No Arabic abstract
In this note, we briefly review the current lattice of the NLC extraction line which was designed for the nominal NLC beam parameters. Then we describe the beam parameters for the high luminosity option with larger beam disruption parameter and discuss its effect on beam loss in the extraction line. Finally, we present a summary of the optics study aimed at minimizing the beam loss with high disruption beams.
The NLC extraction line provides a secondary focal point with a low beta function and 2 cm dispersion which can be used for measurement of the beam energy spectrum. In this study, tracking simulations were performed to transport the 0.5 TeV electron beam from the Interaction Point (IP) to the secondary focus (SF), ``measure the resultant transverse beam profile and reconstruct the disrupted IP energy spread. In the simulation, the obtained energy spectrum reproduced the initial IP spread reasonably well, especially with the vertical dispersion at SF which provides larger ratio of dispersion to the betatron beam size.
Properties of the disrupted NLC beam at the Interaction Point (IP) and particle loss in the extraction line are analyzed as a function of beam-to-beam position and angular offset at IP. The simulations show that disruption and beam loss maximize when the vertical beam separation at IP is about 20 times the rms vertical beam size. The horizontal offset does not increase the disruption and the beam loss. The angular offsets cause particle loss in the extraction line mainly because of the beam orbit oscillations.
The goal of this study is to evaluate the impact of the latest ILC beam parameters at the Interaction Point (IP), as specified in the 2013 ILC Technical Design Report (TDR), on beam losses in the extraction line. The previous beam loss evaluation was based on the parameters specified in the 2007 ILC Reference Design Report (RDR). The results of this study are compared to the results obtained in the past for the ``nominal and the ``low power (low-P) parameter options of the RDR. The initial disrupted beam distribution at IP was generated using Guinea-Pig code, and the beam losses were obtained in tracking simulations using DIMAD. The study is performed for 500 GeV center-of-mass beam energy and the extraction line optics corresponding to the latest final focus optics with L* = 4.5 m, with and without detector solenoid.
The two main functions of the NLC extraction line include: 1) transmission of the outgoing disrupted beam and secondary particles to the dump with minimal losses; and 2) beam diagnostics and control. In this report, we describe the extraction line optics, present the results of tracking studies, and discuss the extraction line instrumentation.
A new laser-wire is being installed in the extraction line of the ATF at KEK. This device aims at demonstrating that laser-wires can be used to measure micrometre scale beam size.