arXiv subjects

Wei-Yuan Chiang

Publications and source records attributed to Wei-Yuan Chiang.

6 recordsLinked to original sources

arXiv2026

Systematic Derivation of Reliable Wake Functions for Complex Structures from Mesh-Based Wakefield Simulations

Wakefield calculations are essential for analyzing beam-driven electromagnetic structures in accelerators. Although analytical wake functions are available for simple symmetric structures, complex geometries generally require mesh-based electromagnetic simulations, which provide finite-bunch wake potentials rather than point-charge wake functions directly. In this study, we present a systematic deconvolution-based method for extracting reliable wake functions from numerically calculated wake potentials using the prescribed drive-bunch distribution. The method is validated with a rectangular dielectric-lined waveguide (DLW), where the extracted longitudinal wake functions agree well with analytical solutions in both the short- and long-range regimes when the drive bunch is sufficiently short. The extracted wake function is further implemented in particle-tracking simulations, producing phase-space distributions consistent with those obtained using a built-in analytical wake-function model. The method is also applied to a modified rectangular DLW with a non-uniform horizontal dielectric distribution. The extracted longitudinal and transverse wake functions and corresponding beam impedances show that the dominant deflecting wakefield can be substantially reduced without significantly degrading the longitudinal wakefield. These results demonstrate the reliability and applicability of the proposed method for complex dielectric-loaded structures.

physics.acc-ph↗

arXiv2026

Phase synchronization recovery in energy-compressed LWFA electron beams for free-electron lasers via undulator tapering

Laser wakefield accelerators (LWFAs) are attractive compact drivers for free-electron lasers (FELs) because they can generate femtosecond electron beams with high peak current over centimeter-scale acceleration distances. However, their relatively large energy spread remains a major obstacle to high-gain FEL operation. Although bunch energy compression can reduce the slice energy spread to a level suitable for FEL amplification, it also introduces a strong energy chirp. The energy chirp detunes the FEL resonance along the planar undulator, causing phase slippage between the electrons and the radiation field, reduced bunching efficiency, and degraded radiation power and spectral quality. Here we investigate a longitudinally tapered undulator for compensating the chirp-induced resonance mismatch in a self-amplified spontaneous-emission (SASE) FEL driven by an energy-compressed LWFA beam. Using three-dimensional unaveraged simulations, we show that an optimized taper profile restores electron-radiation phase synchronization and significantly improves both the saturation power and the spectral properties relative to the untapered case. We also assess the sensitivity of the scheme to shot-to-shot beam-energy fluctuations characteristic of LWFA operation. Our results show that undulator tapering is an effective method for mitigating chirp-induced performance degradation in compact plasma-based FELs.

physics.acc-ph↗

arXiv2025

Simulation Study of Energy Chirp Induced Effects in Laser Wakefield Accelerator Driven Free Electron Laser

Beam energy compression via chicane magnets has been proved to be an effective method to reduce the slice energy spread of electron beams generated by laser wakefield accelerators (LWFAs). This technique has been widely adopted by leading research teams in experiments targeting future compact, high-gain free electron lasers (FELs). However, after energy compression, a strong beam energy chirp is introduced into the electron beam, which substantially hinders the microbunching process and impairs spectral coherence. Here, we present a detailed, unaveraged three-dimensional simulation that examines the effects of this energy chirp, and the results can be applied to the design of a proposed LWFA-driven VUV FEL. The energy chirp in a LWFA-produced electron beam causes FEL interactions at multiple resonant frequencies across the entire electron bunch, simultaneously, which prevents sustained radiation power growth at the designed frequency along the undulator. Consequently, spectral purity is significantly degraded. Additionally, due to undulator dispersion, the energy chirp leads to an elongation of the bunch length, which increases microbunch separation. This results in a noticeable redshift in the radiation frequency and further disruption of spectral purity. These effects are compared to the ideal scenario in which the energy chirp is removed following energy compression. Simulation results indicate that the implementation of a beam dechirper is a crucial step for improving the saturation of radiation power. Insights gained from this simulation of energy chirp-induced mechanisms will aid in the development of more effective compensation strategies, ultimately optimizing LWFA-driven FEL designs.

physics.acc-ph↗

arXiv2022

Taiwan Axion Search Experiment with Haloscope: Designs and operations

We report on a holoscope axion search experiment near $19.6\ {\rm μeV}$ from the TASEH collaboration. The experiment is carried out via a frequency-tunable cavity detector with a volume $V = 0.234\ {\rm liter}$ in a magnetic field $B_0 = 8\ {\rm T}$. With a signal receiver that has a system noise temperature $T_{\rm sys} \cong 2.2\ {\rm K}$ and experiment time about 1 month, the search excludes values of the axion-photon coupling constant $g_{\rm aγγ} \gtrsim 8.1 \times 10^{-14} \ {\rm GeV}^{-1}$, a factor of 11 above the KSVZ model, at the 95\% confidence level in the mass range of $19.4687-19.8436\ {\rm μeV}$. We present the experimental setup and procedures to accomplish this search.

physics.ins-det↗

arXiv2022

First Results from the Taiwan Axion Search Experiment with Haloscope at 19.6 $μ$eV

This Letter reports on the first results from the Taiwan Axion Search Experiment with Haloscope, a search for axions using a microwave cavity at frequencies between 4.70750 and 4.79815 GHz. Apart from the non-axion signals, no candidates with a significance more than 3.355 were found. The experiment excludes models with the axion-two-photon coupling $\left|g_{aγγ}\right|\gtrsim 8.2\times 10^{-14}$ GeV$^{-1}$, a factor of eleven above the benchmark KSVZ model, reaching a sensitivity three orders of magnitude better than any existing limits in the mass range 19.4687 < $m_a$ < 19.8436 $μ$eV. It is also the first time that a haloscope-type experiment places constraints on $g_{aγγ}$ in this mass region.

hep-ex↗

arXiv2022

Taiwan Axion Search Experiment with Haloscope: CD102 Analysis Details

This paper presents the analysis of the data acquired during the first physics run of the Taiwan Axion Search Experiment with Haloscope (TASEH), a search for axions using a microwave cavity at frequencies between 4.70750 and 4.79815 GHz. The data were collected from October 13, 2021 to November 15, 2021, and are referred to as the CD102 data. The analysis of the TASEH CD102 data excludes models with the axion-two-photon coupling $|g_{aγγ}| \gtrsim 8.2\times 10^{-14}$ GeV$^{-1}$, a factor of eleven above the benchmark KSVZ model for the mass range 19.4687 < ma < 19.8436 $μ$eV.

hep-ex↗