arXiv subjects

Samantha M. Lewis

Publications and source records attributed to Samantha M. Lewis.

5 recordsLinked to original sources

arXiv2026

A tunable photonic band gap resonator for axion dark matter searches

Axions are a well-motivated dark matter candidate particle. Haloscopes aim to detect axions in the galactic halo by measuring the photon signal resulting from axions interacting with a strong magnetic field. Existing haloscopes are primarily targeting axion masses which produce microwave-range photons and rely on microwave resonators to enhance the signal power. Only a limited subset of resonator modes are useful for this process, and current cylindrical-style cavities suffer from mode mixing and crowding from other fundamental modes. The majority of these modes can be eliminated by using photonic band gap (PBG) resonators. The band gap behavior of these structures allows for a resonator with mode selectivity based on frequency. We present results from the first tunable PBG resonator, a proof-of-concept design with a footprint compatible with axion haloscopes. We have thoroughly characterized the tuning range of two versions of the structure and report the successful confinement of the operating TM$_{010}$ (transverse magnetic) mode and the elimination of all transverse electric modes within the tuning range.

physics.ins-det↗

arXiv2026

Design of ALPHA Phase I: A Plasma Haloscope for 10--20 GHz Post-Inflation Axions

The axion is a well-motivated hypothetical particle capable of resolving both the strong CP problem and the dark matter mystery, with recent post-inflationary cosmological simulations favoring masses above 40 μeV. Plasma haloscopes serve as a promising experimental approach to reach theoretically preferred sensitivities in this mass range. ALPHA, hosted at Yale Wright Laboratory, is an international collaboration developing plasma haloscopes to search for QCD dark matter axions. In this letter we present the detailed design and sensitivity projection for the first phase of the ALPHA experiment, which will search the mass range from 10 GHz to 20 GHz (~40 μeV to 80 μeV). This search will make use of wire-array plasma resonators to decouple the physical size from the resonant frequency, a limitation typically faced by traditional microwave cavities, allowing broadband sensitivity approaching KSVZ coupling strengths.

hep-ex↗

arXiv2022

Design, fabrication, and tuning of a THz-driven electron gun

We present the design, fabrication, and low power testing of a THz-driven field emission electron gun. The two cell standing-wave gun is designed to be powered by a 110 GHz gyrotron and produce 360 keV electrons with 500 kW of input power. Several gun structures were fabricated using a high precision diamond turned mandrel and copper electroforming. The field emission source is a copper tip with a 50 $μ$m radius inserted halfway into first cell. The frequencies of the cavity resonances were mechanically tuned using azimuthal compression. This work presents electromagnetic and particle simulations of the design and cold test measurements of the fabricated structures.

physics.acc-ph↗

arXiv2019

Characterization of the HAYSTAC axion dark matter search cavity using microwave measurement and simulation techniques

Many searches for axion cold dark matter rely on the use of tunable electromagnetic resonators. Current detectors operate at or near microwave frequencies and use cylindrical cavities with cylindrical tuning rods. The cavity performance strongly impacts the signal power of the detector, which is expected to be very small even under optimal conditions. There is strong motivation to characterize these microwave cavities and improve their performance in order to maximize the achievable signal power. We present the results of a study characterizing the HAYSTAC (Haloscope At Yale Sensitive to Axion Cold dark matter) cavity using bead perturbation measurements and detailed 3D electromagnetic simulations. This is the first use of bead perturbation methods to characterize an axion haloscope cavity. In this study, we measured impacts of misalignments on the order of 0.001 in and demonstrated that the same impacts can be predicted using electromagnetic simulations. We also performed a detailed study of mode crossings and hybridization between the TM$_{010}$ mode used in operation and other cavity modes. This mixing limits the tuning range of the cavity that can be used during an axion search. By characterizing each mode crossing in detail, we show that some mode crossings are benign and are potentially still useful for data collection. The level of observed agreement between measurements and simulations demonstrates that finite element modeling can capture non-ideal cavity behavior and the impacts of very small imperfections. 3D electromagnetic simulations and bead perturbation measurements are standard tools in the microwave engineering community, but they have been underutilized in axion cavity design. This work demonstrates their potential to improve understanding of existing cavities and to optimize future designs.

physics.ins-det↗

arXiv2017

Photonic-Band-Gap Gyrotron Amplifier with Picosecond Pulses

We report the amplification of 250~GHz pulses as short as 260~ps without observation of pulse broadening using a photonic-band-gap circuit gyrotron traveling-wave-amplifier. The gyrotron amplifier operates with 38~dB of device gain and 8~GHz of instantaneous bandwidth. The operational bandwidth of the amplifier can be tuned over 16 GHz by adjusting the operating voltage of the electron beam and the magnetic field. The amplifier uses a 30~cm long photonic-band-gap interaction circuit to confine the desired TE$_{03}$-like operating mode while suppressing lower order modes which can result in undesired oscillations. The circuit gain is $>$55~dB for a beam voltage of 23~kV and a current of 700~mA. These results demonstrate the wide bandwidths and high gain achievable with gyrotron amplifiers. The amplification of picosecond pulses of variable lengths, 260-800~ps, shows good agreement with theory using the coupled dispersion relation and the gain-spectrum of the amplifier as measured with quasi-CW input pulses.

physics.app-ph↗