections are presented compared 250 to the neutron-rich isotopes with a minimum for even-odd nuclei 167Er

200 (mb)

eff 166 162 Er 162Er 150 Er 164Er 164Er 100 166Er 167Er

Photo-disintegration (γ, n) σ 50 168Er

0 170 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2.58 2.60 Er

A / Z Brink-Axel model Experimental Goriely’s model Hartree-Fock model Theoretical photo-disintegration cross section (TALYS) 180 250 160

200 140 (mb) (mb) eff

eff 120

150 100

80 100 60

40 Photo-disintegration (γ, n) σ

Photo-disintegration (γ, n) σ 50

0 0 2.34 2.36 2.38 2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2.58 2.60 2.62 2.64 2.66 2.68

A / Z A / Z Brink-Axel model Experimental Goriely’s model Hartree-Fock model Brink-Axel model Experimental Goriely’s model Hartree-Fock model For neutron-deficient isotopes higher cross sections are presented compared to the A quite constant cross sections is presented with a minimum for p-nuclei 168Yb neutron-rich isotopes Planned photoactivation experiments (2018-2020) v Average cross-section data of Ce, Gd, Sm, Dy, Er, Yb p-nuclei of (γ,n), (γ,p) reactions v Photoactivation with bremsstarhlung beams up to 25 MeV v Collaboration vLaboratory of Atomic and Nuclear Physics, School of Physics, A.U.Th (Dr. Stylianos Stoulos) vRadiotherapy Department, School of Medicine Larisa, Greece (Dr. Kyriaki Theodorou) v Madison Accelerator Laboratory, Virginia, USA (Dr. Adriana Banu) vELBE Laboratory, Dresden, Germany (Dr. Ronald Beyer, Dr. Arnd Junghans) Rare Earth

p-nuclei Synergies

JMU Madison Accelerator Laboratory, Virginia, USA Photoactivation project at MAL: Determination of Astrophysical Photodisintegration Reaction Rates toward Understanding the Origin of p-Nuclei using a medical e-Linac (proposed NSF Grant). Planned photoactivation experiments at a 15 MeV medical linac-> experimental photon spectrum using the B(γ,γ’) reaction Assoc. Prof. Adriana Banu

Invited Speaker Workshop on Bremsstrahlung Research with a Medical Linac at James Madison University, July 2017, USA. Workshop on Bremsstrahlung Research with a Medical Linac at James Madison University, July 2017, USA. The Astrophysical Journal Supplement Series,201:26(16pp),2012August Rauscher

Table 1 Sensitivities of the Astrophysical Reaction Rates to Variations of Different Widths at 24 Plasma Temperatures r r r r r r r r Element ZA MA Proj. Ejec. sg sn sp sa X ... sg sn sp sa X T 0.1GK T 10.0GK = = ... mo 42 92 ng 0.56 0.35 0.00 0.00 1.000 ... 0.87 0.07 0.02 0.00 1.02 10 1 − × − mo 42 92 np 0.37 0.47 1.00 0.00 1.000 ... 0.01 0.08 0.79 0.01 6.57 10 4 − − − × − mo 42 92 na 0.25 0.31 0.00 1.00 1.000 ... 0.00 0.11 0.15 0.96 6.09 10 5 − − × − mo 42 92 pg 0.00 0.00 1.00 0.00 1.000 ... 1.00 0.06 0.09 0.00 1.56 10 1 − × − mo 42 92 ag 0.00 0.00 0.00 1.00 1.000 ... 0.65 0.49 0.10 0.96 3.86 10 1 − − × − ...

Note. Ground-state contributions to the stellar rate are also given (see the text for details). (This table is available in its entirety in a machine-readable form in the online journal. A portion is shown here for guidance regarding its form and content.)

Table 2 Ground-state Contributions X to the Stellar Rate at 24 Plasma Temperatures for Reactions with Negative Q-values (Except Captures; See the Text for Details)

Element ZA MA Proj. Ejec. XX... XX T 0.1GK T 0.15 GK T 9.0GK T 10.0GK = = = = ... mo 42 92 pn3.73 10 6 3.73 10 6 ... 2.53 10 3 1.39 10 3 × − × − × − × − mo 42 92 pa1.00 100 1.00 100 ... 2.98 10 4 1.09 10 4 × × × − × − mo 42 92 an1.00 100 1.00 100 ... 6.27 10 2 2.63 10 2 × × × − × − mo 42 92 ap1.00 100 9.98 10 1 ... 3.25 10 2 1.17 10 2 × × − × − × − mo 42 93 pn8.72 10 1 8.84 10 1 ... 3.36 10 2 1.53 10 2 × − × − × − × − ...

(This table is available in its entirety in a machine-readable form in the online journal. A portion is shown here for guidance regarding its form and content.)

Table 3 Ground-state Contributions X to the Stellar Rate at 24 Plasma Temperatures for Photodisintegration Reactions (See the Text for Details) EXFOR Library Element ZA MA Ejec. XX... XX T 0.1GK T 0.15 GK T 9.0GK T 10.0GK = =Neutron-induced reactions= = ... 0.4 7 7 4 4 mo 42 92 n 5.93 10− 5.93 10− ... 4.14 10− 3.32 10− × 4 × 4 × 3 × 3 mo 42 92 p 2.03 10− 2.03 10− ... 2.09 10− 1.56 10− 78 79 × × × × mo 42 92 a 1.00 100 1.43 v10 Elements heavier than iron are created by neutron capture1 ... 1.48 10 3 6.36 10 4 0.3 Se(n,γ) Se × × − × − × − mo 42 93 n 3.92 10 2 3.92 10 2 ... 3.13 10 3 2.14 10 3 × − × − × − × − mo 42 93 p 2.15 10 5 2.15 v10 Neutron capture cross sections 5 ... 3.50 10 4 2.69 in the 10 4 keV neutron energy × − × − × − × − ... region are of key importance for the production of isotopes (e.g 0.2

78 68 Cross Section (barns) (This table is available in its entirety in a machine-readable form in the online journal. ASe portion, isZn shown) in massive stars. here for guidance regarding its form and 0.1 content.) (n,γ) photodisintegration cross-section on a target nucleus in the g.s. 90 1 0 does not provide much information on the stellar rate. More- -6 -4 -2 0.9 10 10 10 1 over, it exhibits a different sensitivity to the input as can be seen 80 Incident Energy (MeV) from the tables provided in Section 4.1.2.Toprovideaquick 0.8 70 overview, Figures 2–7 show X at 1.5 GK for captures and photo- 0.7 2 disintegrations involving neutrons, protons, and α-particles. The 1 68 69 60 0.6 Zn(n,γ) Zn g.s. contributions will be smaller at higher temperatures. Values 0.5 of X for (n, γ )closetostabilityats-processtemperatureshave 50 0.5 been discussed in Rauscher et al. (2011). 0.2 0.4 The general behavior of the sensitivities can be understood 40 10-1 proton number g.s. contribution by recalling a few simple facts. First, it has to be noted that 0.3 . 30 5 10-2 in astrophysical applications forward and backward rates are 0.2 in equilibrium at temperatures above 5–6 GK. Above this tem- 2.10-2 20 0.1 perature, individual rates are not important and the attained Cross Section (barns) 10-2 equilibrium abundances are governed by the reciprocity rela- 10 0 5.10-3 tions in Equations (7a)and(7b). The temperature dependence 0 20 40 60 80 100 120 140 160 180 200 neutron number of the sensitivity of a reaction rate to a given width is compar- 2.10-3 atively weak below 5 GK. This is because the relevant energy Figure 2. Ground-state contribution X to stellar (n, γ )ratesat1.5GK. 10-8 10-6 10-4 10-2 1 range covered in the integration for the rate (Equation (3)) is T. Rauscher, (A color versionApJSS of this ﬁgure201 is(2012) 26 available in the online journal.) Incident Energy (MeV) 5 Neutron-induced reactions using medical Linacs

Selected reactions Part of my PhD thesis Average weighted (#15) 190Ir(n,γ)191Ir Exp. neutron spectrum medical Linac neutron flux: 197Au(n,γ)198gAu 5 2 152Sm(n,γ)153Sm Φn=2.50 (±0.16) x10 n/cm /s 75As(n,γ)76As Exp. neutron spectrum: 186W(n,γ)187W • multi-thick foils activation 116Cd(n,γ)117m1Cd technique 170Er(n,γ)171Er 115In(n,γ)116m1In • unfolding the data (Minuit / 55 56 Migrad minimizers) Mn(n,γ) Mn 64Ni(n,γ)65Ni 114Cd(n,γ)115gCd Pros using a medical linac 58Ni(n,p)58Co 67Zn(n,p)67Cu • Limited Energy spectrum-> 74Se(n,γ)75Se expands till the 1 MeV 80Se(n,γ)81mSe neutron energy. E.Vagena, K. Theodorou and S.Stoulos, NIMA, accepted for publication • Make the unfolding E.Vagena, S.Stoulos and M.Manolopoulou,Nuclear Instruments and Methods A procedure easier. 806, pp. 271-278 (2016) Neutron-induced reactions-present work 64Zn(n,γ)63Zn Reactions of Interest: 2 68Zn(n,γ)69mZn 1 0.5 Lack of data EXFOR

0.2 70 71g,m Zn(n,γ) Zn 10-1 Cross Section (barns) 0.2 5.10-2 64Zn(n,γ)63Zn 10-1 Lack of data EXFOR 2.10-2 . -2 5 10 10-6 10-4 10-2 1 Incident Energy (MeV) 2.10-2

10-2 Challenge:

. -3 Cross Section (barns) 5 10 Reduce the uncertainties of the Averaged Cross 70Zn(n,γ)71g,mZn Sections that is required by stellar modelers for 2.10-3 reliable nucleosynthesis calculations (< 10%)

10-6 10-4 10-2 1 Incident Energy (MeV) Synergies

WP1 WP2 WP3 WP4 Astronomical observations Tools, techniques, knowledge Nuclear data for astrophysics: Modelling pipelines and interpretation exchange and innovation needs, coordination and connecting nuclear processes WG3 leader: Andreas Korn WG4 leader: Daniel Bemmerer dissemination to astronomical observables WG1 leader: Alessandra WG2 leader: Georges Meynet Guglielmetti

ChETEC: European Cooperation in Science and Technology Action (COST) Action 2017 - 2021 (CA16117) Muon Tomography project

• cosmic ray muon tomography: access to the density structure of geological targets (e.g volcanoes, tumulus)

The first attempt of muon tomography Discovery of a big void in Khufu’s pyramid for archaeological internal structures by observation of cosmic-ray muons

two muon flux ~ 50 years later.. excesses correspond to the Grand Gallery and the new void.

Khafre’s Pyramid Khufu’s Pyramid L.W.Alvarez et.al, Science 167 (1970) K.Morishima et.al, Nature 552 (2017) 832 Hellenic Muon Tomography –proposed- project (2019-2022)

2018-2019: 2019 – 2022 Campaign in Apollonia Tumulus Proposed Detector Scintillator detectors detector station: 3X1m2 The DIAPHANE muon detectors MICROMEGAS chambers

Group leader: Dr. Jacques Marteau Institut de Physique Nucléaire de Lyon Université de Lyon, France Collaboration A.U.Th Physics Department: Prof. Ch. Petridou, Ass.Prof. D. Samsonidis Geology Department: Prof. G Tsokas

My contribution to the project • GEANT4 Simulations (MM detectors) • Data Collection Scintillator telescope (Diaphane Project) ISOLDE-CERN - GEANT4 in large complex geometries

Issues • Complicated geometries • Several materials • CAD format • Great number of volumes to be designed

CADMesh – Read CAD-type files and import to Geant4-CAD models to be directly loaded as geometry without the need for commercial software GEANT4 simulations

Simulating the optical physics of a single scintillation bar (part of VANDLE detector)

W.A. Peters et al. / Nuclear Instruments and Methods in Physics Research A 836 (2016) 122–133 131

Fig. 18. Small VANDLE module intrinsic efficiency from a 252Cf source with a 31 133 Fig. 19. Image of the VANDLE beta-delayed neutron decay setup from 2012 at keVee threshold measured by the full photo-absorption of Ba decay. The solid HRIBF with 48 VANDLE modules and two HPGe clovers that where removed from line follows the efficiency as calculated by the VANDLE simulation code. Data are their left-right mounts for this picture. The beam comes in from the right to im- the same as the third set in Fig. 15. plantVANDLE on the movable (detect tape in the centerlow of energy the setup, where neutrons): a thin beam pipe highly efficient at the plastic-scintillator array end of the tape drive is surrounded by two thin beta-particle scintillators, used as the induced scintillation light, the VANDLE simulation can accu- theconstructed TOF start for VANDLE.for decay and transfer reaction experimental setups rately model position sensitivity of both the low threshold and that require neutron detection saturation effects of the acquisition without rejecting otherwise isotopes from near 78Ni to around 132Sn. A beta detector sur- good data, increasing our efficiency to low-energy neutrons. The rounded the implantation point and provided the “start” time for resulting efficiency plots match our data in both high-gain and the neutron TOF. For many of these nuclei it was the first time low-gain modes (see Figs. 13 and 18). Further details will be pre- their beta-delayed neutron energy spectrum had been studied. sented in a comprehensive publication by S. Ilyushkin et al. [41]. Details of this experiment and the analysis of 83,84Ga spectra are included in a recent publication by Madurga et al. [46]. VANDLE has since been used in similar beta-delayed neutron spectroscopy 9. Experimental setups experiments at RIKEN and CARIBU at Argonne National Lab, with small and medium VANDLE modules. VANDLE easily couples to a variety of other auxiliary detectors enabling a range of experiments involving neutron detection. 9.2. Reaction experiments (α,n) and (d,n) Current efforts include beta-delayed neutron spectroscopy, and neutron-ejecting reaction experiments like (α,n) and proton Proton transfer in inverse kinematics on radioactive nuclei can transfer (d,n) experiments. Future plans involve additional reac- probe the single-particle structure of nuclei. Spectroscopic in- tion ((d,n) and (α,n)) and beta-decay spectroscopy experiments at formation can be extracted such as level energies, orbital angular various laboratories as well as studying neutron correlations with momentum transfer, and spectroscopic factors. Knowing these fission fragments. properties for nuclei near closed shells can be important bench marks, analogous to the goals of (d,p) neutron transfer experi- 9.1. Beta-delayed neutron spectroscopy ments [47]. Such proton transfer experiments can also inform the nucleosynthesis proton-capture reaction rates for select nuclei For nuclei approaching the neutron dripline, the energy re- where the single-proton spectroscopic factors can be used to de- leased in beta decay increases as the neutron separation energy termine the resonance widths. VANDLE was used for (d,n) ex- decreases leading to the emission of a neutron. While the neutron periments, whose analyses are ongoing, at the National Super- branching ratio can sometimes be determined directly using 3He conducting Cyclotron Facility at Michigan State University, and at neutron counters [42] or indirectly by identifying γ rays from the the Nuclear Science Lab at the University of Notre Dame. decay chain of these (A-1) daughters [43], more information about VANDLE is also suited for measuring (α,n) cross sections on the Gamow–Teller strength distribution can be extracted by also select nuclei that, in addition to being important for astrophysical measuring the neutron energy spectrum. This extra information reactions, are of interest to the nuclear safeguard community. For fl can be used to compare with and guide models for predicting the example, uranium-hexa uoride (UF6) is used in many parts of the half-lives and neutron emission branching ratios of neutron-rich uranium fuel cycle and one technique used by nonproliferation isotopes beyond the reach of current production methods. These agencies to monitor and account for 235U-enriched material con- half lives play an important role in determining the final abun- sists of measuring gross neutron rates induced by uranium-decay dance pattern from the r process and can even help to pin down alpha particles reacting with the fluorine and emitting a neutrons. the stellar environment that induces it [44,45]. The 19F(α,n)22Na cross section is vital for this non-destructive as- Fig. 19 shows an image of a setup using 48 modules in an arch say method. Some (α,n) reactions are also a source of background around an ion-stopping station with room for two high-purity for highly sensitive underground experiments [48]. Neutrons re- germanium (HPGe) clover detectors. This setup was used in a leased by (α,n) reactions with equipment or the surrounding commissioning experiment to measure the beta-delayed neutron material can become the dominant source of unknown back- spectra from short-lived fission fragments. Fission fragments from ground rates. the Holifield Radioactive Ion Beam Facility at Oak Ridge National A challenge for these neutron-ejecting reactions is that an ex- Lab were collected on a moving tape system and the γ-ray and ternal timing signal related to the incoming beam is needed for neutron spectra were recorded following beta decay for over 30 VANDLE to determine the energy of the detected neutrons. Timing GEANT4 simulations - HPGe detector γ-spectroscopy

Experimental determination of the Experimental determination of the photo-peak photo-peak efficiency of the HPGe efficiency of the HPGe 152 1o set of measurements using three γ-ray 2nd set of measurements using a collimated source Eu (40.12, 121.78, 244.69 & 344.27 keV) sources (109Cd (88 keV), 57Co (122 & 136 keV), 54Mn (835 keV)) Geant4 ~ 400 different geometries (!) Geant4 • Geometry details provided Difference (%) between the by the manufacturer experimental and simulated efficiency Difference (%) between the experimental and simulated efficiency

volume Active ~ 10 % < 2% Ge Aluminum cap

Vagena et.al, NIMA, 806 (2016) 271-278 GEANT4 simulations - Medical Linac Flattened-Unflattened beams Challenges • Hadronic model: QGSP_BIC_HP Binary cascade intra nucleus model • Complex accelerator head (up to 10 GeV-high precision for geometry neutron energies <20 MeV) • • Data: ENDF/B-VI & NGATLAS library Lack of information for the metastable isotopes concerning the materials • To increase the neutron production from (γ,n) reactions, I used the cross-section biasing technique. Photons spatial distribution

Neutron Neutron spatial spectrum at distribution the isocenter

Electron spatial distribution

Vagena et.al, Rad. Phys. and Chem., 120 (2016) 89-97 Measurements of radioactivity from the Fukushima reactor accident in Thessaloniki (2011)

04-05 April 2011 131I:480μBqm-3

137Cs:150μBqm-3 134Cs:80μBqm-3 Post-Chernobyl 137Cs in the atmosphere of Thessaloniki: a consequence of the financial crisis in Greece

137Cs was detected during the Jan-Feb 2013

Pattern: higher concentrations during w/k & holidays!

Time variation of 137Cs concentrations measured in the atmosphere of Thessaloniki during the winter of 2013 together with hourly data of precipitation rate. The determination limit for 137Cs concentrations in the atmosphere is 2 mBq m 3 (horizontal line). The vertical lines delimit the weekends and holidays periods. In the lower part the average night-time (19:00-07:00) temperature and wind speed.

S. Stoulos et al., J. of Env. Rad. 128 (2014) Publications 1. E.Vagena and S.Stoulos, “Ytterbium photodisintegration average cross sections data near to (γ, n) reaction threshold”, Phys. Rev. C, under review 2. E.Vagena, K. Theodorou and S.Stoulos, “Thick-foils activation technique for neutron spectrum unfolding with the MINUIT routine-Comparison with GEANT4 simulations, NIMA, accepted for publication 3. E.Vagena and S.Stoulos, “Photodisintegration average cross-sections of dysprosium p-nuclei near (γ,n) reaction threshold” European Physical Journal A 53 (5), 85 (2017) 4. E.Vagena and S.Stoulos, “Average cross section measurement for 162Er(γ,n) reaction compared with theoretical calculations using TALYS”, Nuclear Physics A 957, pp. 259-273 (2017) 5. P. Koseoglou, E.Vagena, S. Stoulos and M. Manolopoulou, “Neutron spectrum determination in a sub- critical assembly using the multi-disc neutron activation technique”, Radiation Effects and Defects in Solids 171 (9-10), pp. 766-774 (2016) 6. E.Vagena, S.Stoulos and M.Manolopoulou, “GEANT4 Simulations on Medical LINAC operation at 18 MV: experimental validation based on activation foils, Radiation Physics and Chemistry 120, pp. 89-97 (2016) 7. E.Vagena, S.Stoulos and M.Manolopoulou, “Analysis of improved neutron activation technique using thick foils for application on medical LINAC environment”, ,Nuclear Instruments and Methods A 806, pp. 271-278 (2016) Publications 8. S. Stoulos, A.Ioannidou, E.Vagena, P.Ko se o g l o u , M.Manolopoulou Post-Chernobyl 137Cs in the atmosphere of Thessaloniki: a consequence of financial crisis in Greece, J. of Env. Rad. 128, pp. 68-74 (2014) 9. A.Ioannidou,..., E.Vagena,...and F.Groppi, “Radionuclides from Fukushima accident in Thessaloniki, Greece (40N) and Milano, Italy (45), J. of Rad. and Nucl. Chem. 299, pp. 855-860 (2014) 10. A.Ioannidou,..., E.Vagena,...and F.Groppi, “An air-mass trajectory study of the transport of radioactivity from Fukushima to Thessaloniki, Greece and Milan, Italy”, Atm. Env. 75, pp. 163-170 (2013) 11. M.Manolopoulou, S.Stoulos, A.Ioannidou, E.Vagena and C.Papastefanou, “Radioecological indexes of fallout measurements from the Fukushima nuclear accident”, Ecological Indicators 25, pp. 197-199 (2013) 12. M.Manolopoulou, M.Fragopoulou, S.Stoulos, E.Vagena, W.Weistmeier and M.Zamani, “Neutron Spectrometry with He-3 proportional counters”, Journal of Physics: Conference Series 366 (1), 012033 (2012) 13. M.Manolopoulou, S.Stoulos, A.Ioannidou, E.Vagena and C.Papastefanou, “Radiation measurements and radioecological aspects of fallout from the Fukushima Nuclear Accident”, J. of Rad.. and Nucl. Chem. 292 (1), pp. 155-159 (2012) 14. O.Masson,..., E.Vagena,... and O.Zhukova, “Tracking of Airborne Radionuclides from the damaged Fukushima Daiichi Nuclear Reactors by European Networks”, “Env. Sc. and Tech. 45 (18), pp. 7670-7677 (2011) 15. M.Manolopoulou, E.Vagena, S.Stoulos, A.Ioannidou, C.Papastefanou, “Radioiodine and radiocesium in Thessaloniki, Northern Greece due to the Fukushima nuclear accident”, J. of Env. Rad. 102 (8), pp. 796-797 (2011)