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A Verdict on the Annual Modulation: Settling a 20-Year Dark Matter Debate
Published:
A new combined analysis from the COSINE-100 and ANAIS-112 experiments provides the strongest evidence yet against the long-standing DAMA/LIBRA dark matter claim.
The Kernel Trick: A Guide to High-Dimensional Feature Spaces
Published:
A technical explanation of how the kernel trick allows linear models to solve non-linear problems by implicitly operating in high-dimensional feature spaces.
A Scalpel of Electrons: The Promise and Clinical Reality of Laser-Driven Radiotherapy
Published:
An analysis of laser-wakefield accelerators for cancer therapy, exploring how this remarkable technology has overcome physics barriers but now faces the challenge of clinical necessity.
The Next Light: Can Particle Accelerators Power the Future of Moore’s Law?
Published:
An overview of the push for next-generation EUV light sources, comparing the incumbent laser-produced plasma technology against emerging accelerator-based Free-Electron Laser concepts.
Reconstructing Electron Bunch Current Profiles with Conditional Diffusion Models
Published:
This work proposes using a conditional diffusion model to solve the ill-posed inverse problem of reconstructing electron bunch current profiles from downstream diagnostics in plasma wakefield accelerators.
QLu: A Novel Oscillatory Activation Function for Neural Networks
Published:
Will a new activation function with oscillatory behavior improve performance of neural networks?
Laser frequency combs: a precision revolution
Published:
How laser frequency combs evolved from precision metrology tools to ubiquitous sensing devices powering quantum technologies and autonomous systems.
WIMP detection reaches critical threshold
Published:
Four decades of WIMP searches reach 2.2×10^-48 cm² sensitivity—just one order of magnitude from the neutrino floor that will either reveal dark matter or redirect physics toward axions.
Cover Letter Lessons from High-Impact Journal Submissions
Published:
Modern academic publishing has shifted toward more egalitarian, merit-focused evaluation. Cover letter tone and broad appeal matter more than author credentials or publication history when targeting high-impact journals.
The quiet decline of recombination X-ray lasers
Published:
While X-ray laser research thrives globally, plasma-based recombination schemes that showed promise in the 1990s have quietly faded from mainstream science.
Is the DAMPE 1.4 TeV peak real?
Published:
CALET contradicts DAMPE’s 2017 claim of a 1.4 TeV peak in cosmic-ray electrons at greater than 4-sigma significance—an intriguing discrepancy that warrants further investigation with additional data.
portfolio
FREP: Femtosecond Relativistic Electron Probe
An innovative diagnostic to probe the microscopic and transient plasma wakefields with micrometer and femtosecond spatialtemporal resolution. 
PELLA: Platform for Electron- and Laser-enabled Laboratory Astrophysics
A novel platform to study kinetic instabilities in plasmas, bridging the gaps between theory, laboratory experiments and astrophysical phenomena. 
publications
Generating High-Brightness Electron Beams via Ionization Injection by Transverse Colliding Lasers in a Plasma Wakefield Accelerator
Published in Physical Review Letters, 2013
Novel ionization injection scheme using transverse colliding lasers produces ultra-bright electron beams with unprecedented low emittance in plasma wakefield accelerators.
Recommended citation: Fei Li, Jianfei Hua, Xinlu Xu, Chaojie Zhang, Lixin Yan, Yingchao Du, Wenhui Huang, Huaibi Chen, Chuanxiang Tang, Wei Lu, Chan Joshi, Warren B. Mori, Yuqiu Gu, "Generating High-Brightness Electron Beams via Ionization Injection by Transverse Colliding Lasers in a Plasma Wakefield Accelerator," Phys. Rev. Lett. 111, 015003 (2013).
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Phase-Space Dynamics of Ionization Injection in Plasma-Based Accelerators
Published in Physical Review Letters, 2014
Theoretical and simulation study revealing the complex phase-space evolution of electron beams in ionization injection, providing analytical framework for achieving ultralow emittance beams.
Recommended citation: Xinlu Xu, Jianfei Hua, Fei Li, Chaojie Zhang, Lixin Yan, Yingchao Du, Wenhui Huang, Huaibi Chen, Chuanxiang Tang, Wei Lu, Peicheng Yu, Weiming An, Chan Joshi, Warren B. Mori, "Phase-Space Dynamics of Ionization Injection in Plasma-Based Accelerators," Phys. Rev. Lett. 112, 035003 (2014).
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Low emittance electron beam generation from a laser wakefield accelerator using two laser pulses with different wavelengths
Published in Physical Review Special Topics - Accelerators and Beams, 2014
Novel two-color laser scheme separating wakefield excitation from injection process enables generation of ultralow emittance electron beams with more than one order of magnitude improvement.
Recommended citation: Xinlu Xu, Yipeng Wu, Chaojie Zhang, Fei Li, Yang Wan, Jianfei Hua, Chi-Hao Pai, Wei Lu, Peicheng Yu, Chan Joshi, Warren B. Mori, "Low emittance electron beam generation from a laser wakefield accelerator using two laser pulses with different wavelengths," Phys. Rev. ST Accel. Beams 17, 061301 (2014).
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Generating 10–40 MeV high quality monoenergetic electron beams using a 5 TW 60 fs laser at Tsinghua University
Published in Chinese Physics C, 2015
Demonstration of high-quality monoenergetic electron beam generation using a compact 5 TW 60 fs laser system at Tsinghua University, achieving 10-40 MeV beams with excellent beam quality.
Recommended citation: Hua Jian-Fei (华剑飞), Yan Li-Xin (颜立新), Pai Chih-Hao (白植豪), Zhang Chao-Jie (张超杰), Li Fei (李飞), Wan Yang (万阳), Wu Yi-Peng (吴益鹏), Xu Xin-Lu (徐新路), Du Ying-Chao (杜应超), Huang Wen-Hui (黄文会), Chen Huai-Bi (陈怀壁), Tang Chuan-Xiang (唐传祥), Lu Wei (鲁巍), "Generating 10–40 MeV high quality monoenergetic electron beams using a 5 TW 60 fs laser at Tsinghua University," Chinese Physics C 39(1), 017001 (2015).
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Colliding ionization injection in a plasma wakefield accelerator
Published in Plasma Physics and Controlled Fusion, 2016
Novel scheme for generating high-quality electron bunches using counter-propagating laser pulse for ionization injection in beam-driven plasma wake with tunable injection distance and synchronized electron release.
Recommended citation: Yang Wan, Chaojie Zhang, Fei Li, Yipeng Wu, Jianfei Hua, Chi-Hao Pai, Wei Lu, Yuqiu Gu, Xinlu Xu, Chan Joshi, Warren B. Mori, "Colliding ionization injection in a plasma wakefield accelerator," Plasma Phys. Control. Fusion 58, 034015 (2016).
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Low-energy-spread laser wakefield acceleration using ionization injection with a tightly focused laser in a mismatched plasma channel
Published in Plasma Physics and Controlled Fusion, 2016
Improved ionization injection scheme using tightly focused laser in mismatched plasma channel achieving ultrashort electron bunches with narrow energy spread through shortened injection distance and envelope oscillation effects.
Recommended citation: Fei Li, Chaojie Zhang, Yang Wan, Yipeng Wu, Xinlu Xu, Jianfei Hua, Chi-Hao Pai, Wei Lu, Yuqiu Gu, Warren B. Mori, Chan Joshi, "Low-energy-spread laser wakefield acceleration using ionization injection with a tightly focused laser in a mismatched plasma channel," Plasma Phys. Control. Fusion 58, 034004 (2016).
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Physics of phase space matching for staging plasma and traditional accelerator components using longitudinally tailored plasma profiles
Published in Physical Review Letters, 2016
Novel approach using longitudinally tailored plasma density profiles to achieve phase space matching between plasma accelerator stages and traditional accelerator components with negligible emittance growth.
Recommended citation: Xinlu Xu, Jianfei Hua, Yipeng Wu, Chaojie Zhang, Fei Li, Yang Wan, Chi-Hao Pai, Wei Lu, Weiming An, Peicheng Yu, Mark J. Hogan, Chan Joshi, Warren B. Mori, "Physics of phase space matching for staging plasma and traditional accelerator components using longitudinally tailored plasma profiles," Phys. Rev. Lett. 116, 124801 (2016).
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Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator
Published in Physical Review Accelerators and Beams, 2016
Development of optical deflecting cavity for sub-femtosecond resolution measurement of ultrashort electron bunches.
Recommended citation: Chaojie Zhang, Jianfei Hua, Yang Wan, Bo Guo, Chi-Hao Pai, Yipeng Wu, Fei Li, Hsu-Hsin Chu, Yuqiu Gu, Warren B. Mori, Chan Joshi, Jyhpyng Wang, Wei Lu, "Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator," Phys. Rev. Acc. Beams, 19(6), 062802 (2016).
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Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe
Published in Scientific Reports, 2016
Novel femtosecond electron probing method for visualizing relativistic plasma wakefields with unprecedented resolution.
Recommended citation: Chaojie Zhang, Jianfei Hua, Xinlu Xu, Fei Li, Chi-Hao Pai, Yang Wan, Yipeng Wu, Yuqiu Gu, Warren B. Mori, Chan Joshi, Wei Lu, "Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe," Sci. Rep. 6, 29485 (2016).
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Nanoscale electron bunching in laser-triggered ionization injection in plasma accelerators
Published in Physical Review Letters, 2016
Theoretical analysis and 3D simulations revealing nanoscale electron bunching in ionization injection due to phase-dependent tunneling ionization and nonlinear trapping dynamics, enabling coherent transition radiation generation.
Recommended citation: Xinlu Xu, Chi-Hao Pai, Chaojie Zhang, Fei Li, Yang Wan, Yipeng Wu, Jianfei Hua, Wei Lu, Weiming An, Peicheng Yu, Chan Joshi, Warren B. Mori, "Nanoscale electron bunching in laser-triggered ionization injection in plasma accelerators," Phys. Rev. Lett. 117, 034801 (2016).
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Physical mechanism of the transverse instability in radiation pressure ion acceleration
Published in Physical Review Letters, 2016
Theoretical model and 2D PIC simulations revealing the physical mechanism behind transverse instability in radiation pressure ion acceleration, analogous to oscillating two-stream instability in ICF research.
Recommended citation: Yang Wan, Chi-Hao Pai, Chaojie Zhang, Fei Li, Yipeng Wu, Jianfei Hua, Wei Lu, Yuqiu Gu, Luis O. Silva, Chan Joshi, Warren B. Mori, "Physical mechanism of the transverse instability in radiation pressure ion acceleration," Phys. Rev. Lett. 117, 234801 (2016).
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Femtosecond probing of plasma wakefields and observation of the plasma wake reversal using a relativistic electron bunch
Published in Physical Review Letters, 2017
First demonstration of femtosecond relativistic electron microscopy for visualizing plasma wakefields.
Recommended citation: Chaojie Zhang, Jianfei Hua, Yang Wan, Chi-Hao Pai, Bo Guo, Jie Zhang, Yue Ma, Fei Li, Yipeng Wu, Hsu-Hsin Chu, Yuqiu Gu, Xinlu Xu, Warren B. Mori, Chan Joshi, Jyhpyng Wang, Wei Lu, "Femtosecond probing of plasma wakefields and observation of the plasma wake reversal using a relativistic electron bunch," Phys. Rev. Lett. 119, 064801 (2017).
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Evolution of plasma wakes in density up- and down-ramps
Published in Plasma Physics and Controlled Fusion, 2018
Theoretical and simulation study of plasma wakefield evolution in non-uniform density profiles.
Recommended citation: Chaojie Zhang, Chan Joshi, Xinlu Xu, Warren B. Mori, Fei Li, Yang Wan, Jianfei Hua, Chi-Hao Pai, Jyhpyng Wang, Wei Lu, "Evolution of plasma wakes in density up- and down-ramps," Plasma Phys. Control. Fusion 60, 024003 (2018).
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On the feasibility of sub-100 nm rad emittance measurement in plasma accelerators using permanent magnetic quadrupoles
Published in Plasma Physics and Controlled Fusion, 2018
Systematic analysis of permanent magnetic quadrupole-based emittance measurement accuracy and reliability for sub-100 nm rad emittance beams from plasma accelerators, identifying key error sources and alignment requirements.
Recommended citation: Fei Li, Yipeng Wu, Zan Nie, Bo Guo, Xiaohui Zhang, Shan Huang, Jie Zhang, Zhi Cheng, Yue Ma, Yu Fang, Chaojie Zhang, Yang Wan, Xinlu Xu, Jianfei Hua, Chi-Hao Pai, Wei Lu, Yuqiu Gu, "On the feasibility of sub-100 nm rad emittance measurement in plasma accelerators using permanent magnetic quadrupoles," Plasma Phys. Control. Fusion 60, 014029 (2018).
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Phase locked multiple rings in the radiation pressure ion acceleration process
Published in Plasma Physics and Controlled Fusion, 2018
Theoretical and simulation study revealing phase-locked double ring structures in ion phase space during radiation pressure acceleration, caused by ponderomotive trapping in moving standing waves from laser contrast effects.
Recommended citation: Yang Wan, Jianfei Hua, Chi-Hao Pai, Fei Li, Yipeng Wu, Wei Lu, Chaojie Zhang, Xinlu Xu, Chan Joshi, Warren B. Mori, "Phase locked multiple rings in the radiation pressure ion acceleration process," Plasma Phys. Control. Fusion 60, 034012 (2018).
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Probing plasma wakefields using electron bunches generated from a laser wakefield accelerator
Published in Plasma Physics and Controlled Fusion, 2018
Experimental demonstration of probing plasma wakefield structures using femtosecond relativistic electron bunches from laser wakefield accelerators, capturing wake evolution in density gradients and parallel wake structures.
Recommended citation: Chaojie Zhang, Yang Wan, Bo Guo, Jianfei Hua, Chi-Hao Pai, Fei Li, Jie Zhang, Yue Ma, Yipeng Wu, Xinlu Xu, Warren B. Mori, Hsu-Hsin Chu, Jyhpyng Wang, Wei Lu, Chan Joshi, "Probing plasma wakefields using electron bunches generated from a laser wakefield accelerator," Plasma Phys. Control. Fusion 60, 034011 (2018).
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Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles
Published in Plasma Physics and Controlled Fusion, 2018
Development and application of permanent magnetic quadrupole-based transverse phase space diagnostics for characterizing ionization injection electron beams in laser plasma acceleration with high precision.
Recommended citation: Fei Li, Zan Nie, Yipeng Wu, Bo Guo, Xiaohui Zhang, Shan Huang, Jie Zhang, Zhi Cheng, Yue Ma, Yu Fang, Chaojie Zhang, Yang Wan, Xinlu Xu, Jianfei Hua, Chi-Hao Pai, Wei Lu, Warren B. Mori, "Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles," Plasma Phys. Control. Fusion 60, 054008 (2018).
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Tri-stage quasimonoenergetic proton acceleration from a multi-species thick target
Published in Physics of Plasmas, 2018
Novel tri-stage acceleration mechanism for generating quasimonoenergetic proton beams from multi-species thick targets, achieving 200 MeV protons with narrow energy spread suitable for medical applications using 100s TW lasers.
Recommended citation: Yang Wan, Chi-Hao Pai, Jianfei Hua, Yipeng Wu, Wei Lu, Fei Li, Chaojie Zhang, Xinlu Xu, Chan Joshi, Warren B. Mori, "Tri-stage quasimonoenergetic proton acceleration from a multi-species thick target," Phys. Plasmas 25, 073105 (2018).
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Physical mechanism of the electron-ion coupled transverse instability in laser pressure ion acceleration for different regimes
Published in Physical Review E, 2018
Extended one-dimensional two-fluid theory clarifying the physical mechanism of transverse instability in radiation pressure ion acceleration, demonstrating electron-ion coupling via ponderomotive force as the dominant instability source.
Recommended citation: Yang Wan, Chi-Hao Pai, Chaojie Zhang, Fei Li, Yipeng Wu, Jianfei Hua, Wei Lu, Chan Joshi, Warren B. Mori, Victor Malka, "Physical mechanism of the electron-ion coupled transverse instability in laser pressure ion acceleration for different regimes," Phys. Rev. E 98, 013202 (2018).
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Relativistic single-cycle tunable infrared pulses generated from a tailored plasma density structure
Published in Nature Photonics, 2018
Breakthrough demonstration of tunable relativistically intense single-cycle infrared pulses (5-14 μm) generated from tailored plasma density structures with 1.7% conversion efficiency and locked carrier-envelope phase for strong-field physics applications.
Recommended citation: Zan Nie, Chi-Hao Pai, Jianfei Hua, Chaojie Zhang, Yipeng Wu, Yang Wan, Fei Li, Jie Zhang, Zhi Cheng, Qianqian Su, Shuang Liu, Yue Ma, Xiaonan Ning, Yunxiao He, Wei Lu, Hsu-Hsin Chu, Jyhpyng Wang, Warren B. Mori, Chan Joshi, "Relativistic single-cycle tunable infrared pulses generated from a tailored plasma density structure," Nature Photonics 12, 489–494 (2018).
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Phase space dynamics of a plasma wakefield dechirper for energy spread reduction
Published in Physical Review Letters, 2019
Demonstration of plasma wakefield dechirper achieving 10-fold reduction in electron beam energy spread from 1.28% to 0.13% FWHM, bringing plasma accelerator beam quality to levels needed for coherent light sources and colliders.
Recommended citation: Yipeng Wu, Jianfei Hua, Zheng Zhou, Jie Zhang, Shuang Liu, Bo Peng, Yu Fang, Zan Nie, Xiaonan Ning, Chi-Hao Pai, Yingchao Du, Wei Lu, Chaojie Zhang, Warren B. Mori, C. Joshi, "Phase space dynamics of a plasma wakefield dechirper for energy spread reduction," Phys. Rev. Lett. 122, 204804 (2019).
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High-resolution phase-contrast imaging of biological specimens using a stable betatron X-ray source in the multiple-exposure mode
Published in Scientific Reports, 2019
First demonstration of high-resolution (5 μm) phase-contrast imaging using stable betatron X-ray source with <5% jitter in multiple-exposure mode, achieving biological imaging with modest 30-40 TW lasers for practical tabletop applications.
Recommended citation: Bo Guo, Xiaohui Zhang, Jie Zhang, Jianfei Hua, Chi-Hao Pai, Chaojie Zhang, Hsu-Hsin Chu, Warren B. Mori, Chan Joshi, Jyhpyng Wang, Wei Lu, "High-resolution phase-contrast imaging of biological specimens using a stable betatron X-ray source in the multiple-exposure mode," Sci. Rep. 9, 7796 (2019).
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Ultrafast optical field-ionized gases- A laboratory platform for studying kinetic plasma instabilities
Published in Science Advances, 2019
Establishment of a laboratory framework for studying kinetic plasma instabilities using ultrafast optical field-ionized gases.
Recommended citation: Chaojie Zhang, Chen-Kang Huang, Ken A. Marsh, Chris E. Clayton, Warren B. Mori, Chan Joshi, "Ultrafast optical field-ionized gases- A laboratory platform for studying kinetic plasma instabilities," Sci. Advances 5(6), eaax4545 (2019).
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Effect of fluctuations in the down ramp plasma source profile on the emittance and current profile of the self-injected beam in a plasma wakefield accelerator
Published in Physical Review Accelerators and Beams, 2019
Comprehensive 2D/3D PIC simulation study of down ramp injection for FACET-II, demonstrating ultra-low emittance beams (~0.03 μm) and investigating the effects of ramp profile fluctuations on beam quality and current profiles.
Recommended citation: Chaojie Zhang, Chen-Kang Huang, Ken A. Marsh, Xinlu Xu, Fei Li, Mark Hogan, Vitaly Yakimenko, Sebastien Corde, Warren B. Mori, Chan Joshi, "Effect of fluctuations in the down ramp plasma source profile on the emittance and current profile of the self-injected beam in a plasma wakefield accelerator," Phys. Rev. Accel. Beams 22, 111301 (2019).
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Near-ideal dechirper for plasma-based electron and positron acceleration using a hollow channel plasma
Published in Physical Review Applied, 2019
Novel near-ideal dechirper concept using hollow channel plasma to reduce energy spread from few-percent to ≲0.1% without emittance growth, enabling applications to free-electron lasers and colliders through large-scale 3D PIC simulations.
Recommended citation: Yipeng Wu, Jianfei Hua, Chi-Hao Pai, Weiming An, Zheng Zhou, Jie Zhang, Shuang Liu, Bo Peng, Yu Fang, Shiyu Zhou, Xinlu Xu, Chaojie Zhang, Fei Li, Zan Nie, Wei Lu, Warren B. Mori, C. Joshi, "Near-ideal dechirper for plasma-based electron and positron acceleration using a hollow channel plasma," Phys. Rev. Applied 12, 064011 (2019).
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Initializing anisotropic electron velocity distribution functions in optical-field ionized plasmas
Published in Plasma Physics and Controlled Fusion, 2020
Demonstrates controlled generation of anisotropic electron velocity distributions in optical-field ionized helium plasmas through laser polarization control, enabling systematic study of plasma kinetic instabilities with Thomson scattering diagnostics.
Recommended citation: Chen-Kang Huang, Chaojie Zhang, Ken A. Marsh, Chris E. Clayton, Chaojie Joshi, "Initializing anisotropic electron velocity distribution functions in optical-field ionized plasmas," Plasma Phys. Control. Fusion 62, 025023 (2020).
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Probing thermal Weibel instability in optical-field-ionized plasmas using relativistic electron bunches
Published in Plasma Physics and Controlled Fusion, 2020
Proposes using ultrashort relativistic electron beams to probe the spatiotemporal evolution of self-generated magnetic fields in thermal Weibel instability, demonstrating how laser polarization controls magnetic field topology in optical-field-ionized plasmas.
Recommended citation: Chaojie Zhang, Chen-Kang Huang, Ken A. Marsh, Chan Joshi, "Probing thermal Weibel instability in optical-field-ionized plasmas using relativistic electron bunches," Plasma Phys. Control. Fusion 62, 024010 (2020).
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Ion acceleration with an ultra-intense two-frequency laser tweezer
Published in New Journal of Physics, 2020
Introduces a novel ultra-intense optical tweezer concept using two counter-propagating circularly polarized lasers of different frequencies to create controlled electron displacement and generate narrow-energy-spread ion beams from nano-foil targets with high efficiency.
Recommended citation: Yang Wan, Igor A. Andriyash, Chi-Hao Pai, Jianfei Hua, Chaojie Zhang, Fei Li, Yipeng Wu, Zan Nie, Warren B. Mori, Wei Lu, Victor Malka, Chan Joshi, "Ion acceleration with an ultra-intense two-frequency laser tweezer," New J. Phys. 22, 052002 (2020).
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Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses
Published in Nature Communications, 2020
Demonstrates experimental generation of high-power (~100 GW) near single-cycle wavelength tunable (3–20 µm) infrared pulses using photon deceleration in laser-produced plasma wakes, enabling novel applications in relativistic nonlinear optics and molecular fingerprint spectroscopy.
Recommended citation: Zan Nie, Chi-Hao Pai, Jie Zhang, Xiaonan Ning, Jianfei Hua, Yunxiao He, Yipeng Wu, Qianqian Su, Shuang Liu, Yue Ma, Zhi Cheng, Wei Lu, Hsu-Hsin Chu, Jyhpyng Wang, Chaojie Zhang, Warren B. Mori, Chan Joshi, "Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses," Nat. Commun. 11, 2787 (2020).
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Conservation of angular momentum in second harmonic generation from under-dense plasmas
Published in Communications Physics, 2020
Verifies conservation of total angular momentum in photons through experimental measurement of helical phase in second harmonic radiation from underdense plasma, demonstrating conversion between spin and orbital angular momentum using Laguerre-Gaussian beams.
Recommended citation: Chen-Kang Huang, Chaojie Zhang, Zan Nie, Ken A. Marsh, Chris E. Clayton, Chan Joshi, "Conservation of angular momentum in second harmonic generation from under-dense plasmas," Commun. Phys. 3, 213 (2020).
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Measurements of the growth and saturation of electron Weibel instability in optical-field ionized plasmas
Published in Physical Review Letters, 2020
Direct measurements of electron Weibel instability growth and saturation using femtosecond relativistic electron probes.
Recommended citation: Chaojie Zhang, Jianfei Hua, Yipeng Wu, Yu Fang, Yue Ma, Tianliang Zhang, Shuang Liu, Bo Peng, Yunxiao He, Chen-Kang Huang, Ken A. Marsh, Warren B. Mori, Wei Lu, Chan Joshi, "Measurements of the growth and saturation of electron Weibel instability in optical-field ionized plasmas," Phys. Rev. Lett. 125(25), 255001 (2020).
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Ultra-short pulse generation from mid-IR to THz range using plasma wakes and relativistic ionization fronts
Published in Physics of Plasmas, 2021
Demonstrates numerical and experimental techniques for generating ultra-short pulses covering 1-150 μm wavelength range using plasma wakes for frequency downshifting and relativistic ionization fronts for upshifting, enabling comprehensive coverage of the molecular fingerprint region.
Recommended citation: Zan Nie, Yipeng Wu, Chaojie Zhang, Warren B. Mori, Chan Joshi, Wei Lu, Chi-Hao Pai, Jianfei Hua, Jyhpyng Wang, "Ultra-short pulse generation from mid-IR to THz range using plasma wakes and relativistic ionization fronts," Phys. Plasmas 28, 023106 (2021).
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Extremely dense gamma-ray pulses in electron beam-multifoil collisions
Published in Physical Review Letters, 2021
Demonstrates that high-current ultrarelativistic electron beams interacting with multiple submicrometer-thick conducting foils undergo strong self-focusing with efficient gamma-ray synchrotron emission, achieving femtosecond collimated beams with number density exceeding that of a solid.
Recommended citation: Archana Sampath, Xavier Davoine, Sebastien Corde, Laurent Gremillet, Max Gilljohann, Maitreyi Sangal, Christoph H. Keitel, Robert Ariniello, John Cary, Henrik Ekerfelt, Claudio Emma, Frederico Fiuza, Hiroki Fujii, Mark Hogan, Chan Joshi, Alexander Knetsch, Olena Kononenko, Valentina Lee, Mike Litos, Kenneth Marsh, Zan Nie, Brendan O’Shea, John R. Peterson, Pablo San Miguel Claveria, Doug Storey, Yipeng Wu, Xinlu Xu, Chaojie Zhang, Matteo Tamburini, "Extremely dense gamma-ray pulses in electron beam-multifoil collisions," Phys. Rev. Lett. 126, 064801 (2021).
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High-throughput injection–acceleration of electron bunches from a linear accelerator to a laser wakefield accelerator
Published in Nature Physics, 2021
Demonstrates external injection from a conventional linear accelerator into a laser wakefield accelerator with nearly 100% coupling efficiency and subsequent acceleration without charge loss, representing a crucial step toward hybrid conventional-plasma-based accelerators.
Recommended citation: Yipeng Wu, Jianfei Hua, Zheng Zhou, Jie Zhang, Shuang Liu, Bo Peng, Yu Fang, Xiaonan Ning, Zan Nie, Fei Li, Chaojie Zhang, Chih-Hao Pai, Yingchao Du, Wei Lu, Warren B. Mori, Chan Joshi, "High-throughput injection–acceleration of electron bunches from a linear accelerator to a laser wakefield accelerator," Nat. Phys. 17, 801–806 (2021).
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Ionization induced plasma grating and its applications in strong-field ionization measurements
Published in Plasma Physics and Controlled Fusion, 2021
Novel technique using ionization-induced plasma gratings for absolute ionization degree measurements in strong-field physics.
Recommended citation: Chaojie Zhang, Zan Nie, Yipeng Wu, Mitchell Sinclair, Chen-Kang Huang, Ken A Marsh, Chan Joshi, "Ionization induced plasma grating and its applications in strong-field ionization measurements," Plasma Phys. Control. Fusion 63, 095011 (2021).
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Electron Weibel instability induced magnetic fields in optical-field ionized plasmas
Published in Physics of Plasmas, 2022
Presents comprehensive experimental and theoretical study of electron Weibel instability in optical-field ionized plasmas using time-resolved measurements with external electron probe bunches, extending previous work to both non-relativistic and quasi-relativistic regimes.
Recommended citation: Chaojie Zhang, Yipeng Wu, Mitchell Sinclair, Audrey Farrell, Kenneth A. Marsh, Jianfei Hua, Irina Petrushina, Navid Vafaei-Najafabadi, Rotem Kupfer, Karl Kusche, Mikhail Fedurin, Igor Pogorelsky, Mikhail Polyanskiy, Chen-Kang Huang, Wei Lu, Warren B. Mori, Chan Joshi, "Electron Weibel instability induced magnetic fields in optical-field ionized plasmas," Phys. Plasmas 29, 062102 (2022).
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Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements
Published in Optics Express, 2022
Develops a highly sensitive cross-polarized common-path temporal interferometer with balanced detection achieving ~0.6 mrad sensitivity for plasma density measurements, enabling comprehensive verification of strong-field ionization models across multiple regimes and gas types.
Recommended citation: Zan Nie, Noa Nambu, Kenneth A. Marsh, Eric Welch, Daniel Matteo, Chaojie Zhang, Yipeng Wu, Serguei Patchkovskii, Felipe Morales, Olga Smirnova, Chan Joshi, "Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements," Opt. Express 30, 25696–25706 (2022).
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Highly spin-polarized multi-GeV electron beams generated by single-species plasma photocathodes
Published in Physical Review Research, 2022
Demonstrates generation of highly spin-polarized electron beams using single-species ytterbium plasma photocathodes, achieving 56% net spin polarization and 15 GeV acceleration in 41 cm through combined time-dependent Schrödinger equation and particle-in-cell simulations.
Recommended citation: Zan Nie, Fei Li, Felipe Morales, Serguei Patchkovskii, Olga Smirnova, Weiming An, Chaojie Zhang, Yipeng Wu, Noa Nambu, Daniel Matteo, Kenneth A. Marsh, Frank Tsung, Warren B. Mori, Chan Joshi, "Highly spin-polarized multi-GeV electron beams generated by single-species plasma photocathodes," Phys. Rev. Research 4, 033015 (2022).
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Mapping the self-generated magnetic fields due to thermal Weibel instability
Published in Proceedings of the National Academy of Sciences, 2022
First experimental mapping of magnetic fields generated by thermal Weibel instability in laser-ionized plasmas.
Recommended citation: Chaojie Zhang, Yipeng Wu, Mitchell Sinclair, Audrey Farrell, Kenneth A. Marsh, Irina Petrushina, Navid Vafaei-Najafabadi, Apurva Gaikwad, Rotem Kupfer, Karl Kusche, Mikhail Fedurin, Igor Pogorelsky, Mikhail Polyanskiy, Chen-Kang Huang, Jianfei Hua, Wei Lu, Warren B. Mori, Chan Joshi, "Mapping the self-generated magnetic fields due to thermal Weibel instability," PNAS 119(50), e2211713119 (2022).
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Efficient generation of tunable magnetic and optical vortices using plasmas
Published in Physical Review Research, 2023
Demonstrates efficient generation of multimegagauss magnetic and tunable optical vortices through interaction of relativistic ionization fronts with Laguerre-Gaussian laser pulses, achieving up to 90% conversion efficiency and controllable topological charges via plasma density and orbital angular momentum manipulation.
Recommended citation: Yipeng Wu, Xinlu Xu, Chaojie Zhang, Zan Nie, Mitchell Sinclair, Audrey Farrell, Kenneth A. Marsh, Jianfei Hua, Wei Lu, Warren B. Mori, Chan Joshi, "Efficient generation of tunable magnetic and optical vortices using plasmas," Phys. Rev. Research 5, L012011 (2023).
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Underdense plasma lens with a transverse density gradient
Published in Physical Review Accelerators and Beams, 2023
Presents theoretical model for transverse density gradients in underdense plasma lenses based on 3D particle-in-cell simulations, enabling analytical study of beam dynamics and estimation of witness electron bunch deflection for density uniformity tolerance studies in plasma accelerators.
Recommended citation: Christopher E. Doss, Robert Ariniello, John R. Cary, Sebastien Corde, Henrik Ekerfelt, Elias Gerstmayr, Spencer J. Gessner, Max Gilljohann, Claire Hansel, Bernhald Hidding, Mark J. Hogan, Alexander Knetsch, Valentina Lee, Ken A. Marsh, Brendan O’Shea, Pablo San Miguel Claveria, Douglas Storey, Andrew Sutherland, Chaojie Zhang, Michael D. Litos, "Underdense plasma lens with a transverse density gradient," Phys. Rev. Accel. Beams 26, 031302 (2023).
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Self-organization of photoionized plasmas via kinetic instabilities
Published in Reviews of Modern Plasma Physics, 2023
Comprehensive review of self-organization in strong-field photoionized, non-equilibrium plasmas through kinetic instabilities.
Recommended citation: Chaojie Zhang, Chen-Kang Huang, Chan Joshi, "Self-organization of photoionized plasmas via kinetic instabilities," Reviews of Modern Plasma Physics 7, 34 (2023).
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Correlations between X-rays, visible light and drive-beam energy loss observed in plasma wakefield acceleration experiments at FACET-II
Published in Journal of Plasma Physics, 2024
Experimental study documenting correlations between betatron X-ray signals, visible plasma light, and drive beam energy loss in plasma wakefield acceleration, demonstrating non-invasive diagnostics for energy transfer monitoring.
Recommended citation: Chaojie Zhang, Doug Storey, Pablo San Miguel Claveria, Zan Nie, Kenneth A. Marsh, Warren B. Mori, Erik Adli, Weiming An, Robert Ariniello, Gevy J. Cao, Christine Clark, Sebastien Corde, Thamine Dalichaouch, Christopher E. Doss, Claudio Emma, Henrik Ekerfelt, Elias Gerstmayr, Spencer Gessner, Claire Hansel, Alexander Knetsch, Valentina Lee, Fei Li, Mike Litos, Brendan O’Shea, Glen White, Gerry Yocky, Viktoriia Zakharova, Mark Hogan, Chan Joshi, "Correlations between X-rays, visible light and drive-beam energy loss observed in plasma wakefield acceleration experiments at FACET-II," J. Plasma Phys. 90, 905900101 (2024)."
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Generation of meter-scale hydrogen plasmas and efficient, pump-depletion-limited wakefield excitation using 10 GeV electron bunches
Published in Plasma Physics and Controlled Fusion, 2024
This paper demonstrates efficient wakefield excitation in meter-scale beam-ionized hydrogen plasmas at FACET-II.
Recommended citation: Chaojie Zhang, Doug Storey, Pablo San Miguel Claveria, Zan Nie, Ken A. Marsh, Mark Hogan, Warren B. Mori, Eric Adli, Weiming An, Robert Ariniello, Gevy J Cao, Christine Clarke, Sebastien Corde, Thamine Dalichaouch, Christopher E. Doss, Claudio Emma, Henrik Ekerfelt, Elias Gerstmayr, Spencer Gessner, Claire Hansel, Alexander Knetsch, Valentina Lee, Fei Li, Michael Litos, Brendan O’Shea, Glen White, Gerald Yocky, Viktoriia Zakharova, Chan Joshi, "Generation of meter-scale hydrogen plasmas and efficient, pump-depletion-limited wakefield excitation using 10 GeV electron bunches," Plasma Phys. Control. Fusion 66, 025013 (2024).
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Efficient generation and amplification of intense vortex and vector laser pulses via strongly-coupled stimulated Brillouin scattering in plasmas
Published in Communications Physics, 2024
Demonstrates strongly-coupled stimulated Brillouin scattering in plasmas as a promising amplification technique for vortex and vector laser pulses with up to 65% energy transfer efficiency, enabling all-optical polarization control and novel angular momentum couplings for plasma-based optical devices.
Recommended citation: Yipeng Wu, Chaojie Zhang, Zan Nie, Mitchell Sinclair, Audrey Farrell, Kenneth A. Marsh, Eduardo Paulo Alves, Frank Tsung, Warren B. Mori, Chan Joshi, "Efficient generation and amplification of intense vortex and vector laser pulses via strongly-coupled stimulated Brillouin scattering in plasmas," Commun. Phys. 7, 18 (2024).
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Plasma electron acceleration driven by a long-wave-infrared laser
Published in Nature Communications, 2024
Demonstration of laser-driven plasma acceleration using a long-wave-infrared CO2 laser, achieving relativistic electron acceleration with sub-TW power and observing transition from self-modulation to bubble-regime acceleration.
Recommended citation: Rafal Zgadzaj, James Welch, Yuxuan Cao, Ligia D. Amorim, Aiqi Cheng, Apurva Gaikwad, Pietro Iapozzutto, Prabhat Kumar, Vladimir N. Litvinenko, Irina Petrushina, Roman Samulyak, Navid Vafaei-Najafabadi, Chan Joshi, Chaojie Zhang, Marcus Babzien, Mikhail Fedurin, Rotem Kupfer, Karl Kusche, Mark A. Palmer, Igor V. Pogorelsky, Mikhail N. Polyanskiy, Christina Swinson, Mike C. Downer, "Plasma electron acceleration driven by a long-wave-infrared laser," Nat. Commun. 15, 4395 (2024).
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Wakefield generation in hydrogen and lithium plasmas at FACET-II: Diagnostics and first beam-plasma interaction results
Published in Physical Review Accelerators and Beams, 2024
Experimental progress at FACET-II toward demonstrating high-gradient plasma wakefield acceleration with simultaneous high energy transfer efficiency and beam quality preservation, including advanced diagnostics and initial beam-plasma interaction results.
Recommended citation: Doug Storey, Chaojie Zhang, Pablo San Miguel Claveria, Gevy J. Cao, Erik Adli, Lauren Alsberg, Robert Ariniello, Christine Clarke, Sebastien Corde, Thamine N. Dalichaouch, Christopher E. Doss, Henrik Ekerfelt, Claudio Emma, Elias Gerstmayr, Spencer Gessner, Max Gilljohann, Carsten Hast, Alaxander Knetsch, Valentina Lee, Michael Litos, Ryan Loney, Ken A. Marsh, Aime Matheron, Warren B. Mori, Zan Nie, Brendan O’Shea, Marcellus Parker, Glen White, Gerald Yocky, Viktoriia Zakharova, Mark J. Hogan, Chan Joshi, "Wakefield generation in hydrogen and lithium plasmas at FACET-II: Diagnostics and first beam-plasma interaction results," Phys. Rev. Accel. Beams 27, 051302 (2024).
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Thermal Weibel instability induced magnetic fields co-exist with linear wakes in laser-ionized plasmas
Published in Physics of Plasmas, 2024
Experimental and simulation study demonstrating coexistence of Weibel instability-induced magnetic fields and linear plasma wakes in laser-ionized plasmas, with implications for multi-bunch acceleration schemes.
Recommended citation: Yipeng Wu, Audrey Farrell, Mitchell Sinclair, Chaojie Zhang, Irina Petrushina, Navid Vafaei-Najafabadi, Marcus Babzien, William Li, Igor Pogorelsky, Mikhail Polyanskiy, Mikhail Fedurin, Karl Kusche, Mark Palmer, Ken A. Marsh, Chan Joshi, "Thermal Weibel instability induced magnetic fields co-exist with linear wakes in laser-ionized plasmas," Phys. Plasmas 31, 072108 (2024).
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Bidirectional cascaded superfluorescent lasing in air enabled by resonant third harmonic photon exchange from nitrogen to argon
Published in Physical Review Letters, 2024
Discovery of a new mechanism for cavity-free lasing in atmospheric air through third-harmonic photon mediated resonant energy transfer from nitrogen to argon, enabling bidirectional two-color cascaded superfluorescent lasing.
Recommended citation: Zan Nie, Noa Nambu, Kenneth A. Marsh, Daniel Matteo, C. Kumar Patel, Chaojie Zhang, Yipeng Wu, Stefanos Carlström, Felipe Morales, Serguei Patchkovskii, Olga Smirnova, Misha Ivanov, Chan Joshi, "Bidirectional cascaded superfluorescent lasing in air enabled by resonant third harmonic photon exchange from nitrogen to argon," Phys. Rev. Lett. 133, 063201 (2024).
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Plasma-Wakefield Accelerator Simultaneously Boosts Electron Beam Energy and Brightness
Published in Nature Communications, 2025
Demonstrates that a plasma wakefield accelerator can act as a dual transformer to convert an input electron beam into a new one with much higher energy and brightness.
Recommended citation: Chaojie Zhang, Douglas Storey, Alexander Knetsch, Brendan O’Shea, Robert Ariniello, Gevy J. Cao, Sebastien Corde, Thamine N. Dalichaouch, Claudio Emma, Ole G. Finnerud, Spencer Gessner, Claire Hansel, Elias Hansen, Valentina Lee, Carl A. Lindstrom, Mike Litos, Nathan Majernik, Kenneth A. Marsh, Warren B. Mori, Ivan Rajkovic, Mark J. Hogan, and Chan Joshi, "Plasma-Wakefield Accelerator Simultaneously Boosts Electron Beam Energy and Brightness," Nat. Communications. (2025).
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talks
Probing plasma wakefield using femtosecond relativistic electron bunches
Published:
Abstract: This plenary presentation introduced the groundbreaking technique of using femtosecond relativistic electron bunches to probe plasma wakefields with unprecedented temporal and spatial resolution. The talk described the inception and first experimental demonstration of femtosecond relativistic electron microscopy and its applications to wakefield visualization.
Measurements of Weibel magnetic fields in optical-field ionized plasmas
Published:
Abstract: Generation and amplification of magnetic fields in plasmas is a long-standing topic that is of great interest to both fundamental and applied physics. Weibel instability is a well-known mechanism responsible for self-generating magnetic fields in anisotropic plasmas and has been extensively investigated in both theory and simulations, yet its experimental verification has proven challenging. Recently, we have demonstrated a new experimental platform that enables initialization of the plasma electron velocity distribution in a controllable manner and then measure the evolution of Weibel magnetic fields using an external ultrashort relativistic electron probe. Here we will first present experimental results on time-resolved measurements of Weibel magnetic fields in non-relativistic plasmas produced by optical field ionization using an ultrashort IR laser (0.8 µm). It was found that the Weibel magnetic fields self-organize into a quasistatic structure consistent with a helicoid topology within a few picoseconds and such a structure lasts for tens of picoseconds. The magnetic fields show a well-defined wave vector. The growth rate and saturated magnetic field magnitude were measured and agree well with kinetic theory predictions. We then discuss the feasibility of extending the study to quasi-relativistic regime by using intense CO2 (10 µm) lasers to produce much hotter anisotropic plasmas. The platform we have demonstrated is suitable for exploring a broad range of plasma phenomena such as magnetic reconnection, annihilation and island formation thereby opening a new avenue for studying astrophysical phenomena in the laboratory.
High-efficiency wake excitation in meter-scale beam-ionized hydrogen plasmas at FACET-II
Published:
Abstract: Plasma wakefield acceleration has witnessed rapid progress in the past decades and is considered a promising route for building future linear colliders that demand both high repetition rates and high energy efficiency. In this talk, I will present the results that start to address the issues of repetition rate and energy transfer efficiency. These results were obtained from the Plasma Wakefield Acceleration Experiments (E300 Collaboration) at the newly commissioned FACET-II facility at SLAC. By self-ionizing a continuous hydrogen gas flow integrated into the accelerator beamline via a differential pumping system using time-structured 10 GeV electron bunches, we have generated plasmas with meter-scale lengths. This plasma source makes it possible to significantly increase the PWFA repetition rates by rapidly replenishing the gas between shots. Our experiments have also demonstrated high-gradient acceleration with high drive-bunch to wake energy transfer efficiency. At pressures ≥1.5 Torr, we observed the onset of pump depletion, which is an important first step towards achieving high overall energy transfer efficiency from the drive to the witness electron bunch in future two-bunch experiments. We also observed that the back of the drive bunch gains multi-GeV energy. These experimental findings are supported by particle-in-cell simulations, revealing a beam-to-wake energy transfer efficiency of approximately 60% at ~2 Torr. Our results not only demonstrate efficient wake excitation but also underscore the potential of continuous flow hydrogen plasmas in achieving the high energy transfer efficiencies required for PWFA-based linear colliders.
Latest results on PWFA experiments from FACET-II
Published:
Abstract: FACET-II is a national user facility that offers a unique capability for developing advanced acceleration and coherent radiation generation techniques using high-energy electron beams. In this talk, we will present the latest results from plasma wakefield acceleration (PWFA) experiments at FACET-II, focusing on the following topics. First, we provide evidence of energy depletion of the 10 GeV drive beam and efficient energy transfer from the beam to the wake, in both beam-ionized and laser-preionized plasmas, which is a crucial stepping stone towards achieving high energy transfer efficiency from the drive to the witness bunch in the ultimate two-bunch PWFA configuration. We will also show examples of machine-learning-enabled beam tuning to increase drive beam density, thereby enhancing energy transfer efficiency. Next, we present results on generating high-energy, low-emittance beams via downramp and ionization trapping in PWFA. Using density downramp injection, we achieve the generation of electron bunches exceeding 20 GeV with small energy spread and emittance. Additionally, we show the generation of multi-GeV, multi-color electron beams via ionization injection, resulting from periodic injection induced by betatron oscillations of the drive bunch. Finally, we will discuss the first experimental attempts at beam matching to a lithium density upramp and share preliminary results from the two-bunch PWFA experiment.
teaching
Graduate Student Mentoring and Research Training
Research Mentoring, UCLA and Tsinghua University, 2010
Research Mentoring and Training (2010 - Present)
- Current: Co-mentoring 2 graduate students at UCLA in experimental plasma physics
- 2017-2022: Co-mentored 1 graduate student during postdoctoral research
- 2010-2016: Guided multiple graduate and undergraduate students at Tsinghua University