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11 pages, 5709 KiB

Open AccessArticle

Drive Bunch Train for the Dielectric Trojan Horse Experiment at the Argonne Wakefield Accelerator

by Gerard Andonian, Nathan Burger, Nathan Cook, Scott Doran, Tara Hodgetts, Seongyeol Kim, Gwanghui Ha, Wanming Liu, Walter Lynn, Nathan Majernik, John Power, Alexey Pronikov, James Rosenzweig and Eric Wisniewski

Instruments 2024, 8(2), 28; https://doi.org/10.3390/instruments8020028 - 10 Apr 2024

Viewed by 1312

Abstract

The recently demonstrated concept of the plasma photocathode, whereby a high-brightness bunch is initialized by laser ionization within a plasma wakefield acceleration bubble, is informally referred to as Trojan Horse wakefield acceleration. In a similar vein, the dielectric Trojan Horse concept incorporates a [...] Read more.

The recently demonstrated concept of the plasma photocathode, whereby a high-brightness bunch is initialized by laser ionization within a plasma wakefield acceleration bubble, is informally referred to as Trojan Horse wakefield acceleration. In a similar vein, the dielectric Trojan Horse concept incorporates a dielectric-lined waveguide to support a charged particle beam-driven accelerating mode and uses laser initiated ionization of neutral gas within the waveguide to generate a witness beam. One of the advantages of the dielectric Trojan Horse concept is the reduced requirements in terms of timing precision due to operation at a lower frequency. In this paper, we present experimental results on the generation and characterization of a four-bunch drive train for resonant excitation of wakefields in a cylindrical dielectric waveguide conducted at the Argonne Wakefield Accelerator facility. The results lay the foundation for the demonstration of a plasma photocathode scheme within a dielectric wakefield accelerating structure. Modifications to improve capture efficiency with improved beam transmission are suggested as well. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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32 pages, 23973 KiB

Open AccessArticle

A High-Flux Compact X-ray Free-Electron Laser for Next-Generation Chip Metrology Needs

by James B. Rosenzweig, Gerard Andonian, Ronald Agustsson, Petr M. Anisimov, Aurora Araujo, Fabio Bosco, Martina Carillo, Enrica Chiadroni, Luca Giannessi, Zhirong Huang, Atsushi Fukasawa, Dongsung Kim, Sergey Kutsaev, Gerard Lawler, Zenghai Li, Nathan Majernik, Pratik Manwani, Jared Maxson, Janwei Miao, Mauro Migliorati, Andrea Mostacci, Pietro Musumeci, Alex Murokh, Emilio Nanni, Sean O’Tool, Luigi Palumbo, River Robles, Yusuke Sakai, Evgenya I. Simakov, Madison Singleton, Bruno Spataro, Jingyi Tang, Sami Tantawi, Oliver Williams, Haoran Xu and Monika Yadav Show full author list Hide full author list

Instruments 2024, 8(1), 19; https://doi.org/10.3390/instruments8010019 - 1 Mar 2024

Cited by 1 | Viewed by 2588

Abstract

Recently, considerable work has been directed at the development of an ultracompact X-ray free-electron laser (UCXFEL) based on emerging techniques in high-field cryogenic acceleration, with attendant dramatic improvements in electron beam brightness and state-of-the-art concepts in beam dynamics, magnetic undulators, and X-ray optics. [...] Read more.

Recently, considerable work has been directed at the development of an ultracompact X-ray free-electron laser (UCXFEL) based on emerging techniques in high-field cryogenic acceleration, with attendant dramatic improvements in electron beam brightness and state-of-the-art concepts in beam dynamics, magnetic undulators, and X-ray optics. A full conceptual design of a 1 nm (1.24 keV) UCXFEL with a length and cost over an order of magnitude below current X-ray free-electron lasers (XFELs) has resulted from this effort. This instrument has been developed with an emphasis on permitting exploratory scientific research in a wide variety of fields in a university setting. Concurrently, compact FELs are being vigorously developed for use as instruments to enable next-generation chip manufacturing through use as a high-flux, few nm lithography source. This new role suggests consideration of XFELs to urgently address emerging demands in the semiconductor device sector, as identified by recent national need studies, for new radiation sources aimed at chip manufacturing. Indeed, it has been shown that one may use coherent X-rays to perform 10–20 nm class resolution surveys of macroscopic, cm scale structures such as chips, using ptychographic laminography techniques. As the XFEL is a very promising candidate for realizing such methods, we present here an analysis of the issues and likely solutions associated with extending the UCXFEL to harder X-rays (above 7 keV), much higher fluxes, and increased levels of coherence, as well as methods of applying such a source for ptychographic laminography to microelectronic device measurements. We discuss the development path to move the concept to rapid realization of a transformative XFEL-based application, outlining both FEL and metrology system challenges. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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15 pages, 6466 KiB

Open AccessArticle

Improving Cathode Testing with a High-Gradient Cryogenic Normal Conducting RF Photogun

by Gerard Emile Lawler, Fabio Bosco, Martina Carillo, Atsushi Fukasawa, Zenghai Li, Nathan Majernik, Yusuke Sakai, Sami Tantawi, Oliver Williams, Monika Yadav and James Rosenzweig

Instruments 2024, 8(1), 14; https://doi.org/10.3390/instruments8010014 - 24 Feb 2024

Viewed by 1569

Abstract

Future electron accelerator applications such as X-ray free electron lasers and colliders are dependent on significantly increasing beam brightness. With the observation that linac beam manipulation’s best preservation of max brightness is at the cathode, we are incentivized to create an environment where [...] Read more.

Future electron accelerator applications such as X-ray free electron lasers and colliders are dependent on significantly increasing beam brightness. With the observation that linac beam manipulation’s best preservation of max brightness is at the cathode, we are incentivized to create an environment where we can study how to achieve the highest possible photogun brightness. In order to do so, we intend to extract beams from high-brightness photocathodes with the highest achievable accelerating gradients we can manage in a klystron-powered radiofrequency (RF) photogun. We utilize here cryogenic normal conducting cavities to achieve ultra-high gradients via limitation of breakdown rates (BDR). The low temperatures should also reduce cathode emittance by reducing the mean transverse energy (MTE) of electrons near the photoemission threshold. To this end, we have designed and produced a new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG) for use in a new beamline at UCLA. We will introduce the enabling RF and photoemission physics as a primer for the new regime of high field low temperature cathodes we intend to enter. We further report the current status of the beamline commissioning, including the cooling of the photogun to 100 K, and producing 0.5 MW of RF feed power, which corresponds to cathode accelerating fields in the range of 80–90 MV/m. We further plan iterative improvements to both to 77 K and 1 MW corresponding to our ultimate goal >120 MV/m. Our discussion will include future beamline tests and the consideration of the initial realization of an ultra-high-gradient photoinjector concept. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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10 pages, 903 KiB

Open AccessArticle

Manipulation and Wakefield Effects on Multi-Pulse Driver Beams in PWFA Injector Stages

by Fabio Bosco, Gerard Andonian, Obed Camacho, Martina Carillo, Enrica Chiadroni, Anna Giribono, Gerard Lawler, Nathan Majernik, Pratik Manwani, Mauro Migliorati, Andrea Mostacci, Luigi Palumbo, Gilles Jacopo Silvi, Bruno Spataro, Cristina Vaccarezza, Monika Yadav and James Rosenzweig

Instruments 2024, 8(1), 12; https://doi.org/10.3390/instruments8010012 - 20 Feb 2024

Viewed by 1532

Abstract

Particle-driven plasma wakefield acceleration (PWFA) exploits the intense wakefields excited in a plasma by a high-brightness driver beam in order to accelerate a trailing, properly delayed witness electron beam. Such a configuration offers notable advantages in achieving very large accelerating gradients that are [...] Read more.

Particle-driven plasma wakefield acceleration (PWFA) exploits the intense wakefields excited in a plasma by a high-brightness driver beam in order to accelerate a trailing, properly delayed witness electron beam. Such a configuration offers notable advantages in achieving very large accelerating gradients that are suitable for applications in particle colliders and photon production. Moreover, the amplitude of the accelerating fields can be enhanced by resonantly exciting the plasma using a multi-pulse driver beam with a proper time structure. Before the injection into the plasma stage, the pulsed electron beam, conventionally termed the comb beam, is usually produced and pre-accelerated in a radio-frequency (RF) linear accelerator (linac). In this pape, we discuss challenging aspects of the dynamics that comb beams encounter in the RF injector stage preceding the plasma. In particular, the examples we analyze focus on the use of velocity bunching to manipulate the time structure of the beam and the impact of dipole short-range wakefields on the transverse emittances. Indeed, both processes crucially affect the phase space distribution and its quality, which are determinant features for an efficient acceleration in the plasma. In addition, the analyses we present are performed with the custom tracking code MILES, which utilizes semi-analytical models for a simplified evaluation of wakefield effects in the presence of space charge forces. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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10 pages, 3701 KiB

Open AccessArticle

An Ultra-Compact X-ray Regenerative Amplifier Free-Electron Laser

by Madison Singleton, James Rosenzweig, Jingyi Tang and Zhirong Huang

Instruments 2024, 8(1), 2; https://doi.org/10.3390/instruments8010002 - 5 Jan 2024

Cited by 1 | Viewed by 2364

Abstract

There is a growing interest in designing and building compact X-ray Free Electron Lasers (FELs) for scientific and industry applications. In this paper, we report an X-ray Regenerative Amplifier FEL (XRAFEL) design based on a proposed Ultra Compact X-ray FEL configuration. Our results [...] Read more.

There is a growing interest in designing and building compact X-ray Free Electron Lasers (FELs) for scientific and industry applications. In this paper, we report an X-ray Regenerative Amplifier FEL (XRAFEL) design based on a proposed Ultra Compact X-ray FEL configuration. Our results show that an XRAFEL can dramatically enhance the temporal coherence and increase the spectral brightness of the radiation in the hard X-ray regime without increasing the footprint of the FEL configuration. The proposed compact, fully coherent, and high-flux hard X-ray source holds promise as a valuable candidate for a wide range of high-impact applications in both academia and industry. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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11 pages, 6072 KiB

Open AccessArticle

Overview and Commissioning Status of the UCLA MITHRA Facility

by Oliver Williams, Atsushi Fukasawa, Yusuke Sakai, Gerard Andonian, Fabio Bosco, Martina Carillo, Pratik Manwani, Sean O’Tool, Jessica Pan, Monika Yadav and James Rosenzweig

Instruments 2023, 7(4), 54; https://doi.org/10.3390/instruments7040054 - 14 Dec 2023

Viewed by 1616

Abstract

Presented here are the first results of commissioning of the S-Band hybrid photoinjector and laser systems at the new accelerator and light source facility, MITHRA, at UCLA. The radiation bunker and capabilities of the facility are described with motivation for detailed measurement of [...] Read more.

Presented here are the first results of commissioning of the S-Band hybrid photoinjector and laser systems at the new accelerator and light source facility, MITHRA, at UCLA. The radiation bunker and capabilities of the facility are described with motivation for detailed measurement of beam parameters explained. Following thorough characterization of the photoinjector, a 1.5 m linac is to be installed and experiments up to 30 MeV will begin. These will include experiments in basic plasma physics, space plasma, terahertz production in dielectric structures, and inverse Compton scattering and applications for the X-rays produced. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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10 pages, 6352 KiB

Open AccessArticle

First Simulations for the EuAPS Betatron Radiation Source: A Dedicated Radiation Calculation Code

by Andrea Frazzitta, Alberto Bacci, Arianna Carbone, Alessandro Cianchi, Alessandro Curcio, Illya Drebot, Massimo Ferrario, Vittoria Petrillo, Marcello Rossetti Conti, Sanae Samsam, Luca Serafini and Andrea Renato Rossi

Instruments 2023, 7(4), 52; https://doi.org/10.3390/instruments7040052 - 8 Dec 2023

Cited by 3 | Viewed by 1721

Abstract

X-ray production through betatron radiation emission from electron bunches is a valuable resource for several research fields. The EuAPS (EuPRAXIA Advanced Photon Sources) project, within the framework of EuPRAXIA, aims to provide 1–10 keV photons (X-rays), developing a compact plasma-based system designed to [...] Read more.

X-ray production through betatron radiation emission from electron bunches is a valuable resource for several research fields. The EuAPS (EuPRAXIA Advanced Photon Sources) project, within the framework of EuPRAXIA, aims to provide 1–10 keV photons (X-rays), developing a compact plasma-based system designed to exploit self-injection processes that occur in the highly nonlinear laser-plasma interaction (LWFA) to drive electron betatron oscillations. Since the emitted radiation spectrum, intensity, angular divergence, and possible coherence strongly depend on the properties of the self-injected beam, accurate preliminary simulations of the process are necessary to evaluate the optimal diagnostic device specifications and to provide an initial estimate of the source’s performance. A dedicated tool for these tasks has been developed; electron trajectories from particle-in-cell (PIC) simulations are currently undergoing numerical analysis through the calculation of retarded fields and spectra for various plasma and laser parameter combinations. The implemented forward approach evaluation of the fields could allow for the integration of the presented scheme into already existing PIC codes. The spectrum calculation is thus performed in detector time, giving a linear complex exponential phase; this feature allows for a semi-analitical Fourier transform evaluation. The code structure and some trajectories analysis results are presented. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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8 pages, 487 KiB

Open AccessCommunication

Asymmetric Dual-Grating Dielectric Laser Accelerator Optimization

by Sophie Crisp, Alexander Ody and Pietro Musumeci

Instruments 2023, 7(4), 51; https://doi.org/10.3390/instruments7040051 - 7 Dec 2023

Viewed by 1439

Abstract

Although hundreds of keV in energy gain have already been demonstrated in dielectric laser accelerators (DLAs), the challenge of creating structures that can confine electrons for multiple millimeters remains. We focus here on dual gratings with single-sided drive, which have experimentally demonstrated energy [...] Read more.

Although hundreds of keV in energy gain have already been demonstrated in dielectric laser accelerators (DLAs), the challenge of creating structures that can confine electrons for multiple millimeters remains. We focus here on dual gratings with single-sided drive, which have experimentally demonstrated energy modulation numerous times. Using a Finite-Difference Time-Domain simulation to find the fields within various DLA structures and correlating these results with particle tracking simulation, we look at the impact of teeth height and width, as well as gap and offset, on the performance of these structures. We find a tradeoff between electron throughput and acceleration; however, we also find that for any given grating geometry, there is a gap and offset that will allow some charge acceleration. For our 780 nm laser wavelength, this results in a 1200 nm optimal gap size for most gratings. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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21 pages, 2808 KiB

Open AccessArticle

Analytical Scaling Laws for Radiofrequency-Based Pulse Compression in Ultrafast Electron Diffraction Beamlines

by Paul Denham and Pietro Musumeci

Instruments 2023, 7(4), 49; https://doi.org/10.3390/instruments7040049 - 29 Nov 2023

Cited by 1 | Viewed by 1605

Abstract

We present an envelope equation-based approach to obtain analytical scaling laws for the shortest pulse length achievable using radiofrequency (RF)-based bunch compression. The derived formulas elucidate the dependencies on the electron beam energy and beam charge and reveal how relativistic energies are strongly [...] Read more.

We present an envelope equation-based approach to obtain analytical scaling laws for the shortest pulse length achievable using radiofrequency (RF)-based bunch compression. The derived formulas elucidate the dependencies on the electron beam energy and beam charge and reveal how relativistic energies are strongly desirable to obtain bunches containing 1 million electrons with single-digit femtosecond pulse lengths. However, the non-linearities associated with the RF curvature and the beam propagation in drift spaces significantly limit the attainability of extreme compression ratios. Therefore, an additional higher frequency RF cavity is implemented, which linearizes the bunch compression, enabling the generation of ultrashort beams in the sub-femtosecond regime. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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10 pages, 817 KiB

Open AccessArticle

Opportunities for Bright Beam Generation at the Argonne Wakefield Accelerator (AWA)

by Emily Frame, Afnan Al Marzouk, Oksana Chubenko, Scott Doran, Philippe Piot, John Power and Eric Wisniewski

Instruments 2023, 7(4), 48; https://doi.org/10.3390/instruments7040048 - 28 Nov 2023

Cited by 1 | Viewed by 1668

Abstract

Bright electron beams have played a critical role in many recent advances in accelerator technology. Producing bright beams via photo-emission is ultimately limited by the mean transverse energy (MTE), which is determined by the photocathode. This paper discusses the opportunity to generate bright [...] Read more.

Bright electron beams have played a critical role in many recent advances in accelerator technology. Producing bright beams via photo-emission is ultimately limited by the mean transverse energy (MTE), which is determined by the photocathode. This paper discusses the opportunity to generate bright electron beams using an upgraded version of the Argonne Wakefield Accelerator (AWA) photo-injector. The focus of this study is to examine the optimal configurations of the AWA photo-injector to produce 100 pC with a ∼100 nm transverse emittance (corresponding to a 5D brightness

B_{5} \geq 10^{15}

A·m

^{- 2}

). The numerical optimization of the AWA photo-injector operating point, including realistic electromagnetic field maps, is presented for the different types of photocathodes under consideration. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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13 pages, 3856 KiB

Open AccessArticle

Modeling Field Electron Emission from a Flat Au (100) Surface with Density-Functional Theory

by Yiming Li, Joshua Mann and James Rosenzweig

Instruments 2023, 7(4), 47; https://doi.org/10.3390/instruments7040047 - 28 Nov 2023

Cited by 1 | Viewed by 1751

Abstract

Field electron emission, or electron tunneling through a potential energy (PE) barrier under the influence of a strong electrostatic (ES) or radio frequency (RF) field, is of broad interest to the accelerator physics community. For example, it is the source of undesirable dark [...] Read more.

Field electron emission, or electron tunneling through a potential energy (PE) barrier under the influence of a strong electrostatic (ES) or radio frequency (RF) field, is of broad interest to the accelerator physics community. For example, it is the source of undesirable dark currents in resonant cavities, providing a limit to high-field operation. Field electron emission can also be applied to quasi-statically model electron emission induced by the electric field in a laser pulse. The classical approach to field electron emission is the Fowler–Nordheim (FN) framework, which incorporates a simplified PE profile and various assumptions. Here, we build a more realistic model using the PE and charge densities derived from a density-functional theory (DFT) calculation. We examine the correction factors associated with each model assumption. Compared to the FN framework, our results can be extended up to 80 GV/m, a limit that has been reached in laser-induced strong field emission scenarios. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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9 pages, 944 KiB

Open AccessCommunication

Kernel Density Estimators for Axisymmetric Particle Beams

by Christopher M. Pierce and Young-Kee Kim

Instruments 2023, 7(4), 44; https://doi.org/10.3390/instruments7040044 - 21 Nov 2023

Viewed by 1771

Abstract

Bright beams are commonly represented by sampled data in the numerical algorithms used to simulate their properties. However, in these calculations and the analyses of their outputs, the beam’s density is sometimes required and must be calculated from the samples. Axisymmetric beams, which [...] Read more.

Bright beams are commonly represented by sampled data in the numerical algorithms used to simulate their properties. However, in these calculations and the analyses of their outputs, the beam’s density is sometimes required and must be calculated from the samples. Axisymmetric beams, which possess a rotational symmetry and are naturally expressed in polar coordinates, pose a particular challenge to density estimators. The area element in polar coordinates shrinks as the radius becomes small, and weighting the samples to account for their reduced frequency may cause unwelcome artifacts. In this work, we derive analytical expressions for two kernel density estimators, which solve these problems in the spatial coordinates and in the transverse phase space. We show how the kernels can be found by averaging the Gaussian kernel in Cartesian coordinates over the polar angle and demonstrate their use on test problems. These results show that particle beam symmetries can be taken advantage of in density estimation while avoiding artifacts. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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8 pages, 557 KiB

Open AccessCommunication

FAST Low-Energy Beamline Studies: Toward High-Peak 5D Brightness Beams for FAST-GREENS

by Frederick Cropp, Jinhao Ruan, James Santucci, Daniel MacLean, Alex H. Lumpkin, Christopher C. Hall, Jonathan P. Edelen, Alex Murokh, Daniel Broemmelsiek and Pietro Musumeci

Instruments 2023, 7(4), 42; https://doi.org/10.3390/instruments7040042 - 17 Nov 2023

Viewed by 1479

Abstract

The FAST beamline is the injector for the planned Gamma-Ray Electron ENhanced Source (GREENS) program, which aims to achieve the demonstration and first application of a high-efficiency, high-average-power free-electron laser at 515 nm. FAST-GREENS requires high 5D peak brightness; transverse normalized projected emittances [...] Read more.

The FAST beamline is the injector for the planned Gamma-Ray Electron ENhanced Source (GREENS) program, which aims to achieve the demonstration and first application of a high-efficiency, high-average-power free-electron laser at 515 nm. FAST-GREENS requires high 5D peak brightness; transverse normalized projected emittances of 3 mm-mrad and a peak current of 600 A are the minimum beam requirements for the FEL to reach the 10% efficiency goal. In this work, studies of the low-energy section of the FAST beamline are presented toward these ends, including preliminary measurements of beam compression and beam emittance. An effort toward developing a high-fidelity simulation model that could be later optimized for FAST-GREENS is presented. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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13 pages, 2913 KiB

Open AccessArticle

Multipulse Optical-Rectification-Based THz Source for Accelerator Applications

by Maximilian Lenz and Pietro Musumeci

Instruments 2023, 7(4), 39; https://doi.org/10.3390/instruments7040039 - 9 Nov 2023

Viewed by 1556

Abstract

THz sources offer the potential for higher frequencies and higher breakdown thresholds in accelerating structures in comparison with conventional RF sources. They also benefit from larger field strengths, field gradients, better beam synchronization and compactness. In this work, we first present the development [...] Read more.

THz sources offer the potential for higher frequencies and higher breakdown thresholds in accelerating structures in comparison with conventional RF sources. They also benefit from larger field strengths, field gradients, better beam synchronization and compactness. In this work, we first present the development of a

49 μ

J single-cycle THz source centered at 0.6 THz that provides fields over 30 MV/m. With further modifications, multicycle pulses were produced, narrowing the bandwidth of the source and potentially easing the coupling of THz radiation to relativistic electron beams and increasing the usability in other areas of research. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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17 pages, 1714 KiB

Open AccessArticle

Shaping Micro-Bunched Electron Beams for Compact X-ray Free-Electron Lasers with Transverse Gradient Undulators

by River R. Robles and James B. Rosenzweig

Instruments 2023, 7(4), 35; https://doi.org/10.3390/instruments7040035 - 26 Oct 2023

Viewed by 1787

Abstract

Laser-modulator-based micro-bunching of electron beams has been applied to many novel operating modes of X-ray free-electron lasers from harmonic generation to attosecond pulse production. Recently, it was also identified as a key enabling technology for the production of a compact XFEL driven by [...] Read more.

Laser-modulator-based micro-bunching of electron beams has been applied to many novel operating modes of X-ray free-electron lasers from harmonic generation to attosecond pulse production. Recently, it was also identified as a key enabling technology for the production of a compact XFEL driven by a relatively low-energy beam. In traditional laser modulator schemes with low-energy and high-current bunches, collective effects limit the possible working points that can be employed, and thus it is difficult to achieve optimal XFEL performance. We propose to utilize transverse longitudinal coupling in a transverse gradient undulator (TGU) to shape micro-bunched electron beams so as to optimize their performance in a compact X-ray free-electron laser. We show that a TGU added to a conventional laser modulator stage enables much more flexibility in the design, allowing one to generate longer micro-bunches less subject to slippage effects and even lower the slice emittance of the micro-bunches. We present a theoretical analysis of laser-based micro-bunching with an added TGU, simulation of compression with collective effects in such systems, and finally XFEL simulations demonstrating the gains in peak power enabled by the TGU. Although we focus on the application to compact XFELs, what we propose is a general phase space manipulation that may find utility in other applications as well. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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10 pages, 1035 KiB

Open AccessArticle

Attosecond Pulses from Ionization Injection Wakefield Accelerators

by Paolo Tomassini, Vojtech Horny and Domenico Doria

Instruments 2023, 7(4), 34; https://doi.org/10.3390/instruments7040034 - 24 Oct 2023

Viewed by 1411

Abstract

High-quality ionization injection methods for wakefield acceleration driven by lasers or charged beams (LWFA/PWFA) can be optimized so as to generate high-brightness electron beams with tuneable duration in the attosecond range. We present a model of the minimum bunch duration obtainable with low-emittance [...] Read more.

High-quality ionization injection methods for wakefield acceleration driven by lasers or charged beams (LWFA/PWFA) can be optimized so as to generate high-brightness electron beams with tuneable duration in the attosecond range. We present a model of the minimum bunch duration obtainable with low-emittance ionization injection schemes by spotting the roles of the ionization pulse duration, of the wakefield longitudinal shape and of the delay of the ionization pulse position with respect to the node of the accelerating field. The model is tested for the resonant multi-pulse ionization injection (ReMPI) scheme, showing that bunches having a length of about 300 as can be obtained with an ionization pulse having a duration of 30 fs FWHM. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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11 pages, 802 KiB

Open AccessArticle

Effect of Molybdenum Coatings on the Accelerating Cavity Quality Factor

by Pablo Vidal García, Stefano Sarti, Martina Carillo, Lucia Giuliano, Augusto Marcelli, Bruno Spataro, Andrea Alimenti, Kostiantyn Torokhtii, Enrico Silva and Nicola Pompeo

Instruments 2023, 7(4), 33; https://doi.org/10.3390/instruments7040033 - 21 Oct 2023

Viewed by 1513

Abstract

In this work, a detailed parametric study assessing the impact of low-conductivity coatings on the radio-frequency accelerating cavity quality factor and resonance frequency shift is presented. In particular, this study is aimed at proving the feasibility of molybdenum oxides deposited on copper to [...] Read more.

In this work, a detailed parametric study assessing the impact of low-conductivity coatings on the radio-frequency accelerating cavity quality factor and resonance frequency shift is presented. In particular, this study is aimed at proving the feasibility of molybdenum oxides deposited on copper to reduce the dark current in high-gradient applications due to its intrinsically high work function. In order to compute the effective surface impedance of the resulting layered structure, a transmission line-based approach is adopted. The present analysis demonstrates the potential effectiveness of molybdenum thin-films, which only slightly affects the accelerating cavity quality factor, with very low sensitivity to thickness and resistivity inhomogeneities. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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7 pages, 809 KiB

Open AccessCommunication

Demonstration of Autonomous Emittance Characterization at the Argonne Wakefield Accelerator

by Ryan Roussel, Dylan Kennedy, Auralee Edelen, Seongyeol Kim, Eric Wisniewski and John Power

Instruments 2023, 7(3), 29; https://doi.org/10.3390/instruments7030029 - 20 Sep 2023

Cited by 2 | Viewed by 1290

Abstract

Transverse beam emittance plays a key role in the performance of high-brightness accelerators. Characterizing beam emittance is often carried out using a quadrupole scan, which fits beam matrix elements to experimental measurements using first-order beam dynamics. Despite its simplicity at face value, this [...] Read more.

Transverse beam emittance plays a key role in the performance of high-brightness accelerators. Characterizing beam emittance is often carried out using a quadrupole scan, which fits beam matrix elements to experimental measurements using first-order beam dynamics. Despite its simplicity at face value, this procedure is difficult to automate due to practical limitations. Key issues that must be addressed include maintaining beam size measurement validity by keeping beams within the radius of diagnostic screens, ensuring that measurement fitting produces physically valid results, and accurately characterizing emittance uncertainty. We describe a demonstration of the Bayesian exploration technique towards solving this problem at the Argonne Wakefield Accelerator, enabling a turn-key, autonomous quadrupole scan tool that can be used to quickly measure beam emittances at various locations in accelerators with limited operator input. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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8 pages, 619 KiB

Open AccessBrief Report

Effects of Plasma Temperature in the Blowout Regime for Plasma Accelerators

by Gevy Jiawei Cao

Instruments 2023, 7(4), 37; https://doi.org/10.3390/instruments7040037 - 31 Oct 2023

Viewed by 1641

Abstract

Research on plasma accelerators for high-energy colliders has rapidly progressed over the past few decades. Plasma acceleration with a high repetition rate will enable higher collider luminosity, but results in a heated plasma. This study investigates two phenomena—beam breakup instability and ion motion—in [...] Read more.

Research on plasma accelerators for high-energy colliders has rapidly progressed over the past few decades. Plasma acceleration with a high repetition rate will enable higher collider luminosity, but results in a heated plasma. This study investigates two phenomena—beam breakup instability and ion motion—in the nonlinear blowout regime in plasma accelerators and how the plasma temperature affects them. It was found that increasing the plasma temperature enhances the beam breakup instability by reducing the blowout radius while suppressing the on-axis ion-density spike caused by ion motion. This imposes a stringent demand on alignment tolerances, but it offers promising prospects for mitigating ion motion. Full article

(This article belongs to the Special Issue Selected Papers from the Workshop on Physics and Applications of High Brightness Beams)

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