The aim of this project is to tune the reflectivity of fiber-couple supermirrors through wet etching, assemble said supermirrors into a microns-long optical cavity, and characterize the cavities. Ultimately, we plan to insert ultralow-noise trampoline micromechanical systems within these cavities and control their motion using radiation pressure from laser light.

Students will perform wet chemistry to etch the existing Bragg mirrors, assemble fiber optical circuits and high-finesse optical cavities, and use a combination of low-noise lasers and RF electronics to characterize the performance of these cavities at each step. Upon finding suitable mirrors, students will then assist graduate students in assembling vibration isolated optomechanical systems and studying the mechanical properties of light in an ultrahigh vacuum system at room temperature.

For more information contact: Jack Sankey (Childress) (jack at physics dot mcgill dot ca).

Posted on 2019/01/04

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a new radio telescope recently built in Penticton, BC, funded by the Canada Foundation for Innovation (CFI). CHIME is a world-leading detector of Fast Radio Bursts (FRBs), a new and mysterious astrophysical phenomenon in which short (few ms) radio bursts appear randomly in the sky. FRBs are thought to be extragalactic due to their dispersion measures that are far higher than the maximum amount available in our Milky Way. With FRB event rates of ~1000 /sky/day, they raise an interesting puzzle regarding their origin, which may like at cosmological distances. CHIME's great sensitivity and large field-of-view (250 sq deg) enable the detection of many FRBs per day ? in contrast to the fewer than 2 dozen discovered since 2007. The proposed research project is to assist the McGill group, in collaboration with colleagues at U. Toronto, UBC and elsewhere, in the design, implementation and testing of algorithms and software for the FRB back-end instrument for CHIME. The project will involve becoming familiar with the hallmark signatures of FRBs and with the planned software pipeline, and contributing to the software development either by testing out new algorithms or implementing ones already tested.

The student, who should have experience and familiarity with programming in the Linux environment, will be given astrophysical data sets from CHIME or other radio telescopes (possibly including Arecibo and the Green Bank Telescopes) to first familiarize themselves with source properties. Then, depending on exact interest, may help develop and test new algorithms for distinguishing such signals from Terrestrial interference, or may help develop and interpret a database of source properties, or may help with multi-wavelength observations of localized FRBs.

For more information contact: Victoria Kaspi (vkaspi at physics dot mcgill dot ca).

Posted on 2019/01/07

The varied surfaces and atmospheres of planets make them interesting places to live, explore, and study from afar. Unfortunately, the great distance to even the closest exoplanets makes it impossible to resolve their disk with current or near-term technology. It is still possible, however, to deduce spatial inhomogeneities in exoplanets provided that different regions are visible at different times. In the past decade, we have been able to construct thermal maps and reflectance maps of short-period giant planets using the Spitzer and Kepler space telescopes, respectively. Future instruments should enable exo-cartography of smaller and/or cooler planets.

The student will master and modify existing Python code for mapping planets in reflected light based on disk-integrated photometry. They will use this code to construct albedo maps of short-period planets using data from Kepler, and/or test the impact of instrument noise and cadence on the quality of inferred maps, in order to the inform the design of experiment for next-generation instruments. Depending on interest, they can implement modules to account for non-diffuse reflection or time-variable clouds.

For more information contact: Nicolas Cowan (cowan at physics dot mcgill dot ca).

Posted on 2019/01/15

In this collaborative project between the Reisner and Grutter groups, the USRA student will help develop a new technique for making precisely positioned sub 5 nm nanopores. The successful demonstration of nanopore sequencing via engineered protein pores has created considerable industrial interest in nanopore based technologies. The next research frontier in nanopore physics is the development of solid-state nanopore devices, which admit of more scalable fabrication processes and will potentially have higher resolution, decreasing the high sequencing error-rates that are currently the main drawback in nanopore sequencing. We have developed a new approach for fabrication of sub 5 nm pores via local dielectric breakdown induced by a conductive AFM tip across a ~10nm nitride membrane. In our approach, a conductive AFM tip is brought into contact with a nitride membrane sitting on top of an electrolyte reservoir. Application of a voltage pulse leads within seconds to formation of a nanoscale pore that can be detected by a subsequent AFM scan. This approach combines the ease of classic dielectric breakdown with the nanoscale pore positioning capability of high energy particle milling techniques such as TEM and FIB. The student will learn to create pores in nitride membranes using an AFM setup in the Grutter group and then will perform DNA translocation measurements in the Reisner group with the pores. The student will meet on a weekly basis with supervisors Prof. Reisner and Grutter.

For more information contact: Walter Reisner (reisner at physics dot mcgill dot ca).

Posted on 2019/01/17

A crucially unexplored part of our Universe?s history is the Epoch of Reionization. During this epoch, the first galaxies systematically ionized the intergalactic medium, taking our Universe from being almost entirely neutral to being entirely ionized. This reionization process took place gradually, with ionized bubbles first appearing around galaxies, then growing larger and larger until they overlapped. The complex geometry of these bubbles imprints non-Gaussian signatures in radio observations of reionization. One way to quantify this non-Gaussianity is to compute the so-called line correlation function (LCF), which is a recently proposed measure of filamentary structure in the cosmic matter distribution. The goal of this project is to determine whether the LCF is a viable observational statistic for radio surveys to probe reionization.

The student will gain a mathematical understanding of the LCF, and then write Python code to compute it from simulations of reionization. They will then interpret the results in terms of the physics of reionization. If time permits, they will perform statistical forecasts of how well the LCF can be measured by upcoming radio telescopes.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2019/01/19

The halo mass function (HMF), i.e., the number density of dark matter halos (essentially gravitationally bound quasi-spherical concentrations of matter) in the Universe as a function of their mass and time, is a fundamental quantity in cosmology. It quantifies how rapidly structure forms and grows, and is an essential ingredient of galaxy formation models, since galaxies inhabit dark matter halos, making the abundance of halos a vital quantity. Unfortunately, there is considerable uncertainty to the precise form of the HMF. The goal of this research project is to explore the consequences of this uncertainty on a variety of areas such as galaxy formation theory, reionization, and 21cm cosmology.

The student will first gain an understanding of current models of the HMF. They will then devise fitting forms and interpolation schemes for various HMF models. Finally, they will incorporate new parameterizations of the HMF into the Accelerated Reionization Era Simulations Python package, and if time permits, explore the ways in which this affects predictions for 21cm cosmology.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2019/01/21

During the era of Cosmic Dawn, the first generation of stars and galaxies formed, dramatically altering their surroundings. For example, X-ray photons from these first luminous objects heated the intergalactic medium, while the UV photons ionized it. Unfortunately, simulating these processes is an extremely computationally expensive process, given the variety of lengthscales involved. For example, star formation on small scales produces photons that often travel for hundreds of millions of light years before being absorbed. An attractive alternative to simulating Cosmic Dawn using traditional methods is to appeal to machine learning. With machine learning, a small number of expensive simulations can be used as training simulations to train algorithms to generate a large number of synthetic simulations.

The student will first gain a working knowledge of convolutional neural networks (CNNs). They will then learn to run simple Cosmic Dawn simulations to produce training data, which will then be fed into a CNN designed for texture synthesis, enabling the generation of synthetic simulations.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2019/01/21

The Hydrogen Epoch of Reionization Array (HERA) is a new radio telescope in construction in the South African Karoo desert. It operates in the frequency range of ~50 to 225 MHz, allowing it to make radio observations of Cosmic Dawn (when the first generation of stars and galaxies were forming). When complete in 2020, it will consist of 350 radio dishes, each 14 m in diameter. Currently, ~100 dishes have been built and are taking data. As with any new telescope, however, there are a large number of possible systematics in early data. The goal of this project is to dive into HERA data, diagnosing possible problems and investigating data quality in a quantitative way.

Students will master the use of the HERA collaboration software pipeline for data analysis. They will then perform statistical tests on real data (such as various null tests and jackknife tests). In the process, they will contribute Python code to be incorporated?following review?into the standard codebase of the collaboration.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2019/01/21

Cosmic muons are very abundant and were among the first particles to be observed in the laboratory. A spark chamber is now used to detect them at McGill. When the electrically charged muons traverse a series of metal plates under high voltages, the ionization of the gas creates sparks in the gaps thus making the muon trajectories visible to the eye.

The project consists in developing the current chamber for operation in outreach and training events. Several particle physics techniques are used in this project: mechanical construction, gas system, high voltages, photomultipliers, electronic signals and their logic, data acquisition devices and analysis methods. Intensity and angle distributions of the muons would be the goal of the measurements.

The student should familiarize him-/herself first with the above techniques through reading and experimentation with the current setup. The next step would be to design and build a new container and optimize the performance of the gas system and the spark generating devices. Finally, a new data taking apparatus should equip the chamber and be tested to allow systematic analysis of all cosmic muons events.

For more information contact: Profs François Corriveau and Thomas Brunner (corriveau at physics dot mcgill dot ca and brunnerat physics dot mcgill dot ca).

Posted on 2019/01/24

Stimulated-emission depletion (STED) microscopy is one member of a group of new super-resolution microscopy techniques that are able to image biomolecules with spatial resolution below the light diffraction limit of conventional optical microscopes. Image correlation spectroscopy (ICS) techniques are a form of fluorescence fluctuation analysis that calculate correlation functions from microscopy images to extract molecular densities and transport properties. Although STED has been used in combination with single spot fluorescence correlation spectroscopy (FCS), extensions to full image analysis with ICS are limited to date. The goal of this project will be to optimize a STED super-resolution microscope for ICS measurements. This will entail characterizing the point spread function focal volume with sub-diffraction size fluorescent spheres in both confocal and STED imaging modes using different power settings for the depletion beam to test different sizes of focus down to 50 nm. Fluctuation sampling in space and time will be tested for diffusing samples of fluorescent microsphere in order to optimize ICS correlation function signal to noise. Finally, optimized spatial ICS measurements will be attempted on fixed cells with labelled CFTR channels imaged both in confocal and STED imaging modes.

The student will acquire knowledge of Matlab based image analysis, fluorescence correlation/fluctuation analysis, experimental biophysics sample preparation, confocal fluorescence and super-resolution STED microscopy.

For more information contact: Paul Wiseman (wiseman at physics dot mcgill dot ca).

Posted on 2019/01/28

The CRISPR/Cas9 gene editing tool has become an important platform for genome editing and imaging. This approach has been the basis of genome- and drug target screening, but off-target binding is a major roadblock in these efforts and could result in unintended mutations. An important question is how Cas9 searches through millions of base pairs in a genome to locate specific base pair targets.

For this project, a student will work with a graduate student who uses confinement microscopy to examine the DNA-Cas9/RNA interaction at the single-molecule level. The student will implement and refine an analysis software package to investigate the interactions between Cas9, RNA, and DNA. The student may also participate in experimental protocol optimization and sample preparation and assist in microscopy experiments.

Weekly meetings with the supervisor and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2019/01/31

Fluorescence Cross-Correlation Spectroscopy (FCCS) is the study of the fluctuations and kinetics of interacting molecules. In many experimental implementations, the background fluorescence presents a significant source of noise. A wide-field implementation of FCCS, using confinement microscopy, can dramatically improve background suppression and extend observation times, enabling new measurements of weak and slow DNA-DNA, protein-DNA and protein-protein interactions under previously inaccessible conditions.

In this summer project, the student will apply and further develop FCCS image analysis tools, to analyze fluorescence images of freely diffusing and interacting molecules, at micromolar reagent concentrations and over long timescales. By comparing results to theoretical models, the student will extract meaningful system parameters such as binding and unbinding rates and diffusivity.

The student will receive training in microscopy (optics, experiment design, device control) and quantitative data analysis (Matlab) as well as theory, and work closely with a graduate student on this project. Weekly meetings with the supervisor and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2019/01/31

DNA-DNA and protein-DNA interactions are crucial to cellular processes, with errors in these reactions sometimes leading to genetic diseases such as cancer. Emerging single-molecule microscopy techniques allow for multiple, independent interactions to be imaged at once, allowing for measurements of both the expected behaviour, as well as deviations from the norm. Single molecule imaging, however, suffers from limitations in signal-to-background. This presents an opportunity to develop computer-vision algorithms to extract salient information about the molecules.

For this project, the student will develop an analysis software package to study the interactions between fluorescent probe molecules and supercoiled DNA trapped in microwell arrays. Statistical mechanics theory predicts the probability of specific DNA structural transitions. As background to this project, PhD students have collected fluorescence images of mixtures of DNA molecules and probe molecules (oligonucleotides, proteins). This computational project focuses on implementing computer vision and principal component analysis (PCA) algorithms to improve measurements of binding kinetic rates and stoichiometries, and on running simulations to test the analysis methods.

The student will receive training in quantitative data analysis (Matlab) as well as theory, and work closely with a graduate student on this project. Weekly meetings with the supervisor and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2019/01/31

Supercoiled DNA exists in all cells, however the impact of DNA supercoiling on local structure, and thus on gene regulation, is not fully understood. Local DNA structural changes are driven by the torsional strain created through supercoiling. These structural changes can have crucial implication in gene regulation, and errors in these reactions can potentially lead to genetic disease such as cancer.

For this project, the student will study supercoil-driven structural transitions in bulk experiments, to compare with confinement microscopy experiments. Students will learn how to culture cells, extract DNA and supercoil the DNA. They will learn how to measure supercoiling and structural transitions with gel electrophoresis. And they will compare their results to microscopy data taken in the lab and to statistical mechanical models.

The student will receive hands-on training in confinement microscopy as well as sample design and preparation, and work closely with a graduate student on this project. Weekly meetings with the supervisor and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2019/01/31

Nanoparticles are increasingly used in pharmaceutical applications. This research project will use single-particle confinement microscopy to investigate the biophysical properties, stoichiometry and kinetics of nanoparticle assemblies and their interactions. This technique entraps particles in femto-liter reaction wells and allows prolonged monitoring of reactions. It also enables direct visualization of interactions between chemical species and nanoparticles.

For this project, the student will develop analysis approaches to quantify probe-nanoparticle interactions. For example, particle tracking algorithms can be used to extract valuable information such as binding/unbinding kinetics, encapsulation dynamics and adsorption kinetics.

The student will receive training in quantitative image analysis (Matlab) as well as hands-on training in confinement microscopy and will work closely with a research fellow and graduate student. Weekly meetings with the supervisor and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2019/01/31

An exciting frontier of radio astronomy is using the redshifted 21-cm emission of neutral hydrogen to reconstruct a 3D map of large-scale structure in the universe.� The distribution of matter encodes a faint imprint, known as baryon acoustic oscillations (BAOs), that correspond to remnant ripples left behind by sound waves echoing through the plasma of the early universe.� Precise measurements of BAOs will allow us to understand the universe's expansion history and probe the nature of dark energy.� The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new radio telescope array that will measure BAOs by mapping the southern sky over a frequency range of 400-800 MHz, and the experiment will be sited in the Karoo desert in South Africa.� The project complements the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which is surveying the northern sky.� The final HIRAX array will consist of 1024 dishes, and prototyping is currently in progress with an eight-element pathfinder array in South Africa.� The aim of this proposed project is to develop a two-element interferometer, to be sited at the Dominion Radio Astronomy Observatory in Penticton, that will serve as a North American test bed for the continued development of HIRAX instrument subsystems.

The student who takes on this project will have the opportunity to work on a variety of aspects related to the two-element test bed. Possible areas of work include designing and/or constructing mounts for the dishes and receivers (two prototype dishes have already been fabricated in Penticton), installing readout electronics, subsystem characterization and calibration, and data analysis following end-to-end integration.

For more information contact: Cynthia Chiang (chiang at physics dot mcgill dot ca).

Posted on 2019/02/01

At TRIUMF, in Vancouver, beams of exotic isotopes are produced by proton-induced nuclear reactions, sent through a series of ion guides, and finally collected in an ion trap system called TITAN (TRIUMF Atom Trap for Atomic and Nuclear Science). Our laser spectroscopy group has developed a technique to pulse ions out of the TITAN trap, and to overlap these pulsed beams with a laser beam. Tuning the laser frequency or changing the ion velocity allows us to collect a high-resolution spectrum of atomic transitions. The hyperfine splitting of these atomic levels is used to deduce changes in nuclear radii, to measure nuclear magnetic dipole and electric quadrupole moments and to probe the variation of nuclear shape and size over a series of isotopes.

Currently the laser spectroscopy group (a collaboration between McGill and TRIUMF) uses a system based upon a stabilised Helium-Neon (He-Ne) laser. An improved system can be referenced instead to rubidium transitions (often used as frequency standards). In this project, a student will assemble the new system and compare its performance and stability with that of the existing He-Ne reference.

For more information contact: John Crawford (crawford at physics dot mcgill dot ca).

Posted on 2019/02/01

VERITAS is an array of four 12-m reflectors in Arizona that are used to detect and study astrophysical sources of very high-energy (VHE; energies from 100 GeV to above 10 Tev) gamma rays. The McGill gamma-ray astrophysics group participated in the construction of VERITAS and continues to participate in its calibration, operation and data analysis (see veritas.sao.arizona.edu/).

Fermi is an orbiting gamma-ray observatory (see fermi.gsfc.nasa.gov/) whose LAT instrument is sensitive to gamma rays in the MeV-to-GeV regime.

This project will comprise analysis of VERITAS and Fermi data. Known sources of VHE gamma-rays include supernova remnants and active galactic nuclei, and potential signals include dark-matter annihilation.

The research will be managed through frequent (at least weekly) meetings with the supervisor and daily interactions with other members of the gamma-ray group, and a written report will be prepared at the end of the summer.

For more information contact: Ken Ragan (ragan at physics dot mcgill dot ca).

Posted on 2017/02/16

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 1.8 × 10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. One of these technologies are silicon photomultipliers (SiPMs). The collaboration is working on developing these devices sensitive to Xe-scintillation light at 175nm.

In this project, you will assemble and commission a test setup that allows one to cool SiPMs to -100C and measure their characteristic I-V curves. You will develop test protocols to allow quality control on SiPMs with fast turn-around times for a large number of SiPMs. This will be a crucial step in the future assembly process of the nEXO detector.

You will join the local EXO group at McGill and learn about neutrino physics and detection techniques using liquid Xe. You will be working on the development and testing of photon sensors as part of an international team of researchers. Your project will be well defined with achievable goals. You will perform every day lab work, and most studies and experiments within a small team of undergraduate and graduate students in our lab at McGill. Senior scientists at McGill and within the nEXO collaboration are happy to help you get started and will help you conduct your measurements.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2019/02/01

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 1.8 × 10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. One of those is the so-called Ba-tagging technique. Here, the Xe-decay daughter Ba-136 is located inside the detector volume after the decay, extracted from the volume and identified. This Ba-tagging technique will allow the unambiguous identification of �� decays by clearly distinguishing them from background events. This technique will be particularly important to verify an observation once a positive 0νββ signal has been observed.

A Ba-tagging technique is being developed at McGill with the focus on the extraction and identification of Ba-ions from xenon gas. For systematic studies and to determine the efficiency of the identification process we require a single Ba-ion source. The summer projects focuses on the optimization and characterization of a laser-driven single Ba-ion source. A pulsed laser beam is focused on a surface with a known elemental composition where it ablates atoms and ions. Ions are guided away from the surface by electrostatic lenses and injected into the ion identification setup. These well-known ions are used to calibrate the identification setup and determine transport efficiencies throughout the system.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and ion manipulation techniques. Ion optics geometry and ion transport will be simulated and optimized using the SimIon software. Based on these simulations, initial ion-ablation tests will be performed and ion production will be optimized.

This project is aimed at undergraduate students at all levels, i.e., no special skills, apart from a general understanding of physics and the possibility to fit data using python, are required. All you need is an interest in learning and improving lab skills, and an interest in particle and nuclear physics. We use SolidWorks, LabView, Mathematica, and Python in every-day-business. Some knowledge in any of these programs/languages will help you get started, but is absolutely not required as we have local experts that are happy to assist you.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2019/02/01

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 1.8 × 10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. One of those is the so-called Ba-tagging technique. Here, the Xe-decay daughter Ba-136 is located inside the detector volume after the decay, extracted from the volume and identified. This Ba-tagging technique will allow the unambiguous identification of ββ decays by clearly distinguishing them from background events. This technique will be particularly important to verify an observation once a positive 0νββ signal has been observed.

A Ba-tagging technique is being developed at McGill with the focus on the extraction and identification of Ba-ions from xenon gas. Central part of this technique is the so-called radiofrequency (RF) ion funnel to extract ions of interest from neutral xenon gas. The McGill group is currently designing an improved RF funnel, which must be optimized in gas-flow simulations. The summer project focuses on the optimization of the RF funnel by calculating the flow patter for various funnel geometries and background pressures. In addition, you will be helping the group build a xenon gas-handling system for use during ion-extraction studies.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and ion manipulation techniques. Ion optics geometry and ion transport will be simulated and optimized using the SimIon software; gas flow simulations will be performed with ANSYS or COMSOL.

This project is aimed at undergraduate students at all levels, i.e., no special skills, apart from a general understanding of physics, are required. All you need is an interest in learning and improving lab skills, and an interest in particle and nuclear physics. A background in ANSYS or COMSOL is a plus.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2019/02/01

The birth of the first stars, galaxies, and black holes during the first ~200 Myr of the Universe is a subject of intense study in modern cosmology. One of the most promising approach to understand when this period occur and learn about the properties of the first luminous sources is through measurements of the sky-averaged, redshifted 21-cm signal at low radio frequencies. This signal traces the evolution of neutral hydrogen in the intergalactic medium during the formation of the first sources, and can enable us to characterize the sources themselves. The intensity of this cosmological signal is extremely small compared to other sources of radiation. Teams from around the world are trying to conduct this measurement and detect this signal with high significance above the measurement uncertainties. At McGill we are developing a new instrument, MIST, that will measure the radio spectrum with high accuracy with the purpose of detecting the cosmological 21 cm signal that characterizes the first stars.

The student who joins this project will be involved in the instrumental development of MIST. Depending on the interests of the student, work will include the calibration of the radio-frequency signal path, the programming of the hardware for analog-to-digital signal conversion, the programming of the receiver thermal control circuit, and the electromagnetic simulation of antennas. Interest and experience in radio-frequency applications, analog and digital hardware, and programming, would be advantageous.

For more information contact: Jonathan Siever (jonathan  dot sieversat mcgill dot ca).

Posted on 2019/02/02

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 1.8 × 10²⁵ years. The nEXO observatory is planned to be placed deep underground, submerged in a large volume of water allowing for significant reductions of external backgrounds. As a consequence of this, the outer detector (water tank) will be sensitive to neutrino interactions from core-collapse supernovae.

In this simulation/analysis project, you will explore different outer detector PMT configurations and analyse their effects on the supernova detection capabilities of nEXO. As a starting point, you will be aiding in the development of an event reconstruction algorithm for inverse-beta decay interactions in the water via Cherenkov-ring detection on instrumented PMTs.

Throughout the summer you will be embedded in the local nEXO group at McGill and will learn about neutrino physics, multi-messenger astrophysics, and Monte-Carlo techniques in low-background particle physics.

This project is aimed at all undergraduate students who are proficient in coding in Python and have some familiarity with the UNIX OSX/Linux terminal. Knowledge of C++ and Geant4 will be useful but is not mandatory and the development of these skills is expected throughout the summer.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2019/02/02

The Haggard research group has been experimenting with using the PESTO (Planétes Extra-Solaires en Transit et Occultations) instrument at l'Observatoire du Mont-Mégantic (OMM) to study rapid optical/IR transients, including stellar-mass black holes undergoing outbursts and short gamma-ray bursts. We aim to develop this capacity both with an eye toward understanding these sources, but also in service to our follow-up efforts for electromagnetic counterparts to LIGO-Virgo gravitational wave sources. Localization of upcoming GW targets will continue to be a crucial step in connecting these GW events to astrophysics, by associating the GW source with an EM emitter and a galaxy/stellar population. This project will focus on revisions to our group's existing OMM/PESTO data analysis pipeline (written primarily in Python) and analysis of observations for new explosive transients targeted this summer.

The student will develop Python and other specialize coding skills as they analyze rapid time-series data from the PESTO instrument on OMM. They will learn model fitting and error analysis, and develop both written and oral presentation skills.

The student will develop Python and other specialize coding skills as they analyze rapid time-series data from the PESTO instrument on OMM. They will learn model fitting and error analysis, and develop both written and oral presentation skills.

For more information contact: Daryl Haggard (dhaggard at physics dot mcgill dot ca).

Posted on 2019/02/04

The discovery of GW170817, the first neutron star collision detected via both gravitational waves (GW) and electromagnetic (EM) radiation, has ushered in a new era of multimessanger astrophysics. The Haggard group at McGill successfully led observations of GW170817 with the Chandra X-ray Observatory and joined the massive observational effort to characterize this revolutionary astrophysical source. The LIGO-Virgo detectors have also enabled the first unambiguous detections of binary black hole mergers, while detection of the first neutron star-black hole merger is still on the horizon. Localization of upcoming GW targets will continue to be a crucial step in connecting these GW events to astrophysics, by associating the GW source with an EM emitter and a galaxy/stellar population. This summer project aims to build on our success by developing an analysis pipeline for photometric data from the Canada-France-Hawaii Telescope (CFHT) and potentially to employ this pipeline to study new targets identified during O3.

The student will develop Python and other specialized coding skills as they analyze data from the CFHT, and potentially other multiwavelength data. They will learn model fitting and error analysis, and develop both written and oral presentation skills.

Weekly meetings with the supervisor and daily interactions with other members of Professor Haggard's astronomy group will keep the research on track. A written report will be submitted at the end of the summer.

For more information contact: Daryl Haggard (dhaggard at physics dot mcgill dot ca).

Posted on 2019/02/04

Recent works in our groups have identified mathematical connections between models of cellular decision-making (adaptive proofreading) and simple classifiers in machine learning (/a>arxiv.org/abs/1807.04270). The goal of the project is to further extend this connection by studying if there are structural connections between those models. We will study several examples of classifiers in machine learning, and will attempt to identify what are the main components of the decisions and how they can me matched to what is observed in cellular decision-making. A working hypothesis is that a "prototype" based classification implements a computation similar to cellular adaptive proofreading, while feature-based classifications are closer to detection systems such as found in olfaction.

The student will train simple neural networks to perform classifications, then will study numerically aspects such as parameter sensitivity, or influences of individual nodes. He/she will compare the different mechanisms for robustness and in particular the impact of different perturbations close to the boundary, and relate them to what is observed in biophysical systems. He/she will have daily interactions with the supervisor and a senior graduate student.

For more information contact: Paul François (paulf at physics dot mcgill dot ca).

Posted on 2019/02/04

Gapless majorana modes are fermionic quasiparticles that arise in certain quantum Hamiltonians and which can be used to encode topologically protected quantum qubits. They can be braided with one another to realize non-abelian operations and thus serve as a basis for quantum computers. But while majoranas are well understood in effective non-interacting descriptions of quantum wires and chiral superconductors, it is less clear how the braiding works if interactions, disorder, and errors are non-negligible. Related to this, we want to investigate the possibility of using time-dependent protocols such as repeated driving, and/or dynamical decoupling, to stabilize majorana modes from noise and decoherence, while systematically studying the role of interactions and disorder. We will study this problem using numerical techniques such as exact diagonalization, density-matrix renormalization group, and Lanczos-based time-evolution, besides employing a variety of analytical arguments.

The student should be an advanced undergraduate motivated towards research in physics. They should have a very good understanding of quantum mechanics, at the undergraduate-to-advanced level. They will be tasked with learning the background theoretical material (~ 1 month), developing code for implementing the simulations (~ 1 month), and using the simulations on Compute Canada clusters to get a clearer picture of the physics of this problem (~1 month). If all those steps are carried out successfully, students can expect a paper in a top journal, the writing of which will take further time (~1 month).

For more information contact: Kartiek Agarwal (agarwal at physics dot mcgill dot ca).

Posted on 2019/02/05

It is often the case that physical models are expensive to compute. For example, phase field simulation of microstructure evolution in materials can often take many days to complete, depending on process parameters simulated. Deep learning promises to offer a cure to this problem; namely, instead of computing materials microstructure directly from the physical model, neural networks can be trained to produce adequate approximations of microstructure features that result at a specific set of process conditions, at a faster rate than direct phase field simulations. Such improvements can be done in different ways; in particular through "intelligent" interpolation and short-term / long-term time-series prediction. These improvements can have dramatic advantages when applied to microstructure prediction at industrially relevant process conditions. However, knowledge gained from this research can also be transferable to, and of great interest to, other areas of physics that deal with analysis of complex spatio-temporal data. This project therefore seeks to produce a proof-of-concept for deep learning-aided prediction of solidification microstructure evolution.

The student will use his or her knowledge of programming languages and of deep learning to produce efficient neural networks for the aforementioned proof-of-concept research project. In order to train the model, the student will also be given access to my research group's codes and high performance computing clusters, as well as the McGill High-Performance Computing Centre.

The project will consist of working with other members of my computational materials science group in the department of physics, and weekly meetings with the supervisor to assess progress. A written report is expected at the end of the project.

For more information contact: Nikolas Provatas (provatas at physics dot mcgill dot ca).

Posted on 2019/02/14

The aim of this project is to further develop a recently purchased commercial terahertz time-domain spectrometer based on a femtosecond laser system and photoconductive switches. The student will become familiar with time-domain spectroscopic techniques, femtosecond laser systems, and optical alignment. They will develop software for data acquisition as well as analysis of transmitted and reflected THz waveforms to extract the real and imaginary components of the optical response functions in the THz spectral range. This will become a valuable tool for characterizing the conductivity of materials in a non-contact manner (e.g. two dimensional samples) as well as identifying optical phonon in thin film, bulk and powder form.

For more information contact: David Cooke (cooke at physics dot mcgill dot ca).

Posted on 2018/02/18