Triton Emission Research Articles

Determination of Excitation Function of Triton Emission Reaction on Aluminum from Threshold up to 30 MeV via Activation in Diverse Neutron Fields and Unfolding Code Calculations

Aluminum samples, together with sets of 12 flux monitor foils having different reaction thresholds, were irradiated in 6 different deuteron/beryllium neutron fields (Ed = 17.5 to 30 MeV). The shape...

Azimuthal correlations between light particles emitted in 12O induced reactions on 12C and 197Au at 400 MeV

Azimuthal correlations between light particles emitted to polar angles of 40 and 70 degrees with respect to the beam axis were measured for 16O induced reactions on 12C and 197Au at 400 MeV. Coincident light particles are preferentially emitted in a plane which contains the beam axis. For reactions on 12C, coincident light particles are preferentially emitted to opposite sides of the beam axis. These correlations may be understood in terms of the phase constraints imposed by momentum conservation on systems with finite number of nucleons. For reactions on 197Au, on the other hand, preferential emission of coincident deuterons and tritons to the same of the beam axis may be caused by the shadowing of preequilibrium particles by the adjacent cold spectator nuclear matter.

Observation of β-delayed triton emission

11Li β- delayed charged particles have been identified with a ΔE E telescope; β- delayed triton emission is observed with a branching ratio of (0.010±0.04)%.

Reaction mechanisms in 3He projectile breakup at 52MeV on 12C, 28Si and 58Ni

Inclusive proton and deuteron spectra from 3He-induced reactions on 12C, 28Si and 58Ni have been studied. Each spectrum contains a continuum part that may be separated into a broad bump, centred around beam velocity energies at forward angles, and an exponential tail. The properties of each of these components have been investigated as function of outgoing particle, detection angle and target mass. The centroid position of the bump and the bump width are found to be almost independent of target mass and detection angle. The total (energy- and angle-integrated) cross sections for the bump show a mass dependence almost proportional to A 2 3 for both protons and deuterons. The total cross section for the exponential tail has a different mass dependence for protons and deuterons: proportional to A and A 1 3 , respectively. The results for the proton tail are qualitatively reproduced by calculations assuming absorption of the projectile. Charged particle-proton coincidences have been measured and analysed in order to identify the major contributors to the inclusive proton and deuteron spectra at θ = 10°. The following processes have been identified: (i) elastic and inelastic breakup in which the projectile breaks up into two constituents leaving the target in its ground state or an excited state, (ii) absorptive breakup in which one part of the projectile continues virtually undisturbed while the other part is captured, and (iii) a process resulting in the preequilibrium emission of deuterons or tritons followed by the statistical emission from the residual compound system. These three processes account for 75–100% of the inclusive cross section. A semi-empirical model is presented that allows the calculation of the relative coincidence yields from the total inclusive cross sections. The total projectile breakup cross section amounts to about 20% of the total reaction cross section independent of target. A quasi-free breakup model is proposed for the description of the breakup spectra. The model reproduces the data qualitatively very well. The absolute cross sections are not reproduced since the absorption of the spectator is not included. The normalization constant for proton spectator processes are consistently a factor 4 larger than for the corresponding deuteron processes. It is suggested that this is related to the difference in transmission of the peripheral region of the nucleus.

Pre-equilibrium description of fast light particle emission in heavy-ion reactions

Fast light particle emissions in heavy-ion reactions are described as a pre-equilibrium process. Reactions between a “light” heavy-ion projectile and a heavy target are considered in the energy region of the incident energy / the projectile mass ⪅ 10 MeV. Calculations are carried out by an extended exciton model in which the finiteness of the time needed for the fusion process is included. The spectrum shapes of proton, alpha, deuteron and triton emissions are well explained for an example case, 14 N+ 181 Ta at 115 MeV .

Localized l-Window for Partial Fusion Reactions Accompanied by Proton, Deuteron and Triton Emissions

Localized l-Window for Partial Fusion Reactions Accompanied by Proton, Deuteron and Triton Emissions

Localizedlwindow from partial fusion reactions accompanied by proton, deuteron, and triton emission

A high and localized spin population associated with partial fusion reactions has been established through the measurement of $\ensuremath{\gamma}$-ray multiplicity in coincidence with fast forward $p$, $d$, or $t$ produced by 167-MeV $^{14}\mathrm{N}$ on $^{154}\mathrm{Sm}$. The average $\ensuremath{\gamma}$ multiplicities are constant (${M}_{\ensuremath{\gamma}}=31$) for all the yrast transitions up to spin $26\ensuremath{\hbar}$ in $^{158}\mathrm{Er}$, which implies that no spins up to $26\ensuremath{\hbar}$ were populated initially. The deduced average angular momentum transferred is $63\ensuremath{\hbar}$, which is comparable to the critical angular momentum ${l}_{\mathrm{cr}}$ predicted for the fusion of $^{13}\mathrm{C}$ and $^{154}\mathrm{Sm}$. The mass distribution of the residual nuclei is appreciably narrower than that for compound nuclear reactions, and this gives another indication of the narrow $l$ window.NUCLEAR REACTIONS Partial fusion $^{154}\mathrm{Sm}$ [$^{14}\mathrm{N}$, ($p$,$d$, or $t$) $\mathrm{xn}\ensuremath{\gamma}$] $^{156\ensuremath{-}160}\mathrm{Er}$; $E(^{14}\mathrm{N})=167$ MeV; measured $\ensuremath{\gamma}$-ray multiplicity, mass distribution of residual nuclei; deduced localized $l$ window of entrance channel; discussed massive transfer model.

Massive Transfer Accompanying Proton, Deuteron, and Triton Emission in Heavy-Ion Reactions

Fast, forward-peaked protons, deuterons, and tritons observed in the reactions of 135-and 165-MeV $^{14}\mathrm{N}$ ions with $^{152,154}\mathrm{Sm}$ and 166-MeV $^{19}\mathrm{F}$ ions with $^{148}\mathrm{Nd}$ are shown to originate in massive-transfer reactions. These reactions are also demonstrated to have merit as probes of angular momentum space in nuclei at very high spin.

A search for resonances in 9Be + 12C reactions in the energy range from 11.4 MeV to 14.8 MeV (CM)

Excitation curves for 9Be + 12C induced reactions with emission of protons, deuterons, tritons, α-particles and 8Be ions have been measured in the energy range from 11.4 MeV to 14.8 MeV (c.m.). Two strong maxima in the 8Be channel have been found at backward angles but no interchannel correlations were observed indicating the presence of a resonance. Three angular distributions of 8Be were measured in the vicinity of the 12.6 MeV maximum and analysed with a DWBA model.

Triton emission in the interactions of fast neutrons with nuclei

Cross sections have been measured for the formation of tritium in the interactions with Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, Ca, V, Co, As, Y, La, Pr, Tb, Ho and Tl of fast neutrons produced via break-up of 53 MeV deuterons on a Be target ( E n = 11.5–43.5 MeV; I max at 22.5 MeV; FWHM = 15.8 MeV). The activation technique in combination with vacuum extraction and low-level gas phase β − counting of tritium was employed. Furthermore, cross sections were measured for isotopes of the elements Ne, Mg, Ar, Ca, Ti, Cr, Fe, Ni, Zn, Ge, Se, Zr, Mo, Pd, Te, Ba, Pr, Dy, W, Tl and Pb by γ-ray spectroscopic analysis of the radioactive reaction products. A comparison of the two sets of cross sections shows that for nuclei with A > 40 the emission of three single particles (lp2n) is much more probable than the emission of a bound tri-nucleon ( 3H). The cross-section data obtained via tritium counting show that the (n, t) cross sections for the lightest nuclei are exceptionally large, probably due to direct interactions, and the process competes with other modes of de-excitation; for elements with Z > 20, on the other hand, the cross section is low (< 0.25 % of σ n.e.) and practically constant, showing thereby that in the medium and heavy mass regions the probability of emission of a triton is relatively independent of the target nucleus. A comparison of the cross-section systematics at E n = 14.6 MeV and for the neutron spectrum described above is presented; the trends are somewhat similar.

Fast stable particles from light nuclei of emulsion following the interaction of 1.5 GeV/ c K − mesons

From measurements on grey tracks of 1214 light nuclear interaction stars of K − mesons the emission probability for proton, deuteron and triton is found respectively to be: 0.31 −0.03 +0.02, 0.25 −0.03 +0.04, 0.075 −0.009 +0.013. It has been estimated that inelastic scattering of positive pions and Σ + hyperons, and absorption of pions, Σ + hyperons contributes to proton emission in 5.9%, 2.3% and 15.6%, 5.8% of the cases respectively. About 60% of protons are emitted due to the elastic scatterings taking place in the light (CNO) nuclei. It has been concluded that deuteron emission is due mainly to pick-up processes and pion absorption, and that absorption of pions gives rise also to the emission of tritons of energy up to 200 MeV. About 10–15% of tritons with energy exceeding 200 MeV may be expected from the absorption of incident K − mesons on alpha clusters in light nuclei.

Production of energetic he nuclei and tritons in 24 GeV/c proton interactions with Ag and Br nuclei

708 stars withNh⩾7 have been analysed to study the production mechanism of fast He nuclei and tritons. On the basis of the\(\bar D\)-distribution for He nuclei, it has been concluded that the majority of the He nuclei in the momentum range (0.6÷1.5) GeV/c are3He. The frequencies of emission of tritons and He nuclei have been observed to be nearly equal. The shape of the energy spectrum of3He nuclei is similar to the one obtained for tritons. It has been suggested that the pick-up as well as the pion absorption by nuclear α-clusters present near the nuclear surface may be operating in the production of these particles.

24.—The Origin of the Short-range Alpha Particles of Fission

SynopsisThe suggestion is made, and rendered plausible by detailed calculation, that the short-range α-particles of fission, identified by Kugler and Clarke [1], are emitted, in competition with ‘prompt’ γ-rays, from highly excited post-neutron-emission fragments of even neutron number N and, predominantly, of mass number A in the range 140 ≦ A ≧ 145. A similar process is energetically forbidden in relation to triton emission.

Emission of fast helium nuclei and tritons from high-energy nuclear disintegrations

On the basis of the result that from high-energy nuclear disintegration fast helium nuclei and tritons with energies greater than 50 MeV are emitted with equal frequencies, various known mechanisms for the emission of these particles are examined. It is suggested that such emission can also take place through the absorption of mesons in4Heclusters present in the outer region of the nucleus.

Fast helium nuclei emitted from high-energy nuclear disintegrations

Secondary helium nuclei having energies between 80 and 500 MeV emitted from cosmie-ray disintegration have been studied. Mass measurements of these particles indicate that the majority of them are3He. The differential energy spectra of secondary tritons and helium nuclei are found to be identical. The star-size distributions for stars emitting tritons and helium nuclei are also similar. These observations indicate that the mechanism of emission of tritons and helium nuclei is the same.

Emission of fast deuterons and tritons from K--mesons captured at rest in nuclear emulsion and a search for the hypernucleus (Σ-n)

The results of mass measurements on the fast baryons emitted in the capture at rest of 7600 K--mesons are described. The analysis has been restricted to those interactions from which neither charged π-mesons, nor slowΣ-hyperons (kinetic energy ⩽ 60 MeV), nor hyperfragments are emitted. As already reported in a prelious work (see ref. (1)), a substantial number of deuterons and tritons is present among the fast baryons: the proportion of deuterons of kinetic energy exceeding 84 MeV is (11.1±2.5)%, that of tritons is (2.3±1.0)%. Fast deuterons and tritons of ranges greater than 1 cm are emitted from at least (1±0.2)% of K--mesons interactions at rest in nuclear emulsion. Among the fast baryons a number ofΣ-hyperons decaying in flight has been observed and measured: no (Σ-n) hypernucleus has been detected.

On the observation of fast Σ-hyperons emitted from the interactions of K−-mesons with emulsion nuclei

A study of fast baryons emitted from 12 150 K− meson interactions at rest in emulsion has been made in order to determine the nature and extent of K− meson-multinucleon capture processes. Fast Σ hyperons are produced in at least 9 per cent of all interactions while direct fast Λ0 hyperon production is indicated by the presence of 3 protons with energies exceeding 200 MeV. An upper limit of 30% is obtained for multinucleon processes (not producing π mesons) from consideration of π meson emission. The energy spectra for fast Σ hyperons and fast protons are given and mass determinations on a sample of so-called fast protons have revealed about 10% of deuterons and tritons. The suggestion in K− European Collaboration Part II of an apparent infrequency of the reaction K−+n+n→Σ−+n has been confirmed and anα-particle model of K− meson multinucleon interaction has been put forward to explain both this and the emission of deuterons and tritons.

The disintegration of nitrogen by fast neutrons

The disintegration of nitrogen by fast neutrons has been studied using a grid-type ionization chamber filled with nitrogen or a nitrogen-argon mixture. Monoenergetic neutrons for studying the reactions from a neutron energy of 1.3 to 8.2 MeV were produced by the T 3(p, n)He 3 and D(d, n)He 3 reactions. One group of protons, three alpha particle groups, and a group of tritons were observed as disintegration products of the neutron reactions in nitrogen. The N 14(n, p)C 14 reaction leaving C 14 in its ground state was studied from 1.3 to 4.3 MeV and the maximum cross section observed was 230 mb. Four groups of α-particles leading to the ground, 2.14, 4.46, and 5.03 MeV levels in B 11 were observed in the experiment. The cross section for the α-particle group leading to the ground state of B 11 varied from 5 mb at a neutron energy of 1.3 MeV to 390 mb at 4.2 MeV and decreased for higher neutron energies. Triton emission leading to the ground state of C 12 was observed above a neutron energy of 5.6 MeV. Above 7 MeV, the cross sections for disintegration by emission of each of the alpha groups and by triton emission were about equal and were approximately 40 mb. The cross sections show many narrow resonances in the neutron energy range studied. The data show that alpha emission relative to proton and neutron emission from these highly excited states of N 15 is much more probable than expected on shell model considerations.

Spallation-Fission Competition in Heaviest Elements: Triton Production

Stacked foils of ${\mathrm{Au}}^{197}$, ${\mathrm{Th}}^{232}$, and ${\mathrm{U}}^{238}$ were bombarded, in a series of experiments, with 48-Mev helium ions, 24-Mev deuterons, and 32-Mev protons. Tritium from each foil was collected and then measured by a gas-counting technique. The qualitative results indicate that high-energy tritons are emitted in relatively large abundance from all targets and with each of the bombarding particles. Cross sections for triton production from fissionable ${\mathrm{U}}^{238}$ and ${\mathrm{Th}}^{232}$ and from nonfissionable ${\mathrm{Au}}^{197}$ are comparable. The integrated ($\ensuremath{\alpha}, t$) cross sections thus determined for ${\mathrm{U}}^{238}$ and ${\mathrm{Th}}^{232}$ are nearly the same as the integrated cross sections for the "($\ensuremath{\alpha}, p2n$)" reactions as determined by measuring the yield of the product heavy isotopes in radiochemical experiments. All of the facts are consistent with a picture of emission of high-energy tritons (whether due to a stripping, pickup, or other mechanism) in which fissionable intermediate nuclei are formed mainly at levels of excitation below their fission thresholds.