BEAM POSITION MONITOR SYSTEM FOR 2 MEV ELECTRON COOLER FOR COSY

Abstract The 2 MEV electron cooler for COSY storage ring FZJ is assembling in BINP. Beam position monitor (BPM) system for orbit measurements has been developed and fabricated at BINP. The system contains 2 BPMs inside the cooling section and 10 BPMs in transport channels. Continuous electron beam is modulated with a 3 MHz signal for capability to get signals from pickup electrodes. The beam current modulation can be varied in the range of 0.3-1.5 mA. The BPMs inside the cooling section can measure both electron and proton beams. It is achieved by means of switching the reference signals inside the BPM electronics. The BPM electronics provides highly precise beam position measurements. Position measurement error doesn't exceed 1 micron. Design features of the BPM system, its parameters and testing results are presented in this paper

Precise measurement of RudsR_{\text{uds}} and RR between 1.84 and 3.72 GeV at the KEDR detector

The present work continues a series of the KEDR measurements of the $R$ value that started in 2010 at the VEPP-4M $e^+e^-$ collider. By combining new data with our previous results in this energy range we measured the values of $R_{\text{uds}}$ and $R$ at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than $2.6\%$ at most of energy points with a systematic uncertainty of about $1.9\%$. Together with the previous precise $R$ measurement at KEDR in the energy range 1.84-3.05 GeV, it constitutes the most detailed high-precision $R$ measurement near the charmonium production threshold.Comment: arXiv admin note: text overlap with arXiv:1610.02827 and substantial text overlap with arXiv:1510.0266

Measurement of the branching fraction of J/ψ→ρπJ/\psi\rightarrow\rho\pi at KEDR

We present the study of the decay $J/\psi \rightarrow \rho \pi$. The results are based on of 5.2 million $J/\psi$ events collected by the KEDR detector at VEPP-4M collider. The branching fraction is measured to be $\mathcal{B}(J/\psi\rightarrow\rho\pi) = \big(2.072\pm 0.017 \pm 0.056 \big)\cdot 10^{-2}$ where the first uncertainty is statistical, the second one is systematic. This is the most precise single measurement of this quantity at the moment

Beam Instrumentation for the Cosy electron cBeooler

The report deals with beam instrumentation of the electron cooler for COSY storage ring. The electron cooler is an electrostatic accelerator designed for beam energy up to 2 MeV and electron current up to 3 A with recuperation. The electron beam is immersed in longitudinal magnetic field so the electron motion is strongly magnetized. The control electrode in the electron gun is composed of four electrically isolated sectors. Applying AC voltage to one sector allows tracing of motion of that particular part of the beam. The electron beam shape is registered with the combination of 4-sector electron gun and the BPMs. This method allows observing both dipole and quadruple (galloping) modes of electron beam oscillation. Compass probe for measuring and tuning the direction of magnetic field in the cooling section is described. A profile monitor based on a few small Faraday cups for measuring distribution of the electron beam is presented