Characterization of the beam loading effects in a laser plasma accelerator (original) (raw)
Related papers
Controlled electron injection in a laser-plasma accelerator
Plasma Physics and Controlled Fusion, 2007
A few years ago, several experiments showed that laser-plasma accelerators can produce high-quality electron beams, with quasi-monoenergetic energy distributions at the 100 MeV level. These experiments were performed by focusing a single ultra-short and ultraintense laser pulse into an underdense plasma. Here, we report on recent experimental results of electron acceleration using two counter-propagating ultra-short and ultraintense laser pulses. We demonstrate that the use of a second laser pulse provides enhanced control over the injection and subsequent acceleration of electrons into plasma wakefields. The collision of the two laser pulses provides a pre-acceleration stage which provokes the injection of electrons into the wakefield. The experimental results show that the electron beams obtained in this manner are collimated (5 mrad divergence), monoenergetic (with relative energy spread <10%), tuneable (between 50 and 250 MeV) and, most importantly, stable.
Numerical Analysis of Space Charge Effects in Electron Bunches at Laser-Driven Plasma Accelerators
Central European Journal of Physics, 2010
Laser-driven Plasma Accelerators (LPA) have successfully generated high energy, high charge electron bunches which can reach many kA peak current, over short distances. Space charge issues, even in transport lines as simple as a drift section, have to be carefully taken into account since they can degrade the beam quality, preventing any further application of such electron beams. We analyse the space charge effects within an electron bunch with numerical simulations in order to assess their effect on the beam. We use LPA beam parameters published in previous experimental studies. These studies can give an indication of the working point where space charge can dominate the beam dynamics and has to be taken into account in the application of such beams.
Controlled injection and acceleration of electrons in plasma wakefields by colliding laser pulses
Nature, 2006
In laser-plasma-based accelerators 1 , an intense laser pulse drives a large electric field (the wakefield) which accelerates particles to high energies in distances much shorter than in conventional accelerators. These high acceleration gradients, of a few hundreds of gigavolts per metre, hold the promise of compact high-energy particle accelerators. Recently, several experiments have shown that laser-plasma accelerators can produce high-quality electron beams, with quasi-monoenergetic energy distributions at the 100 MeV level 2-4 . However, these beams do not have the stability and reproducibility that are required for applications. This is because the mechanism responsible for injecting electrons into the wakefield is based on highly nonlinear phenomena 5 , and is therefore hard to control. Here we demonstrate that the injection and subsequent acceleration of electrons can be controlled by using a second laser pulse 6 . The collision of the two laser pulses provides a pre-acceleration stage which provokes the injection of electrons into the wakefield. The experimental results show that the electron beams obtained in this manner are collimated (5 mrad divergence), monoenergetic (with energy spread ,10 per cent), tuneable (between 15 and 250 MeV) and, most importantly, stable. In addition, the experimental observations are compatible with electron bunch durations shorter than 10 fs. We anticipate that this stable and compact electron source will have a strong impact on applications requiring short bunches, such as the femtolysis of water 7 , or high stability, such as radiotherapy with high-energy electrons 8,9 or radiography 10 for materials science.
Nature Physics, 2021
Plasma-based accelerators (PBAs) driven by either intense lasers (laser wakefield accelerators, LWFAs) 1 or particle beams (plasma wakefield accelerators, PWFAs) 2 , can accelerate charged particles at extremely high gradients compared to conventional radio-frequency (RF) accelerators. In the past two decades, great strides have been made in this field 3-10 , making PBA a candidate for next-generation light sources and colliders 11. However, these challenging applications necessarily require beams with good stability, high quality, controllable polarization and excellent reproducibility 12,13. To date, such beams are generated only by conventional RF accelerators. Therefore, it is important to demonstrate the injection and acceleration of beams first produced
Design and Interpretation of Colliding Pulse Injected Laser-Plasma Acceleration Experiments
The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtaining GeV scale electron bunches with reduced emittance and energy spread. Colliding Pulse Injection (CPI) experiments are being performed by groups around the world. We present recent particlein-cell simulations, using the parallel VORPAL framework, of CPI for physical parameters relevant to ongoing experiments of the LOASIS program at LBNL. We perform parameter scans in order to optimize the quality of the bunch, and compare the results with experimental data. Effect of non-ideal gaussian pulses and laser self-focusing in the plasma channel on the trapped bunch are evaluated. For optimized parameters accessible in the experiment, a 20 pC electron beam can be accelerated to 300 MeV with percent level energy spread.
Comptes Rendus Physique, 2009
A summary of progress at Lawrence Berkeley National Laboratory is given on: (1) experiments on down-ramp injection; (2) experiments on acceleration in capillary discharge plasma channels; and (3) simulations of a staged laser wakefield accelerator (LWFA). Control of trapping in a LWFA using plasma density down-ramps produced electron bunches with absolute longitudinal and transverse momentum spreads more than ten times lower than in previous experiments (0.17 and 0.02 MeV/c FWHM, respectively) and with central momenta of 0.76 ± 0.02 MeV/c, stable over a week of operation. Experiments were also carried out using a 40 TW laser interacting with a hydrogen-filled capillary discharge waveguide. For a 15 mm long, 200 urn diameter capillary, quasi-monoenergetic bunches up to 300 MeV were observed. By detuning discharge delay from optimum guiding performance, self-trapping was found to be stabilized. For a 33 mm long, 300 pm capillary, a parameter regime with high energy bunches, up to 1 GeV, was found. In this regime, peak electron energy was correlated with the amount of trapped charge. Simulations show that bunches produced on a down-ramn and injected into a channel-guided LWFA can produce stable beams with 0.2 MeV/c-class momentum spread at high energies.
Experimental and Numerical Study of Laser-Plasma Electron Accelerators
The work presented in this thesis describes the experimental and numerical study of laser-plasma electron accelerators done over the last five years at the Grupo de Lasers e Plasma (GoLP) of the Instituto Superior Técnico (IST). This work is the result of a collaboration between this group, the Rutherford Appleton Laboratory (RAL, UK) and the Plasma Simulation Group from the University of California - Los Angeles, (California, USA). In the scope of this project we have built a broad range electron spectrometer for the study laser-plasma electron accelerators and we present here the development and implementation of this system. This spectrometer allows for the characterization of a 3.2:1 energy range and a maximum energy of 230 MeV. We also present the work done on the numerical simulation of laser-plasma electron accelerators, namely the laser wakefield accelerator (LWFA), the channeled laser wakefield accelerator and the channeled self-modulated laser wakefield accelerator. During this work a computer cluster for numerical computational was also developed which is, to our knowledge, the most powerful machine for numerical computation in Portugal.
Laser plasma acceleration experiment at the naval research laboratory
2007 IEEE Particle Accelerator Conference (PAC), 2007
A relativistically intense laser pulse is focused into a gas jet and quasi-monoenergetic electrons emitted at a 37 degree angle with respect to the laser axis are observed. The average energy of the electrons was between 1 and 2 MeV and the total accelerated charge was about 1 nC emitted into a 10 degree cone angle. The electron characteristics were sensitive to plasma density. The results are compared with three dimensional particle-incell simulations. This electron acceleration mechanism might be useful as a source of injection electrons in a laser wakefield accelerator.
Electron beam characteristics of a laser-driven plasma wakefield accelerator
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999
The properties of an electron beam trapped and accelerated in a laser wake"eld have been investigated. Plastic scintillating "bers were employed together with position sensitive photomultiplier tubes (PMT) and a series of dipole electro-magnets to study the beam. The measured momentum spectrum peaks around 7 MeV/c with an exponential fall-o! at high momenta up to (70.3$ 19.9) MeV/c. The number of electrons detected per bunch is determined to be (2.6$0.3);10.
arXiv: Plasma Physics, 2019
An experimental study on 55fs laser driven plasma accelerator using mixed gas-jet target with varying plasma density is used to identify the role of different acceleration mechanisms, viz. Direct Laser Acceleration (DLA) and wakefield. At lower electron density electron acceleration could be attributed mainly to DLA with ionization induced injection. With increase in density, increasing role of wakefield was observed leading to hybrid regime, and at densities higher than self-injection threshold, observed experimentally for He target contribution of DLA and wakefield was found to be comparable. Dominant DLA mechanism was also observed in case of pure nitrogen target. 2D PIC simulations performed using the EPOCH code corroborate the above scenario, and also showed generation of surface waves, considered as a potential mechanism of pre-acceleration to DLA.