2019 Undergraduate Research Symposium
Five APAM students presented research posters at the 8th Annual Undergraduate Research Symposium on October 3, 2019 organized by Columbia Engineering.
Edita Bytyqi, SEAS ‘21, Applied Physics
Title: Targeted Correction of Point-Like Aberrations with High-Order Thermal Compensation
Abstract: Large scale interferometry has a crucial role in detecting gravitational waves which provide us with information about the early universe. The key to a good interferometer is its sensitivity which is directly proportional to the circulating power inside its cavities. The Laser Interferometer Gravitational Wave Observatory (LIGO) uses Fabry-Perot cavities to achieve high circulating power from the resonant build-up of a low power input. However, due to point-like aberrations located at the end mirrors, the amplitude of the resonant fundamental mode in the cavity is significantly limited. A large fraction of the circulating power is scattered into higher order modes (HOMs) which increase the cavity loss as they approach resonance. The most problematic HOM in the LIGO interferometers is the 7th order mode, which we try to actuate. We propose a thermal compensation system consisting of a heater and a spherical reflector which reduces the effect of point absorbers by centrally heating the mirror at 1.9 cm wide spots. The produced heat pattern allows for actuation of the cavity losses by reducing the heat gradient across the mirrors. While we were able to achieve the desired heat focus, further testing and a consideration of LIGO noise requirements is necessary to obtain a more effective design. Eventually, an array of these heating elements could be used to actively actuate for different HOMs. (Supervisor: Jon Richardson, Aidan Brooks, Rana X Adhikari, LIGO, Caltech)
Mikhaela Diaz, SEAS ‘22, Applied Math (not pictured)
Title: Identifying nontoxic concentrations of sodium selenate for therapeutic intervention of blast traumatic brain injury
Abstract: Traumatic brain injury (TBI) is a major health concern worldwide and there is growing evidence that exposure increases the risk for neurodegeneration. Preclinical TBI studies have reported impaired cognitive behavior associated with increased tau phosphorylation, which is also implicated in the pathology of Alzheimer’s Disease. Protein phosphatase 2A (PP2A) is the major phosphatase responsible for dephosphorylating tau. The aim of this study is to identify a range of nontoxic concentrations of sodium selenate (SS) to increase PP2A activity as a potential therapeutic intervention for cognitive impairments post-TBI. Rat organotypic hippocampal cultures (OHSCs) were treated either with full serum alone (negative control), 10 mM glutamate (positive control), or SS at different concentrations. The cultures were exposed to a single blast TBI 2 hours after treatment and cell death was measured using propidium iodide staining 24 hours after injury. Cultures treated with either full serum alone or 10 and 50 μM SS exhibited less than 5% cell death. On the other hand, glutamate and 100 μM SS treatment induced more than 30% cell death in these cultures. Our study shows that SS at certain concentrations is nontoxic to the tissue cultures. Future work will include performing western blots to quantify changes in PP2A and tau phosphorylation protein expression in these cultures. Additionally a phosphatase assay will be used to quantify changes in PP2A activity. Since there are no FDA approved drugs to treat the neurological consequences of TBI, this study can help develop novel therapeutics targeting tau pathology post injury. (Supervisors: Barclay Morrison and Sowmya Sundaresh, Johnson & Johnson Summer Scholar, Neurotrauma & Repair Lab, Columbia Engineering)
Ava Doyle, SEAS ‘22, Applied Physics
Title: Mapping the Stellar Density of the Milky Way Disk
Abstract: We map the star density in the Milky Way disk by collecting star data from stellar surveys, statistically determining the distance of each star, then graphically representing the density of stars in the Milky Way. In data from Sloan Digital Sky Survey (SDSS) Data Release 14 and the Panoramic Survey Telescope and Rapid Response System (Pan-ST ARRS) Data Release 2, potential substructure has been identified and linked to galactic wiggles, the Hercules Aquila Cloud, and the Hercules Halo Stream. (Supervising Faculty: Dr. Heidi Newberg, Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute)
Joseph Lee, SEAS ‘21, Applied Physics
Title: Quantum Inspired Algorithms for Quantum Chemistry
Abstract: In quantum chemistry, chemists can use the Hartree-Fock ground state energy calculations to achieve about 99% accuracy to the exact values. However, quantum chemists aim to achieve chemical accuracy, requiring at least four digits of accuracy. We explore the possibility of using the Gottesman-Knill theorem with results from Bravyi et al. and Bennink et al. to run a quantum-inspired algorithm for solving the energies of the quantum chemical systems completely classically. We specifically focus on a solid state model known as the half-filled Hubbard Model. We create a quantum circuit based off of the unitary coupled cluster (UCC) approach in quantum chemistry and restrict ourselves to small rotations and Clifford operations. These limited operations allow us to run the circuit on a classical computer in reasonable time. Prior work by Nam et al. have shown that the UCC ansatz required only Clifford operations and small angle rotations for energy calculations of the water molecule.
In future work, we will run these quantum circuits for the half-filled cases of the four site Hubbard Model and beyond. We will then check the overlap with known ground state energy values to see how accurate our results are. We would like this algorithm to work for any value of Coulomb repulsion. Our initial state will take the form of the ground state vector when Coulomb repulsion is equal to zero. Then, the UCC operation will be applied to this initial product state. The angles in the UCC will be adjusted according to the set Coulomb repulsion values. (Supervisor: Jim Freericks, Georgetown Physics Department, Materials Physics REU)
Michael Wahrman, SEAS ‘21, Applied Physics
Title: Optimizing Superconducting Radiofrequency Cavities for Particle Accelerators
The Facility for Rare Isotope Beams (FRIB) at Michigan State University has been under construction and, once completed, will produce rare isotope beams at higher levels of power than ever before. A crucial part of this facility is the superconducting linear accelerator, capable of accelerating heavy ion beams, including uranium ions, up to 200 MeV /u beam energy with 400 kW beam power. Along with FRIB construction, research and development have begun for future energy upgrades to double the heavy ion beam energy, which allows higher isotope production yield. In order to do this, carefully crafted, niobium cavities are used to generate the accelerating gradient up to 17.5 MV/m. The FRIB Superconducting Radiofrequency (SRF) group optimizes the performance of these cavities. To quantify cavity performance, physicists use a quality factor that relates power loss to electromagnetic field strength.
To have a good quality factor, the temperature-independent residual component of the RF surface resistance needs to be minimized. We experimentally studied the effect of cool down speed on the trapped magnetic flux on the superconducting niobium surfaces. In addition, the electromagnetic fields need to be uniformly distributed among five cells to prevent potential field emission/quench at a low accelerating gradient due to unpredictable, high-electric/magnetic field in a particular cell. We measured field flatness and tuned the cavity such that the field is uniformly distributed.
We found that a faster cool down speed caused more of the magnetic field to be expelled from the cavity, which potentially improves cavity performance. Additionally, we were able to achieve 98% uniformity of cell-to-cell field distribution using a manual tuning method. These findings have contributed to our understanding of the various factors that influence cavity performance. Any improvement in the quality factor translates to lower wall dissipation power into liquid helium at the operating accelerating gradient, meaning more efficient operation of the superconducting linear accelerator. (Supervisor: Peter Ostroumov, REU, NSF Facility for Rare Isotope Beams, Michigan State University)