Seminar Tuesday August 25 – Paul Smith

Speaker: Paul Smith
Location: Physics 175
Time: August 25 2015

All dressed up and ready to go: a quick look at dressed fields.

Abstract: Exotic states not predicted by the conventional quark model, such as X(3872), have been discovered en masse over the past decade. Traditionally, exotic heavy-light diquark correlation functions formulated using Schwinger strings have been used to study these states. In this talk I explore the possibility of using a “dressed” field as an alternative means of gathering gauge-invariant information about diquark interactions.

Alternative Abstract: Join me on a magical journey through the realms of particle physics, quantum field theory, and locally gauge invariant fields! A brief gander through history will be taken as I look (very briefly) at the development of the standard model. The major players (gluons, pions, quarks, and more!) will be introduced in a casual, almost personal, fashion and their characteristics and interactions will be introduced. Of course, this will only be done after laying down a little bit of world-building through the establishment of some of the main components that drive the QCD life. Action and drama is the name of the game as the struggle for gauge invariant information is brought to a shocking conclusion.

Be there. Experience QCD, gauges, and Bohr bashing like never before (In all reality, it’ll probably just be a generic grad student seminar, but let’s keep that on the dl).

Seminar Tuesday August 18 – Masaru Nakajima

Speaker: Masaru Nakajima
Location: Physics 175
Time: 3:30 August 18, 2015

Geodesic acoustic mode in STOR-M

Abstract: Our study pertains to plasma physics in application for nuclear fusion energy. Numerous instabilities and turbulent transport have plagued fusion devices such as tokamak, and their cause and effect are topics of active research today. My topic, geodesic acoustic mode (GAM), falls under such a category of work. GAM was first predicted as a standing wave of density on flux surfaces in toroidal devices. The last two decades have seen observations of GAM in many toroidal devices and further development in its theory. The increasing interest in GAM is due to the roles that GAM can play in (in)stability, turbulent transport, and other oscillations.

Our focus is to detect GAM in SOTR-M device, the tokamak device at University of Saskatchewan, and study its behaviour under external effects such as electrode biasing. To date, we obtained a signature of GAM in our preliminary experiments. In my presentation I will discuss
basic plasma physics for GAM, our experiments and first findings.

Seminar Tuesday August 11 – Caelia Gardiner

Speaker: Caelia Gardiner
Location: Physics 175
Time: 3:30 August 11 2015

Forecasting Space Weather with SuperDARN

Abstract: Space weather can interfere with human activity in a variety of ways. Satellites and spacecraft can be damaged, human lives in orbit endangered, communications and GPS on the surface disrupted and power grids impaired. Due to the large effect space weather can have on our lives, research is conducted worldwide to help predict space weather patterns. Currently, the Canadian Space Weather Forecast Center of Natural Resources Canada is performing forecast services, collecting data on the magnetic field of the Earth at different points and issuing geomagnetic storm warnings. Because SuperDARN also provides international research stations with information on plasma motion in the ionosphere, it would be advantageous to have a similar forecast system based on radar readings. This system can be used to collaborate with existing magnetometer predictions to produce a more robust forecast process.

Convection patterns in the ionosphere arise due to the solar wind plasma and the interplanetary magnetic field orientation. These patterns are inferred from particle velocity readings taken by the SuperDARN. The combination of convection maps and particle velocity line graphs will help predict plasma motion in the atmosphere. The existing convection maps, created using IDL and the Go library, display a rudimentary outline of the polar coast. It would be more beneficial to the reader to have a more explicit image of the polar coast under the convection maps, with the added functionality of labeling specific locations. Existing equirectangular map projections are warped to provide a polar stereographic view, with a conversion from geographic latitude/longitude to geomagnetic coordinates. This warped image is placed under the convection map in place of the coastal outline to provide a more visually coherent image. While this projection functionality will make the convection maps less ambiguous, it will also be useful in future polar maps, for educational or outreach purposes.

Seminar Tuesday August 4 – Tristan de Boer

Speaker: Tristan de Boer
Location: Physics 175
Time: 3:30 August 04 2015

Abstract: Broadly speaking, an important factor behind our ever-improving standards of living is the continuous improvement of the basic materials used in the devices around us. Synthesizing new materials and characterizing them is an essential part of developing new and improved devices. To this end I’ll present recent work on two material systems, MSiN2 (M = Mg, Ca) and In2O3. Our approach utilizes spectroscopic X-ray measurements sensitive to the partial electronic density of states together with first principles density functional theory (DFT) calculations to gain insight into the electronic properties of material systems.

Nitridosilicates MSiN2 (M = Mg, Ca) are promising candidates for manifold industrial applications which require excellent thermal, mechanical and electronic properties, as well as for rare-earth doped LED-Phosphors. For MgSiN2 the band gap has been determined to be 5.6 ± 0.2 eV, in agreement with a theoretically predicted band gap of 5.72 eV. For CaSiN2 the band gap has been determined to be 3.8 ± 0.2 eV in contrast with a theoretically predicted value of 4.88 eV. Good agreement between the measured and calculated spectra is obtained, supporting the calculated electronic density of states of these materials.

Recent studies on In2O3  have revealed a rich phase diagram and led to the discovery of new polymorphs, including the synthesis and ambient recovery of Pbcn In2O3. The electronic properties of this new phase are studied together with other better known polymorphs (Ia-3 and R-3c) using soft X-ray absorption and emission spectroscopy. Together with complementary full-potential all electron DFT calculations, this allows important material parameters, such as the electronic band gap and partial density of states, to be elucidated. Excellent agreement between experiment and theory is obtained, with band gaps of  3.2±0.3, 3.1±0.3 and $2.9±0.3 eV determined for the  Ia-3, R-3c and Pbcn In2O3 polymorphs, respectively. The effective mass of carriers in Pbcn In2O3 is predicted to be 12% less than in the widely used Ia-3 polymorph while having a similar effective optical band gap.