Events on Monday, October 27th, 2025
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Operation and Performance of the Centrifugal Mirror Fusion Experiment
- Time: 12:00 pm - 1:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Carlos Rovero-Talamas, University of Maryland, Baltimore County
- Abstract: The Centrifugal Mirror Fusion Experiment (CMFX), a research effort led by UMBC in partnership with the University of Maryland, College Park, has been funded since 2020 by ARPA-E to test the physics of centrifugal mirrors and demonstrate magnetic confinement at parameters relevant to sustained fusion production. The CMFX is the second-generation centrifugal mirror at Maryland, but the first one in the world to use superconducting coils, with a maximum field of 3-T. It is also the first one to achieve sustained operation (limited only by the passive cooling of components). Temperatures, densities, and momentum confinement times in CMFX are now high enough to produce small amounts of fusion energy when experimenting with deuterium plasmas. The applied voltages result in supersonic E x B rotation, with velocities in the azimuthal direction exceeding 1,700 km/s in deuterium plasmas. The high velocities also generate flow shear and heating, resulting in total sustained neutron productions estimated at 10^7 neutrons per second. These neutron rates indicate plasma temperatures must be around 1 keV for plasma densities of 2 – 4 x 10^18 m^-3. Neutral gas can be added in bursts during plasma discharges, leading to an increase in density and neutron production that slowly decays with confinement times of tens to hundreds of milliseconds. Experiments are underway with two He-3 detectors to time-resolve the neutron production with respect to applied voltage, and to spatially resolve the plasma region producing the neutrons.
- Theory Seminar (High Energy/Cosmology)
- Taming Axion Rotation: Dark Vector-like Confinement for Axiogenesis
- Time: 1:00 pm - 2:30 pm
- Place: Chamberlin 5280
- Speaker: Pouya Asadi, UC, Santa Cruz
- Abstract: I show that extending the Standard Model with two axions and a dark vector-like confining gauge group can simultaneously account for both the observed dark matter abundance and the baryon asymmetry of the Universe - a step toward resolving the matter coincidence problem. Starting from a review of sphaleron dynamics, I derive both (i) the axion-induced contributions to fermion asymmetries and (ii) the back-reaction of these fermion asymmetries on axion-like fields, which manifests as a friction on the axions. This analysis clarifies why the minimal axiogenesis scenario cannot produce the correct dark matter and baryon abundances simultaneously. We then show that introducing a second axion and an additional vector-like dark confining sector - a natural infrared realization in the well-motivated axiverse frameworks - resolves this tension by providing a distinct source of friction in the axion dynamics. Finally, we discuss possible UV completions of this setup in extra-dimensional models of high-quality axions. Beyond its cosmological implications, this framework motivates searches for the QCD axion and predicts complementary Light-Shining-through-Wall signatures probing the second axion in the ~eV mass range. Event recording:
- Host: Lisa L Everett
- Preliminary Exam
- Scalable autotuning of high-temperature quantum dot spin qubits
- Time: 2:00 pm - 4:00 pm
- Place: B343 Sterling or
- Speaker: Tyler Kovach
- Abstract: Developing automatic, scalable hardware control is a universal challenge when assembling the physical qubit layer of a large quantum computer. For quantum dot spin qubits—a semiconductor-based platform notable for its high device tunability and its compact size—one key hurdle arises from device non-uniformity. An example of this non-uniformity is the trapped charges in the device’s oxide layers, which induce offset voltage shifts on gate electrodes. These unknown offsets need to be accounted for and calibrated away before any qubits are formed. In this talk, I will introduce a streamlined, five-step physically intuitive algorithm for initializing and bootstrapping these devices, allowing for fully autonomous calibration and characterization. Next, I will demonstrate this methodology experimentally at a high temperature of 1.3K using our in-house developed automatic tuning system, BATIS (Bootstrapping Autonomously Testing Initialization System), to configure a four quantum dot Si/SiGe hetero-structure device. Finally, I will discuss our on-going development of FAlCon (Framework for Algorithmic Control), a soon-to-be open-source software platform designed to facilitate the design, deployment, sharing, and testing of quantum dot tuning algorithms. FAlCon’s platform-agnostic architecture addresses a critical bottleneck in quantum dot scalability, paving the way for the broader implementation of large quantum dot arrays.
- Host: Mark Eriksson