We present a new approach that demonstrates the deflection and guiding of relativistic electron beams over curved paths by means of the magnetic field generated in a plasma-discharge capillary. We ...experimentally prove that the guiding is much less affected by the beam chromatic dispersion with respect to a conventional bending magnet and, with the support of numerical simulations, we show that it can even be made dispersionless by employing larger discharge currents. This proof-of-principle experiment extends the use of plasma-based devices, that revolutionized the field of particle accelerators enabling the generation of GeV beams in few centimeters. Compared to state-of-the-art technology based on conventional bending magnets and quadrupole lenses, these results provide a compact and affordable solution for the development of next-generation tabletop facilities.
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Abstract
The high longitudinal electric fields generated in plasma wakefields are very attractive for a new generation of high gradient plasma based accelerators. On the other hand, the strong ...transverse fields increase the demand for a proper matching device in order to avoid the spoiling of beam transverse quality. A solution can be provided by the use of a plasma ramp, a region at the plasma injection/extraction with smoothly increasing/decreasing plasma density. The transport of a beam inside a plasma ramp, beside its parameters, depends on the profile of the ramp itself. Establishing the transfer matrix for a plasma ramp represent a very useful tool in order to evaluate the beam evolution in the plasma. In this paper a study of a cosine squared ramp is presented. An approximate solution of the transverse equation of motion is evaluated and exploited to provide a simple transfer matrix for the plasma ramp. The transfer matrix is then employed to demonstrate that this kind of ramp has the effect to minimize the emittance growth due to betatron dephasing. The behavior of a squared cosine plasma ramp will be compared with an experimentally measured plasma ramp profile in order to validate the applicability of the transfer matrix to real cases.
C-band technology is emerging as an exciting innovative approach to the creation of compact new accelerators. Besides the possibility to sustain higher gradients and higher repetition rate operation ...at normal conducting temperature, it also allows one to increase the machine performance in terms of beam brightness. We propose the design study of a normal conducting, high gradient C-band injector aiming at the production of high brightness electron beams—up to 2.6×10^{3} TA/m^{2}—at high repetition rate—up to 1 KHz—as desired to enhance the capabilities of modern radiation sources. This paper reports on beam dynamics studies that guided the injector design looking for a good compromise between the machine compactness and performances. For this purpose, a new standing wave C-band gun consisting of 2.6 cells has been designed to enhance the final beam brightness together with its own mode launcher to ensure the needed peak field at the cathode—up to 180 MV/m. Several working points in terms of peak current, transverse emittance and brightness are explored, showing the flexibility allowed by the proposed photoinjector. The integration of the gun mode launcher, that relies on a four-port configuration, in the injector design and its effect on the beam quality are also reported.
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Abstract
In this article, we share our experience related to the new photo-injector commissioning at the SPARC_LAB test facility.
The new photo-injector was installed into an existing machine and our ...goal was not only to improve the final beam parameters themselves but to improve the machine handling in day-to-day operations as well. Thus, besides the pure beam characterization, this article contains information about the improvements, that were introduced into the new photo-injector design from the machine maintenance point of view, and the benefits, that we gained by using the new technique to assemble the gun itself.
Abstract
High brightness electron beams enable a wide spectrum of applications ranging from short wavelength radiation sources to high gradient wakefield acceleration. The rich dynamics that are ...intrinsic in charged particles accelerated in complex systems require a careful description in the analysis and design of a given machine, particularly regarding its stability. Numerous computer codes are in use by the accelerator community for such purposes. In particular, MILES is a simple tracking code we have developed that allows fast evaluations of collective effects in RF linacs. In this paper we extend the simple models previously developed to describe specific, diverse applications that can benefit from the fast simulation tools developed in MILES. Examples of this kind include particle driven acceleration schemes in a plasma where driver and witness beams propagate in the “comb” pulse-train configuration. Specifically, we investigate the self-induced fields excited within the X-band rf-linac stage of EuPRAXIA@SPARC_LAB. Further, we discuss additional advanced topics such as resistive wall wakefield effects in planar FEL undulators and their impact on the radiation emitted.
Abstract
The SPARC_LAB test facility at the LNF (Laboratori Nazionali di Frascati, Rome) holds a high brightness photo-injector used to investigate advanced beam manipulation techniques. High ...brightness electron bunch trains (so-called comb beams) can be generated striking on the photo-cathode of a Radio Frequency (RF) photo-injector with a ultra-short UV laser pulse train in tandem with the velocity bunching technique. Beam dynamics studies have been performed with the aim of optimizing the dynamics of the double beam (driver and witness) used to perform particle driven plasma wake field acceleration (PWFA). In this scenario different scans on beam parameters were carried on adopting the ASTRA simulation code, in order to optimize the witness beam quality and improve the plasma booster stage performances. A benchmark of the simulations has been then performed, reproducing the experimental data obtained from the optimization of machine performances, and a good agreement was found.
Abstract
The interest in plasma-based accelerators as drivers of user facilities is growing worldwide thanks to their compactness and reduced costs. The EuPRAXIA@SPARC_LAB collaboration is preparing ...a technical design report for a multi-GeV plasma-based accelerator with outstanding electron beam quality to pilot an X-ray FEL, the most demanding in terms of beam brightness. The beam dynamics has been studied aiming to a reliable operation of the RF injector to generate a so-called comb-beam with 500 MeV energy suitable as driver of the Beam-driven Plasma Wakefield Accelerator. A case of interest is the generation of a trailing bunch with 1 GeV energy, less than 1 mm-mrad transverse emittance and up to 2 kA peak current at the undulator entrance. The comb-beam is generated through the velocity bunching technique, an RF compression tool that enables high brightness beams within relatively compact machine. Since it is based on a rotation of the beam phase space inside the external RF fields, it could be particularly sensitive to amplitude and phase jitters in the RF injector. The electron beam dynamics and the machine sensitivity to the possible jitters are presented in terms of effect on the beam quality so to provide the basis for the jitter tolerances.
Plasma wakefield acceleration represented a breakthrough in the field of particle accelerators by pushing beams to gigaelectronvolt energies within centimeter distances. The large electric fields ...excited by a driver pulse in the plasma can efficiently accelerate a trailing witness bunch paving the way toward the realization of laboratory-scale applications like free-electron lasers. However, while the accelerator size is tremendously reduced, upstream and downstream of it the beams are still handled with conventional magnetic optics with sizable footprints and rather long focal lengths. Here we show the operation of a compact device that integrates two active-plasma lenses with short focal lengths to assist the plasma accelerator stage. We demonstrate the focusing and energy gain of a witness bunch whose phase space is completely characterized in terms of energy and emittance. These results represent an important step toward the accelerator miniaturization and the development of next-generation table-top machines.Plasma wakefield acceleration represented a breakthrough in the field of particle accelerators by pushing beams to gigaelectronvolt energies within centimeter distances. The large electric fields excited by a driver pulse in the plasma can efficiently accelerate a trailing witness bunch paving the way toward the realization of laboratory-scale applications like free-electron lasers. However, while the accelerator size is tremendously reduced, upstream and downstream of it the beams are still handled with conventional magnetic optics with sizable footprints and rather long focal lengths. Here we show the operation of a compact device that integrates two active-plasma lenses with short focal lengths to assist the plasma accelerator stage. We demonstrate the focusing and energy gain of a witness bunch whose phase space is completely characterized in terms of energy and emittance. These results represent an important step toward the accelerator miniaturization and the development of next-generation table-top machines.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Abstract
The realization of a plasma based user facility on the model of EuPRAXIA@SPARC_LAB requires to design a working point for the operation that allows to get an high accelerating gradient ...preserving a low emittance and low energy spread of the accelerated beam. Such beam is supposed to pilot a soft x-ray free electron laser with a wavelength of 2-4 nm. In this work several simulation scans are presented, varying at the same time the plasma density and driver-witness separation in order to show that, in a realistic working point for EuPRAXIA@SPARC_LAB, it is possible to find an ideal compromise for a witness with a peak current ¿1kA that allows to preserve the energy spread of the core (80% of the charge) below 0.1%, while maintaining an accelerating gradient inside the plasma module around of 1 GV/m. The study is completed with a parametric analysis with the aim of establishing the stability requirements of the RF working point and the plasma channel in order to preserve the energy jitter at the same level of the energy spread.
Abstract
At EuPRAXIA@SPARC_LAB an X-ray FEL user facility is driven by a plasma accelerator in the particle-driven configuration where an ultra-relativistic beam, the driver, through a plasma ...generates a wake of charge density useful for accelerating a witness beam. The electron bunches are generated through the so-called comb technique in an RF injector that consists of a 1.6-cell S-band gun followed by four S-band TW accelerating structures. The main working point foresees a 30pC witness and a 200pC driver longitudinally compressed in the first accelerating structure operated in the velocity-bunching regime, which allows to accelerate and manipulate the beam to reach proper transverse and longitudinal parameters. The optimization of the witness emittance is performed with additional magnetic field around the gun and the velocity bunching S-band structures and by shaping the laser pulse at the cathode. The paper reports on beam dynamics studies performed also with the insertion of an X-band RF cavity after the gun that is proposed to shape the beam current distribution and stabilize it with respect to RF jitters.
