119104094
Modulator simulations for coherent electron cooling using a variable density electron beam
Increasing the luminosity of relativistic hadron beams is critical for the advancement of nuclear physics. Coherent electron cooling (CEC) promises to cool such beams significantly faster than alternative methods. We present simulations of 40 GeV/nucleon Au+79 ions through the first (modulator) section of a coherent electron cooler. In the modulator, the electron beam copropagates with the ion beam, which perturbs the electron beam density and velocity via anisotropic Debye shielding. In contrast to previous simulations, where the electron density was constant in time and space, here the electron beam has a finite transverse extent, and undergoes focusing by quadrupoles as it passes through the modulator. The peak density in the modulator increases by a factor of 3, as specified by the beam Twiss parameters. The inherently 3D particle and field dynamics is modeled with the parallel VSim framework using a $\delta$f PIC algorithm. Physical parameters are taken from the CEC proof-of-principle experiment under development at Brookhaven National Lab.
124006309
Compensating effect of the coherent synchrotron radiation in bunch compressors
Typical bunch compression for a high-gain free-electron laser (FEL) requires a large compression ratio. Frequently, this compression is distributed in multiple stages along the beam transport line. However, for a high-gain FEL driven by an energy recovery linac (ERL), compression must be accomplished in a single strong compressor located at the beam line’s end; otherwise the electron beam would be affected severely by coherent synchrotron radiation (CSR) in the ERL’s arcs. In such a scheme, the CSR originating from the strong compressors could greatly degrade the quality of the electron beam. In this paper, we present our design for a bunch compressor that will limit the effect of CSR on the e-beam’s quality. We discuss our findings from a study of such a compressor, and detail its potential for an FEL driven by a multipass ERL developed for the electron-Relativistic Heavy Ion Collider.
55266179
HIGH-FIDELITY 3D MODULATOR SIMULATIONS OF COHERENT ELECTRON COOLING SYSTEMS
Next generation electron-hadron colliders will require effective cooling of high-energy, high-intensity hadron beams. Coherent electron cooling (CeC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques [1]. The parallel Vorpal framework is used for 3D delta-f PIC simulations of anisotropic Debye shielding in a full longitudinal slice of the co-propagating electron beam, choosing parameters relevant to the proof-of-principle experiment under development at BNL. The transverse density conforms to an exponential Vlasov equilibrium for Gaussian velocities, with no longitudinal density variation. Comparison with 1D1V Vlasov/Poisson simulations shows good agreement in 1D. Parallel 3D simulationsat NERSC show 3Deffects for ions moving longitudinally and transversely. Simulation results are comparedwith theconstant-densitytheoryof Wang and Blaskiewicz [2].
23683095
Study of electron-proton beam-beam interaction in eRHIC
Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of eRHIC design, an electron beam accelerated in a superconducting energy recovery linac collides with a proton beam circulating in the RHIC ring. There are some features of beam-beam effects, which require careful examination in linac-ring configuration. First, the beam- beam interaction can induce specific head-tail type instability of the proton beam referred to as 'kink' instability. Thus, beam stability conditions should be established to avoid proton beam loss. Also, the electron beam transverse disruption by collisions has to be evaluated to ensure beam quality is good enough for the energy recovery pass. In addition, fluctuations of electron beam current and/or electron beam size, as well as transverse offset, can cause proton beam emittance growth. The tolerances for those factors should be determined and possible countermeasures should be developed to mitigate the emittance growth. In this paper, a soft Gaussian strong-strong simulation is used to study all of mentioned beam-beam interaction features and possible techniques to reduce the emittance growth.
117790137
Influence of electron beam parameters on coherent electron cooling
Coherent electron cooling (CeC) promises to revolutionize the cooling of high energy hadron beams. The intricate dynamics of the CeC depends both on the local density and energy distribution of the beam. The variations of the local density (beam current) are inevitable in any realistic beam. Hence, in this paper we propose a novel method of beam conditioning. The conditioning provides compensation of effect from such variation by a correlated energy modulation. We use our analytical FEL model for an electron bunch with Gaussian line charge density and cosine-type energy variation along bunch. We analyze the phase variation between the electron density modulation at the exit of the FEL-amplifier and the ions inducing it in the modulator as a function of the peak current and the electron beam energy. Based on this analysis, electron bunch parameters for optimal CeC cooling are found numerically.
55365774
THE TRANSVERSE LINAC OPTICS DESIGN IN MULTI-PASS ERL
In this paper, we analyzed the linac optics design requirement for a multi-pass energy recovery linac (ERL) for arbitrary number of linacs. A set of general formula of constrains for the 2-D transverse matrix is derived to ensure design optics acceptance matching throughout the entire accelerating and decelerating process. Meanwhile, the rest free parameters can be adjusted for fulfilling other requirements or optimization purpose. As an example, we design the linac optics for the future MeRHIC (Medium Energy eRHIC) project and show the optimization for small {beta} function.
110270067
PRELIMINARY DESIGN OF FAST KICKER SYSTEM FOR BEPC II
With in BEPC II injection system there are two sets injection lines in storage ring each consisting of a pair of kicker magnets and one Lambertson magnet for e + and e injection respectively. The incoming beam is injected horizontally inside the storage ring. The linac provides the short pulsed bunch train of 3 micro bunches. There are six e + and six e -- bunch trains countermove in a same ring. The single bunch train injection is chosen. The duration of bunch train is 16ns. The kick of field is 130 Gauss-meter. The type of lumped ferrite inductance magnet with ceramic vacuum chamber is chosen. Per magnet consists of four modules each of 30 cm long, The field strength of magnet is 108 gauss. Excitation current is 631 A .The pulse field of magnet is a trapezoidal wave with duration less than 110ns, rise / fall time of K1 and fall / rise time of K2 is 33ns / 50ns respectively. The lumped LC network with impedance of 30ohm and voltage of 38kV is chosen as a pulser. The stray inductance of lead is controlled to be small enough by an air-insulated coaxial construction. Field rise time is reduced by the compensating capacitance and the fall time is reduced by second switch and saturable reactor. A ZVS PWM type of high voltage power supply is chosen as the charger for PFN. The details are described in this paper.