NLCTA injector experimental results

Abstract

The purpose of the Next Linear Collider Test Accelerator (NLCTA) at SLAC is to integrate the new technologies of X-band accelerator structures and RF systems for the Next Linear Collider (NLC), demonstrate multibunch beam-loading energy compensation and suppression of higher-order deflecting modes, measure the transverse components of the accelerating field, and measure the dark current generated by RF field emission in the accelerator [1]. For beam loading R&D, an average current of about 1 A in a 120 ns long bunch train is required. The initial commissioning of the NLCTA injector, as well as the rest of the accelerator have been progressing very well. The initial beam parameters are very close to the requirement and we expect that injector will meet the specified requirements by the end of this summer.

Beam loading compensation in the NLCTA

“…In the injector of the NLCTA, an electron beam from a thermionic gun is bunched at X-band using two prebunchers followed by a capture section in the upstream end of the first accelerator structure [3]. This structure is a half-length version of the 1.8 m long detuned structure that was developed for the NLC.…”

Beam current monitors in the NLCTA

“…A single pulse of -126 ns duration contains a train of over 1400 bunches. This bunch train must be brought intact through the injector [2], a phase -space tailoring-chicane, and the accelerator proper, into a spectrometer and beam dump. A beam .…”

“…A single pulse of ~126 ns duration contains a train of over 1400 bunches. This bunch train must be brought intact through the injector [2], a phase space tailoring chicane, and the accelerator proper, into a spectrometer and beam dump. A beam loading compensation scheme [3] is used to achieve uniform acceleration in the structures, minimizing energy variation along the pulse as it travels through the steering and focusing lattice.…”

Beam profile monitors in the NLCTA

“…Along with four wire scanners, these profile monitors allow us to view the transverse charge distribution of the electron beam at various positions along the beam line. They are of great utility for monitoring beam shape, verifying transmission, and, in the high dispersion region of the chicane and spectrometer, measuring energy spread in the long bunch train [2], [3]. In addition, they are employed in data acquisition for beam emittance and TWISS parameter measurement.…”