Development of high-resolution gamma-ray detectors for high-energy density plasma experiments
Supervisors: Boon Kok-Tan and Gianluca Gregori
Since the invention of the chirped pulse amplification technique by Strickland and Mourou (2018 Nobel prize in Physics), high intensity lasers focused onto solid foils are now able to accelerate electrons in the matter to relativistic velocities by their strong electric fields. These electrons then interact with the nuclei and produce copious electron-positron pair jets. These jets mimic properties of gamma-ray fireballs and can be used to investigate the microphysics of extreme astrophysical phenomena as well as tools for fundamental physics investigations. The goal of this project is to develop a novel gamma-ray detector using superconducting quantum technologies to study the high-energy gamma ray emission during pair production in order to optimise the jet emission and characterise its properties. The developed detectors can also be used for detecting gamma-ray from other non-astronomical sources such as lab-based radiometry, as long as it is within the designated mass range.
There are several promising candidates for developing such novel superconducting quantum gamma-ray detector. For this project, we expect to explore the possibility of using superconducting tunnel junctions (STJs) and/or Kinetic Inductance Detectors (KIDs) technology as gamma-ray detector. Both technologies have been widely used in astronomy in the past. STJs have been one of the main workforces for millimetre and sub-millimetre astronomy, while KIDs have been deployed for detecting photon ranging from microwave up to X-ray regime. Here, the student will first investigate the feasibility of using one of these technologies for gamma-ray detection with high energy resolution. Once the most suitable technology is identified, the student will proceed to design and fabricate the devices, along with setting up the experiment arrangement required to test the performance of the gamma-ray detector.
This programme is comprising two complementary science topics. First, a focus on the development of the superconducting quantum gamma-ray detectors, and second using the developed detector to understand the microphysics of extreme astrophysical phenomena. The project will suit a student who enjoys reading and understanding the underlying theoretical work of quantum sensors, superconducting electromagnetism, as well as state-of-the-art astrophysics development while enjoying coding, lab-based experimental works and data analysis. We have a state-of-the-art cryogenic detector laboratory comprising several sub-Kelvin dilution refrigerators and many high-end test and measurement equipment. The student will also be supported by a technician and postdocs in addition to the supervisors. He/she will also have access to commercial and our own software/code in order to perform the research.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.015003
https://link.springer.com/article/10.1007/s11432-020-2932-8
https://www.sciencedirect.com/science/article/pii/S0921453417300643
Superconducting quantum detectors for millimetre and sub-millimetre astronomy
Supervisors: Boon Kok-Tan and Dimitra Rigopoulou
The physical and chemical conditions in star-forming regions can be determined by observing at millimetre and submillimetre wavelengths, where a host of atomic (CO), ionic (C+, N+, O+++ etc.) and molecular lines (CO, HCN, HCO+) can be found. In recent years, spectroscopic and interferometric observations of these lines have refined our knowledge of the gas dynamics and kinematics of nearby and distant galaxies, as well as enabling the first direct detection of black hole images. These observations have only been possible because of the extraordinary characteristics of near quantum-noise-limited Superconductor-Insulator-Superconductor (SIS) heterodyne receivers. SIS mixers are used routinely on observatories such as the Northern Extended Millimeter Array (NOEMA), the Atacama Large Millimetre/sub-millimetre Array (ALMA), and the Herschel space observatory, to name a few, enabling numerous observations of faint objects with high spectral and spatial resolution. However, there are two major limitations in utilising SIS receivers for near future astronomical observation, either ground-based or space-borne.
First, the quantum-limited performance of SIS mixers is restricted to frequencies below its superconducting energy gap, commonly about 700 GHz. Above this frequency, RF loss in the superconducting transmission lines increases, resulting in a rapid deterioration in mixer sensitivity. In the past few years, therefore, considerable effort has been invested in the development of new materials with larger superconducting gaps and physical properties compatible with thin film fabrication to improve the performance of these quantum mixers near and beyond the THz frequency range.
Secondly, most of the major mm/sub-mm heterodyne facilities in the world have only a one-pixel receiver equipped in each telescope. Installing more pixels at the focal plane of each telescope will allow fast mapping of an extended object such as nearby galaxies, that otherwise would have to be carried out with mosaicking of individual pointing.
This programme is comprising two complementary science topics. First, a focus on the development of the quantum detectors, and second an observation project.
On the instrumentation side, we have already built an experimental system to test an SIS mixer that operates in the frequency range of 780-950 GHz, and have obtained preliminary experimental tests of the mixer performance. We have also another experimental setup for testing a dual-polarisation 4-pixel array at the 220 GHz range, in collaboration with Smithsonian Centre for Astrophysics in Harvard. In this project we are seeking a student to extend one of these works:
- Improve the existing experimental setup and make an extensive test of the mixer performance.
- Study quantum mixing theory and improve our code to apply it above the superconducting gap to analyse the experimental results.
- Use the above work to design and test a THz mixer, or
- Improve the array performance by integrating multiple dual-polarisation pixels onto a single chip
Observationally, the student will be expected to work on a Galaxy Evolution project focusing on dusty infrared (IR) luminous galaxies. This project focuses on the molecular gas content of IR luminous galaxies and in particular the link between gas content, Star Formation Efficiencies (SFE) and kinematics stage of the galaxies. The project involves reduction and analysis of spectroscopic data from large millimetre and submillimetre observatories, in particular NOEMA and ALMA.
The project will suit a student who enjoys reading and understanding the underlying theoretical work of quantum sensors, superconducting electromagnetism, as well as state-of-the-art astrophysics development while enjoying coding, lab-based experimental works and data analysis. We have a state-of-the-art cryogenic detector laboratory and the student will be supported by a technician and postdocs in addition to the supervisors. He/she will also have access to commercial and our software in order to perform the research.
Further Reading:
https://www2.physics.ox.ac.uk/sites/default/files/profiles/tanb/paper-isstt-2018-mixer-43538.pdf
http://iopscience.iop.org/article/10.1086/423245/pdf
https://ieeexplore.ieee.org/iel7/8062840/8068347/08068508.pdf
https://ui.adsabs.harvard.edu/abs/2022MNRAS.512.2371H/abstract
Superconducting parametric amplifiers for astronomy and quantum computing
Supervisors: Boon Kok-Tan and Dimitra Rigopoulou
The emergence of a new type of amplifier technology, the superconducting parametric amplifiers (SPAs), had drawn considerable attention from the astronomical, quantum computing and dark matter search communities. This is because SPAs can achieve quantum-limited sensitivity over a very broad bandwidth. They are compact, easy to fabricate with planar circuit technology, have ultra-low heat dissipation, and can potentially be integrated directly with other detector circuits. Their performance is far superior to the state-of-the-art cryogenic low noise amplifier used currently in fundamental physics experiments. These devices therefore can revolutionise ultra-sensitive instrumentation in astronomy and qubit technologies, from microwave to sub-millimetre (sub-mm) wavelengths. In particular, they can be used as readout amplifiers to improve the heterodyne receiver sensitivity significantly, and enable the construction of large bolometric arrays as a result of the negligible dissipation. Their large bandwidth, high power handling and quantum-limited noise performance will have a profound effect on quantum computing architecture and improve the fidelity to process hundreds of qubits, opening up the possibility of building a practical quantum computer and speeding up the searching speed of axion dark matter experiments.
This programme is comprising two complementary science topics. First, a focus on the development of the quantum amplifiers, and second an observation project.
On the instrumentation side, the student will start by studying the theoretical background along with learning to use commercial electromagnetism software to design the amplifiers. The student will then have the chance to get involved in the fabrication of the devices using state-of-the-art clean room facilities, either here in Oxford, or with our other collaborators (Paris, Chalmers, IRAM etc). The student will also learn how to use the sub-Kelvin cryogenics system and other experimental techniques, for measuring the performance of the amplifiers. In particular, the student will investigate the amplifier sensitivity and gain dependence on both the temperature and the losses of superconducting materials. Finally, the student will integrate the amplifier into an existing astronomical receiver/quantum computing receiver and assess the impact on the receiver's performance.
Observationally, the student will be expected to work on a Galaxy Evolution project focusing on dusty infrared (IR) luminous galaxies. This project focuses on the molecular gas content of IR luminous galaxies and in particular the link between gas content, Star Formation Efficiencies (SFE) and kinematics stage of the galaxies. The project involves reduction and analysis of spectroscopic data from large millimetre and submillimetre observatories, in particular NOEMA and ALMA.
The Superconducting Quantum Detector Group in Oxford have a well-equipped laboratory, with all the required instruments to perform the design and test of the amplifiers. He/she will also be assisted by an experienced technician, working along with post-docs and other DPhil students in the group, with the support from the electronics, mechanical and photo-fabrications expertise in Oxford Physics.
Further Reading:
https://www.nature.com/articles/nphys2356
http://science.sciencemag.org/content/350/6258/307
https://ui.adsabs.harvard.edu/abs/2022MNRAS.512.2371H/abstract