Recent Beam-Beam Effects at VEPP-2000 and VEPP-4M

Budker INP hosts two e+e- colliders, VEPP-4M operating in the beam energy range of 1-5.5 GeV and the low-energy machine VEPP-2000, collecting data at 160-1000 MeV per beam. The latter uses a novel concept of round colliding beams. The paper presents an overview of observed beam-beam effects and obtained luminosities.Comment: Presented at the ICFA Mini-Workshop on Beam-Beam in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 March 201

Erhic – electron-proton collider with polarized beams

The layout and main parameters of the e-ring for eRHIC project are presented. The optics properties to fulfill the so-called spin-transparency condition to obtain sufficient polarization degree at IP are given. The possibility of using super-bends for the polarization time in a wide energy range be decreased is also discussed.Представлені основні параметри і розташування e-кільця в проекті eRHIC. Дані оптичні властивості для виконання так званої умови спінової прозорості для одержання достатнього ступеня поляризації в IP. Також обговорюється можливість використання надвигинів для зменшення часу поляризації в широкому енергетичному діапазоні.Представлены основные параметры и расположение e-кольца в проекте eRHIC. Даны оптические свойства для выполнения так называемого условия спиновой прозрачности для получения достаточной степени поляризации в IP. Также обсуждается возможность использования сверхизгибов для уменьшения времени поляризации в широком энергетическом диапазоне

Beam-Breakup Instability Theory for Energy Recovery Linacs

Here we will derive the general theory of the beam-breakup instability in recirculating linear accelerators, in which the bunches do not have to be at the same RF phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where bunches are recirculated at a decelerating phase of the RF wave and for other recirculator arrangements where different RF phases are of an advantage. Furthermore it can be used for the analysis of phase errors of recirculated bunches. It is shown how the threshold current for a given linac can be computed and a remarkable agreement with tracking data is demonstrated. The general formulas are then analyzed for several analytically solvable cases, which show: (a) Why different higher order modes (HOM) in one cavity do not couple so that the most dangerous modes can be considered individually. (b) How different HOM frequencies have to be in order to consider them separately. (c) That no optics can cause the HOMs of two cavities to cancel. (d) How an optics can avoid the addition of the instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator interferes with itself. Furthermore, a simple method to compute the orbit deviations produced by cavity misalignments has also been introduced. It is shown that the BBU instability always occurs before the orbit excursion becomes very large.Comment: 12 pages, 6 figure

Study of the process e+e−→ppˉe^+e^-\to p\bar{p} in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector

Using a data sample of 6.8 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider we select about 2700 events of the $e^+e^- \to p\bar{p}$ process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio $|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30$