Below you will find information on the UROP projects which are being run in the Physics department over the summer 2018 break. Please note that all places have already been filled.
Physics UROP Projects
|Angular Momentum Evolution of Low Mass Stars|
|Supervisors||Dr. Subhanjoy Mohanty / Prof. Alan Heavens|
|Status||Filled for summer 2018 (6 weeks)|
All stars rotate, i.e., possess angular momentum. In low mass stars like the sun, the rotation rate changes with age due to a complex interplay between the evolution of the stellar interior structure, and stellar magnetic fields which couple to outflowing stellar winds. Understanding this rotational evolution remains one of the oldest unsolved problems in astrophysics. In 2012, S. Mohanty at Imperial College, together with his collaborator A. Reiners (IfA Göttingen), formulated a revised theory of angular momentum evolution in low mass stars by revisiting the manner in which the stellar magnetic field evolves) that explained for the first time many of the hitherto puzzling features in the observed rotation rates as a function of stellar mass. However, there are crucial simplifications in this theory that must be treated with more rigorous physics, in order to validate the theory more stringently and quantitatively improve its agreement with the data.
In particular, first, the driving mechanism of the magnetised stellar winds is currently treated in an ad hoc fashion. This does not account for the qualitative change in rotational evolution between stars that are slow rotators (and hence have winds launched by thermal pressure) and those that are rapid rotators (and thus have winds driven by magnetocentrifugal flinging). Second, the current theory assumes a radial magnetic field, which is roughly true only at large distances from the star; close to the stellar surface, where the winds are launched, a more realistic field geometry – e.g., a dipole – is required for better correspondence with observations.The goal of this project is to address both these concerns: to implement a correct wind-launching mechanism (thermal pressure for slow rotators and magnetocentrifugal force for fast ones), and a dipolar field geometry close to the star. The equational framework for this has now been constructed by Mohanty; however, analytic solutions are not possible: the equations must be solved numerically instead. The specific task for the student will be to implement these equations numerically in the Python programming language, under the guidance of Prof. Alan Heavens (who is an expert in numerical methods) and in collaboration with Mohanty, and derive solutions for various rotation rates that will then be incorporated into the rest of the theoretical framework. The expected duration of this project is 6 weeks. Incorporating its results, we expect to submit a paper on the full revised theory by December 2018.
|Bespoke modelling of evaporating planetary birthplaces|
|Supervisors||Dr. Thomas Haworth|
|Status||Filled for summer 2018 (6 weeks)|
|Project Description||This project involved state of the art modelling of evaporating planet-forming discs of material around young stars. These models will be tailored to interpret real observed systems and to infer the consequences for their planet formation. It is primarily a numerical project, but will involve working with real data too.|
|Supervisors||Prof. Ben Sauer|
|Status||Five places filled for summer 2018|
|List of Projects||
|Supervisors||Dr. Matthew Foreman|
|Status||Four places filled for summer 2018|
|List of Projects||
1. Tracking optical vortices in dynamic speckle patterns using neural networks
2. Anderson localisation on circular and spherical domains
3. Hybrid plasmonic-photonic surface modes in metal coated microspheres
4. Counting buried particles with compound speckle
High energy density laboratory astrophysics experiments on the MAGPIE pulsed power generator
|Supervisors||Dr. Simon Bland|
|Status||Three places filled for summer 2018|
MAGPIE is a house sized pulsed-power generator which sits in the basement of the Department of Physics at Imperial College London. It creates a 1.4 mega ampere current pulse with a rise time of 250 ns, which converts solid matter (such as thin metal wires) into high-energy-density plasma, at temperatures of over one million Kelvin. We study these extreme states of matter in order to understand the underlying physics behind some of the most energetic and spectacular events in the universe, such as solar flares, young stellar jets and the unstable accretion disks around black holes.We are looking for two students this summer to work as part of our team. There is no specific project proposed, you will help out with research in the lab, which rapidly changes focus depending on our latest results. Applicants should be practically minded, keen to experiment, good at working as part of a large team and patient with the inevitable delays associated with cutting edge laboratory research. Knowledge of plasma physics is by no means necessary, but applicants should at the very least have significant experience with electronics, oscilloscopes and optics, as well as programming in Python or Matlab.
|Extreme Lasers Stopping Electrons in their Tracks|
|Supervisors||Dr. Stuart Mangles|
|Status||Two places filled for summer 2018|
Accelerating charges radiate electromagnetic energy, so must feel an associated force which tries to slow them down. When a light wave interacts with an electron the amount of energy lost is normally completely negligible, but if the light is extremely intense and the electron energy is moving very close to the speed of light then the energy loss can be significant. Various models exist to predict this effect, but at very high laser intensities these “strong-field quantum radiation models” are untested. Such extreme conditions can occur in cutting edge laser experiments and in some extreme astrophysical conditions such as bear the surface of quasars and near black holes.
Recent work, led by the Imperial Group, has shown the first experimental evidence for “radiation reaction” in the collision of a high energy electron beam with a high intensity laser pulse (https://journals.aps.org/prx/abstract/10.1103/PhysRevX.8.011020).
This project will use the EPOCH particle in cell code to model what happens in these experiments and develop a new tool for predicting what happens in realistic experimental geometries.
A large number of 1D simulations of the collision of narrow energy spread electron beams will be performed (using Imperial’s HPC facilities) varying the laser intensity and electron beam energy. These will be combined to create a model that can rapidly predict the radiation reaction effects (i.e. the electron energy losses and emitted gamma ray spectrum) for arbitrary electron beam and laser intensity distributions in 3D. By benchmarking these results against full 3D EPOCH simulations this project will develop a useful new tool for the analysis of data in upcoming experiments on the Gemini laser at the Rutherford Appleton Laboratory.
|Supervisors||Dr. Yasmin Andrew/Dr. Michael Coppins|
|Contact||Yasmin Andrew/ Michael Coppins|
|Status||Four places filled for summer 2018|
|List of Projects
||Characterisation and Prediction of Tritium Induced Noise in VUV/XUV Spectrometer Detectors on JET
Impurity behaviour studies in tokamak fusion plasmas, particularly during shots with additional heating, are of fundamental importance because of their contribution to increased radiated power and fuel dilution . Spectroscopic measurements of metallic ions, therefore provide important data necessary for the monitoring of impurity densities over the course of an experimental campaign. These spectra are used for real-time monitoring of the plasma to avoid disruptions or to indicate potential damage to the tokamak inner wall. Spectroscopic data are also used in the calculation of the plasma effective atomic number, Zeff , and to provide important benchmarks for comparison with plasma simulations.
This summer project will focus on vacuum ultraviolet (VUV) and extreme ultraviolet (XUV), spectrometers on the JET tokamak which use microchannel plate, MCP, detectors. The spectrometers typically register VUV spectra in the wavelength range of 100-110 x10-10 m and XUV spectra in the wavelength range 40-70 x10-10 m . For one VUV spectrometer the MCP detectors are situated outside the JET torus biological shield, at a distance of 22 m from the plasma, through a vacuum beamline. The line of sight, l-o-s, of the diagnostic lies along the vacuum vessel’s mid-plane via a gold coated spherical mirror, with an angle of incidence of 75°. This remote configuration effectively shields the detectors from neutrons produced by the plasma and reduces the amount of tritium pumped through the spectrometer vacuum system. For the remaining instruments the detectors are located inside the biological shield in close proximity to the JET plasma. This makes them more vulnerable to tritium contamination than for the remote spectrometer.
The next series of operations on JET will include a 100% tritium plasma campaign; it is therefore important to characterise this effect on tritium detector contamination on the VUV diagnostic noise levels. During the JET trace tritium campaign in 2003, the MCP detector of the remote configuration VUV spectrometer was subject to a relatively low level of tritium contamination. At this time the tritium gas injection module on JET was located at the torus end of the VUV diagnostic beamline. This configuration allows the tritium gas injection to be monitored with VUV (and visible) spectroscopy. However, the proximity of the tritium gas source to the entrance of beamline results in approximately 1x10-4 % of the injected tritium enters the spectrometer chamber . The diagnostic MCP detector became contaminated by tritium and the associated beta decay introduced noise to the spectrometer data.
The aim of this project will be to study the change in the tritium induced MCP detector noise levels over the 2003 trace tritium campaign and subsequent (non tritium) campaigns. This data will then be used to predict the expected noise level in the upcoming 100% tritium experiments, for the suite of VUV/XUV spectrometers on JET, and to assess the effect on the measured impurity spectra.Classification of Tungsten Spectra on JET
Impurity behaviour studies in tokamak fusion plasmas, particularly during shots with additional heating, are of fundamental importance because of their contribution to increased radiated power and fuel dilution. Spectroscopic measurements of metallic ions, therefore provide important data necessary for the monitoring of impurity densities over the course of an experimental campaign. These spectra are used for real-time monitoring of the plasma to avoid disruptions or to indicate potential damage to the tokamak inner wall. Spectroscopic data are also used in the calculation of the plasma effective atomic number, Zeff , and to provide important benchmarks for comparison with a wide range of plasma simulations.
The next step-fusion device, ITER, is planned to operate with a full tungsten divertor wall. The main function of the divertor is to extract power from the radiative, conductive and convective heat flux in the outermost, open field-line plasma known as the scrape-off layer (SOL) and the divertor region. The divertor is also used to ensure that most of the plasma surface interaction, such as mechanical or chemical sputtering, takes place at some distance away from the confined plasma, at the divertor target plates, to help reduce impurity contamination and fuel dilution. Tungsten is therefore expected to be present in measureable levels in the confined plasma. Detailed spectroscopic studies of this element are therefore an important area of ongoing research for the characterisation and diagnosis of ITER relevant, tokamak plasmas.
In this project, spatially resolved, tungsten spectroscopic profiles of will be studied as a function of a wide range of JET plasma parameters, including but not limited to, plasma shape, divertor configuration, X-point height, plasma magnetic field, plasma current, plasma isotope, heating power and additional heating method. The most intense tungsten ion photon emission (about I-like W21+ to Mn-like W49+) in the VUV to the soft x-ray region will be analysed. The relative radial shape of the fractional abundances of different ionisation stages, for example, Se-like W40+ to Ni-like W46+, and of the bundle of ionization stages between Sn-like W24+ and Y-like W35+, will be determined and analysed.
Effect of Non-Maxwellian Electron Distribution on Spectroscopic Emission in the Scrape Off Layer
The scape-off layer of a tokamak plasma is characterised by open field lines and large spatial variations in plasma parameters. The scrape off layer has much lower density in comparison to the confined tokamak plasma, resulting in lower collisisonality. The electrons in the SOL and diverter plasma are therefore not always sufficiently collisional to be fully thermalised. Since, the electron-electron collision mean free path can be longer than the temperature gradient scale-lenths, especially close to the divertor target plates, these plasmas are often characterised by bi-modal electron temperatures. A cool bulk plasma, with divertor and SOL electron temperatures in the range of 3 – 20 (???) eV, and a high energy tail electron population, with temperatures of in the region of 10–125 (???) eV. This is an area of particular concern for the next step fusion device ITER, which is planned to operate with a lower temperature divertor plasma in contact with the target plates. Such a scenario is expected to minimise target erosion due to the strong dependence of process such physical sputtering on ion kinetic energy. These cooler plasma regions with steep temperature gradient, however, are where high energy election populations are most likely found. The presence of a high energy electron population leads to an increase in the plasma sheath potential, which in turn increases sputtering rates at the plasma facing materials.
The aim of this summer project is to study non-maxwellian election distributions in the JET SOL plasma using both spectroscopic analysis and collisional radiative modelling. The presence of a high energy tail in the distribution of the electron energies has the effect of lowering the ionisation potential and cross-sections. and A wide range of spatially resolved carbon and beryllium spectra will be used study the effects of non-maxwellian plasmas and to develop kinetic corrections. The presence and effects of non-maxwellian electron distributions will be investigated by comparing experimental spectral emission data with calculated values based different velocity distributions.Transient Impurity Event Characterisation in the JET Plasma
It is well known that plasma surface interactions, along with in-vessel maintenance work, can lead to the formation of microscopic droplets and particles or dust in tokamaks. Dust can be transported and ablated in to the scrape-off layer plasma region, providing a source of impurity contamination of the core plasma and potentially significantly affecting confined plasma conditions. These effects are particularly significant for high-Z impurities, such as the tungsten which will be the divertor material in ITER. In vessel dust has substantial implications for plasma operations in tokamaks; potentially causing disruptions due to sharp increases in radiated power and safety issues due to tritium retention. While, the operation conditions of present day fusion devices are very different to those expected in ITER, it is important to assess the impact and behaviour of dust production over a side range of scenarios in ITER-like plasmas.
Existing software will be further developed to extract information from the JET TIE database and VUV spectroscopy data to identify the composition of the dust recorded with the visible and I/R cameras. The TIEs are usually accompanied by a spike in radiation, which will also be studied to measure time scales over which radiation levels return to normal following the impurity event. The associated radiation timescales will be used to further characterise JET TIEs under a wide range of operating scenarios. The energy and power balance of the associated plasmas will also be calculated and considered.
Space and Atmospheric Physics
|Mirror-mode structures in the Earth’s magnetosphere investigated using data from the Cluster FGM magnetometers|
|Status||2 places filled for 2018|
In space plasma physics the magnetic field is an important quantity measured using an instrument known as a magnetometer. The instruments on the four ESA Cluster spacecraft (Balogh et al. 2001) were built at Imperial College and will continue returning ground-breaking multi-point measurements of the Solar-terrestrial space environment into the next decade. In order to check the accuracy of these measurements, theoretical properties of the space- plasma magnetic field are compared with experimental data. Waves in space plasmas can be described as Alfvénic (non-compressible, characterised by a rotation of the magnetic field vector with constant magnitude). Measurements of these fluctuations are used to check and adjust the magnetometers’ calibrations: with a well-calibrated instrument, the field will appear to rotate with constant magnitude.
However, Alfvénic fluctuations are not available at all points in the satellites’ orbits. Recently, researchers on the NASA Themis mission (Plaschke and Narita 2016) proposed a method based on non-Alfvénic (compressional) fluctuations known as mirror-modes. The aim of this project is to apply the method described by Plaschke and Narita to the Cluster magnetometer measurements and assess whether this can be used as a new method for checking the instrument calibration.
Through this project you will gain experience in the analysis of space-plasma datasets and will develop software in either Python or Matlab. The work will directly contribute to active research within the Cluster magnetometer team at Imperial and will be supported by staff and researchers within the SPAT group.
|Supervisors||Dr. Caroline Clewley|
|Status||Filled for summer 2018|
This funded UROP project is an exciting opportunity to help realise one of the programmes funded by the Excellence Fund in Learning and Teaching Innovation.
You can view the visualisations created in last year’s UROP project at:
http://visualisations.ph.ic.ac.uk (only accessible when connected to the College network; Chrome recommended).
From June through September 2018 we aim to develop a suite of interactive visualisations for education. These visualisations will be designed to enhance understanding of abstract concepts and fall within the broad subject areas of Maths, Core Physics, and Modern Physics, both for the Physics department and selected departments from the Faculty of Engineering.
2. Investigating student engagement with online interactive visualisations in different learning settings
Topological Effects in Photonic Crystals
|Supervisors||Prof. Richard Craster|
|Status||Two places filled for summer 2018|
It has been found that one can direct light (sound or other waves) by altering the geometry of periodic media. This project is about investigating some of this using codes we have created and/or other codes and developing theory. This project would suit a more mathematically inclined physics student who would like to do some coding coupled with quite abstract thinking.
National Physics Laboratory
Building a robust spectroscopy system for laser cooling caesium atoms
|Status||Filled for 2018|
The second is defined in terms of a microwave transition frequency in caesium atoms. Caesium atomic clocks use very well isolated caesium atoms as a reference to fix the frequency of a microwave signal to this transition, such that the microwave signal then becomes an accurate realisation of the second. In the best atomic clocks, the atoms are laser-cooled to temperatures of about 1 microkelvin, so that their thermal motion is very small and they can be probed for a long time. Keeping the lasers that perform this cooling tuned to the correct frequency is often the biggest limitation on such a clock’s running time.
The main goal of the project is to build a robust and compact caesium saturated absorption spectroscopy setup and use it to lock a laser’s output to a fixed, well-known frequency. By building a system to generate multiple beams from this laser, each of which has a carefully controlled amplitude and frequency, you will be able to produce samples of ultracold trapped caesium atoms. If successful, the optical systems you build will form part of a prototype atomic clock that we are developing.