As a result of the synchrotron radiation from a positivelycharged beam, an electron cloud is expected to develop in the vacuum chamber from the combined effects of the photoelectric and secondary emission processes [1–3]. We provide here a first estimate of the electron-cloud effect on individual particles of the beam. We focus on the spacecharge tune spread, the distortion of the beta function...

In the LHC beam pipe, photoemission and secondary emission give rise to a quasi-stationary electron cloud, which is established after a few bunch passages. The response of this electron cloud to a transversely displaced bunch resembles a short-range wake eld and can cause a fast instability. In addition, beaminduced multipacting of the electrons may lead to an enhanced gas desorption and an ass...

Electron-cloud instabilities are expected to be important in most high-lu-minosity double-ring colliders. In this report, I describe a few parameter regimes and some critical parameter dependences of this type of instability, and illustrate these with simulation results for the PEP-II and KEK B factories , the LHC, the VLHC, and DAPHNE. In addition, I study the possibility and the potential imp...

Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders such as ILC and CLIC [1, 2]. In the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed vacuum chambers with rectangular grooves in a straight magnet...

The central role that non‐covalent interactions play in many fields of science and technology has been widely recognized for many years. Between this kind of interactions, those that involve π‐systems deserve a particular interest because their great importance in biological environments. The participation of tyrosine, phenylalanine, tryptophan and histidine residues in the ...

By means of ab-initio calculations on the basis of the FPLAPW method, we compared the energy loss near edge structure (ELNES) of carbon K edges in crystalline phenanthrene and its isomer, anthracene. In these two organic compounds, different non-equivalent carbon atoms can result in distinct K edge spectra due to the different carbon-carbon bond lengths, as a characteristic behavior of the mole...

In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The...