The characterization of extrasolar planets is currently performed using instruments that were not designed for this purpose. As a result, the signatures of atmospheric clouds, winds, and composition are mixed with a variety of detector systematics. When data on the science target outnumber calibration data, the best way to disentangle astrophysical and detector signals is often to self-calibrate the data. This is the approach currently used with the Hubble and Spitzer Space Telescopes, and will likely continue to be the norm in the era of the James Webb Space Telescope. Our project entails constructing and testing high-fidelity detector models to enable atmospheric characterization. The models will be tested on synthetic data and on recently acquired Spitzer observations of hot Jupiters.

The student will develop Python coding skills as they construct mathematical models of the Spitzer detectors. They will learn model fitting and error analysis via gradient descent and Markov Chain Monte Carlo. Finally, they will evaluate the predictive power of their models using cross-validation, and by estimating the Bayesian evidence for competing models.

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

Posted on 2016/01/07

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 2016/01/12

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.

Our technique requires stabilization of the laser frequency to very high precision over lengthy experimental runs. One component of the feedback system that locks this frequency is a scanning Fabry-Perot interferometer, a device that produces sharp fringes at specific optical wavelengths. A student participating in the project will construct and test a new interferometer for use in the visible wavelength region. 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 2016/01/12

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*, which resides in the center of the Milky Way Galaxy.

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 2016/01/13

DNA PAINT is a new technique in the field of super-resolution imaging, which relies on the spontaneous association and dissociation of small DNA ‘imager strands’ from nanostructures. Being able to characterize and precisely control the kinetics of the binding and unbinding of these strands could lead to substantial improvements in this technology, such as the resolution and imaging time. This project advances DNA PAINT by combining it with Convex Lens-induced Confinement (CLiC), a novel microscopy technique that confines DNA nanostructures to a finely-tunable chamber, offering additional control over conformations, orientations, and local reagent concentrations experienced by constituent nanostructures. This project will enable new studies of DNA nanotubes, as a function of adjustable structural and binding properties, using this combination of CLiC and PAINT imaging. It will involve close collaboration with both the PI, two of her graduate students, as well as chemistry collaborators both at McGill and in the Max Planck Institute of Biochemistry in Germany.

For this project, the student will conduct experiments on DNA nanotube samples using the DNA PAINT technique and Leslie's CLiC microscope. The student will be in charge of assembling the DNA PAINT images using a custom software package, as well as performing analysis of the kinetics of this data. 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). This research is expected to lead toward publication in an international peer-reviewed journal and presentations at conferences and workshops, providing the student with training in writing and oral communication.

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

Posted on 2016/01/18

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is the first major new telescope to be built on Canadian soil for decades. Now in its commissioning phase, the telescope will have the capability of mapping the largest volume of the universe ever observed in a single survey. It may unlock mysteries of Dark Energy as well as strange radio bursts that have been seen on the sky. Importantly, it is a new paradigm of telescope - it has no moving parts and images the sky by digitally processing information from several thousand antennas.

The goal for this summer project will be to participate in the calibration and science observations of the CHIME pathfinder instrument, which is 1/5 the size of the full CHIME telescope. In addition, the student will contribute to the testing of systems for the full CHIME telescope, now under construction. This may include travel to the telescope site in British Columbia.

The student will be involved with analyzing sky signals from the pathfinder to measure the instrument's beams and create images of the sky, as well as participating in the construction, assembly and characterization of the electronic system for the full CHIME telescope. The student will perform hands-on lab work, write computer code and test scripts to characterize and calibrate circuit boards, as well as computer-based analysis of the data.

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

Posted on 2016/01/19

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. The study of these proton-proton collisions allows scientists to test the validity of the (incomplete) Standard Model of particle physics and search for new physics phenomena. In December 2015, the ATLAS collaboration presented results showing a small discrepancy between the measured rate of collisions resulting in two photons, and the prediction of the Standard Model of particle physics. In this context, there is renewed interest in better understanding the performance of the algorithm used to identify photons in the ATLAS detector. The goal of this summer research project will be to participate in data analysis development, possibly involving both the analysis of data collected by the ATLAS experiment and simulated data.

The student will study the performance of the photon reconstruction algorithm. Particular emphasis will be given to the study of the different types of particles that can be wrongly identified as a photon, and their associated fake rate. The student will write computer code and scripts for the analysis of data and will be expected to review some of the litterature on the subject.

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

Posted on 2016/01/22

Having a means to transfer quantum information and states between very different kinds of physical systems is crucial to quantum computing and quantum information processing. A promising approach for moving quantum information between superconducting microwave circuits and optical photons is to use a mechanical resonator which couples to both systems. A variety of different schemes are possible, including those that make use of interference and adiabatic evolution to protect the transferred state from mechanical dissipation. The goal of this summer research project is to develop quantum master equation simulations of various transfer protocols, and help determine optimal approaches given realistic experimental constraints. The student should have taken quantum mechanics courses at the level of McGill courses PHYS 357 and 457.

The student will learn and use standard theoretical techniques used to describe quantum optical systems and dissipative quantum systems. Numerical simulations will be done using Python and the QuTIP quantum simulation toolbox. The student will meet at least weekly with the supervisor, and will also interact regularly with both graduate students and postdocs.

For more information contact: Aashish Clerk (clerk at physics dot mcgill dot ca).

Posted on 2016/02/02

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 ~3000 /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 early 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 other radio telescopes (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 2016/02/02

Electron microscopy is a powerful tool in biological imaging, but typically it requires working in vacuum conditions, so that it cannot be used to image dynamic processes in biology. The Reisner and Hilke labs are developing a new single-molecule imaging technology based on dynamic imaging of Au nanoparticle (NP) labeled DNA in an electron microscope. In our approach, Au-NP labeled DNA is placed in special graphene sealed nanochannel structures. The graphene seals the fluid against the vacuum and is electronically transparent, so the molecules can be imaged in free solution at sub 10nm resolution. The nanofluidic dimensions of the cell permit simultaneous confinement based manipulation. Undergraduates on the project will work under the supervision of a postdoctoral researcher, participate in biweekly meetings with our genome center collaborators and meet with the supervisor once a week. USRA/SURA projects will involve developing data analysis procedures in matlab to reconstruct single chain polymer conformation from electron microscopy data.

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

Posted on 2016/02/03

This project will involve using spatio-temporal image correlation spectroscopy (STICS) to map protein transport in cells plated on circularly symmetric adhesive islands on coverslips. 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. STICS will be applied to fluorescence microscopy image time series of actin dynamics of cells plated on the circularly symmetric adhesion zones. Previous work has shown that the actin transport is initially centripetal and radial, but there is a symmetry breaking event and the actin flows begin to rotate, but always in the same direction (unless another actin binding protein called alpha-actinin in introduced). The goal of the project with be to generate and analyse the actin vector maps, and extend the analysis applying a curl operator to obtain a quantitative measure of the rotational dynamics which can probe the biomechanics of the symmetry breaking event/rotation under different conditions.

Part of the project will also involve optimizing temporal filters on the method to remove noise vectors (false fits) in the time dependent studies. The student will learn aspects of experimental biophysics, fluorescence microscopy (laser scanning confocal and evanescent wave excitation microscopy), Matlab based image analysis and image correlation spectroscopy which the Wiseman Lab developed. If interested, the student can be trained in cell tissue culture and try some live cell imaging in addition to analysing existing image series data. The student will have daily contact with the supervisor or a graduate student/post doctoral fellow for supervision of the research.

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

Posted on 2016/02/03

Measuring the electrical resistivity in electrical conducting materials is key because it is an intrinsic property that tells us how well it conducts an electrical current. In our case, we want to measure the resistivity of thin conducting organic molecular films that can be used to produce next-generation solar cells. These organic films are grown and stored under ultra-high vacuum conditions, and we want to measure the electrical resistivity of these films directly inside the vacuum chamber.

To perform electrical resistivity measurements, we will use a very versatile robotic micromanipulator arm inside the vacuum chamber to contact our samples and to perform measurements. This manipulator arm can be moved in almost any position we want and makes it perfect for us to contact our organic film samples.

So far we control and position the tip of this micromanipulator manually with a PlayStation Controller, but wouldn't it be great to interface it with the computer so that we can automatically approach our samples, perform measurements at specific points on the sample and make a mapping out of the collected data? This automation of the micromanipulator will lead to more accurate and reproducible measurements and will make it easier for everyone to perform measurement and collecting data and will save us a lot of time aligning our samples.

We are thus looking for a talented, motivated student who is interested in robotics, electronics and programming in general and likes to work in a scientific environment. Your project would be to program a software, most likely with PYTHON that allows us to access the micromanipulator, to build a graphical interface to control the micromanipulator, to perform measurements and to collect data. There are various packages for PYTHON already available (pySerial, Spinmob, Numpy, PyQtGraph etc.), and we expect you to know how to load packages in general, and how to use them for our purposes. It is favorable if have already programmed a little software before with PYTHON or a similar language such as MATLAB/Labview and understand the logical thinking behind the PYTHON programming language. You will build the software step by step and you will be working with a PhD student together that will help, lead and guide you through the whole process. We don't expect that you know everything already, it should be a learning process for both you and us. All the equipment and knowledge is already available in our laboratory and the project should be doable within a period of 2-3 months. You will also be able to produce and test your own samples and can help working on the ultra-high vacuum chamber.

About us: we are an international renowned nanoscience & materials group with about 15 memeber, ranging from undergraduate students up to PostDocs. We are a dynamic and highly collaborative team and our research is motivated by exciting fundamental science questions from physics, industry and societal relevance. The project you will be working on will help us in daily research process of measuring and collecting data and will give you an insight in the daily business of a scientific research group. We believe this is a fun and rewarding project and are already excited to work with you together.

For more information contact: Peter Grütter (grutter at physics dot mcgill dot ca).

Posted on 2016/02/08

The masses and radii of hundreds of transiting exoplanets have now been measured, allowing their average densities and therefore average compositions to be determined. To go further in probing the internal structure of planets, we need to measure higher moments of the mass distribution, such as the tidal Love number which quantifies the extent to which a planet is distorted by a tidal gravitational field. The Love number of the transiting planet HAT-P-13B was recently measured. In this project, the student will numerically model the internal structures of gas giant planets using a variety of different equations of state for the rock and gas to investigate what kind of constraints on internal structure can be derived from a Love number measurement.

The student will learn about the physics of planetary interiors and develop code to numerically model them. The student will meet at least weekly with the supervisor, and will also interact regularly with both graduate students and postdocs in the astrophysics group.

For more information contact: Andrew Cumming (cumming at physics dot mcgill dot ca).

Posted on 2016/02/18

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. One of these techniques is the so-called Ba-tagging. Here, the Xe-decay daughter Ba-136 is located inside the detector volume, extracted from the volume and identified. This Ba-tagging technique will allow measurements of the 0νββ half life without background contribution from naturally occurring radioactivity and thus dramatically increase the measurement's sensitivity.

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. The student 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 tested.

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

Posted on 2016/02/22

The aim of this project is to measure conductivity and electromechanical properties in a perfectly defined molecular junction of C60 by using a unique experimental setup: a combined scanning tunneling/atomic force/field ion microscope system (STM/AFM/FIM). These experiments will allow us to determine the crucial role of contacts in determining the electronic properties of this system.

The student will prepare an atomically defined single crystal of Cu(001) by sputtering and annealing in ultrahigh vacuum (UHV). The chemical cleanliness of the Cu surface will be characterized by Auger Electron Spectroscopy, while the surface structure will be evaluated by STM. A UHV evaporator will be used to deposit C60 on this bottom electrode. Suitable deposition conditions that lead to small islands and even individual molecules of C60 need to be determined. C60 is known to have a high diffusion barrier on Cu(100) - even rotations are inhibited at RT. In addition, the strong binding of C60 is indicative of a high conductivity metal-molecule junction. This is a result of a strong wave function overlap and rehybridization of Cu and C orbitals - thus making this system a good challenge for thoroughly testing theoretical models.

As a second (parallel) project, based on existing expertise in the Grütter group, the student will prepare sharp W(111) STM tips suitable for imaging by FIM. These tips need to be electrochemically polished, then annealed in UHV and characterized by FIM. Suitable tips will be used to contact the individual C60 on Cu(100), defining an atomically characterized molecular 2 terminal device. Careful measurements of the I-V curves as a function of different tip atomic structures should lead to deep insights into the electronic transport properties in this system.

For more information contact: Peter Grütter (grutter at physics dot mcgill dot ca).

Posted on 2016/02/24