[en] The canonical formulation and the cancellation effect for bunch dynamics under collective interaction on a curved orbit were presented in Ref. [*]. Some possible controversial representations of the cancellation effect were later addressed by Geloni et al.** In this study, we discuss all the points raised in Ref. [**] based on our canonical treatment, and show how these points can be perceived from the view point of the cancellation picture

[en] Electron-ion colliders with a center of mass energy between 15 and 100 GeV, a luminosity of at least 10³³ cm^-2S^-1, and a polarization of both beams at or above 80% have been proposed for future studies of hadronic structure. The scheme proposed here would accelerate the electron beam using the CEBAF recirculating linac with energy recovery. If all accelerating structures presently installed in the CEBAF tunnel are replaced by ones with a ∼20 MV/m gradient, then a single recirculation results in an electron beam energy of about 5 GeV. After colliding with protons/light ions circulating in a figure-of-eight storage ring (for flexibility of spin manipulation) at an energy of up to 100 GeV, the electrons are re-injected into the CEBAF accelerator for deceleration and energy recovery. In this report several layout options and their respective feasibilities will be presented and discussed, together with parameters which would provide a luminosity of up to 1 · 10³⁵ cm^-2s^-1. The feasibility of combining such a collider at a center-of-mass energy √s of up to 43 GeV with a fixed target facility at 25 GeV is also explored

[en] Electron-ion colliders with a center of mass energy between 15 and 100 GeV, a luminosity of at least 10³³cm^-1s^-1, and a polarization of both beams at or above 80% have been proposed for future studies of hadronic structure. The scheme proposed here would accelerate the electron beam using the CEBAF recirculating linac with energy recovery. If all accelerating structures presently installed in the CEBAF tunnel are replaced by ones with a ∼20 MV/m gradient, then a single recirculation results in an electron beam energy of about 5 GeV. After colliding with protons/light ions circulating in a figure-of-eight storage ring (for flexibility of spin manipulation) at an energy of up to 100 GeV, the electrons are re-injected into the CEBAF accelerator for deceleration and energy recovery. In this report several lay-out options and their respective feasibilities will be presented and discussed, together with parameters which would provide a luminosity of up to 1 x 10³⁵ cm^-2s^-1. The feasibility of combining such a collider at a center-of-mass energy [sq rt] s of up to 43 GeV with a fixed target facility of 25 GeV is also explored

[en] Energy Recovery Linacs (ERL) have significant potential uses in High Energy Physics and Nuclear Physics. We describe some of the potential applications which are under development by our laboratories in this area and the technology issues that are associated with these applications. The applications that we discuss are electron cooling of high-energy hadron beams and electron-nucleon colliders. The common issues for some of these applications are high currents of polarized electrons, high-charge and high-current electron beams and the associated issues of High-Order Modes. The advantages of ERLs for these applications are numerous and will be outlined in the text. It is worth noting that some of these advantages are the high-brightness of the ERL beams and their relative immunity to beam-beam disturbances

[en] Electron cooling of completely stripped gold ions ¹⁹⁷Au⁷⁹⁺ in RHIC is considered for the store energy, γ=108. The optimal parameters of the required electron storage ring are discussed and proposed. The cooling time is calculated as 15 min, which would allow not only to avoid the beam loss due to the intra-beam scattering, but also reduce the transverse emittance and increase the luminosity several times

[en] The transverse space charge forces in a high current, low energy beam can be reduced by mean of a large increase of the beam's transverse sizes while maintaining the beam area in the 4D phase space. This can be achieved by transforming the beam area in phase space of each of two normal 2D transverse (either plane or circular) modes from a spot shape into a narrow ring of a large amplitude, but homogeneous in phase. Such a transformation results from the beam evolution in the island of a dipole resonance when the amplitude width of the island shrinks adiabatically. After stacking (by using stripping foils or cooling) the beam in such a state and accelerating to energies sufficiently high that the space charge becomes insignificant, the beam then can be returned back to a normal spot shape by applying the reverse transformation. An arrangement that can provide such beam gymnastics along a transport line after a linac and before a booster and/or in a ring with circulating beam will be described and numerical estimates will be presented. Other potential applications of the method will be briefly discussed

[en] A CEBAF accelerator based electron-light ion collider (ELIC) of rest mass energy from 20 to 65 GeV and luminosity from 10³³ to 10³⁵ cm^-2 s^-1 with both beams polarized is envisioned as a future upgrade to CEBAF. A two step upgrade scenario is under study: CEBAF accelerator-ring-ring scheme (CRR) as the first step, and a multi-turn ERL-ring as the second step, to attain a better electron emittance and maximum luminosity. In this paper we report results of our studies of the CRR version of ELIC.

[en] An increase in the luminosity of circular hadron-lepton collider HERA may be achieved via electron cooling of hadrons in the PETRA-preaccelerator. The cooling of high-energy (15-20 GeV) protons requires a high electron beam current (few amperes) with low emittances (<4 π mm mrad normalized) to reach reasonable cooling times of <10 min. For this purpose a linac-based scheme has been considered. Electron bunches from a magnetized thermal cathode are longitudinally compressed, accelerated in a traveling wave structure and, after reducing their energy spread, subsequently debunched to match the bunch length in PETRA. The entire electron accelerator, as well as the cooling section, is immersed in a kG magnetic field; matching is provided for the technically unavoidable gaps in the solenoidal field. This paper presents the status of the development of the magnetized gun, accelerating structure and different variants of the debuncher

[en] It is under discussion to operate HERA with heavy ions instead of protons. Because of the heavily increased intrabeam scattering of heavy ions compared to protons, the achievable luminosity is much smaller than desired by the experiments. A way to increase luminosity could be electron cooling of the heavy ion beam. Because of the high electron energy of 180 MeV necessary for cooling heavy ions in HERA the conventional approach using electrostatic DC sources is not possible. Instead an electron storage ring could be used. For this ring there are special requirements like small damping times, emittances and energy spread. The feasibility of such an electron storage ring has been studied, and the results with a possible solution are presented in this paper. Electron cooling of the HERA proton beam is also discussed briefly

[en] A method of fast non-destructive absolute spin monitoring for a bunched beam in an accelerator ring based on use of the RF techniques is considered. The coherent spin of the beam is driven by RF magnets in the spin echo regime. A passive superconducting resonator is proposed to respond to the flipping spin. A possibility is established to enhance the spin-related excitation of the resonator using the charge-resonator dipole interaction and spin-orbit coupling induced by the quadrupoles. It is shown that the spin impedance can be gauged via measurements of the beam dipole impedance. The noise demands are evaluated. Numerical examples are given