M.J. Smith

Bio: M.J. Smith is an academic researcher from University of British Columbia. The author has contributed to research in topics: Radio-frequency quadrupole & Ion beam. The author has an hindex of 3, co-authored 3 publications receiving 138 citations. Previous affiliations of M.J. Smith include TRIUMF.

TITAN's Digital RFQ Ion Beam Cooler and Buncher, Operation and Performance

Abstract: We present a description of the Radio Frequency Quadrupole (RFQ) ion trap built as part of the TITAN facility. It consists of a gas-filled, segmented, linear Paul trap and is the first stage of the TITAN setup with the purpose of cooling and bunching radioactive ion beams delivered from ISAC-TRIUMF. This is the first such device to be driven digitally, i.e., using a high voltage ( V pp = 400 V ), wide bandwidth ( 0.2 f 1.2 MHz ) square-wave as compared to the typical sinusoidal wave form. Results from the commissioning of the device as well as systematic studies with stable and radioactive ions are presented including efficiency measurements with stable 133Cs and radioactive 124,126Cs. A novel and unique mode of operation of this device is also demonstrated where the cooled ion bunches are extracted in reverse mode, i.e., in the same direction as previously injected.

First direct mass measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He.

Abstract: The first direct mass measurement of $^{6}\mathrm{He}$ has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of $^{8}\mathrm{He}$ was determined with improved precision over our previous measurement. The obtained masses are $m(^{6}\mathrm{He})=6.018\text{ }885\text{ }883(57)\text{ }\text{ }\mathrm{u}$ and $m(^{8}\mathrm{He})=8.033\text{ }934\text{ }44(11)\text{ }\text{ }\mathrm{u}$. The $^{6}\mathrm{He}$ value shows a deviation from the literature of $4\ensuremath{\sigma}$. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) and 1.959(16) fm for $^{6}\mathrm{He}$ and $^{8}\mathrm{He}$, respectively. We present a detailed comparison to nuclear theory for $^{6}\mathrm{He}$, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.

A High Frequency Mosfet Driver for the Titan Facility at TRIUMF

Abstract: TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) Radio Frequency Quadrupole (RFQ) Beam Cooler is a device that cools and collects short-lived isotopes, with half-lives as short as 10 ms, created by an Isotope Separator and Accelerator (ISAC). An RF square wave driver (RFSWD), that must have rise and fall times of less than 125 ns (10% to 90%), performs 2-dimensional focusing of the ion beam within the RFQ, along planes normal to the beam's intended trajectory, to confine ion motion along a stable path; hence the ions can be trapped and collected for extraction. The RFSWD, which is based on previous kicker designs developed at TRIUMF, employs stacks of MOSFETs, operating in push-pull, to generate high voltage (HV) rectangular waveforms at a prescribed frequency and duty cycle. Currently a 500 V, 2 MHz drive system is undergoing tests, however, the system configuration allows for operation with higher voltage amplitudes and a repetition rate from 300 kHz up to 3 MHz, continuous. Technical details of the design, operation and performance of the RFQ system, in particular of the drive system, are presented.

Precision Atomic Physics Techniques for Nuclear Physics with Radioactive Beams

Abstract: Atomic physics techniques for the determination of ground-state properties of radioactive isotopes are very sensitive and provide accurate masses, binding energies, Q-values, charge radii, spins and electromagnetic moments. Many fields in nuclear physics benefit from these highly accurate numbers. They give insight into details of the nuclear structure for a better understanding of the underlying effective interactions, provide important input for studies of fundamental symmetries in physics, and help to understand the nucleosynthesis processes that are responsible for the observed chemical abundances in the Universe. Penning-trap and storage-ring mass spectrometry as well as laser spectroscopy of radioactive nuclei have now been used for a long time but significant progress has been achieved in these fields within the last decade. The basic principles of laser spectroscopic investigations, Penning-trap and storage-ring mass measurements of short-lived nuclei are summarized and selected physics results are discussed.

Modern Ab Initio Approaches and Applications in Few-Nucleon Physics with A \ge 4

Abstract: We present an overview of the evolution of ab initio methods for few-nucleon systems with A \ge 4, tracing the progress made that today allows precision calculations for these systems. First a succinct description of the diverse approaches is given. In order to identify analogies and differences the methods are grouped according to different formulations of the quantum mechanical many-body problem. Various significant applications from the past and present are described. We discuss the results with emphasis on the developments following the original implementations of the approaches. In particular we highlight benchmark results which represent important milestones towards setting an ever growing standard for theoretical calculations. This is relevant for meaningful comparisons with experimental data. Such comparisons may reveal whether a specific force model is appropriate for the description of nuclear dynamics.

Electromagnetic reactions on light nuclei

Abstract: Electromagnetic reactions on light nuclei are fundamental to advance our understanding of nuclear structure and dynamics. The perturbative nature of the electromagnetic probes allows to clearly connect measured cross sections with the calculated structure properties of nuclear targets. We present an overview on recent theoretical ab initio calculations of electron-scattering and photonuclear reactions involving light nuclei. We encompass both the conventional approach and the novel theoretical framework provided by chiral effective field theories. Because both strong and electromagnetic interactions are involved in the processes under study, comparison with available experimental data provides stringent constraints on both many-body nuclear Hamiltonians and electromagnetic currents. We discuss what we have learned from studies on electromagnetic observables of light nuclei, starting from the deuteron and reaching up to nuclear systems with mass number A = 16.