Triton Beam Research Articles

Charge-exchange reactions with a secondary triton beam

A secondary triton beam from fragmentation of 560-MeV alpha-particles has been used in a high-resolution (t,He-3) charge-exchange experiment at intermediate bombarding energies. The experiment was carried out at the National Superconducting Cyclotron Laboratory using a He-4 beam from the K1200 cyclotron. The radioactive triton beam of (0.5-1.0)x 10(6) particles/s with a mean energy of 350 MeV was produced in a production target of the A1200 fragment separator and transported to the target position of the S800 magnetic spectrometer. Ray-tracing and dispersion matching techniques were employed to detect He-3 particles from the C-12(t,He-3)B-12 reaction near 0 degrees. An energy resolution of Delta E approximate to 160 keV or Delta E/E approximate to 4.6 x 10(-4) (FWHM) was achieved. This is an improvement over our previous results and opens the possibility for studying high-resolution (n,p)-type reactions at intermediate bombarding energies. (C) 1999 Elsevier Science B.V. All rights reserved.

Gamow-Teller strengths from (t,3He) charge-exchange reactions on light nuclei

Zero-degree cross sections have been measured for (t, 3 He) reactions on the light target nuclei 9 Be, 10 B, 11 B, 12 C, and 13 C at a bombarding energy of 127 MeV/A. The triton beam was produced by ( 4 He,t+p) breakup on a Be production target using a 4 He beam of 155 MeV/A. Dispersion matching was applied to obtain good energy resolution ( Δ E/E=0.002, Δ E=780 keV). The zero-degree (t, 3 He) cross sections are used to discuss Gamow-Teller strengths in 10 Be and 11 Be.

(t, 3He) Reaction; New tool for studying spin-isospin excitations in neutron rich nuclei

Initial experiments were carried out to study spin-isospin transitions in nuclei using (t, 3He) measurements. A triton beam was produced from the breakup reaction ( 4He,t-p) on a 9.25 g/cm 2 Be production target using a 4He beam of 620 MeV. With a beam of 70 enA a yield of 381 MeV tritons with 4.5 × 10 6 particles/s was achieved. The first half of the A1200 beam transport system at NSCL was used to analyze the triton beam. The energy spread at the target position was estimated to be about 23 MeV. The second half of the A1200 was used to analyze the energy of 3He particles from the (t, 3He) reaction. The dispersion matching method was applied to obtain good energy resolution despite the significant energy spread of the incident tritons. The achromatic properties of the A1200 system made it possible to obtain high-resolution (t, 3He) spectra at θ = 0° with a resolution of ΔE E = 0.002 ( ΔE = 780 keV).

Low Energy Triton Beams for Astrophysical Studies — Requirements for the Tritium Systems of the Accelerator

Opportunities for a triton induced nucleosynthesis program using low energy (0-500 keV) beams from dedicated small accelerators are presented. The program is necessary because the role of tritons in the process of light elements primordial nucleosynthesis, via 4 He(t,γ) 7 Li, 7 Li(t, n) 9 Be and 9 Be(t,n) 11 B reactions, is an important discriminator for the two essential models of the Universe formation: standard (homogeneous) Big Bang model (SM) and inhomogeneous Big Bang model (IM). Some aspects concerning necessary experimental conditions - intense triton beams with high energy resolution, stability and reproducibility are briefly discussed. Accelerating intense triton beams imposes severe safety regulations. The intention to use for such a program the electrostatic accelerator, based on rotating disks-DISKTRON D400-4HVG, of the Bucharest Cyclotron Laboratory is presented. Technical requirements for the tritium systems of the accelerator are discussed in two variants: non-intense ( lμA on the target) triton beams (tritium inventory up to 11 kCi).

(sd)2 states in 12Be.

The $^{10}\mathrm{Be}$(t,p${)}^{12}$Be reaction has been studied with 15- and 17-MeV triton beams. At 17 MeV, angular distributions were measured for five low-lying states, and disorted-wave Born-approximation calculations were used to analyze the data. Contributions from $^{10}\mathrm{Be}$(g.s.)\ensuremath{\bigotimes}(sd${)}^{2}$ and complete 1p-shell wave functions were investigated. Comparsion is made with (sd${)}^{2}$ states in $^{14}\mathrm{C}$ and $^{16}\mathrm{C}$.

Two-quasiproton configurations in dysprosium-164

The two-quasiproton structure of 164Dy has been investigated in a study of the 165Ho(t, α) 164Dy reaction. The experiment was performed using a 37.3 MeV triton beam delivered by the Daresbury tandem Van de Graaff accelerator. Magnetic analysis of ejectile ions was achieved using a QMG/2 magnetic spectrometer, and ion identification and detection employed a hybrid gas-filled, multielement, focal-plane detector. The two-quasiproton strengths accessed in this reaction are discussed with reference to the detailed spectroscopy of 164Dy. In particular, a rotational band built on a K π = 1 + state, previously interpreted as a collective structure, was observed and assigned as a two-quasiproton excitation which at zero deformation is based on the spherical ( h 11 2 ) 2 shell-model state. The structure of the octupole-vibrational band and that of other states in the final nucleus have been elucidated.

Measurements on the mobility of Ions and Ionic clusters in gases using24mNa+ as 20 msec tracer

Mobilities of sodium ions and their clusters in gases have been measured by gamma-ray spectrometry using the 20 ms isomeric state of24Na as tracer. This isomer is obtained through the decay of24Ne which was produced by bombarding22Ne with a 7 MeV triton beam.

Two-quasiproton structures in ytterbium-174

The two-quasiproton structure of 174Yb has been investigated in a study of the 175Lu(t,α) 174Yb reaction. The reaction was performed using a 35.5 MeV triton beam delivered by the Daresbury tandem Van de Graaff accelerator. Magnetic analysis of ejectile ions was achieved using a QMG 2 magnetic spectrometer and ion identification and detection employed a hybrid gas-filled, multielement, focal plane detector. Elements of the detailed nuclear structure of 174Yb are discussed in terms of the two-quasiproton configurations populated. Of particular interest is a low-lying K π = 3 + band, observed in this reaction and discussed in terms of hexadecapole collectivity. No K π = 1 + bands were observed, and the consequences of this for a microscopic description of the magnetic-dipole-strength distribution in 174Yb are discussed.

Nuclear structure of 159Tb, 161Tb and 163Tb studied with the (t, α) reaction

The 160Dy(t, α) 159Tb, 162Dy(t, α) 161Tb, and 164Dy(t, α) 163Tb reactions have been studied using a 17 MeV triton beam from the McMaster University Tandem Accelerator. The α-spectra were analyzed with a magnetic spectrograph and the resolution obtained in the best spectra was 16–19 keV FWHM (full-width half maximum). Transferred l-values were determined by comparing the measured angular distributions with distorted-wave Born-approximation predictions. The results were interpreted in terms of the Nilsson model with pairing and Coriolis-mixing effects included. Prior to these experiments the only information available on excited states of 163Tb was from an unpublished (d, 3He) experiment. Now several rotational bands based on single-proton Nilsson states have been assigned. The 3 2 +[411] , 1 2 +[411] , 5 2 −[532] , 7 2 −[532] , 5 2 +[413], 1 2 +[420] and 3 2 −[541] bands have been observed.

Differential flux and spectrum calculations for a novel high-intensity 14-MeV cutoff neutron source based on the1H(t,n)3He source reaction

Flux and spectrum calculations for a novel high-intensity, high-energy neutron source recently proposed for fusion materials testing are presented. The usefulness of the source, whose technical feasibility has been demonstrated in a separate journal paper, depends not only on the possibility to produce high neutron fluxes in large test volumes, but also on the possibility of reasonably tailoring fluxes, flux gradients and neutron spectra to irradiation conditions in future fusion reactors. To meet the needs for fusion materials testing, a source concept has been proposed that involves two intense triton beams incident on two separate water-jet targets in facing geometry for irradiation of a common test cell. Small variations of the relative orientation angle, the distance of the two target centres from their common vertex, and the diameter of the incident triton beams, provide good opportunity to modify spatial and spectral neutron distributions in the test cell according to materials testing needs. Calculated flux contours and spatial neutron spectra are presented for a limited range of orientation angles, of distances of the beam centres from the vertex, and of triton beam diameters. Results for the differential flux contours, flux-dependent volumes, and space-dependent neutron spectra are given, and their advantages for special materials testing conditions are discussed.

Proposal for a High-lntensity 14-MeV Cutoff Neutron Source Based on the1H(t,n)1He Source Reaction

AbstractA high-intensity, high-energy neutron source for fusion materials testing is proposed. Utilizing the 1H(t,n)3He neutron source reaction and bombarding a thick (totally absorbing) hydrogen-rich target with an intense beam of 21-MeV tritons provides a powerful continuous-energy-spectrum neutron source. The global spectrum of such a source is almost flat over the energy range from ∼1 to 14 MeV and exhibits a sharp energy cutoff level at 14.6 MeV. To meet near-term needs for fusion materials testing, a source concept is considered that involves multiple linear accelerator modules providing two 250-mA triton beams to bombard two water jet targets that face each other and irradiate the same test volume. Calculations of the source properties from well-established neutron production cross-section data for the 1H(t,n)3He reaction predict a test volume of 4.2 dm3 in which an average flux of ≥1 × 1014 n·cm-2·s-1 is achieved. The relevant properties of this source and the possibility of its realization, well ...

9Be(t,p)11Be and the structure of 11Be.

The $^{9}\mathrm{Be}$(t,p${)}^{11}$Be reaction has been used to populate the low-lying states with a 15-MeV triton beam. Differential cross sections were measured for nine low-lying states and distorted-wave Born-approximation calculations were used to analyze the data. Contributions from p-shell, $^{10}\ensuremath{\bigotimes}$(sd${)}^{1}$, and $^{9}\mathrm{Be}$(g.s.)\ensuremath{\bigotimes}(sd${)}^{2}$ configurations were investigated. The dominant structure is suggested for nearly all states investigated in the present work.

Beam-target fusion in a dense Z-pinch

It is shown that a beam of tritons, whose energy is of the order of 200 keV striking a deuterium plasma can produce fusion energy in excess of their kinetic energy provided the plasma temperature is higher than 2.3.107 (K). In very dense Z-pinches the range of such T-beams is compatible with the length of the pinch. In particular if the pinch becomes m=0 unstable and produces D and T beams in situ one may expect a very large neutron output as a result of beam-plasma interaction.

Acceleration of Tritons in a Cyclotron

At the Physics Department of the Technical University Munich a compact cyclotron is equipped with a sophisticated vacuum system, which allows a very safe handling of tritium gas. The triton beam with a maximum energy of 7.2 MeV and beam currents up to 100 µA is used for radioisotope production mainly for biological and medical research. This system after being approved by the ministry of environment is now in use since several years without major complications.

Stopping powers for MeV tritons in solids

Numerous studies of stopping power have been reported. In these studies, most of the authors used protons or deuterons for their experiments, while the data from tritons are very rare. This study was performed using a tandem Van de Graaff accelerator, and two experimental methods were used for obtaining the triton beams; one was the acceleration method in which the tritons were directly accelerated from an ion source, and the other was the reaction method in which reaction products from 13C(d, t) 12C reaction were used. Several thin metal foils (Al, Ti, Ni, Nb, Ag, Sn, Gd, Ta, Pt, Au, Pb, Bi) were used to obtain the stopping powers for MeV tritons. These data were compared to those of protons; with the assumption that the stopping power depends on the Z (atomic number), but not on the A (mass number) of projectile. This actually means that the stopping power values of protons, deuterons and tritons are equal at the same velocity. The present experiments show consistency with this theoretical assumption within the experimental error of a few percent.

The114Cd(t, p)116Cd reaction at 15 MeV

The reaction 114Cd(t, p)116Cd has been studied with a 15 MeV triton beam. 21 energy levels in 116Cd have been identified up to approximately 3.5 MeV excitation, four of which were previously unreported. Angular distributions were measured and compared with distorted-wave Born-approximation calculations in order to make L transfer (and hence Jpi ) assignments. The assignments to 13 of the states are reported for the first time.

36 MeV triton inelastic scattering and one-nucleon transfer reactions

Differential cross sections have been obtained for inelastic scattering and one nucleon transfers on targets of 28,30Si and 26Mg using a 36 MeV beam of tritons. CCBA and DWBA fits have been applied to these data and the deformation parameters and spectroscopic factors obtained compared to previous measurements and shell model predictions. Comparisons are made of the fits obtained with zero-range, local energy approximation and exact finite range calculations. High energy tritons are shown to be a precise and valuable spectroscopic tool.

Level structures of 61Co via the reaction 59Co(t,p)61Co.

The reaction $^{59}\mathrm{Co}$(t,p${)}^{61}$Co has been investigated with a 15-MeV triton beam. Fifty-eight energy levels of $^{61}\mathrm{Co}$ were identified ranging in energy up to about 5.4 MeV excitation. Angular distributions were measured and compared with distorted-wave Born approximation calculations.

Routine Production of a Triton Beam for an FN Accelerator

The use of triton beams from tritiated titanium inserts in a sputter ion source has become a significant part of the McMaster Nuclear Physics programme. Tritium beams have been run on the McMaster University FN Tandem since 1978 on the basis of one scheduled running period per year accumulating a total of over 4000 hours of running time. Beams of up to one microamp are routinely put on target. Procedures for safe maintenance and operation of such a source have been developed, and techniques for handling up to 40 TBq (about 1000 Ci) of tritium have been approved by the Atomic Energy Control Board.

Se82from theSe80(t,p)Se82reaction

The reaction $^{80}\mathrm{Se}$(t,p)$^{82}\mathrm{Se}$ has been studied with a 15 MeV triton beam. Twenty-four energy levels in $^{82}\mathrm{Se}$ have been identified up to approximately 5.0 MeV excitation, 12 of which were previously unreported. Angular distributions were measured and compared with distorted-wave Born approximation calculations in order to make $L$ (and hence ${J}^{\ensuremath{\pi}}$) assignments.