arXiv subjects

James Rosenzweig

Publications and source records attributed to James Rosenzweig.

18 recordsLinked to original sources

arXiv2025

Charged-particle control via spatio-temporally tailored pulses from gas-based nonlinear optics

Gas-filled waveguides enable few-cycle, spatio-temporally coupled (STC) pulses with programmable structure, opening new routes to control charged particles with optical fields. This review maps the landscape of optical-field-driven photoemission, then surveys gas-based nonlinear drivers, photonic crystal fibers (PCFs) for low-energy, high-repetition operation and hollow-core capillaries (HCCs) for high-power, few-cycle synthesis. We highlight mechanisms for deterministic pulse shaping, including four-wave-mixing-based spectral-phase transfer in HCCs, and show how tailored STC waveforms steer emission dynamics from the multiphoton to tunneling regimes, enabling sub-cycle gating, momentum control, and brightness scaling. We conclude with open challenges: phase stability, mid-IR scalability, coupling to nanophotonic emitters, metrology of vectorial fields, and outline a path toward compact, ultrafast, phase-coherent electron sources and emerging quantum applications powered by nonlinear photonics.

physics.optics↗

arXiv2025

Simulating Unruh Radiation in High-Intensity Laser-Electron Interactions for Near-Term Experimental Tests

The Unruh effect predicts that a uniformly accelerating observer perceives the vacuum as a thermal bath, yet direct observation remains elusive [1]. We simulate Unruh radiation in realistic high-intensity laser-electron collisions relevant to FACET-II and LUXE using fully three-dimensional Monte Carlo methods. In our model, Unruh emission is treated as scattering from a rest-frame thermal spectrum with Klein-Nishina cross sections, while nonlinear Compton radiation is computed across many harmonic orders with photon recoil. We map the laboratory-frame spectral-angular distributions and identify phase-space regions where the Unruh-to-Compton ratio is maximized. For current FACET-II-like parameters (a0 = 5), favorable windows for observing Unruh radiation occur at 200-400 microrad and 2-3 GeV, although the absolute signal is small. For future LUXE Phase-1 (a0 = 23.6), the ratio increases by more than two orders of magnitude, with optimal angles around 800 microrad and photon energies 2-6 GeV. Our results suggest that targeted off-axis, mid-energy selections can enhance sensitivity to Unruh-like signatures, motivating dedicated measurements and further theoretical scrutiny of the emission model at high field strengths.

hep-ex↗

arXiv2024

Lattice Boltzmann method for warm fluid simulations of plasma wakefield acceleration

A comprehensive characterization of lattice Boltzmann (LB) schemes to perform warm fluid numerical simulations of particle wakefield acceleration (PWFA) processes is discussed in this paper. The LB schemes we develop hinge on the moment matching procedure, allowing the fluid description of a warm relativistic plasma wake generated by a driver pulse propagating in a neutral plasma. We focus on fluid models equations resulting from two popular closure assumptions of the relativistic kinetic equations, i.e., the local equilibrium and the warm plasma closure assumptions. The developed LB schemes can thus be used to disclose insights on the quantitative differences between the two closure approaches in the dynamics of PWFA processes. Comparisons between the proposed schemes and available analytical results are extensively addressed.

physics.plasm-ph↗

arXiv2023

Improving Interface Physics Understanding in High-Frequency Cryogenic Normal Conducting Cavities

As progress towards real implementations of cryogenic high gradient normal conducting accelerating cavities continues, a more mature understanding of the surface physics in this novel environment becomes increasingly necessary. To this end, we here focus on developing a deeper understanding of one cavity figure of merit, the radiofrequency (RF) surface resistivity, $R_s$. A combination of experimental measurements and theory development form the basis of this work. For many cases, existing theory is sufficient but there are nuances leading to systemic errors in prediction which we address here. In addition, for certain cases there exist unexpected local minimum in $R_s$ found at temperatures above 0K. We compare here several alternative models for RF surface resistivity those which incorporate thin film like behavior which we use to predict the location of the local minimum in surface resistivity. Our experimental results focus on C-band frequencies for the benefit of several future cryogenic linear accelerator concepts intended to operate in this regime. To this end we have measured factor of $2.89\pm 0.05$ improvements in quality factor at $77$K and $4.61\pm 0.05$ at 45K. We further describe the test setup and cooling capabilities to address systematic issues associated with the measurements as well as a comparison of RF cavity preparation and the significant effect on $R_s$. Some implications of our measurements to linear accelerators combined with the theoretical considerations are extended to a wider range of frequencies especially the two additional aforementioned bands. Additional possible implications for condensed matter physics studies are mentioned.

physics.acc-ph↗

arXiv2023

Observation of Skewed Electromagnetic Wakefields in an Asymmetric Structure Driven by Flat Electron Bunches

Relativistic charged-particle beams which generate intense longitudinal fields in accelerating structures also inherently couple to transverse modes. The effects of this coupling may lead to beam break-up instability, and thus must be countered to preserve beam quality in applications such as linear colliders. Beams with highly asymmetric transverse sizes (flat-beams) have been shown to suppress the initial instability in slab-symmetric structures. However, as the coupling to transverse modes remains, this solution serves only to delay instability. In order to understand the hazards of transverse coupling in such a case, we describe here an experiment characterizing the transverse effects on a flat-beam, traversing near a planar dielectric lined structure. The measurements reveal the emergence of a previously unobserved skew-quadrupole-like interaction when the beam is canted transversely, which is not present when the flat-beam travels parallel to the dielectric surface. We deploy a multipole field fitting algorithm to reconstruct the projected transverse wakefields from the data. We generate the effective kick vector map using a simple two-particle theoretical model, with particle-in-cell simulations used to provide further insight for realistic particle distributions.

physics.acc-ph↗

arXiv2023

Flat beam plasma wakefield accelerator

Particle beams with highly asymmetric emittance ratios are expected at the interaction point of high energy colliders. These asymmetric beams can be used to drive high gradient wakefields in dielectrics and plasma. In the case of plasma, the high aspect ratio of the drive beam creates a transversely elliptical blowout cavity and the asymmetry in the ion column creates asymmetric focusing in the two transverse planes. The ellipticity of the blowout depends on the ellipticity and normalized charge density of the beam. In this paper, simulations are performed to investigate the ellipticity of the wakefield based on the initial driver beam parameters. The matching conditions for this elliptical cavity are discussed. Example cases for employment using the attainable parameter space at the AWA and FACET facilities are also presented.

physics.acc-ph↗

arXiv2023

Advanced Accelerator Concepts: From Birth to High Impact Science

This recounting of the history of the last three-and-a-half decades of advanced accelerator concepts is offered from a decidedly parochial point of view -- that of the career of the author, Prof. James Rosenzweig of the UCLA Dept. of Physics and Astronomy. This short voyage through a by-now long career will illustrate the very beginning of the compelling field of advanced accelerators, proceed through their maturation into one of the fastest growing areas of beam-based science, and give a look into their emerging importance in applications. An important aspect of advanced accelerators is their relationship to other burgeoning fields, particularly free-electron lasers. The framework of this retelling lends itself particularly well to illustrating this relationship. Likewise, this quick summary serves to demonstrate the essential team nature of our field, and the contributions of participants from all levels, ranging from students to those scientists whose careers may have developed in previous eras of positive ferment in accelerator science.

physics.acc-ph↗

arXiv2022

C$^3$ Demonstration Research and Development Plan

C$^3$ is an opportunity to realize an e$^+$e$^-$ collider for the study of the Higgs boson at $\sqrt{s} = 250$ GeV, with a well defined upgrade path to 550 GeV while staying on the same short facility footprint. C$^3$ is based on a fundamentally new approach to normal conducting linear accelerators that achieves both high gradient and high efficiency at relatively low cost. Given the advanced state of linear collider designs, the key system that requires technical maturation for C$^3$ is the main linac. This white paper presents the staged approach towards a facility to demonstrate C$^3$ technology with both Direct (source and main linac) and Parallel (beam delivery, damping ring, ancillary component) R&D. The white paper also includes discussion on the approach for technology industrialization, related HEP R&D activities that are enabled by C$^3$ R&D, infrastructure requirements and siting options.

physics.acc-ph↗

arXiv2022

A Coherent Bi-Directional Virtual Detector for the 1-D Schrödinger Equation

The virtual detector is a commonly utilized technique to measure the properties of a wavefunction in simulation. One type of virtual detector measures the probability density and current at a set position over time, permitting an instantaneous measurement of momentum at a boundary. This may be used as the boundary condition between a quantum and a classical simulation. However, as a tool for measuring spectra, it possesses several problems stemming from its incoherent nature. Another form of virtual detector measures the wavefunction's complex value at a set position in real space over time and Fourier analyzes it to produce an energy spectrum. The spectra it produces are exact provided that the wavefunction propagated through the detector in one direction. Otherwise it will produce a spectrum that includes interference between forward and backward propagating wavepackets. Here we propose a virtual detector which maintains all the benefits of this coherent virtual detector while also being able to resolve the direction of propagation and mitigate nonphysical interference by use of a second measurement point. We show that, in the continuum limit, this bi-directional virtual detector can reproduce an equivalent wavefunction assuming a globally constant potential. It is therefore equivalent to the exact spectrum.

quant-ph↗

arXiv2022

XCC: An X-ray FEL-based $γγ$ Collider Higgs Factory

This report describes the design of a $γγ$ Higgs factory in which 62.8 GeV electron beams collide with 1 keV X-ray free electron laser (XFEL) beams to produce colliding beams of 62.5 GeV photons. The Higgs boson production rate is 34,000 Higgs bosons per $10^7$ second year, roughly the same as the ILC Higgs rate. The electron accelerator is based on cold copper distributed coupling (C$^3$) accelerator technology. The 0.7 J pulse energy of the XFEL represents a 300-fold increase over the pulse energy of current soft x-ray FEL's. Design challenges are discussed, along with the R\&D to address them, including demonstrators.

hep-ex↗

arXiv2022

Advanced RF Structures for Wakefield Acceleration and High-Gradient Research

Structure wakefield acceleration (SWFA) is one of the most promising AAC schemes in several recent strategic reports, including DOE's 2016 AAC Roadmap, report on the Advanced and Novel Accelerators for High Energy Physics Roadmap (ANAR), and report on Accelerator and Beam Physics Research Goals and Opportunities. SWFA aims to raise the gradient beyond the limits of conventional radiofrequency (RF) accelerator technology, and thus the RF to beam energy efficiency, by reducing RF breakdowns from confining the microwave energy in a short (on the order of about 10 ns) and intense pulse excited by a drive beam. We envision that the following research topics, within the scope of AF7, are of great interest in the next decade: advanced wakefield structures, terahertz and sub-terahertz (THz) structures, and RF breakdown physics. Research on SWFA in the above directions would directly contribute to long-term large-scale applications, including AAC-based linear colliders and compact light sources. There is also potentially a strong synergy between SWFA and other AAC concepts, when structures are combined with plasmas into hybrid AAC schemes. Research on novel structures is at the core of advancing SWFA, and is critical to future AAC-based linear colliders; at the same, it has a strong synergy with other directions, such as cavity designs, high-power microwave systems and sources, and compact light sources.

physics.acc-ph↗

arXiv2022

Snowmass 2021 Accelerator Frontier White Paper: Near Term Applications driven by Advanced Accelerator Concepts

While the long-term vision of the advanced accelerator community is aimed at addressing the challenges of future collider technology, it is critical that the community takes advantage of the opportunity to make large societal impact through its near-term applications. In turn, enabling robust applications strengthens the quality, control, and reliability of the underlying accelerator infrastructure. The white paper contributions that are solicited here will summarize the near-term applications ideas presented by the advanced accelerator community, assessing their potential impact, discussing scientific and technical readiness of concepts, and providing a timeline for implementation.

physics.acc-ph↗

arXiv2021

C$^3$: A "Cool" Route to the Higgs Boson and Beyond

We present a proposal for a cold copper distributed coupling accelerator that can provide a rapid route to precision Higgs physics with a compact 8 km footprint. This proposal is based on recent advances that increase the efficiency and operating gradient of a normal conducting accelerator. This technology also provides an $e^{+}e^{-}$ collider path to physics at multi-TeV energies. In this article, we describe our vision for this technology and the near-term R&D program needed to pursue it.

hep-ex↗

arXiv2021

Semi-Classical Cutoff Energies for Electron Emission and Scattering at Field-Enhancing Nanostructures with Large Ponderomotive Amplitudes

The uniform field assumption used to derive semi-classical cutoff energies of $10U_p$ for electron emission and $3.17U_p$ for high harmonic generation is applicable for ponderomotive amplitudes ($\propto Eλ^2$) much smaller than the field drop-off scale. For large wavelength and high field experiments at nanoscale structures this assumption may break down by predicting energies beyond the true classical energy limits. Here we provide generalized calculations for these cutoff energies by taking into account the spatial field drop-off. The modified cutoff energies vary significantly from the uniform field results even with ponderomotive amplitudes still an order of magnitude below the field drop-off scale. Electron emission and scattering energy as a function of the time-of-ionization is considered for the nanotip ($\sim1/r^2$) field profile. The cutoff energies as a function of the adiabaticity parameter $δ$, which may be easily calculated for given wavelength, apex field strength, and nanostructure scale, are then determined through maximization for nanotip, nanoblade ($\sim1/r$), and exponential field profiles. These profiles deviate from each other in electron emission energy by up to nearly a factor of the ponderomotive energy, indicating the importance of mid-field profile behavior. The electron emission energy cutoff also attains an additional factor of $U_p$ due to the smooth integrated ponderomotive force in the adiabatic drop-off and very long pulse regime. These results also provided as double-exponential fits for ease of use. We then compare the nanoblade electron emission cutoffs with a quantum simulation of the electron rescattering process. We also consider a short (few-cycle) pulsed field, focusing on a cosine-like pulse and overviewing the general carrier-envelope phase dependencies.

cond-mat.mes-hall↗

arXiv2021

Ultra-Compact Ka-band linearizer for the Ultra-Compact X-Ray Free-Electron Laser at UCLA

Notably innovative technologies will permit compact and affordable advanced accelerators as the linear collider and X-ray free-electron lasers (XFELs) with accelerating gradients over twice the value achieved with current technologies. In particular XFEL is able to produce coherent X-ray pulses with peak brightness 10 orders of magnitude greater than preceding approaches, which has revolutionized numerous fields through imaging of the nanoscopic world at the time and length scale of atom-based systems, that is of femtosecond and Angstrom. There is a strong interest for combining these two fields, to form a proper tool with the goal of producing a very compact XFEL in order to investigate multi-disciplinary researches in chemistry, biology, materials science, medicine and physics. In the framework of the Ultra -Compact XFEL project (UC-XFEL) under study at the UCLA, an ultra high gradient higher harmonic RF accelerating structure for the longitudinal space phase linearization is foreseen. To this aim, a Ka-Band linearizer (34.2 GHz) with an integrated voltage of at least 15 MV working on 6th harmonic with respect to the main Linac frequency (5.712 GHz) is required. We here present the electromagnetic design of a cold ultra compact Ka-band SW linearizer, 8 cm long, working on pi mode with an ultra high accelerating gradient (beyond 100 MV/m) and minimum surface electric field for minimizing the probability of RF breakdown. Moreover, we discuss a TW option and compare it with the initial SW structure, by means of main RF parameters as well as beam-dynamics considerations. The numerical electromagnetic studies have been performed by using the well known SuperFish, HFSS and CST.

physics.acc-ph↗

arXiv2020

Longitudinal current profile reconstruction from wakefield response in plasmas and structures

Present-day and next-generation accelerators, particularly for applications in driving wakefield-based schemes, require longitudinal beam shaping and attendant longitudinal characterization for experimental optimization. Here we present a diagnostic method which reconstructs the longitudinal beam profile at the location of a wakefield-generating source. The methods presented derive the longitudinal profile of a charged particle beam solely from measurement of the time-resolved centroid energy change due to wakefield effects. The reconstruction technique is based on a deconvolution algorithm that is fully generalizable to any analytically or numerically calculable Green's function for the wakefield excitation mechanism. This method is shown to yield precise features in the longitudinal current distribution reconstruction. We demonstrate the accuracy and efficacy of this technique using simulations and experimental examples, in both plasmas and dielectric structures, and compare to the experimentally measured longitudinal beam parameters as available. The limits of resolution and applicability to relevant scenarios are also examined.

physics.acc-ph↗

arXiv2019

Single-Shot Characterization of High Transformer Ratio Wakefields in Nonlinear Plasma Acceleration

Plasma wakefields can enable very high accelerating gradients for frontier high energy particle accelerators, in excess of 10 GeV/m. To overcome limits on total acceleration achievable, specially shaped drive beams can be used in both linear and nonlinear plasma wakefield accelerators (PWFA), to increase the transformer ratio, implying that the drive beam deceleration is minimized relative to acceleration obtained in the wake. In this Letter, we report the results of a nonlinear PWFA, high transformer ratio experiment using high-charge, longitudinally asymmetric drive beams in a plasma cell. An emittance exchange process is used to generate variable drive current profiles, in conjunction with a long (multiple plasma wavelength) witness beam. The witness beam is energy-modulated by the wakefield, yielding a response that contains detailed spectral information in a single-shot measurement. Using these methods, we generate a variety of beam profiles and characterize the wakefields, directly observing beam-loaded transformer ratios up to R=7.8. Furthermore, a spectrally-based reconstruction technique, validated by 3D particle-in-cell simulations, is introduced to obtain the drive beam current profile from the decelerating wake data.

physics.acc-ph↗

arXiv2008

Virtual dielectric waveguide mode description of a high-gain free-electron laser I: Theory

A set of mode-coupled excitation equations for the slowly-growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a high-gain free-electron laser, or FEL, including the effects of longitudinal space-charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input (seeding) and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single gaussian mode.

physics.optics↗