Recirculating energy recovery linacs are a promising technology for delivering high power particle beams (∼GW) while only requiring low power (∼kW) RF sources. This is achieved by decelerating the used bunches and using the energy they deposit in the accelerating structures to accelerate new bunches. We present studies of the impact of the bunch packet filling pattern on the performance of the accelerating

We study experimentally the longitudinal and transverse wakefields driven by a highly relativistic proton bunch during self-modulation in plasma. We show that the wakefields’ growth and amplitude increase with increasing seed amplitude as well as with the proton bunch charge in the plasma. We study transverse wakefields using the maximum radius of the proton bunch distribution measured on a screen

For future linear colliders, a nanometer-scale beam size at the interaction point (IP) is one of the most challenging technical aspects. To explore the feasibility of a final focus system~(FFS) with a high chromaticity level, being comparable to that of the Compact Linear Collider~(CLIC), the ultra-low beta* optics has been proposed and tuned at the KEK-ATF2. In this paper, the recent experimental

In synchrotrons, nonuniform fill patterns, which give rise to beam phase transients and a spread in synchrotron tune between bunches, have been observed to damp longitudinal coupled-bunch instabilities driven by higher-order modes in RF cavities. The transients are especially large in the presence of Landau cavities, which are used commonly in storage-ring light sources and particularly in the new

We have established and also implemented a non-destructive online monitoring system for measuring the stripper foil degradation, such as a foil thinning and pinholes outbreak for the first time during beam operation in a high intensity proton accelerator. We aimed to achieve a realistic and longer lifetime of a stripper foil by ensuring proper uses and determining its end of usefulness without any

In the frame of the Tulip Project, an application for accelerator technology to radiation therapy, supported by a CERN Knowledge Technology Fund, the design, manufacture and test of a compact, fast trimmable iron cobalt (FeCo) accelerator dipole magnet prototype has been performed and completed at CERN. The aim of this project is to illustrate the benefits of a FeCo magnet for medical gantries in which

We propose and we numerically design a working point for beam driven plasma wakefield acceleration that allows to preserve the witness quality. This working point is a new scheme where a low density driver generates a wakefield in linear regime and the witness transverse evolution is dominated by the beam loading effect. We derived optimal matching conditions to prevent the phase space degradation

This paper presents a novel approach for constructing neural networks which model charged particle beam dynamics. In our approach, the Taylor maps arising in the representation of dynamics are mapped onto the weights of a polynomial neural network. The resulting network approximates the dynamical system with perfect accuracy prior to training and provides a possibility to tune the network weights on

Laser plasma accelerators capable of generating electron beams may require plasma mirrors to remove undepleted laser energy at the end of the stage. The electron bunch can interact with light reflected from the mirror resulting in inverse Compton scattering. For realistic conditions, we show that a significant fraction of electrons emit one or more photons, increasing the energy spread of the electron

Longitudinal bunch shaping is gaining increasing attention due to the large impact it has on modern accelerators. The existing methods for controlling the density profile fall into three categories: laser shaping, emittance exchange, or correlations between the energy and one of the other coordinates. These methods require either (i) dispersive elements (e.g., dipole magnet), which generates coherent

Energy recovery linear accelerators (ERLs) are relying on the usage of single axis superconducting radio frequency (SRF) cavities to be efficient sources of relativistic electrons for high energy and nuclear physics and also considered for next-generation photon factories and radio-isotope production facilities. An ultimate energy recovery capability for the accelerator would be the ability of decreasing

The Landau damping mechanism stabilises the impedance driven head-tail modes in hadron synchrotrons. Due to the frequent coherent beam instabilities observed in the Large Hadron Collider in 2012, the Landau damping of the beams was doubted. Therefore, a transverse Beam Transfer Function (BTF) system was installed in order to probe the transverse Landau damping of the beams and compare the measurements

Polarized photon beams provide a unique experimental tool for the study of various polarization dependent physical processes. Here, we report the experimental demonstration of full polarization control of an oscillator free-electron laser (FEL) using helical undulators of opposite helicities. Using two helical undulator magnets of opposite helicities and a buncher magnet in between, we have generated

The extraction efficiency is one of the key parameters of an oscillator-type free electron laser (FEL). An extraction efficiency higher than 5% was observed with the midinfrared (MIR) FEL at Kyoto University using a dynamic cavity desynchronization method . The observed efficiency is the highest extraction efficiency realized in MIR-FEL oscillators driven by normal conducting linacs. A numerical simulation

The Large Hadron Collider (LHC) Schottky monitors have been designed to measure various parameters of relevance to beam quality, namely tune, momentum spread and chromaticity. In this work, we present how this instrument can be used to estimate longitudinal bunch characteristics, such as longitudinal bunch profile or synchrotron frequency distribution. Under the assumption of bunched beams with no

Reducing the intrinsic emittance of photocathodes is one of the most promising routes to improving the brightness of electron sources. However, when emittance growth occurs during beam transport (for example, due to space-charge), it is possible that this emittance growth overwhelms the contribution of the photocathode and, thus, in this case source emittance improvements are not beneficial. Using

We investigate the dynamics of electrons counter-propagating along a radially polarized optical Bessel beam (OBB). (i) It is shown that a significant fraction of the electrons can be transversally trapped by the OBB even in the case of "un-matched’’ injection. Moreover, (ii) these transversally trapped particles (TTP) can be transported without loss along many thousands of wavelengths. As long as there

Recently, laser processing of copper samples has been demonstrated to produce rough surfaces whose nano-structuring ensures unquestionable advantages for electron cloud mitigation in future particle accelerators. The actual application of laser treated surfaces in accelerators implies that this new material is compliant with many issues, going from impedance vacuum properties to many others. A significant

We developed an electron gun system capable of delivering beams with brightness high enough and emittance low enough to drive soft X-ray free-electron lasers (SXFEL). We modified the conventional radio-frequency (RF) gun concept by using a 50-kV gun with a gridded thermionic cathode connected with a 238-MHz acceleration cavity. We achieved a low target emittance by applying the following two methods:

We present a novel method for measurement of ultrashort electron-bunch duration, in principle, as short as zeptosecond(10−21s). The method employs nonlinear Thomson scattering of relativistically-intense laser light, and takes advantage of the nonlinear dependence and coherence of scattered light on electron bunch length. We validate the method and test its range of applicability via simulations by

A prototype quasi-parasitic thermal neutron beam monitor based on isotropic neutron scattering from a thin natural vanadium foil and standard 3He proportional counters is conceptualized, designed, simulated, calibrated, and commissioned. The European Spallation Source designed to deliver the highest integrated neutron flux originating from a pulsed source is currently under construction in Lund, Sweden

As hadron accelerators achieve increasing beam power, damage to targets is becoming increasingly severe. To mitigate this damage, nonlinear beam optics based on octupole magnets is attractive. Nonlinear optics can decrease the beam-focusing hazard due to failure of the rastering magnet. As a side effect of nonlinear optics, the beam size at the tail is known to expand drastically compared with linear

Transverse emittance growth due to space-charge-induced resonance was studied for high-power beam operation in the J-PARC main ring synchrotron. The turn-by-turn beam sizes were measured near the structure resonance at νx=21 and near the non-structure resonance at νx=22. A clear difference in the emittances was observed. The emittance was observed to grow by 5 times at the operating tune νx=21.10,

The Low Energy RHIC Electron Cooler (LEReC) is the world’s first electron cooler using RF-accelerated electron bunches. Recently, the cooling of gold ion beams in RHIC by 1.6 and 2.0 MeV electrons was successfully achieved. Along with the velocity spread and alignment of the electron beam, the space charge force between ions and electrons also plays an important role in the cooling process. In order

Transient beam loading effects and microwave instability are very important in ion synchrotrons. A simulation code Longitudinal Particle Tracking Code (LPTC) based on multi-particle tracking is developed to simulate the beam loading effects and the longitudinal beam instabilities in the booster ring (BRing) of the High Intensity heavy-ion Accelerator Facility (HIAF). A process of beam capture, acceleration

The Integrable Optics Test Accelerator (IOTA) is a novel storage ring at Fermi National Accelerator Laboratory designed (in part) to investigate the dynamics of beams in the presence of highly nonlinear transverse focusing fields that generate integrable single-particle motion with a large spread in the intrinsic betatron tunes. We describe how contemporary geometrical methods from the theory of integrable

We present a systematic comparison of two complementary methods for determining the longitudinal charge density profile of the compressed electron bunches in the soft X-ray free-electron laser FLASH: a frequency-domain technique - coherent transition radiation (CTR) spectroscopy - and a time-domain technique - streaking of the electron beam with a transversely deflecting microwave structure (TDS).

Closed orbit feedback (COFB) systems at synchrotrons used for the global orbit correction rely on the pseudo-inversion of the orbit response matrix (ORM). A mismatch between the model ORM used in the controller and the actual machine ORM can affect the performance of the feedback system. In this paper, the typical sources of such model mismatch such as acceleration ramp ORM variation, intensity-dependent

We exploit echo-enabled harmonic generation (EEHG) to produce fully coherent free-electron laser (FEL) pulses at soft-x-ray wavelengths and shape their spectrotemporal content. In an EEHG FEL, the longitudinal phase space of the relativistic electron beam that amplifies light is precisely tailored using two external seed lasers and two magnetic chicanes. We show that the spectrotemporal properties

An ultrarelativistic electron beam passing through an intense laser pulse emits radiation around its direction of propagation into a characteristic angular profile. Here we show that measurement of the variances of this profile in the planes parallel and perpendicular to the laser polarization, and the mean initial and final energies of the electron beam, allows the intensity of the laser pulse to

A new beam dump has been designed, built, installed and operated to withstand the future proton beam extracted from the Proton Synchrotron Booster (PSB) in the framework of the LHC Injector Upgrade (LIU) Project at CERN. The future proton beam consists of up to 1$10^{14}$ protons per pulse at 2 GeV and is foreseen after the machine upgrades planned for CERN’s Long Shutdown 2 (2019-2020). In order to

We study the effect of a passive harmonic cavity, introduced to cause bunch lengthening, in an electron storage ring. We derive a formula for the induced voltage from such a cavity with high Q, excited by a sequence of bunches, allowing for arbitrary gaps in the sequence and arbitrary currents. Except for a minor term that can be determined iteratively, the voltage is given in terms of a single mode

Ionization cooling is the preferred method for producing bright muon beams. This cooling technique requires the operation of normal conducting, radio-frequency (RF) accelerating cavities within the multi-tesla fields of DC solenoid magnets. Under these conditions, cavities exhibit increased susceptibility to RF breakdown, which can damage cooling channel components and imposes limits on channel length

We show that the properties of the electron beam and bright x-rays produced by a laser wakefield accelerator can be predicted if the distance over which the laser self-focuses and compresses prior to self-injection is taken into account. A model based on oscillations of the beam inside a plasma bubble shows that performance is optimised when the plasma length is matched to the laser depletion length