Proposing a laser based beam size monitor for the future linear collider

Abstract

Compton scattering techniques for the measurement of the transverse beam size of particle beams at future linear colliders (FLC) are proposed. At several locations of the beam delivery system (BDS) of the FLC, beam spot sizes ranging from several hundreds to a few micrometers have to be measured. This is necessary to verify beam optics, to obtain the transverse beam emittance, and to achieve the highest possible luminosity. The large demagnification of the beam in the BDS and the high beam power puts extreme conditions on any measuring device. With conventional techniques at their operational limit in FLC scenarios, new methods for the detection of the transverse beam size have to be developed. For this laser based techniques are proposed capable of measuring high power beams with sizes in the micrometer range. In this paper general aspects and critical issues of a generic device are outlined and specific solutions proposed. Plans to install a laser wire experiment at an accelerator test facility are presented.

Methods of optical diagnostics of electron-positron beams and interaction between plasma and high-current electron beam

“…The main idea of the sensor is the Compton scat tering of the highly focused laser ray by the particle beam [35][36][37]. This kind of diagnostics is formally of the contact type; however, the decrease in the elec tron beam lifetime as a result of interaction with the focused laser ray is negligibly small.…”

“…The pulse power of the laser ray must be equal to several megawatts so that we might obtain several thousands of Compton gamma quanta for a single scanning [36].…”

Future Developments in Electron Linac Diagnostics

“…It is important to understand system requirements, especially for 2), because tuning procedures will depend critically on this and it may be very advantageous to develop devices with good resolution. Several such systems have been built and tested and it seems that laserwires will become an effective tool [15]. The challenge of stabilizing the laser, perhaps at the expense of optical beam power, has been met by the ATF group who built the most heavily used laserwire system to date.…”

Laser-Based Profile Monitor for Electron Beams

“…Whereas the fundamental physics of a laser-based monitor is straightforward, the implementation can be challenging and requires a detailed understanding of the technology. In this paper we examine the design and operation of five laser-based monitors, at 1) the SLC/SLD IP [7], 2) the KEK ATF [8,9], 3) DESY PETRA [10], the CERN CLIC Test Facility [11] and 4) the SNS (H-beam) [12]. In addition, since it was a pioneering device, we also include a reference to the FFTB nanometer interferometer monitor [13].…”