1. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Compilation and Evaluation of %P n and T 1/2 Data for β-delayed Neutron Emitters Balraj Singh, Michael Birch, Alan Chen McMaster University Pre-CRP North American Workshop on Beta-delayed neutron emission 2-3 May 2013 at JIHIR (ORNL, USA)

2. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Outline Status of available compilations/evaluations Current status of beta-delayed neutron probability measurements Compilation/Evaluation procedures A<72 compilation, evaluation, systematics Examples Future plan for A>72, fission region Conclusions

3. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Status of available compilations/Evaluation – G. Rudstam, K. Aleklett, L. Sihver: ADNDT 53, 1 (1993): evaluation and measurements: Cu-75 to La-150: 93 nuclides : only 31 references cited. – B. Pfeiffer, K.L. Kratz, P. Moller: Prog. Nucl. Energy 41, 39 (2002): compilation Cu-73 to La-150: 129 nuclides. No documentation or source references. -- M.C. Brady: Ph.D. Thesis (Texas A&M, 1989; LA-11534-T): evaluation and calculations: Cu-75 to La-149: 89 nuclides. F.M. Mann, M. Schreiber, R.E. Schenter, T.R. England: Nucl. Sci. Eng. 87, 418 (1984): 72 nuclides T. Izak-Biran, S. Amiel: Nucl. Sci. Eng. 57, 117 (1975): 42 nuclides from As-85 to Cs-146 L. Tomlinson: ADNDT 12, 179 (1973): 41 nuclides (Ga-79 to Cs-146; 5 in non-fission region) P. del Marmol: ADNDT A6, 141 (1969): 30 nuclides (As-85 to Cs-144; 4 in non-fission region) Since 2002, many new measurements in all regions up to A=150 No evaluation for non-fission region A<72 No separation of multiple (P 2n,P 3n )neutron emission ENSDF coverage of these data is non-uniform and in many cases inadequate. NUBASE-12 takes data mostly from ENSDF.

4. B. Singh and M. Birch Status of available measurements For all mass regions: potential beta-delayed neutron precursors for 1n, 2n, 3n decays; and those for which measurements have been reported, based on Q values from 2012-AME 02/05/2013Beta-Delayed Neutron Data Evaluation

5. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Beta-Delayed Neutron Emission in Potential Precursors identified using AME-2012 A≤72 Mass Region: 1n Beta-Delayed Neutron Emission in A≤72 Mass Region: 1n

6. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Potential Precursors identified using AME-2012 Beta-Delayed Neutron Emission in A≤72 Mass Region: 2n

7. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Potential Precursors identified using AME-2012 Beta-Delayed Neutron Emission in A≤72 Mass Region: 3n

8. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Beta-Delayed Neutron Emission in Potential Precursors identified using AME-2012, measurements listed in ENSDF database 72<A≤150 Mass Region: 1n Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 1n

9. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 2n Potential Precursors identified using AME-2012, measurements listed in ENSDF database

10. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Potential Precursors identified using AME-2012 Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 3n

11. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Beta-Delayed Neutron Emission in A > 150 Mass Region: 1n Potential Precursors identified using AME-2012, measurement listed in ENSDF database Tl-210 ? (1961ST20 report)

12. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Beta-Delayed Neutron Precursors Mass RegionPredictedMeasured A < 721n203107 2n12719 3n764 4n391 (B-17) 72 < A < 1501n287133 2n1313 3n280 A > 1501n421 (Tl-210 ?): TID-14880 2n10 3n00

13. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Compilation/Evaluation Policies Compile all experimental data, include – T 1/2, P n, methodology – Method: see NDC(NDS)-0599 p. 47; and 1993Ru01 for details) Neutron-beta coincidences Neutron and beta counting γ- γ, β-γ, β-γ-n Ion counting Comparison with a standard Fission yields New method: recoil fragment, fragment-γ coincidence – Whether neutron spectrum measured – Comments concerning experiment/paper Preferred

14. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Evaluation Policies Not just averaging of all experimental numbers, critical assessment of individual measurements Recommended value is the weighted average of the most reliable measurements; or the most reliable measurement out of a set. Most recent value taken when measurements repeated by a group over time using same method. When an average is taken, the assigned uncertainty is not lower than the lowest experimental uncertainty in the dataset that is being averaged. Full documentation is kept concerning how the evaluated result was obtained, e.g. which results were considered for averaging, and why. Primary versus secondary (grey) literature; latter used with caution, and if possible in consultation with the authors.

15. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Work Done So Far: A ≤ 72 The P 1n (including P 2n, P 3n ) probabilities and/or half-lives have been evaluated for a total of 110 nuclides in the A ≤ 72 mass region; another 63 for half-lives only; total of ~200 papers consulted. McMaster+IAEA+GSI+BNL: M. Birch, B. Singh, D. Abriola, I. Dillmann, A. Sonzogni, E. McCutchan, T. Johnson Systematics: – The Kratz-Herrmann Formula (KHF: ZP 263 (1973) 435) does not make accurate predictions in this mass region – The ratio of P n to T 1/2 shows a better correlation with the Q(β-n) energy window for the decay

16. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation A ≤ 72 Systematics Fit Only data with an uncertainty in P n ≤ 25% used Predictions within one order of magnitude a = 0.0282(53) b = 4.351(81)

17. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Example: 137 I NSR ReferenceHalf-life (s)%P(n)MethodComments 2013Ye026.80(88), 6.88(105), 6.95(76) Low-energy recoil β-delayed γ-rays β singles 2010MaZS~6.9nPreliminary Result 1993Ru01*24.13(12)7.46(30)n, β- 1980ReZQ*7.6(8)Ion countingAlso 1977Re05,P(n)=8.5(9) 1980Lu0424.36.7(4)n, β-Same group as 1993Ru01 1978Kr1524.3(8)6.1(5)fissionAlso 1974Kr21: mixed activity 1975As04*24.8(2)6.1(8)n, β- 1974Gr2924.5(2)nSame group as 1993Ru01, also 1974Ru08, 1976Lu02 1972Sc4824.3(8)6.6(8)fissionAdjusted in 1993Ru01 from 5.2(7). Also 1969ScZY 1971De35*24.7(2)8.6(12)Gamma,Xe-137 1964Ar24243.0(5)n, β-Outlier: Chauvenet’s criterion 1959Pe2824.4(4)fission

18. B. Singh and M. Birch Example: 137 I P(n) : weighted average (LRSW) = 7.29 (33) %, reduced χ 2 =1.0. Uncertainty of 0.30 in 1993Ru01 increased to 0.46 to limit its relative weight to 50%. Recommended values in 1993Ru01: 7.14 (23) %; 2002Pf04: 7.02 (54) % T 1/2 : 24.13(12) s from 1993Ru01 or 24.60(19) s: weighted average (NRM) of 1993Ru01, 1975As04, 1971De35. ENSDF value: 24.5(2) from 1974Gr29. NUBASE-12 value: 24.13(12)s

19. B. Singh and M. Birch Example: 138 I

20. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Example: 64 Mn ReferenceP n (%)MethodComments Hannawald, PhD. Thesis (2000) [2000HaZL] 33(2)n- β counting Possible problem with neutron and β efficiency? PRC 86, 064318 (2012) [2012Pa39] 2.7(6)β-γβ-γLevel-scheme details not available

21. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Other 2000HaZL P n Measurements Only measurements available for most Mn isotopes; remained unpublished in regular literature Due to possible discrepant data for 64 Mn, new measurements should be made for these isotopes T 1/2 and Q β-n Syst. 0.144(29) 0.110(41) 0.38(14) 2.96(66) 1.87(43) 6.0(14) 5.9(14) 16.0(54) 16.1(62) 16.7(76)

22. B. Singh and M. Birch 02/05/2013Beta-Delayed Neutron Data Evaluation Future evaluation plan Checks on first draft of A<72 region. Plans to publish this in NDS by the end of 2013. Compilation/evaluation of A=72-150 region starts next week. Much bigger task than A<72 region Hope to complete first draft by the end of 2014. Checking may take another six months or so. Next step is to think about database development: its contents, design, place, who? Database: contents: experimental data, systematics, theory, literature, etc

23. B. Singh and M. Birch Conclusions We feel that a dedicated evaluation of %B-n data and associated half-lives with full details will be useful. It may provide initiative for new experiments where data are lacking or inadequate. McMaster’s group has completed a first draft of evaluation of A<72 region nuclei. It is being checked by collaborators. Work on A=73-150 region will soon start with estimated first draft in about a year and half. Probably ~300 papers. Will keep track of new measurements, and incorporate these in the evaluation of two mass regions as needed. We will take part in discussions of a suitable database of these data. 02/05/2013Beta-Delayed Neutron Data Evaluation