1.1.1 Introduction For linear accelerators, a single bunch instability of a positron bunch due to electrons created by ionization of the residual gas was discussed in Ref. [1], where a coherent oscillation of both electrons and positrons grows from any small initial perturbation of the bunch distribution, e.g. from the statistical fluctuations due to the finite number of beam particles. This in...

A new method of monitoring the luminosity has been developed at CESR. The method involves shaking one bunch at a speciic frequency and observing the resulting oscillations of the corresponding opposing bunch. In initial tests, measurements with 1 accuracy have been obtained in 1 second. Measurements of diierent bunches in a train shows bunch to bunch diierences with the optimum luminosity condi...

The SuperB project has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e+/eSuper Flavor Factory to achieve a peak luminosity > 10**36 cm-2 s-1. The SuperB design is based on collisions with extremely low vertical emittance beams and high beam currents. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signa...

Weak vertical coupled bunch instability with oscillation amplitude at μm level has been observed in SPEAR3. The instability becomes stronger when there is a vacuum pressure rise by partially turning off vacuum pumps and it becomes weaker when the vertical beam emittance is increased by turning off the skew quadrupole magnets. These confirmed that the instability was driven by ions in the vacuum...

A new regime of laser wakefield acceleration of an injected electron bunch is described. In this regime, the bunch charge is so high that the bunch wakefields play an important role in the bunch dynamics. In particular, the transverse bunch wakefield induces a strong self-focusing that suppresses the transverse emittance growth arising from misalignment errors. The decelerating longitudinal bun...

A new bunch-by-bunch beam position measurement (BPM) prototype has been designed and built to monitor the beam instability and analyse the beam trip in the BEPCII (Beijing Electron-Positron ColliderII) machine. The broadband electronics system which employs fast analogy digital converter (ADC) and field programmable gate array (FPGA) can obtain the beam information bunch-by-bunch with high bunc...

The DSP-based bunch-by-bunch feedback system installed in the PEPII high-energy ring (HER) has been used to damp instabilities induced by unwanted higher-order modes (HOMs) at beam currents up to 605 mA during commissioning. Beam pseudospectra calculated from feedback system data indicate the presence of coupled-bunch modes that coincide with a previously observed cavity mode (0-M-2). Bunch cur...

A study of the electron beam dynamics in the linac is conducted for the FERMI free electron laser (FEL) founded for construction at the Sincrotrone Trieste [1]. LAYOUT AND DESIGN PARAMETERS The FERMI accelerator layout is schematically shown in Figure 1. It consists of an injector, four linacs, two bunch compressors, a laser heater, and a spreader used to direct the electron beam into one of tw...

every year large amounts of grapes are stores in normal and cold rooms to offer off-season of grapes to the market which based on several reasons their quality and weight greatly decreases. therefore, in order to decrease the post harvest losses of grapes and selection of suitable cultivars for long time storage, this study was conducted in two experiments, one in a factorial experiment based o...

Coherent bremsstrahlung (CBS) is a specified type of radiation at colliders with short bunches. In the present paper we calculate the main characteristics of CBS for the BEPC collider. At this collider dN γ ∼ 3 · 10 8 dE γ /E γ photons of CBS will be emitted for a single collision of the beams in the energy range E γ < ∼ 240 eV. It seems that CBS can be a potential tool for optimizing collision...