84 research outputs found
A novel transparent charged particle detector for the CPET upgrade at TITAN
The detection of an electron bunch exiting a strong magnetic field can prove
challenging due to the small mass of the electron. If placed too far from a
solenoid's entrance, a detector outside the magnetic field will be too small to
reliably intersect with the exiting electron beam because the light electrons
will follow the diverging magnetic field outside the solenoid. The TITAN group
at TRIUMF in Vancouver, Canada, has made use of advances in the practice and
precision of photochemical machining (PCM) to create a new kind of charge
collecting detector called the "mesh detector." The TITAN mesh detector was
used to solve the problem of trapped electron detection in the new Cooler
PEnning Trap (CPET) currently under development at TITAN. This thin array of
wires etched out of a copper plate is a novel, low profile, charge agnostic
detector that can be made effectively transparent or opaque at the user's
discretion.Comment: 6 Pages. 6 Figures. Submitted to Nuclear Instruments and Methods in
Physics Research Section A: Accelerators, Spectrometers, Detectors and
Associated Equipmen
Adsorbate-Induced Segregation of Cobalt from PtCo Nanoparticles: Modeling Au Doping and Core AuCo Alloying for the Improvement of Fuel Cell Cathode Catalysts
Platinum, when used as a cathode material for the oxygen reduction reaction, suffers from high overpotential and possible dissolution, in addition to the scarcity of the metal and resulting cost. Although the introduction of cobalt has been reported to improve reaction kinetics and decrease the precious metal loading, surface segregation or complete leakage of Co atoms causes degradation of the membrane electrode assembly, and either of these scenarios of structural rearrangement eventually decreases catalytic power. Ternary PtCo alloys with noble metals could possibly maintain activity with a higher dissolution potential. First-principles-based theoretical methods are utilized to identify the critical factors affecting segregation in Pt–Co binary and Pt–Co–Au ternary nanoparticles in the presence of oxidizing species. With a decreasing share of Pt, surface segregation of Co atoms was already found to become thermodynamically viable in the PtCo systems at low oxygen concentrations, which is assigned to high charge transfer between species. While the introduction of gold as a dopant caused structural changes that favor segregation of Co, creation of CoAu alloy core is calculated to significantly suppress Co leakage through modification of the electronic properties. The theoretical framework of geometrically different ternary systems provides a new route for the rational design of oxygen reduction catalysts
Magnetic properties of X-Pt (X=Fe,Co,Ni) alloy systems
We have studied the electronic and magnetic properties of Fe-Pt, Co-Pt and
Ni-Pt alloy systems in ordered and disordered phases. The influence of various
exchange-correlation functionals on values of equilibrium lattice parameters
and magnetic moments in ordered Fe-Pt, Co-Pt and Ni-Pt alloys have been studied
using linearized muffin-tin orbital method. The electronic structure
calculations for the disordered alloys have been carried out using augmented
space recursion technique in the framework of tight binding linearized
muffin-tin orbital method. The effect of short range order has also been
studied in the disordered phase of these systems. The results show good
agreements with available experimental values.Comment: 21 pages, 4 eps figures, accepted for publication in Journal of
Physics Condensed Matte
Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes
Mass measurements continue to provide invaluable information for elucidating
nuclear structure and scenarios of astrophysical interest. The transition
region between the and proton shell closures is particularly
interesting due to the onset and evolution of nuclear deformation as nuclei
become more neutron rich. This provides a critical testing ground for emerging
ab-initio nuclear structure models. Here, we present high-precision mass
measurements of neutron-rich chromium isotopes using the sensitive
electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS)
at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our
high-precision mass measurements of Cr confirm previous results,
and the improved precision in measurements of Cr refine the mass
surface beyond N=40. With the ab initio in-medium similarity renormalization
group, we examine the trends in collectivity in chromium isotopes and give a
complete picture of the N=40 island of inversion from calcium to nickel.Comment: 12 pages, 7 figure
Examining the nuclear mass surface of Rb and Sr isotopes in the A≈104 region via precision mass measurements
Mass measurements of 60–63Ga reduce x-ray burst model uncertainties and extend the evaluated T=1 isobaric multiplet mass equation
We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of Ga60–63 performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of Ga61 and mark the first direct mass measurement of Ga60. The improved precision of the Ga61 mass has important implications for the astrophysical rp process, as it constrains essential reaction Q values near the Zn60 waiting point. Based on calculations with a one-zone model, we demonstrate the impact of the improved mass data on prediction uncertainties of x-ray burst models. The first-time measurement of the Ga60 ground-state mass establishes the proton-bound nature of this nuclide, thus constraining the location of the proton drip line along this isotopic chain. Including the measured mass of Ga60 further enables us to extend the evaluated T=1 isobaric multiplet mass equation up to A=60
Mapping the N=40 island of inversion: Precision mass measurements of neutron-rich Fe isotopes
International audienceNuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS), achieving a resolving power greater than 600000 for the first time, enabled the measurement of Fe63–70, including first-time high-precision direct measurements (δm/m≈10−7) of Fe68–70, as well as the discovery of a long-lived isomeric state in Fe69. These measurements are accompanied by both mean-field and ab initio calculations using the most recent realizations which enable theoretical assignment of the spin-parities of the Fe69 ground and isomeric states. Together with mean-field calculations of quadrupole deformation parameters for the Fe isotope chain, these results benchmark a maximum of deformation in the N=40 island of inversion in Fe and shed light on trends in level densities indicated in the newly refined mass surface
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