{"id":"d94099be-ec0f-404c-ab1c-4e0bf900685f","arxiv_id":"2411.13095","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"high","formal_verification":"none","parameter_count":3,"one_line_summary":"A dual-target reaction chain, 48Ca + 249Cf followed by 294Og + p, is calculated to produce element 119 at rates of about one atom every 173 to 1040 days.","lead":"The paper proposes a two-stage scheme to make element 119 by first producing 294Og (element 118) and then letting it collide with hydrogen or other light nuclei. The authors use a nuclear reaction code to estimate that one atom of element 119 could be made every one to two years with a very intense beam.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Unvalidated INCL+ABLA extrapolation to low-energy p+294Og makes the 'indeed feasible' production-rate claim unsupported.","rationale":"The reader's weakest assumption is essentially exactly our concern: the INCL6.33+ABLA model's quantitative predictive power for 10-100 MeV light-ion reactions on 294Og. We confirmed the arithmetic of the production-rate estimate and found that the central fragility is the survival probability of Z=119 evaporation residues against fission. The paper provides no independent benchmark in the superheavy regime, and its own caveat that the cross sections are theoretical and may not reflect actual rates is dropped in the concluding feasibility sentence. No machine-checked proof or reproducible code is supplied. Since the reader's CONDITIONAL verdict already captures the need for benchmark calculations, uncertainty quantification, and reframing of the conclusion, we see no change to the verdict. A factor-of-10 uncertainty in the survival probability alone changes the claimed synthesis time from 520 days to 14 years, which is exactly the kind of sensitivity that makes the feasibility claim load-bearing on the unvalidated model extrapolation.","tokens_in":7805,"tokens_out":12254,"duration_ms":122260,"concrete_test":"Run the same INCL6.33+ABLA calculation for p+208Pb and p+238U at E_p = 10, 12, 16, and 20 MeV, and compare the total nonelastic and fission-evaporation residue cross sections with experimental values from EXFOR. If the model cannot reproduce the measured data within a factor of ~2 in this energy range, then the predicted 10 mb 294Og+p residue cross section should be treated as an unvalidated extrapolation. As an independent cross-check, recompute the 294Og+p evaporation-residue cross section at 16 MeV with a Hauser-Feshbach statistical code using microscopic fission barriers and compare the resulting survival probability with the INCL+ABLA value.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The feasibility statement ('Therefore, the synthesis of element 119 as designed here is indeed feasible') rests on a single quantitative quantity: the INCL6.33+ABLA evaporation-residue cross section for 294Og + p, quoted as ~10 mb at ~16 MeV and used with 2.22e-8 events/s to claim one 119 event every 520 days. That cross section is not anchored by any benchmark. INCL is an intranuclear-cascade model developed for spallation at projectile energies of roughly 100 MeV to several GeV; at proton kinetic energies of 10-16 MeV the underlying picture of successive binary nucleon-nucleon collisions inside the nucleus is not valid, and the code has no established validation in this regime. The survival probability of an excited Z=119 evaporation residue against fission is computed by ABLA using fission widths whose superheavy fission-barrier inputs are themselves extrapolated; a factor of a few in barrier height changes survival by orders of magnitude. A 10x overestimate in the 294Og+p residue cross section turns 'one event per 520 days' into 'one event per 14 years,' i.e. the difference between a plausible experiment and one that is not feasible within a research program. The paper itself concedes 'these cross sections are theoretical and may not directly reflect the actual synthesis rates' but does not quantify the uncertainty, and the concluding sentence ignores that caveat.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper proposes a dual-target scheme for synthesizing element 119: a 48Ca beam produces 294Og via 48Ca + 249Cf, and the freshly produced 294Og is then accelerated in a proposed superconducting linac and directed onto a light target (hydrogen, deuterium, helium, or lithium) for a secondary reaction that would produce Z = 119, 120, or 121. Using the INCL6.33+ABLA models in inverse kinematics, the authors predict a 294Og+p cross section of about 10 mb near 16 MeV for element 119 production, and estimate one 119 isotope every 520 days with a hydrogen target (or roughly 173 days with deuterium) under assumed beam and target parameters. The paper concludes that 'the synthesis of element 119 as designed here is indeed feasible.' The manuscript is a Perspective-style proposal and explicitly labels the cross sections as theoretical in one passage, but the central quantitative claims are not supported by a validated model extrapolation or by a complete, reproducible rate derivation.","tokens_in":7969,"tokens_out":11194,"duration_ms":110450,"significance":"The conceptual idea is interesting and could be significant if the model extrapolation were defensible: it offers a potential alternative to the fusion-evaporation reactions that have failed to reach element 119 for two decades, and it makes concrete, falsifiable predictions for cross sections and rates with several light-ion targets. The paper also has the virtue of explicitly stating that the computed cross sections are theoretical. However, no benchmark against data in the superheavy regime is provided, no uncertainty estimate is given, and the rate calculation is not derived transparently. The proposal's significance therefore remains conditional on addressing these quantitative gaps; as presented, the feasibility claim is not established.","major_comments":[{"comment":"The event-rate formula printed in this paragraph, N_event = N_proj * (1 - exp(-sigma/T_thick)), describes a single reaction step, but the quoted value of 2.22e-8 events/s can only be obtained by folding in the 48Ca + 249Cf production step as well as the 294Og + p step. The manuscript lists the 249Cf target thickness (0.34 mg/cm^2) and the liquid hydrogen thickness (100 mg/cm^2) but never states the 48Ca + 249Cf cross section used, nor writes the two-step expression. As written, the calculation is not reproducible, and the units in sigma/T_thick are inconsistent with the stated definition of T_thick as a number of nuclei per unit area. Please give the full two-step formula and all numerical inputs.","section":"Rate estimate (paragraph after Fig. 3)"},{"comment":"The central claim that synthesis of element 119 'as designed here is indeed feasible' rests entirely on INCL6.33+ABLA cross sections in a regime where the model is not validated. INCL is a spallation-oriented intranuclear-cascade code benchmarked mainly at incident energies of roughly 100 MeV to several GeV, and no benchmark is shown for 10-100 MeV light-ion reactions on a Z=118 nucleus; the ABLA survival probability for Z=119 evaporation residues depends on fission-barrier inputs that are themselves extrapolated. A factor of 10 error in the ~10 mb cross section changes the quoted 520-day period to about 14 years, crossing the boundary between a feasible and an impractical experiment. The paper's own caveat that 'these cross sections are theoretical and may not directly reflect the actual synthesis rates' is not quantified and is effectively absent from the conclusion. Please add a quantitative uncertainty argument or a validation benchmark, and temper the feasibility statement accordingly.","section":"Figs. 2-4 and concluding paragraph"},{"comment":"The feasibility statement assumes that 294Og recoils produced with 0.13 MeV/nucleon in the 249Cf target can be captured and accelerated in a superconducting linac to the roughly 16 MeV/nucleon needed for the secondary reaction. The manuscript gives no discussion of ion extraction, charge-state distribution, charge breeding, transmission efficiency, or losses in this re-acceleration step. These efficiency factors multiply the overall rate and are likely to be substantial; without a quantitative estimate, the statement that the scheme is feasible 'as designed here' is unsupported. Please provide at least an order-of-magnitude analysis of the re-acceleration stage.","section":"Superconducting linac and recoil re-acceleration paragraph"}],"minor_comments":[{"comment":"The text for Fig. 2 states that the production probability decreases with increasing beam energy, while the text for Fig. 3 states that the total cross section peaks near 16 MeV and declines at higher energies. Please clarify in the text that these are different quantities (probability per reaction versus absolute cross section) so that the apparent tension is resolved.","section":"Figs. 2 and 3"},{"comment":"The sentence 'This density is derived from dividing the target’s molar mass by the number of target nuclei per unit area' is not correct as phrased; the areal number density is obtained by dividing the target thickness in mass per area by the atomic mass. Please rephrase to avoid the impression that the density and the number of nuclei are divided instead of related.","section":"Rate formula definition"},{"comment":"Reference [22] is cited with a 2014 year in the text but the journal volume listed corresponds to 2024; please correct the bibliographic data. Reference [36], used for the 48Ca beam intensity, is a web news source; please provide a primary technical reference or a detailed statement of the beam parameters and their provenance.","section":"References [22] and [36]"},{"comment":"The statement that INCL++6.33 'now also supports the generation of superheavy elements up to element 119 and beyond' is a code-capability claim; it should be accompanied by a reference to a manual, release note, or validation paper so that readers can identify the exact version and its treatment of superheavy remnants.","section":"INCL++6.33 code claim"}],"recommendation":"major_revision","confidential_remarks":"The paper is a Perspective rather than a full experimental or theoretical study, and its main quantitative conclusion is not currently supported. The stress-test concern about the INCL+ABLA extrapolation to low-energy light-ion reactions on 294Og is borne out by the manuscript, which contains only a passing caveat and no uncertainty analysis. In addition, the rate formula does not match the numerical result, which is a fixable but important technical error. I would encourage the editor to request a revision that includes a transparent two-step rate derivation, uncertainty quantification or a nearest-neighbor benchmark case (e.g., light-ion reactions on actinides), and a careful rephrasing of the feasibility conclusion. The involvement of two co-authors in the development of INCL/ABLA is not itself a conflict, but the paper should state the exact code version and validation status so readers can judge the extrapolation."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The thing to know upfront: this paper proposes a genuinely new experimental scheme for reaching element 119, but its central quantitative claim—that the synthesis is \"indeed feasible\"—rests on an unvalidated extrapolation of INCL+ABLA to low-energy reactions on a superheavy nucleus. The idea is worth taking seriously; the number is not.\n\nWhat's actually new: instead of another hot-fusion projectile-target combination, Zhang et al. propose a two-stage target. 48Ca + 249Cf produces 294Og, and the freshly made 294Og immediately reacts with a hydrogen (or D, He-3, Li) target placed right behind the Cf. Because 294Og's half-life is about 1 ms, a dual-target geometry is the only practical way to use it as a secondary 'beam'. The authors compute 294Og+p, 294Og+d, etc. cross sections with INCL6.33+ABLA, give rate estimates (one 119 event every ~520 days with H, ~173 days with D), and note that He-3 or Li targets might also give elements 120 and 121. That specific scheme is not in the cited literature; the general dual-target and inverse-kinematics ideas are, but not this concrete version. For a speculative perspective, that is a useful contribution.\n\nWhere it gets soft. The cross sections are the load-bearing element, and they are pure extrapolation. INCL is an intranuclear-cascade model developed for spallation, and at 10–16 MeV proton energy on a nucleus as heavy as 294Og one is in a regime where the cascade picture is dubious at best. ABLA's survival probability against fission depends on fission barriers that are themselves extrapolated for Z=119. A factor of a few in the barrier can change the survival probability by orders of magnitude. The authors honestly state, in the discussion of Fig. 3, that \"these cross sections are theoretical and may not directly reflect the actual synthesis rates,\" but they do not propagate that caution into the concluding \"indeed feasible.\" They also assume a 48Ca intensity four times higher than RIKEN's current beam, a 100 mg/cm2 liquid hydrogen target, re-acceleration of 294Og in a 72-m linac, and then note energy loss might halve the rate. Each of these is a serious practical hurdle, not a minor detail.\n\nOn the citation pattern: the overlap with the authors' own code is not circular—the model parameters were fixed on earlier spallation data, so the predicted 294Og+p yields are genuine extrapolations. The references to Chinese news sites for beam intensity and linac specifications are weak but not load-bearing.\n\nWho this is for: anyone thinking about superheavy synthesis strategies will want to know this idea. It deserves a serious referee, because the scheme is concrete and in principle testable. A referee should ask for benchmark calculations at low energies, a sensitivity analysis of the survival probability to fission-barrier inputs, and a more measured feasibility statement. I would bring it to a group meeting, but I would not base a beam-time proposal on it.\n\nRecommendation: send it out for review, but with clear instructions that the authors need to quantify uncertainty and scale back the 'feasible' language unless they can anchor the cross sections to data.","headline":"Novel two-stage dual-target route to element 119, but the central feasibility claim rests on unvalidated INCL+ABLA cross sections; the idea is worth a serious but skeptical look.","tokens_in":8647,"tokens_out":2579,"would_cite":false,"duration_ms":25404,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The paper claims that element 119 can be reached by letting freshly made 294Og strike a hydrogen or deuterium target, at roughly one atom every 520 days (173 days with deuterium), and that the same scheme can reach elements 120 and 121.","keywords":["superheavy elements","element 119","294Og","dual-target technique","INCL model","ABLA model","fusion-evaporation reactions","light-ion induced reactions"],"falsifier":"Measure the evaporation-residue cross section for $\\^{294}$Og + p in inverse kinematics at 10-20 MeV; if the element-119 residue cross section is below about 1 mb rather than the predicted ~10 mb, the 520-day estimate becomes a multi-year-or-worse program. A cheaper check is to run the same INCL6.33+ABLA chain against measured p + $\\^{238}$U and d + $\\^{238}$U evaporation-residue cross sections in the same energy range; a systematic miss by more than a factor of about 5 there would show the superheavy extrapolation is not quantitatively reliable.","tokens_in":7504,"feed_emoji":"⚛️","tokens_out":13532,"duration_ms":117979,"temperature":0.7,"pith_summary":"This paper argues that the next row of the periodic table can be reached without inventing a fundamentally new reaction: start from the already-demonstrated production of $\\^{294}$Og from $\\^{48}$Ca and $\\^{249}$Cf, then let the short-lived $\\^{294}$Og immediately strike a light-nucleus target. Model calculations with the INCL6.33+ABLA codes give about 10 mb for the $\\^{294}$Og + p reaction and about 30 mb for $\\^{294}$Og + d, translating to roughly one atom of element 119 every 520 days with hydrogen or 173 days with deuterium at the assumed high-intensity $\\^{48}$Ca beam. Because $\\^{294}$Og production is already established, the paper frames element 119 synthesis as an engineering problem of timing and beam intensity rather than a new reaction mechanism. With helium or lithium targets the same setup is predicted to produce elements 120 and 121 at somewhat lower cross sections. The paper's central conclusion is that the synthesis of element 119 as designed is indeed feasible.","feed_headline":"A new route to element 119: one atom every 520 days","feed_subtitle":"Dual-target setup: make 294Og from 48Ca + 249Cf, then let it hit hydrogen or deuterium.","key_machinery":"The load-bearing machinery is a two-stage reaction simulation: INCL6.33, an intranuclear cascade model that follows the light projectile's collision with $\\^{294}$Og and produces a hot remnant classified by mass, charge, excitation energy, and angular momentum; followed by ABLA, a deexcitation model that decides whether that remnant evaporates particles, emits gamma rays, breaks up, or fissions. The physical device is the dual-target geometry: $\\^{294}$Og formed in the $\\^{249}$Cf target travels, with the help of a superconducting linear accelerator, to the light-nucleus target within its ~1 ms half-life. Yield estimates come from the INCL+ABLA cross sections inserted into the target-thickness formula $N_{\\mathrm{event}} = N_{\\mathrm{proj}} \\times (1 - e^{-\\sigma/T_{\\mathrm{thick}}})$.","core_discovery":"On the paper's own terms, the synthesis of element 119 is 'indeed feasible' using a dual-target scheme. The first target is $\\^{249}$Cf, which a $\\^{48}$Ca beam converts to $\\^{294}$Og; a light-nucleus layer (hydrogen, deuterium, helium-3, helium-4, lithium-7, or lithium-8) is placed immediately behind so that the ~1 ms half-life $\\^{294}$Og reacts before it decays. INCL6.33+ABLA calculations yield a $\\^{294}$Og + p evaporation-residue cross section peaking around 10 mb near 16 MeV beam energy, and about 30 mb for deuterium, giving an estimated one atom of element 119 every 520 days (hydrogen) or 173 days (deuterium). The paper also finds that lower beam energies favor production of mass-294 and mass-293 isotopes of element 119, while higher energies broaden the isotope distribution and lower the yield, and that helium and lithium targets can reach elements 120 and 121 with cross sections that are lower but not by orders of magnitude.","pith_inferences":["The paper's headline rates assume a continuous beam at 9.25 x 10^13 particles per second and quoted target thicknesses; realistic beam duty cycle, target degradation, and chemical separation would likely lengthen the calendar time beyond the 520-day or 173-day numbers.","The paper notes that 295Og lives about 1000 times longer than 294Og but does not exploit this in the production estimate; a dual-target scheme that could start from a neutron-richer oganesson isotope would presumably yield longer-lived element-119 isotopes.","The predicted cross sections could be checked on cheaper surrogate systems before a full superheavy run: applying the same INCL+ABLA chain to proton- and deuteron-induced evaporation-residue reactions on the heaviest available actinide targets at 10-20 MeV would either support or undermine the superheavy extrapolation."],"forward_implications":["Element 119 can be produced in a two-step, dual-target reaction without changing the proven first step, 48Ca + 249Cf producing 294Og.","With a hydrogen target the predicted production rate is about one atom of element 119 every 520 days; switching to deuterium shortens the estimate to about 173 days.","The same setup with helium-3, helium-4, lithium-7, or lithium-8 targets is predicted to produce elements 120 and 121, with cross sections lower but not by orders of magnitude.","The most favorable beam energies give fairly pure production of element 119 with mass 294 or 293; higher energies produce a broader isotope distribution and lower total yield.","Energy loss of the 294Og projectile inside the light target could roughly halve the average reaction rate, doubling the time to one atom."],"supporting_citations":[{"why":"Reports the experimental production of 294Og via 48Ca + 249Cf at 0.13 MeV/nucleon, the starting point of the dual-target design.","marker":"[33]"},{"why":"Introduces the two-step cascade-plus-deexcitation picture on which the INCL+ABLA calculation is built.","marker":"[23]"},{"why":"Documents the INCL model's nucleon potentials and collision dynamics used in the cascade stage.","marker":"[25]"},{"why":"Validates the INCL model version used here against light-ion and spallation reaction data.","marker":"[26]"},{"why":"Presents the ABLA deexcitation model implementation used in the INCL+ABLA chain.","marker":"[31]"},{"why":"Defines the ABLA model parameters, including fission-width and evaporation treatments.","marker":"[32]"},{"why":"Supplies the event-count formula used to convert cross sections into expected production rates.","marker":"[35]"},{"why":"Provides the assumed high-intensity 48Ca beam rate used in the yield estimate.","marker":"[36]"},{"why":"Gives the 249Cf target thickness used in the dual-target yield calculation.","marker":"[37]"}],"fun_headline_variants":["Dual-target trick: 294Og + proton yields element 119 every 520 days","Deuterium target: element 119 every 173 days, H every 520","Two-step fusion to 119: 48Ca + 249Cf, then H or D for the final push","Hydrogen layer after 249Cf enables element 119, maybe 120 and 121","New synthesis path: 294Og + p, d, or He opens 119–121"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The whole feasibility estimate rests on the INCL+ABLA computer model, calibrated on lighter nuclei and spallation reactions, remaining quantitatively accurate for 10-20 MeV proton and deuteron collisions with the superheavy nucleus $\\^{294}$Og, especially for the chance that the element-119 remnant survives fission instead of breaking apart.","fun_headline_variants_meta":{"raw":{"variants":["Dual-target trick: 294Og + proton yields element 119 every 520 days","Deuterium target: element 119 every 173 days, H every 520","Two-step fusion to 119: 48Ca + 249Cf, then H or D for the final push","Hydrogen layer after 249Cf enables element 119, maybe 120 and 121","New synthesis path: 294Og + p, d, or He opens 119–121"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.002238,"raw_usage":{"total_tokens":8689,"prompt_tokens":1018,"completion_tokens":7671,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":634,"completion_tokens_details":{"reasoning_tokens":7550}},"tokens_in":634,"tokens_out":7671,"duration_ms":50473,"temperature":1.0,"reasoning_tokens":7550,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T16:50:55.161238+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the evaporation-residue cross section for $\\^{294}$Og + p in inverse kinematics at 10-20 MeV; if the element-119 residue cross section is below about 1 mb rather than the predicted ~10 mb, the 520-day estimate becomes a multi-year-or-worse program. A cheaper check is to run the same INCL6.33+ABLA chain against measured p + $\\^{238}$U and d + $\\^{238}$U evaporation-residue cross sections in the same energy range; a systematic miss by more than a factor of about 5 there would show the superheavy extrapolation is not quantitatively reliable.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports the experimental production of 294Og via 48Ca + 249Cf at 0.13 MeV/nucleon, the starting point of the dual-target design."},{"cited_title":"Boudard, J","cited_arxiv_id":null,"evidence_quote":"Documents the INCL model's nucleon potentials and collision dynamics used in the cascade stage."},{"cited_title":"Mancusi, A","cited_arxiv_id":null,"evidence_quote":"Validates the INCL model version used here against light-ion and spallation reaction data."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Presents the ABLA deexcitation model implementation used in the INCL+ABLA chain."},{"cited_title":"Keli´ c, M","cited_arxiv_id":null,"evidence_quote":"Defines the ABLA model parameters, including fission-width and evaporation treatments."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the event-count formula used to convert cross sections into expected production rates."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the 249Cf target thickness used in the dual-target yield calculation."}],"review_version":1}