Beam diagnostics and applications

Abstract

Abstract. Particle beams in accelerators are detected through the electromagnetic elds they create. Position and intensity monitors are based on the near eld which stays attached to the charges. A large variety of measurements can be carried out with these devices. The closed orbit is obtained by reading out the position averaged over many turns. Change in the orbit resulting from a controlled de ection reveals the lattice functions. With a fast position monitor the betatron frequency can be measured. Its dependence on energy deviation, current, and quadrupole strength gives information on chromaticity, impedance, and local beta function. Turn-by-turn reading in all monitors allows one to check the optics and to measure the beta function and phase advance around the machine. Diagnostics based on the far eld is done with synchrotron radiation. It is used to form an image of the beam cross section and to get its dimensions. Due to the small natural opening angle of the radiation, di raction e ects are important and limit the resolution. The angular spread of the particles in the beam can be measured by a direct observation of the emitted radiation. ELECTROMAGNETIC FIELDS USED FOR BEAM DIAGNOSTICSThe beam diagnostics considered here are based on the electromagnetic elds created by the charged particles. We distinguish between the`near eld' and thè far' or`radiation eld'. The near eld is the Lorentz-transformed Coulomb eld which now also contains a magnetic eld. The electric eld of a point charge on axis of a circular conducting chamber of radius a induces on the wall a charge distribution q w s having a rms width of = a= p 2 . Since this wall current pulse is very short for a relativistic particle, a bunch with longitudinal current distribution I t induces on the wall a current I W t having practically the same form see Figure 1 . However, the wall current is of the opposite sign and does not contain the average beam current. The latter induces just a static charge which does not represent a current

Optical System Design for High-Energy Particle Beam Diagnostics

“…(1) Powdered phosphor [1,2] A phosphor screen is formed by adhering phosphor powder to a substrate. The scintillation light reflects multiple times before escaping the powder particle, thus lighting up the entire grain.…”

“…With the development of quantitative imaging tools, especially the ever better availability of CCD cameras and digitizers, optical imaging has become a vital part of particle beam diagnostics today. This tutorial is designed to introduce the field to starting young engineers and builds on several tutorials presented at past Beam Instrumentation Workshops [1][2][3]. The readers will also find it beneficial to be informed of progress in other fields that use quantitative imaging tools extensively, such as video microscopy, astronomy, and machine vision.…”

Diffraction and depths-of-field effects in electron beam imaging at SURF III

“…A good example on how to measure transverse beam size was given by Andersson and Tagger [2], who in a very detailed analysis explained the mechanism of using visible light to determine the beam size at MAX in Lund. Several other authors gave more general descriptions of diffraction and depth-of-field contributions in measuring electron beam sizes [3][4][5][6]. It has further been shown that the two effects can be treated consistently, as a single phenomenon, within the frame of classical electrodynamics applied to the emission and focussing of SR [7,8].…”

Signal processing for beam position monitors

“…The BPM applications are not only limited to orbit and trajectory measurements, they can also perform static and dynamic beam parameter measurements by exploiting the large amount of data collected and stored in their memories 1 . By a "turn-by-turn" acquisition on a single monitor, it is possible to measure betatron oscillations, beam response and transfer function.…”