G. Ruprecht's research while affiliated with TRIUMF and other places

Publications (94)

Preprint
Full-text available
During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16-O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the 17O(a,n)20Ne reaction. The effic...
Article
Full-text available
During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the 17O(α,n)20Ne reaction. The effici...
Conference Paper
Full-text available
The electron screening effect and its influence on enhanced 2 H(d,p) 3 H reaction cross-section was investigated based on latest metallic (Zr) target data, as well as much older gaseous target data. The enhancement can result not only from the electron screening effect but also from a suggested 0 + resonance state in the 4 He compound nucleus. This...
Article
Full-text available
An in-depth characterization of the TACTIC detector was performed using data from a ¹⁴⁸Gd alpha source and some test runs with a stable ion beam. The detector is an active target time-projection chamber with a blind central region for maximizing beam tolerance and GEM-based electron amplification, equipped with a modern digitizing data acquisition...
Article
Full-text available
The EROI (Energy Returned On Invested) has been calculated for various systems, especially power plants, applying several different methodologies. This quantity is often used as an argument in discussions about economics to emphasize the performance of a certain technology. Contrary to that, the publications often answer different questions, e.g. a...
Article
The reaction cross-section has been measured for deuteron energies below 25 keV in a deuterized Zr target under improved ultra-high-vacuum conditions and controlled target surface contamination. The increase of reaction enhancement factors towards lower energies is much weaker than that determined before and can result not only from the electron sc...
Article
The Dual Fluid Reactor, DFR, is a novel concept of a fast heterogeneous nuclear reactor. Its key feature is the employment of two separate liquid cycles, one for fuel and one for the coolant. As opposed to other liquid-fuel concepts like the Molten-Salt Fast Reactor (MSFR), both cycles in the DFR can be separately optimized for their respective pur...
Article
At low stellar temperatures the energy release due to the CN cycle is regulated by its slowest reaction N-14(p,gamma)O-15, the rate of which strongly depends on the subthreshold resonance at E-c.m. = -504 keV, which corresponds to the 6.79 MeV state in O-15. By using the Doppler-shift attenuation method and the He-3(O-16,alpha)O-15 reaction to popu...
Article
Nuclear reactions at very low energies can be strongly enhanced due to screening of the Coulomb barrier by surrounding electrons. In the past decade, this effect was intensively studied for the d + d reactions taking place in metallic environments as a model for dense astrophysical plasmas, where the reaction rates can be increased even by many ord...
Article
The heavy-ion radiative capture C12(O16,γSi28) was measured at the sub-Coulomb barrier bombarding energy Elab=15.7 MeV, which corresponds to the lowest important resonance observed in the C12+ O16 fusion excitation function. Thanks to combination of the bismuth germanate (BGO) γ-ray array and the 0∘ DRAGON electromagnetic spectrometer at TRIUMF, th...
Article
The enhanced electron screening effect in nuclear reactions taking place in dense astrophysical plasmas is extremely important for determination of stellar reaction rates in terrestrial laboratories as well as in prediction of cross sections enhancement in interiors of stars such as White and Brown Dwarfs or Giant Planets. This effect resulting in...
Article
We report here a determination of the asymptotic normalization coefficient of the valence neutron in 8Li from a measurement of the angular distribution of the 7Li(8Li,7Li)8Li reaction at 11 MeV. Using isospin symmetry the 8B ANC has also been calculated and used to infer a value for S17(0) of 20.2 ± 4.4 eV b.
Article
Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3He(α,γα,γ)7Be with the DRAGON recoil separator have demonstrated beam suppression >1014>1014 at the 90% confidence level. A measurement of this cross section by observation of 7Be recoils at the focal plane of the separator should be virt...
Article
In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array, the complete γ-decay of the radiative capture channel below the Coulomb barrier has been measured for the first time. This measurement has been performed at two energies Ec.m. = 6.6 and 7.2 MeV. A selective contribution of the entrance spins 2+...
Article
The target-material dependence of the neutron-proton branching ratio and breaking of the isospin symmetry in the the 2H(d, n)3He and 2H(d, p)3H reactions at very low deuteron energies have been investigated. Angular distributions and total cross sections of the proton and neutron mirror channels have been measured for nuclear reactions taking place...
Technical Report
Full-text available
We have performed a heavy ion radiative capture reaction between two light heavy ions, C-12 and (16)Q leading to Si-28. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural effects. Obtained gamma-spectra display a previously unobserved strong feeding of i...
Article
Full-text available
Directly measuring nuclear astrophysics reactions presents unique challenges. Low energy reaction products and small reaction cross sections are just two of the issues that the TACTIC detector addresses. TACTIC is the "TRIUMF Annular Chamber for Tracking and Identification of Charged-particles" detector being developed by TRIUMF and the University...
Article
Full-text available
Observations from gamma ray telescopes indicate that most of the galactic 26Al originates in massive stars. Several sites have been discussed for its production, including proton burning in the winds of very massive stars, and the later, explosive burning stages of these stars. Observations from the RHESSI and INTEGRAL missions currently seem to po...
Conference Paper
Full-text available
We have performed a heavy ion radiative capture reaction between two light heavy ions, C-12 and (16)Q leading to Si-28. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural effects. Obtained gamma-spectra display a previously unobserved strong feeding of i...
Article
The 18F(p,α)15O reaction rate is crucial for understanding the final abundance of 18F predicted by nova models. The γ-ray emission in the first few hours after a nova outburst is expected to be dominated by 511 keV annihilation photons from the decay of 18F, and so understanding its production can provide important constraints on the conditions dur...
Article
Study of the deuteron fusion reactions at very low energies in metallic environments enables us to determine the strength of the astrophysical electron screening effect in the terrestrial laboratories. Experiments performed under high and ultra high vacuum conditions showed that the experimentally determined screening energies corresponding to the...
Article
In nuclear astrophysics, detection of low energy reaction products is often difficult with techniques such as silicon detectors. To this end, the TRIUMF Annular Chamber for Tracking and Identification of Charged-particles (TACTIC) detector has been designed and built by an international collaboration between TRIUMF and the University of York. TACTI...
Article
Full-text available
The lowest-energy resonance in the 23Mg(p,γ)24Al reaction, which is dominant at classical nova temperatures, has been measured directly for the first time using the DRAGON recoil spectrometer. The experiment used a radioactive 23Mg beam (mixed within a significantly stronger 23Na beam) of peak intensity 5×107 s-1, at the ISAC facility at TRIUMF. We...
Article
Full-text available
Ion tracking is still an unusual detection method in nuclear physics. TACTIC (TRIUMF annular chamber for tracking and identification of charged particles) is suitable for tracking low-energy ejectiles. The cylindrical design allows for an electrical separation of target and drift region without hindering the ejectiles to enter the drift region. The...
Article
Full-text available
The s-wave neutron fraction of the 0+ levels in 12Be has been investigated for the first time through the 11Be(d,p) transfer reaction using a 5A MeV11Be beam at TRIUMF, Canada. The reaction populated all the known bound states of 12Be. The ground state s-wave spectroscopic factor was determined to be 0.28−0.07+0.03 while that for the long-lived 02+...
Article
Full-text available
The experimental study of low-energy deuteron fusion reactions in metallic environments shows the importance of the electron screening effect. Experimentally determined screening energies are remarkably higher than predicted theoretically. This discrepancy becomes even larger for the first ultra-high vacuum (UHV) experiment. Thus, a question arises...
Article
The lowest-energy resonance in the (23)Mg(p,gamma)(24)Al reaction, which is dominant at classical nova temperatures, has been measured directly for the first time using the DRAGON recoil spectrometer. The experiment used a radioactive (23)Mg beam (mixed within a significantly stronger (23)Na beam) of peak intensity 5 x 10(7) s(-1), at the ISAC faci...
Article
The β-delayed α decay of N16 has been used to restrict the E1 fraction of the ground state γ transition in the astrophysically important C12(α,γ)O16 reaction in several experiments. A review of the published measurements is given, and GEANT4 simulations and R-matrix calculations are presented to further clarify the observed α spectra. A clear respo...
Article
Full-text available
The beta-delayed alpha-decay of 16N has been used to restrict the E1 fraction of the ground state gamma-transition in the astrophysically important 12C(alpha,gamma)16O reaction in several experiments including those performed at TRIUMF and several other laboratories. A review of the published measurements is given, and GEANT4 simulations and R-Matr...
Article
Active targets are perfect tools for the study of reactions induced by radioactive ion beams of very low intensity. Thus, they make possible the study of direct and compound reactions at the same time. In this talk, we will present the results obtained with the MAYA active target for low energy reactions induced by the halo nucleus 11Li. A method u...
Article
A new time-of-flight (TOF) system has been installed at the recoil mass separator DRAGON at the radioactive beam facility TRIUMF-ISAC in Vancouver, Canada. The addition of a velocity measurement to the existing energy measurement provides an effective separation of heavy ion reaction particles from remaining beam particles reaching the end detector...
Article
The mass of 11Li has been determined from Q-value measurements of the 1H(11Li,9Li)3H reaction. The experiment was performed at TRIUMF laboratory with the GANIL active target MAYA. Energy-energy and angle-angle kinematics reconstruction give a Q value of 8.119(22) MeV for the reaction. The derived 11Li two-neutron separation energy is S2n=363(22) ke...
Article
Full-text available
The deuteron-emission channel in the beta decay of the halo nucleus (11)Li was measured at the Isotope Separator and Accelerator facility at TRIUMF by implanting postaccelerated (11)Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of (11)Li with those of the daughter nuclei. This method all...
Article
The DRAGON facility at TRIUMF/ISAC detects reaction products following radiative capture of a hydrogen or helium target nucleus by an accelerated heavy ion. Capture reactions of interest in nuclear astrophysics may have reaction rates 10–14 orders of magnitude lower than the intensity of the incident beam: as well as efficiently transporting the he...
Article
Recent measurements of the reaction H2(d,p)H3 in metallic environments at very low energies performed by different experimental groups point to an enhanced electron screening effect. However, the resulting screening energies differ strongly for diverse host metals and different experiments. Here, we present new experimental results and investigatio...
Article
The Nuclear Astrophysics program at TRIUMF, particular the one centered around the DRAGON and TUDA facilities, as well as some additional experiments will be discussed. In particular, measurements of the 12C(α,γ)16O, the 26Al(p,γ)27Si and the 40Ca(α,γ)44Ti reactions at DRAGON will be described. For the TUDA facility a measurement of 10B(α,p)13C as...
Article
Full-text available
The p((11)Li, (9)Li)t reaction has been studied for the first time at an incident energy of 3A MeV at the new ISAC-2 facility at TRIUMF. An active target detector MAYA, built at GANIL, was used for the measurement. The differential cross sections have been determined for transitions to the (9)Li ground and first excited states in a wide range of sc...
Article
The 15O(α,γ)19Ne reaction plays a role in the ignition of type I x-ray bursts on accreting neutron stars. The lifetimes of states in 19Ne above the 15O+α threshold of 3.53 MeV are important inputs to calculations of the astrophysical reaction rate. These levels in 19Ne were populated in the 3He(20Ne,α)19Ne reaction at a 20Ne beam energy of 34 MeV....
Article
The O15(α,γ)Ne19 reaction plays a role in the ignition of type I x-ray bursts on accreting neutron stars. The lifetimes of states in Ne19 above the O15+α threshold of 3.53 MeV are important inputs to calculations of the astrophysical reaction rate. These levels in Ne19 were populated in the He3(Ne20,α)Ne19 reaction at a Ne20 beam energy of 34 MeV....
Article
The ground state structure of 9Li has been investigated through the one-neutron transfer reaction at E/A=1.68 MeV. The 8Li sub-system in 9Li was observed in its lowest three energy levels. The spectroscopic factors derived from a DWBA analysis are fairly consistent in trend with model calculations. The understanding of the N=6 sub-shell closure fro...
Article
Full-text available
6 pages, 3 figures, submitted to Physical Review Letters, Détecteur MAYA
Article
The nuclide (44)Ti is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based gamma-ray telescopes. The main production of (44)Ti takes place in the alpha-rich freeze-out phase deep inside the supernova. The key reactions governing the (44)T...
Article
Full-text available
An experiment to measure the 18 F(p,α) 15 O cross section at low centre of mass energies has been performed with the TRIUMF-UK Detector Array (TUDA) facility at TRIUMF. Measurements of the 18 F(p,α) 15 O reaction rate at four separate centre of mass energies; 665 keV, 430 keV, 330 keV and 250 keV, were carried out. The main goal of the experiment w...
Article
The decay rate of 22Na implanted in aluminium has been measured at room temperature and at 10 K. The rate should increase by 40% according to Rolfs (2006 Public Lecture for SLENA (Kolkata, India)) and by about 6% according to Limata et al (2006 Eur. Phys. J. A 28 251). In the latter publication, an increase of only 1.2 ± 0.2% has been measured and...
Article
The nuclide 44Ti is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based γ-ray telescopes. The main production of 44Ti takes place in the α-rich freeze-out phase deep inside the supernova. The key reactions governing the 44Ti abundance ha...
Article
Full-text available
The 15O(alpha,gamma)19Ne reaction plays a role in the ignition of Type I x-ray bursts on accreting neutron stars. The lifetimes of states in 19Ne above the 15O + alpha threshold of 3.53 MeV are important inputs to calculations of the astrophysical reaction rate. These levels in 19Ne were populated in the 3He(20Ne,alpha)19Ne reaction at a 20Ne beam...
Article
We measured the {beta}-decay of the halo-nucleus {sup 11}Li, with particular attention to the deuteron- and triton-emission channels. We employed a post-accelerated beam of {sup 11}Li ions, and the implantation technique in a finely-segmented silicon detector. The channels of interest were identified through the time and space correlations between...
Article
We measured the β-decay of the halo-nucleus 11Li, with particular attention to the deuteron- and triton-emission channels. We employed a post-accelerated beam of 11Li ions, and the implantation technique in a finely-segmented silicon detector. The channels of interest were identified through the time and space correlations between the implantation...
Article
Full-text available
The heavy-ion radiative capture reaction, 12C(12C,γ), has been investigated at energies both on- and off-resonance, with a particular focus on known resonances at Ec.m.=6.0, 6.8, 7.5, and 8.0 MeV. Gamma rays detected in a BGO scintillator array were recorded in coincidence with 24Mg residues at the focal plane of the DRAGON recoil separator at TRIU...
Article
The β-delayed α-decay of ^16N has been used to restrict the E1 fraction of the ground state in the key ^12C(α,γ)^16O reaction. A review of the measurements is given and new R-Matrix and GEANT calculations are presented to further elucidate the observed α spectra. A clear response tail from scattering of α-particles in the catcher foil is observed i...
Article
The short-lived nuclide 44Ti is an important nuclide for the understanding of explosive nucleosynthesis. The main production reaction, 40Ca(α,γ)44Ti, has been studied in inverse kinematics with the recoil mass spectrometer DRAGON located at the TRIUMF-ISAC facility in Vancouver, Canada. The temperature range relevant for α-rich freeze-out during a...
Article
We report here on experiments with radioactive 21Na and 7Be beams performed by Colorado School of Mines students at the ISAC facility of TRIUMF and the Holifield Radioactive Ion Beam Facility (HRIBF) of ORNL. At TRIUMF, the DRAGON recoil separator and its segmented BGO array were used to investigate higher energy resonances in the reaction H(21Na,...
Article
Nuclear reactions play a key role in understanding nucleosynthesis in stars. Recoil mass spectrometers such as DRAGON are well suited to study reactions with respect to astrophysical production because of direct detection of reaction products. Here we present the first stage of an experiment running at the recoil mass spectrometer DRAGON at the ISA...
Article
A new detector for nuclear astrophysics studies is being designed and built by TRIUMF and the University of York. The TRIUMF Annular Chamber for Tracking and Identification of Charged particles (TACTIC) is designed to detect low-energy charged particles from inverse kinematics reaction studies performed at the relevant astrophysical energies. TACTI...
Article
The cascade through the 6.049-MeV state of ^16O has rarely been discussed as contributing to the ^12C (alpha,gamma)^16O cross section at low energies largely due to experimental difficulties in observing this transition. We report here first measurements of this transition in ^12C(alpha,gamma)^16O using the DRAGON separator facility at TRIUMF. The...
Article
We present new measurements of the charge-state distribution (CSD) of a 1.068 MeV/u C beam in He and of the 6+:5+ charge-state population ratio in the recoils of the 12C(α, γ)16O reaction, both measured at the DRAGON recoil mass spectrometer. A computer simulation to model the CSD of both beam and recoil particles in inverse-kinematics experiments...
Article
To study the electron screening of nuclear reactions in metallic environments, angular distributions and thick target yields of the fusion reactions 2H(d,p)3H and 2H(d,n)3He have been measured on deuterons implanted in three different metal targets (Al, Zr and Ta) for beam energies ranging from 5 to 60 keV. The experimentally determined values of t...
Article
The short-lived nuclide Ti-44 is an important nuclide for the understanding of explosive nucleosynthesis. The main production reaction, Ca-40(alpha,gamma)Ti-44, has been studied in inverse kinematics with the recoil mass spectrometer DRAGON located at the TRIUMF-ISAC facility in Vancouver, Canada. The temperature range relevant for alpha-rich freez...
Article
Nuclear reactions play a key role in understanding nucleosynthesis in stars. Recoil mass spectrometers such as DRAGON are well suited to study reactions with respect to astrophysical production because of direct detection of reaction products. Here we present the first stage of an experiment running at the recoil mass spectrometer DRAGON at the ISA...