The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a radio telescope currently being built in Penticton, BC, funded by the Canada Foundation for Innovation (CFI). CHIME was designed for sensitive observations of hydrogen in the distant galaxy for cosmological purposes. However CHIME can also be used as a 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) will enable the detection of tens of FRBs per day — in contrast to the fewer than 2 dozen discovered since 2007. For this reason, we have been granted additional CFI funding to build a real time FRB detector back-end instrument for CHIME. We expect first light for CHIME and our FRB back end in late 2017. The proposed research project is to assist the McGill group, in collaboration with colleagues at U. Toronto, UBC and elsewhere, in the design and implementation 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. Observations of pulsars with the existing CHIME pathfinder may also be possible.

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 interfence, or may help develop a database of source properties for eventual use with CHIME. One other option is to help develop a real time alert system for informing the worldwide astrophysical community of CHIME events to enable multiwavelength follow-up.

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

Posted on 2016/12/20

Rapid growth of supermassive black holes (SMBHs) occurs when gas and dust flow to the innermost regions of a galaxy, spiraling into a hot, bright accretion disk, and falling across the event horizon (hence disappearing from view). Inflowing gas is also responsible for star formation in the galactic bulge. The bulge and the central black hole may even be connected via physical process that are not well understood, a connection across nine orders of magnitude! One candidate is feedback, wherein jets and winds from the accretion disk regulate both the growth of the central black hole (at small scales) and star formation (at much larger ones). During growth cycles, accreting SMBH are highly variable, since the accretion disk, jets, and winds are all dynamic structures. This summer project involves study of accretion onto our closest supermassive black hole, Sgr A*, and other active galactic nuclei (AGN).

The student will develop Python and other specialize coding skills as they analyze Chandra X-ray Observatory and 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 (haggardd at physics dot mcgill dot ca).

Posted on 2016/12/31

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 laser beams. 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, and to measure nuclear magnetic dipole and electric quadrupole moments. Such measurements give us information about the variation of nuclear size and shape over a series of isotopes. We have recently made many modifications to improve the sensitivity of these measurements for nuclear beams of low intensity and very short lifetimes. More details of these developments have been acknowledged in an article on TRIUMF Research Highlights.

The photons emitted in the interaction region of the laser and isotopic beams are detected by a photomultiplier tube. To maximize the signal a spherical mirror system is used to collect the light and guide it to the photomultiplier by multiple reflections. The efficiency of this system has been predicted by computer modeling, but not tested experimentally. A student participating in this project will do offline tests on this system to verify the predicted efficiency and to make modifications to maximize the signal:noise ratio of the measurement. He or she will be assisted by an experienced group of TRIUMF staff, PDFs, and other McGill graduate students. McGill staff members (Crawford, Buchinger) regularly visit TRIUMF to participate in experiments. When I (Crawford) am at McGill, I will supervise the student by a weekly TRIUMF-McGill video link.

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

Posted on 2017/01/06

We are developing an imaging device for hard X-rays and soft gamma rays in the energy range from 0.2 to 2 MeV. Such a detector is useful in safety and security applications where radioactive sources are involved.

An incoming photon will Compton scatter in the detector's front layer and the resulting scattered photon will be absorbed in the detector's rear layer. Knowing the positions and energy deposits associated with these two events enables us to reconstruct the arrival direction of the incident photon up to an azimuthal ambiguity. This ambiguity is resolved by detecting multiple events.

We plan to use CsI scintillator material in the form of bars read out at each end by photomultiplier tubes. The novel feature will be that the position of the interaction along the bar will be determined by comparing the pulse heights from the phototubes at opposite ends, and the longitudinal resolution will be optimized by adjusting the gap between cubes of scintillator that make up the bar. In this way we plan to achieve a significant reduction in the number of required readout channels and the associated cost.

The student will characterize the instrument and participate in design studies leading to a field-deployable version which will emphasize efficiency and ease of use. S/he will develop analysis code and calibration protocols as well as the related documentation.

Weekly meetings with the supervisor and daily interactions with other members of the McGill gamma-ray astronomy group will keep the research on track. A written report will be submitted at the end of the summer.

Experience with electronics and knowledge of Python and/or C++ is an asset but not a requirement.

For more information contact: David Hanna (hanna at physics dot mcgill dot ca).

Posted on 2017/01/09

The Kepler mission and its K2 extension have found over 4000 exoplanet candidates via the transit method. A transit occurs when the exoplanet passes in front of its host star, blocking a small fraction of the light observed from the system. Transit observations require precise monitoring of the light from the star to watch for the periodic dip. Plotting the observed flux from the star vs time (or phase, for periodic events) produces a light curve. The quality of the Kepler photometry makes it possible not only to detect transits, but also more subtle effects such as secondary eclipses. At secondary eclipse, the planet passes behind the star, so any reflected light or thermal emission from the planet is blocked. From the transit, the ratio of the planet radius squared to the stellar radius squared can be determined. The secondary eclipse can constrain the albedo of the planet.

Working with Professor Cowan and Dr Sheets, the student will learn how to create light curves from photometric data, and then how to use the light curves to determine the planet's parameters. Depending on the student's interests, they will then either analyze photometry from Kepler and/or K2, or they will construct model light curves to explore how refraction in the atmosphere of an exoplanet can alter the shape of the light curve just outside of transit.

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

Posted on 2017/01/09

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>1.1x10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. 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 νββ decays by clearly distinguishing them from background events.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and the manipulation of individual ions. A Ba-tagging technique is being developed at McGill with the focus on the extraction of Ba-ions from xenon gas. For systematic studies and to determine the efficiency of the tagging process we require a single Ba-ion source. You will be developing this laser-driven single Ba-ion source. Ion optics geometry and transport will be simulated and optimized using the SimIon package before the source is built and can be tested..

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

Posted on 2017/01/15

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. If this decay is observed it would prove the existence of unknown physics beyond the Standard Model of particle physics. 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 T1/2>1.1x1025 years. In order to greatly increase the sensitivity of this decay, the EXO collaboration started developing a next-generation detector, called nEXO. New types of photon sensors have to be characterized and tested before they can be used in nEXO.

In this summer research project, you will develop an electroluminescent light source. Photoelectrons are created at a cathode and then drifted through xenon gas where they cause the emission of electroluminescent photons at 175 nm. This is the same wavelength that will be detected by the photon sensors in nEXO. Your light source is intended for detailed characterization of these photon sensors.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and detection techniques using xenon. Parts of the light source have been manufactured and have to be assembled. Afterwards, the light source has to be evacuated, i.e., the air has to be removed, and filled with xenon gas. You will then characterize the light output of the source for various operating parameters.

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

Posted on 2017/01/15

Note:This project is through the Faculty of Medicine. See the Faculty of Medicine's USRA sitefor application details.
Deadline: Paper copy to Jennifer Nemes at the Faculty of Medicine's Research Office (McIntyre Building, Rm 637) by 4:00 PM on Thursday, February 9, 2017.

Student must apply for official transcript ASAP!

Neutrons that are generated as unwanted secondary, by-product, radiation during high-energy (> 10 MeV) photon-beam or proton-beam radiation therapy, cannot be shielded and, consequently, exposed patients are susceptible to radio-carcinogenesis. This long-term health risk is well known and generally accepted, although poorly understood. Efforts currently underway within the Canadian medical physics and radiation oncology communities to introduce proton beam radiotherapy into Canada are bringing the issue into focus. Pediatric patients who are considered the main beneficiaries of proton therapy are also the most at risk for second cancers resulting from the unavoidable whole body dose of secondary radiation that arises in large part from neutrons. The NICE research project aims to use Monte Carlo and experimental techniques to improve our understanding of the biophysical effects surrounding neutron dose deposition in human tissue.

The student will (a) assist in the development of Monte Carlo codes to examine the secondary particle spectra deposited in tissue by primary neutrons and (b) assist with neutron spectral measurements in radiotherapy bunkers.

The student should have some computer programming experience (knowledge of C++ and ROOT will be useful but not required) and a desire to learn about medical physics.

Weekly meetings with the supervisor and daily interactions with students and staff in the Medical Physics Unit are anticipated. The student will present their work at the student day of the MUHC Research Institute at the end of the summer. A report will be written by the student at the end of the project. This project will be carried out in the Medical Physics Unit at the Cedars Cancer Centre of the MUHC Glen Site.

For more information contact: John Kildea (john dot kildea at mcgill dot ca).

Posted on 2017/01/20

Observations in the radio band have the potential to image the "dark ages" of cosmic time, just before the universe was "lit up" by the first stars, and the early growth of structure that follows. Detailed observations of these periods will serve to elucidate the origin, fate, and composition of the universe.

New technology is being developed that will allow the world's largest and most sensitive telescopes to be built. This project will involve assembling and testing prototype telescope chains, and using them for basic observations that will serve to characterize the technology.

The student will be involved with assembling hardware in collaboration with graduate students, postdocs and/or engineers, developing software to operate the hardware, and analyzing data from test operations. The student will perform hands-on lab work, write computer code and test scripts to characterize and calibrate the instrumentation, as well as computer-based analysis of the data.

For more information contact: Matt Dobbs (matt dot dobbs at mcgill dot ca).

Posted on 2017/01/25

How do bacteria partition their replicated chromosomes to daughter cells? Remarkably, entropy may provide the driving force for this process. While small, chemically identical particles always mix in equilibrium, self-avoiding polymers like DNA can segregate (i.e. demix) in confined environments as a fundamental consequence of chain interconnectivity and entropy maximization.

The Reisner group has developed an experimental assay to explore this effect in vitro, using two differentially stained DNA molecules compressed against a slit-barrier in a nanochannel. The barrier traps the DNA but allows for fluid flow; we can compress the two chains against the barrier and directly observe chain mixing. We have preliminary data that suggests we observe a first order phase transition at a critical flow between a mixed and segregated state (in analogy to vapor-liquid transitions). In addition, the flow can be switched-off and the disentanglement and relaxation of the chains observed in real time.

In this project the student will work closely with the PI to develop and solve a partial differential equation model to describe the mixing and relaxation process, based on our previous work with single chain dynamics. This will involve a combination of literature review to understand relevant polymer physics and background work, analytic theory and numerical solution methods (implanted via the package flexPDE). If we can successfully develop a model, we will then try to fit predictions to experimental measurements on two chain mixing using custom-designed Matlab codes. This project will provide excellent grounding in polymer physics/soft-matter modelling approaches in biophysics, including application of the Onsager variational approach in single-chain dynamics. I believe this project will provide excellent grounding for future work in soft-matter or biophysics theory. In addition, as time and student motivation/interest permits, there is opportunity for involvement on the experimental side (e.g. operation of devices and acquisition of mixing data).

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

Posted on 2017/02/02

DNA PAINT is a technique in the field of super-resolution imaging that relies on the spontaneous association and dissociation of small DNA “imager strands” from nanostructures. These imager strands, covalently labeled by dye molecules, bind to complementary docking strands attached to the sample being imaged. The imager strands only bind transiently and, when unbound, rapidly diffuse throughout the sample to generate background “noise”, which is traditionally excluded from the data through Total Internal Reflection Fluorescence (TIRF).

For this project, the student will combine confinement microscopy methods with DNA PAINT, to improve the imaging of DNA nanostructures, by more efficiently suppressing the background. Higher background suppression will allow for the use of higher concentrations of imager strands, which can bind over shorter time periods, enabling faster data acquisition and hence access to a broader range of interaction parameters. The project will involve close collaboration with Professors in Physics and Chemistry (weekly meetings), two graduate students working with the PIs, and with international collaborators at the Max Planck Institute of Biochemistry in Germany.

The student will be responsible for conducting new experiments combining DNA PAINT and confinement microscopy. He/she will visualize DNA PAINT imaging as a function of the adjustable nanoscale confinement. He/she will use custom software to reconstruct DNA PAINT images, and explore DNA nanotube and DNA origami visualization experiments in previously inaccessible regimes. The student will receive training in microscopy (optics, experiment design, device control), quantitative data analysis (Matlab), and sample handling and fluorescent staining (DNA nanostructures, stains, passivation agents). The expected outcome of the research is publication in an international peer-reviewed journal and presentations at local workshops and conferences in the Fall, providing the student with skills in writing and oral communication.

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

Posted on 2017/02/08

Fluorescence Cross-Correlation Spectroscopy (FCCS) is the study of the fluctuations and kinetics of interacting molecules; and 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 unprecedented 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 several-minutes-long timescales. By comparing results to theoretical models, the student will extract meaningful system parameters, such as concentration, binding and unbinding rates, and diffusivity, as a function of the applied confinement.

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 the research group, will support and guide the project. Anticipated outcomes of the summer research project include publication in an international peer-reviewed journal and presentations at local conferences and workshops in the fall, providing the student with key training in writing and oral communication.

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

Posted on 2017/02/08

This project will involve using spatio-temporal image correlation spectroscopy (STICS) and pair vector correlation analysis to map waves of protein transport between mechanosensory podosome complexes in human immune dendritic cells. STICS is a fluorescence fluctuation image analysis method that the Wiseman Lab developed that uses correlation functions to measure transport properties of fluorescently tagged proteins in live cells. The output from STICS is the protein transport velocity vector map across the cell. These maps are further analyzed by pair vector correlation (PVC) to establish radial and temporal correlation times between neighboring podosome complexes in cells. STICS and PVC will be applied to analyze fluorescence microscopy image time series of fluorescently labeled podosome components (paxillin, talin and actin) in dendritic cells. Recent work suggests a mechanical coordination between neighbor and next nearest neighbor podosomes, however, new experiments will examine this regulation on cells plated on substrates of varying stiffness.

The student will learn aspects of experimental biophysics, laser excitation fluorescence microscopy, Matlab based image analysis and image correlation spectroscopy which the Wiseman Lab developed. Image series data will be provided by Prof. A. Cambi's lab (Radboud University) which has expertise in immunology, podosome biology and imaging. The student will be directly supervised by the PI and receive in lab training from a graduate student/postdoctoral fellow.

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

Posted on 2017/02/08

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 student will participate in a project aimed at using single defect centers in diamond to map out the magnetic fields generated by driven ferromagnetic circuits. Nanoscale magnetic circuits are critically important to computer hardware, especially in applications that use ferromagnetic domains to encode information. For example, magnetic random access memory (MRAM) could potentially replace standard DRAM while drastically reducing the demands for power. Understanding the dynamics of driven ferromagnetic circuits thus has important applications both in fundamental science and in industry. One challenge is to understand the role of spatial inhomogeneities, and one would thus seek to map out the magnetization of the device on the nanoscale �~@~S and ideally also watch its time evolution. However, there are few techniques that can measure magnetic fields with good sensitivity and excellent spatial and temporal (or, equivalently, spectral) resolution. One possibility is to fabricate the ferromagnetic circuit on the surface of a substrate embedded with tiny magnetic sensors. In particular, the nitrogen-vacancy (NV) defect center in diamond can be used to sense magnetic fields because its spin (which responds to magnetic fields) can be detected via the fluorescence intensity of the defect. Each defect can thereby reveal the magnetic field at its location, with the potential for nanoscale spatial resolution. Moreover, by manipulating the defect, one can select the time at which it senses the magnetic field or (more commonly) the frequency of magnetic fields that affect it. The central goal of this project is thus to use a diamond substrate embedded with NV centers to map out the driven dynamics of a ferromagnetic circuit fabricated on the diamond surface.

The student will develop experimental data acquisition software and hardware to implement precision pulsed spin resonance control for detection of AC magnetic fields with NV centers. Specifically, he or she will learn to program a fast multichannel arbitrary waveform generator to create pulse patterns controlling optical and microwave excitation. These pulse patterns will be used to implement broadband and narrowband detection of AC magnetic fields via single NV spins.

For more information contact: Lily Childress (childress at physics dot mcgill dot ca).

Posted on 2017/02/20

The ATLAS experiment at the CERN's Large Hadron Collider in Geneva records the results of the highest energy particle collisions ever produced in laboratory. In 2012, the ATLAS and CMS collaboration announced the discovery of a new elementary particle of nature, the so-called Higgs boson. In order to more precisely study the properties of this new particle, test the validity of the Standard Model of particle physics and further extend the search for new physics phenomena, the ATLAS detector will be undergoing a major upgrade in 2019. Canada will be constructing approximately one third of the specialized detectors required for this upgrade. The McGill group is responsible for the testing and characterization of these Canadian-made chambers. The production of these "thin gap chambers" is scheduled to begin this Summer 2017. The goal of this summer research project is to participate in the testing and characterization of Canadian-made "thin gap chambers" for the upgrade of the ATLAS experiment. The student will learn about different particle detection techniques and develop a wide range of experimental skills.

The student will be asked to participate in the data taking of cosmic ray data with the new Canadian-made detector. The student may also be required to participate in the analysis of cosmic data and/or simulation studies associated with the optimization of the detector testing. The student will also participate in the development of the testing work flow and associated documentation. The student may also have the opportunities to test readout electronics components.

For more information contact: Brigitte Vachon (vachon at physics dot mcgill dot ca).

Posted on 2017/02/21

The ATLAS experiment at the CERN's Large Hadron Collider (LHC) in Geneva records the results of the highest energy particle collisions ever produced in laboratory. The LHC is scheduled to undergoe a major upgrade in 2025 that will result in an increase of its beam intensity by nearly an order of magnitude. In order to cope with this new extreme environmental conditions, the ATLAS detector will undergoe a major upgrade of several of its subsystem. One of this upgrade consist in replacing the entire readout electronics of the Liquid Argon Calorimeter detector, a sub-system responsible for precisely measuring the energy of electrons/photons produced in proton-proton collisions. The goal of this summer research project is to participate in the ongoing R&D to define the exact design and technology of the future readout electronics (which includes both an analogue and a digital part). The student will learn about different concepts of analogue and digital electronics and develop FPGA programming skills.

The student will be asked to develop a simple digital filtering algorithm on an FPGA (Field Programmable Gate Array) and test its performance. The student may also be required to participate in some simulation studies for the optimization of different possible parameters of the readout chain.

For more information contact: Brigitte Vachon (vachon at physics dot mcgill dot ca).

Posted on 2017/02/21