EGAF Status 2015 Richard B Firestone Lawrence Berkeley

EGAF Status 2015 Richard B. Firestone Lawrence Berkeley National Laboratory and the University of California, Berkeley, 94720, USA 21 st Technical Meeting of the NSDD IAEA Headquarters, Vienna, Austria 20 -24 April 2015

Outline 1. Published results 2013 -2015 (9 journal publications) – 23 Na, 39, 40, 41 K, 152, 154 Eu, 156, 158 Gd, 180, 182, 183, 184, 186 W, 237 Np, 241 Am, 242 Pu(n, g) 2. Evaluations in progress – 2 H, 16, 17, 18 O, 54, 56, 57, 58 Fe, 90 Y, 94 Nb, 140 La, 186 Re(n, g) 3. 57 Fe photon strength function a) Primary g-ray strengths b) Secondary g-ray strengths c) Comparison to Porter-Thomas distribution 4. Future plans

Published Results 2013 -2015 23 Na: R. B. Firestone et al, submitted to Phys. Rev. C 89, 014617 (2014) 39, 40, 41 K: R. B. Firestone et al, Phys. Rev. C 87, 024605 (2013) Isotope s 0 (b) Atlas* s 0 (b) This work 23 Na 0. 517(4) 0. 541(3) 39 K 2. 1(2) 2. 28(4) 40 K 30(8) 90(7) 41 K 1. 46(3) 1. 62(3) Eg 42 K(b-) Pg ENSDF Pg This work 1524. 7 0. 1808(9) 0. 164(4) Sn (ke. V) Isotope 24 Na This work AME 6959. 352(18) 6959. 42(4) 40 K 7799. 57(12) 7799. 62(6) 41 K 10095. 243(15) 10095. 37(6) 42 K 7533. 829(10) 7533. 80(11) New Potassium Nuclear Structure Data Isotope 23 Na 40 K 41 K 42 K # levels below Ecrit (RIPL)† 4 15 11 4 # levels below Ecrit (This work) † 13 21 16 17 New Jp assignments 21 3 2 8 New levels placed 0 18 0 0 Previous levels removed 0 1 0 0 New g-rays placed 27 2 0 0 Ecrit is the excitation energy where the level scheme is complete. *Atlas of Neutron Resonances, S. F. Mughab, Elsevier (2006). †

Published Results 2013 -2015 182, 183, 184, 186 W: A. M. Hurst, et al, Phys. Rev. C 89, 014606 (2014). Tungsten Thermal (n, g) Cross Sections Cross section (b) Isotope This work Atlas 182 W(n, g)183 W 20. 5(14) 19. 9(3) 182 W(n, g)183 Wm 0. 177(18) --183 W(n, g)184 W 9. 4(4) 10. 4(2) 183 W(n, g)184 Wm 0. 025(6) --184 W(n, g)185 W 1. 43(10) 1. 7(1) 184 W(n, g)185 Wm 0. 0062(16) --186 W(n, g)187 W 33. 3(6) 38. 1(5)* 186 W(n, g)187 Wm 0. 400(16) --* Based on old ENSDF decay scheme normalization. 187 W b- decay Pg(686 ke. V) This work 0. 352(9) ENSDF 0. 332(5) Tungsten Neutron Separation Energy Sn (ke. V) Isotope This Work AME 183 W 6190. 88(6) 6190. 81(5) 184 W 7411. 11(13) 7411. 66(25) 185 W 5753. 74(5) 5753. 71(30) 187 W 5466. 62(7) 5466. 79(5)

Published Results 2013 -2015 New Tungsten Nuclear Structure Data Isotope 183 W 184 W 185 W 187 W # levels below Ecrit (RIPL) 11 12 8 3 # levels below Ecrit (This work) 12 18 11 40 New Jp assignments 1 1 3 16 New levels placed 0 0 0 1 Previous levels removed 1 1 0 0 New g-rays placed 1 2 2 5 ENSDF This work Jp of -26. 6 e. V 184 W bound resonance ENSDF This work (0, 1)1 -

Published Results 2013 -2015 180 W(n, g): A. Hurst et al, Nucl. Data Sheets 119, 91, 2014 180 W(0. 12% nat) target enriched to 11. 35% Reference s 0 (b) Pomerance (1952) <15 0 Kang (2007) 22. 6± 1. 7 Vorona (200*) 36. 3± 2. 4 This work 24. 7± 0. 8 181 m. W(14. 6 ms) 6. 8± 0. 9 Sn=6686± 5 ke. V Sn=6668. 79± 20 ke. V AME This work

Published Results 2013 -2015 152, 154 Eu: Basunia et al, Nucl. Data Sheets 119, 88 (2014). 155, 157 Gd: Choi et al, Nucl. Sci. Eng. 177, 219 (2014) Isotope Cross section (b) This work Atlas 152 Eu(n, g)153 Eug 7060(400) 5900(200) 152 Eu(n, g)153 Eum 1 2345(220) 3300(200) 152 Eu(n, g)184 Eug+m 1 9405(460) 9200(100) 154 Eu(n, g)155 Eum 335(10) 310(7) 155 Gd(n, g)156 Gd 56, 700(2100) 60, 900(500) 157 Gd(n, g)158 Gd 239, 000(6000) 254, 000(815) The discrepancy in the 153 Eum 1 cross section due to decay scheme normalization.

Published Results 2013 -2015 241 Am: Genreith et al, Nucl. Data Sheets 119, 69 (2014) Sn (tentative) This work AME 5534. 87(15) 5537. 64(10)

Published Results 2013 -2015 237 Np, 242 Pu: Genreith et al, J. Radioanal. Nucl. Chem. 296, 699 (2013). Sn (tentative) Isotope This work AME 238 Np 5039. 0(4) 5033. 9(26) 243 Pu 5490. 44(5) 5488. 32(20)

EGAF Evaluations in Progress 2 H 16, 17, 18 O(n, g) Multiple internal standards

EGAF Evaluations in Progress 16 O(n, g) Reference Jurney (1963) Mc. Donald (1973) Wuest(1977) This work s 0(mb) 0. 178(25) 0. 185(26)* 0. 187(10) 0. 167(3) *Recalibrated to new standard 17 O(n, g) Reference s 0(mb) Lone (1978) 0. 54(6) This work 0. 66(6)

EGAF Evaluations in Progress 18 O(n, g) 2 H(n, g) Reference Seren (1947) Blaser (1971) Ohsaki(2002) Nagai(2007) This work (prompt) This work (Activation) s 0(mb) 0. 22(4) 0. 16(1) 0. 156(16) 0. 153(10) 0. 139(3) 0. 139(5) Sn=3955. 6(26) ke. V (AME) Sn=3963. 18(19) ke. V (This work) Enriched 2 H 17, 18 O data 1. s 0(2 H)=0. 478(18) mb 2. s 0(2 H)=0. 477(17) mb 2 Hnat. O data s 0(2 H)=0. 535(13) mb This discrepancy appears to be repeatable in our measurements and is not yet understood!

EGAF Evaluations in Progress Isotope 90 Y(2 -) 90 Y (7+) 94 Nb(6+) 140 La(3 -) 186 Re(1 -) CS composition s 0(this work) s 0(Atlas) 99. 75%-1 -, 0. 25%-0 - 1. 34± 0. 03 b 1. 28± 0. 02 b 7+ 1. 9± 0. 3 mb 1. 0± 0. 2 mb 85%-4+, 15%-5+ 1. 27± 0. 08 b 1. 15± 0. 05 b 0. 9%-3+, 99. 1% 4+ 8. 5± 0. 4 b 9. 04± 0. 04 b 47. 4%-2+, 52. 6% 3+ 84± 6 b 112± 2 b Lead researcher Abusaleem (Jordan) Turkoghu (Ohio State) Ureche (UC Berkeley) Lerch (US Army)

56 Fe(n, g) A nearly complete (n, g) decay scheme has been constructed from a Budapest cold neutron measurement on a 56 Fe, target enriched to 99. 94%, and gg coincidence data from the Rez Reactor, Prague. 449 g-rays and 99 levels were placed in this work, including 37 new levels, and 38 previous levels not confirmed. Intensity balance through the level scheme is >99% complete. Level scheme intensity balance Reference s 0 (b) Pomerance (1952) 2. 65(8) Shcherbokov (1977) 2. 57(14) This work 2. 71(4)

Low-energy photon strength enhancement in 57 Fe 56 Fe(3 He, ag) Substantial enhancement in the reduced photon strength is seen in 57 Fe below 2 Me. V. E. Tavukcu, et al, Proceedings of the Eleventh International Capture Gamma Ray Symposium, Pruhonice, Prague, Czech Republic, 2– 6 September 2002. Primary g-ray strength fg definition Gg=0. 9 e. V – capture state (CS) width* D 0=22 ke. V – level spacing at CS* Pg – transition probability per decay of CS Eg – g-ray energy *Mughab Atlas

57 Fe primary g-ray strength The 57 Fe primary g-ray strength can be investigated microscopically with these data. Increased strength at low energies appears to be M 1

57 Fe secondary g-ray strength Photon strengths can also be determined for secondary g-rays from levels with known widths. Here we define individual transition strengths fg’=Gg/Eg 2 l+1 ignoring level spacing. Here f’BA=f. BAD 0 M 1 strength greater than E 1 or E 2 strength

57 Fe g-ray strength level energy dependency No significant dependency of the photon strength on level energy is observed. Notice that the strengths vary over two orders of magnitude at each level.

Test of Porter-Thomas photon strength distribution Transition strengths are assumed to follow a P-T distribution (chi square, n=1). Only the 57 Fe E 1 are found to follow P-T.

Summary 1. Evaluation of (n, g) data for 16 isotopes published 2013 -2015. 2. Evaluation of 12 isotopes in progress. 3. 5 Sn measurement found to have large discrepancies wrt AME. 4. 3 decay scheme normalizations found to be discrepant. 5. Inconsistent cross section measurements for 2 H not yet resolved. 6. Low energy photon strength enhancement in 57 Fe ascribed to M 1 transition strength. 7. M 1 and E 2 transition probabilities were found to be inconsistent with Porter-Thomas distribution.

Future EGAF Plans 1. Complete ENSDF format evaluations of (n, g) nuclei a. Thermal (n, g) data sets 1) Pg and sg normalizations 2) Adopted s 0 values plus summary of all measurements 3) Photon strengths 4) Fitted Sn values b. ARC, Resonance data c. Adopted Levels, Gammas 1) All relevant datasets 2) Recommended RIPL data d. (n, g) activation decay data sets 2. (n, n’x) data a. Baghdad (n, n’g) database b. Data from the literature c. New measurements from FRM-II and LBNL d. Pg and sg normalizations e. Adopted Levels, Gammas as discussed above