Simulation and experiments for the Q _ext of a cavity beam position monitor

Abstract

The external Q (Qext) of the dipole mode is a key parameter of the Cavity Beam Position Monitor (CBPM). It determines the amplitude and length of the dipole mode signal. In this paper, Qext of a CBPM whose waveguides were open to the air was simulated and measured, and the results agreed with each other. Then four waveguide-to-coaxial cable adpaters were adjusted and assembled to the CBPM, and Qext remained unchanged. This progress provides a reliable method to evaluate Qext in the physics design without simulating the structurally complex adapters.

Design and cold test of a rectangular cavity beam position monitor

“…1). It will no longer be a problem in a rectangular one, for the rectangular CBPM has better X-Y isolation and thus limit theoretical resolution better than a cylindrical one [9]. The best resolution ever obtained is 8.72 nm by the rectangular CBPM designed by KEK, which is very close to the theoretical value [10].…”

On the possible effects of gluon number fluctuations on γγ collisions at high energies

“…Although the results have shown some improvement in the description of the observables, they have not been conclusive with respect to the presence of the fluctuations in the experimental data. They have also been studied in the analysis of the pseudo-rapidity distribution of hadron multiplicities of high energy Au+Au collisions at RHIC and in predictions for these observables in Pb+Pb collisions by using Color Glass Condensate dynamics at LHC/ALICE [23]. It has been found that the charged hadron multiplicities at central rapidity are significantly smaller than saturation based calculations and are compatible to those obtained on a study of multiplicities in the fragmentation region with running coupling corrections [24].…”