arXiv subjects

Tianhuan Luo

Publications and source records attributed to Tianhuan Luo.

5 recordsLinked to original sources

arXiv2023

Detecting resonance of radio-frequency cavities using fast direct integral equation solvers and augmented Bayesian optimization

This paper presents a computationally efficient framework for identifying resonance modes of 3D radio-frequency (RF) cavities with damping waveguide ports. The proposed framework relies on surface integral equation (IE) formulations to convert the task of resonance detection to the task of finding resonance frequencies at which the lowest few eigenvalues of the system matrix is close to zero. For the linear eigenvalue problem \rev{with a fixed frequency}, we propose leveraging fast direct solvers to efficiently invert the system matrix; for the frequency search problem, we develop a hybrid optimization algorithm that combines Bayesian optimization with down-hill simplex optimization. The proposed IE-based resonance detection framework (IERD) has been applied to detection of high-order resonance modes (HOMs) of realistic accelerator RF cavities to demonstrate its efficiency and accuracy.

physics.acc-ph↗

arXiv2022

RF Accelerator Technology R&D: Report of AF7-rf Topical Group to Snowmass 2021

Accelerator radio frequency (RF) technology has been and remains critical for modern high energy physics (HEP) experiments based on particle accelerators. Tremendous progress in advancing this technology has been achieved over the past decade in several areas highlighted in this report. These achievements and new results expected from continued R&D efforts could pave the way for upgrades of existing facilities, improvements to accelerators already under construction (e.g., PIP-II), well-developed proposals (e.g., ILC, CLIC), and/or enable concepts under development, such as FCC-ee, CEPC, C3, HELEN, multi-MW Fermilab Proton Intensity Upgrade, future Muon Colloder, etc. Advances in RF technology have impact beyond HEP on accelerators built for nuclear physics, basic energy sciences, and other areas. Recent examples of such accelerators are European XFEL, LCLS-II and LCLS-II-HE, SHINE, SNS, ESS, FRIB, and EIC. To support and enable new accelerator-based applications and even make some of them feasible, we must continue addressing their challenges via a comprehensive RF R&D program that would advance the existing RF technologies and explore the nascent ones.

physics.acc-ph↗

arXiv2022

Snowmass 2021 Community Survey Report

The Snowmass Community Survey was designed by the Snowmass Early Career (SEC) Survey Core Initiative team between April 2020 and June 2021, and released to the community on June 28, 2021. It aims to be a comprehensive assessment of the state of the high-energy particle and astrophysics (HEPA) community, if not the field, though the Snowmass process is largely based within the United States. Among other topics, some of the central foci of the Survey were to gather demographic, career, physics outlook, and workplace culture data on a large segment of the Snowmass community. With nearly $1500$ total interactions with the Survey, the SEC Survey team hopes the findings and discussions within this report will be of service to the community over the next decade. Some conclusions should reinforce the aspects of HEPA which are already functional and productive, while others should strengthen arguments for cultural and policy changes within the field.

hep-ex↗

arXiv2018

Operation of normal-conducting RF cavities in multi-tesla magnetic fields for muon ionization cooling: a feasibility demonstration

Ionization cooling is the preferred method for producing bright muon beams. This cooling technique requires the operation of normal conducting, radio-frequency (RF) accelerating cavities within the multi-tesla fields of DC solenoid magnets. Under these conditions, cavities exhibit increased susceptibility to RF breakdown, which can damage channel components and imposes limits on channel length and transmission efficiency. We present a solution to the problem of breakdown in strong magnetic fields. We report, for the first time, stable high-vacuum, copper cavity operation at gradients above 50 MV/m and in an external magnetic field of three tesla. This eliminates a significant technical risk that has previously been inherent in ionization cooling channel designs.

physics.acc-ph↗

arXiv2009

Effective Time Reversal Symmetry Breaking and Energy Spectra of Graphene Armchair Rings

We study the energy spectra and wavefunctions of graphene rings formed from metallic armchair ribbons, near zero energy, to search for properties which may be identified with "effective broken time reversal symmetry" (EBTRS). Appropriately chosen corner junctions are shown to impose phase shifts in the wavefunctions that at low energies have the same effect as effective flux tubes passing near the ribbon surface. Closing the ribbon into a ring captures this flux and yields properties that may be understood as signatures of EBTRS. These include a gap in the spectrum around zero energy, which can be removed by the application of real magnetic flux through the ring. Spectra of five and seven sided rings are also examined, and it is shown these do not have particle-hole symmetry, which may also be understood as a consequence of EBTRS, and is connected to the curvature induced in the system when such rings are formed. Effects of deviations from the ideal geometries on the spectra are also examined.

cond-mat.mes-hall↗