We would like to thank the reviewer for very helpful comments. We respond to specific issues below. Additionaly we made the following changes to the text: 1) in Table 1 the points for A = 112, 117, 123 were corrected and figure 2 was correspondingly updated. The mode weights were also re-calculated with the corrected data (although with practically the same results); 2) a number of minor grammar and language corrections were made throughout the text (not changing the meaning); 3) a new co-author was added. > Re: CV10344 > Mass yield distributions and fission modes in photofission of 238U > below 20 MeV > by B. S. Ishkhanov, A. A. Kuznetsov, and K. A. Stopani > > PROBLEMS WITH MANUSCRIPT: > > In reviewing the figures of your paper, we note that the following > changes would be needed in order for your figures to conform to the > style of the Physical Review. Please check all figures for the > following problems and make appropriate changes in the text of the > paper itself wherever needed for consistency. > > Figure(s) [1]: > Please check whether the y-axis lable should read > 'Fractional yield...' > > Figure(s) [1]: > Please consider using symbolic references in the artwork (e.g., > 'Jones 2005'); then use the figure captions to map the symbolic > references to actual citations, e.g., '(Jones 2005: [15])'. In > that way you insulate the artwork from changes in the reference > list. > > Figure(s) [all]: > Please begin the text of the figure caption(s) with '(Color > online)'. > > Figure(s) [all]: > Please put units within parentheses and delete commas. Figures and corresponding descriptions fixed. > Table I: > Please rearrange power of 10 as a scale factor, for clarity: > Either (i) place the power of 10 as a factor, without > parentheses, in front of the label quantity, changing the sign > of the power as needed; or (ii) incorporate the power of 10 as a > scale factor in front of the unit. (Please enclose the units in > parentheses.) Column caption corrected. > ---------------------------------------------------------------------- > Report of the Referee -- CV10344/Ishkhanov > ---------------------------------------------------------------------- > > The manuscript "Mass yield distributions and fission modes in > photofission of 238U below 20 MeV" by Ishkhanov et al. discusses the > study of the fission process with bremsstrahlung up to an end point > energy of 67.7 MeV which in term corresponds to an excitation energy > of about 20 MeV. The activation technique was used to determine > fragment yields after prompt neutron emission. Cumulative yields were > calculated based on photo peak yields in gamma ray spectra. > Independent yields are also determined where decay of parent nuclei > were discernible in the spectra. > > From those results the post-neutron emission mass distribution were > constructed. Information on the mode composition of this mass > distribution was then determined by Gaussian distribution fits to the > fractional mass yields. Those results for the fission modes are then > compared with other literature values to deduce dependencies of > fission mode yields as a function of excitation energy and draw some > conclusions. > > The manuscript is well written discusses extensively enough the > determination of the mode contributions and respective literature > values. > > However there are a few minor issues which could be improved. > > 1) On page 2 eq 2 shows the determination of N\textunderscore 0 based > on gamma ray spectra and determination of photopeaks. In lines 95 > onwards a weighted sum was calculated. It would have been nice to give > an idea to the reader how consistent this technique was in either > specifying uncertainties or even better with a figure showing spectra > at different times/ measurements so see the possible variations. Two sample gamma-ray spectra at 1 hour and 3 days after the irradiation are inserted and some peaks from the same decays are marked so that the reader could visually estimate errors. > 2) Since all the results are based on determination of photopeaks from > gamma-ray spectra it would be nice to show also a typical gamma-ray > spectrum to judge its complexity. Although some references are given > which should in principle show the discussion of the experimental > setup and analysis, it would make life easier if such a spectrum > specifically targeted to the experimental condition (fission of 238U) > is added to the manuscript. Some of those references are also not very > commonly available (e.g. Refs. 23, 25). As said in #1, a new figure was inserted. It should be mentioned that the references from the Moscow Univercity Physics Bulletin are available from online libraries: http://link.springer.com/article/10.3103%2FS0027134913040073 http://link.springer.com/article/10.3103%2FS0027134913010049 > 3) Concerning the bremsstrahlung spectrum and the determination of the > average excitation energy of the reaction again several references are > difficult to get (e.g. Refs. 39, 40). Hence to show a typical spectrum > would be handy here, too. A new figure is inserted showing simulated bremsstrahlung spectra at different energies and the evaluated cross section of photofission to illustrate the effect of the beam energy on the excitation energy of fission. > 4) The quality of the mass distribution is also difficult to judge. I > miss a comparison to a mass distribution from literature at similar > end point energies or excitation energies. Based on Fig. 3 there are > data available in literature. Fig. 3 also mixes photofission > experiments and neutron induced fission experiments. Actually in both > cases higher fission chances play a role. This is discussed. However > different experimental techniques lead to different completeness in > the mass distributions. This is not discussed at all, e.g. how missing > of certain masses due to the determination of masses via activation > influences the quality of the deconvolution into fission modes. So the > scatter around 10 to 15 MeV excitation energy in the Peak-to-Valley > determination could be partly attributed to this effect. We also inserted a new figure where our mass distributions are compared to the previusly measured at similar energies. Speaking about the completeness of the mass distributions, a more substantial change was made. Instead of using the author-provided values, we re-analyzed the distributions from the literature in a uniform way and calculated two sets of p/v ratios using the most commonly measured mass numbers. In addition in each case we re-calculated the average excitation energy using GEANT4 in order to eliminate the uncertainty coming from, e.g., the use of the Schiff approximation of bremsstrahlung, etc. As a result a new subfigure was added to Fig. 3 (now Fig. 6) and 3 new tables with the calculated p/v ratios and the average excitation energy. To our knowledge such compilation of photofission data was previously done in [Naik et al., Eur. Phys. J. A 49, 94 (2013)] but in order to get rid of several inconsistencies of their results we prefered to calculate everything in a uniform way. > 5) It is not clear to me why the authors have not included data from > Ref. [15] in their analysis of mode contributions starting on page 7 > lines 236ff. Nevertheless in Fig. 4 contains also data of Ref. 15. The > discussion continued on page 9 lines 259ff taking into account data > from Ref. [15]. Maybe this could be clarified. Ref. [15] contains already calculated mode weights for 235U (n, F), so we did not process their mass distributions in Table 2 (now Table 5), but included the points in the plot. To make this more clear we inserted the following text: "In addition to the data from Table 5 ... we used the data from [15]". > 6) I would also not consider the energy point at 3500MeV in table II > representative for a discussion of disappearing shell effects as the > mean excitation energy is only 50 MeV. Other neutron induced data > (e.g. Zoeller et al., unfortunately never published in a refereed > journal) with E\textunderscore n up to 200 MeV for 238U(n,f) show > still asymmetric mass distributions at this incident neutron energy. > > Information on Zoeller's data (and maybe more) can be found in the > IAEA TECDOC publication on fission yields for transmutation of waste: > > https://www-nds.iaea.org/publications/tecdocs/sti-pub-1286.pdf We included a reference to [Zoeller 1995] in the last paragraph of the discussion.