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A laser plasma accelerator-based collider will necessitate chaining of something of the order of hundreds of individual acceleration stages. Matching the electron beam at the entrance of each stage in order to obtain emittance conservation within and during transition between stages is crucial for beam quality preservation along the entire acceleration chain. Previous studies have addressed the matching conditions for two consecutive stages. In this simulation study, we focus on the matching of a short electron beam in a string of stages, using short down-ramps of the order of the electron beam betatron period, demonstrating emittance conservation for up to six consecutive stages. [ABSTRACT FROM AUTHOR]

Laser-plasma collider designs point to staging of multiple accelerator stages at the 10 GeV level, which are to be developed on the upcoming BELLA laser, while Thomson Gamma source designs use GeV stages, both requiring efficiency and low emittance. Design and scaling of stages operating in the quasi-linear regime to address these needs are presented using simulations in the VORPAL framework. In addition to allowing symmetric acceleration of electrons and positrons, which is important for colliders, this regime has the property that the plasma wakefield is proportional to the transverse gradient of the laser intensity profile. We demonstrate use of higher order laser modes to tailor the laser pulse and hence the transverse focusing forces in the plasma. In particular, we show that by using higher order laser modes, we can reduce the focusing fields and hence increase the matched electron beam radius, which is important to increased charge and efficiency, while keeping the low bunch emittance required for applications. [ABSTRACT FROM AUTHOR]

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 particle-in-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. [ABSTRACT FROM AUTHOR]

Electron injection and trapping in a laser wakefield accelerator by high-order field ionization is studied theoretically and by particle-in-cell simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, such as concentration and length, on the final electron injection number and beam quality are studied. Laser polarization and shape effects on injection number and final electron emittance are also shown. [ABSTRACT FROM AUTHOR]

Next generation accelerators will require a high current, low emittance beam with a low energy spread. Such accelerators will employ advanced beam conditioning systems such as emittance exchangers to manipulate high brightness beams. One of the goals of the Fermilab A0 photoinjector is to investigate the transverse to longitudinal emittance exchange principle. Coherent synchrotron radiation could limit high current operation of the emittance exchanger. In this paper, we report on the preliminary experimental and simulation study of the coherent synchroton radiation (CSR) in the emittance exchange line at the A0 photoinjector. [ABSTRACT FROM AUTHOR]

Phase space manipulation techniques with two degrees of freedom could be essential to the enhancement of the performance of next generation accelerators such as high energy colliders and accelerator-based light sources. At the Fermilab A0 Photoinjector, a proof-of-principle experiment to demonstrate the exchange of the transverse and longitudinal emittance is ongoing. The emittance exchange (EEX) beamline consists of a 3.9 GHz normal conducting deflecting mode cavity positioned between two doglegs as proposed by Kim and Sessler. The experiment is performed using electron bunches with charge of 250 pC and energy of 14.3 MeV. The incoming electron beam has transverse emittance of 2-4 mm mrad and longitudinal emittance of 10-14 mm mrad. After the EEX the measured horizonal emittance is blown up to 13-15 mm mrad while the measured vertical emittance (Non EEX plane) stays the same. At the same time the longitudinal emittance is reduced to 7-9 mm mrad as measued by the current longitudinal diagnostic tools. A linear optics model is established using the beam matrix calculated and measured. A first order simulation based on this model is performed to compare to our experiment results for both EEX measurement and the phase space manipulation experiment. [ABSTRACT FROM AUTHOR]

The University of Maryland electron ring (UMER) is a low-energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space-charge physics issues, both in transverse and longitudinal beam dynamics, which are currently being addressed with UMER: emittance growth and halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, bunch capture and shaping, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space-charge dominated beams. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Particle diffusion and emittance growth induced by numerical discrete-particle effects are analyzed in two-dimensional self-consistent numerical simulations of high-intensity beam dynamics. In particular, an analytical model is presented which describes the slow-time-scale variation of edge emittance for a perfectly matched beam in a periodic (quadrupole or solenoidal) magnetic focusing field. A scaling law for edge emittance growth is obtained. The scaling law is tested in both self-consistent Green-function-based simulations and particle-in-cell (PIC) simulations, and good agreement between theory and simulations is obtained. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A halo generation mechanism in the non-periodic lattices such as the SNS linac MEBT (Medium-Energy Beam-Transport between RFQ and DTL) is reported. We find that the nonlinear space charge force resulting from large transverse beam eccentricity ∼2:1 in the ∼1.6-m-long MEBT chopper section is responsible for halo formation. As a result, the beam distribution, based on the Front End (FE) emittance measurements and multiparticle simulation studies, develops halo that leads to beam loss and radio activation of the SNS linac. Designing lattices with transverse beam eccentricity close to 1:1 suppresses this kind of halo generation. Modifying the MEBT optics and introducing adjustable collimators in the MEBT significantly reduced beam losses in the CCL, which is a preferred scheme for mitigating halo. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

The influence of space charge on emittance growth is studied in simulations of a coasting beam exposed to a strong octupolar perturbation in an otherwise linear lattice, and under stationary parameters. We explore the importance of self-consistency by comparing results with a non-self-consistent model, where the space charge electric field is kept “frozen-in” to its initial values. For Gaussian distribution functions we find that the “frozen-in” model results in a good approximation of the self-consistent model, hence coherent response is practically absent and the emittance growth is self-limiting due to space charge de-tuning. For KV or waterbag distributions, instead, strong coherent response is found, which we explain in terms of absence of Landau damping. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Beam-beam effects in HERA were studied with a self-consistent beam-beam simulation by using the particle-in-cell method. A remarkable agreement between the experimental measurement and the simulation result was observed on the emittance growth, luminosity reduction, and coherent beam-beam tune shifts. The simulation study also showed that the chaotic coherent beam-beam instability could occur in HERA and this collective beam-beam instability could be avoided with a slightly different tune. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Measurements of emittance exchange due to the Montague resonance in the CERN Proton Synchrotron in 2003 have provided detailed data, which are suitable for benchmarking of different simulation codes for high-intensity accelerators. We present here some characteristic features of the Montague resonance by using first simulations obtained with MICROMAP and IMPACT under simplifying conditions. The challenges for the planned code benchmarking are discussed. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]