Design of the beam delivery system for the international linear collider

Abstract

The beam delivery system for the linear collider focuses beams to nanometer sizes at its interaction point, collimates the beam halo to provide acceptable background in the detector and has a provision for state-of-the art beam instrumentation in order to reach the ILCs physics goals. This paper describes the design details and status of the baseline configuration considered for the reference design and also lists alternatives. SYSTEM DESCRIPTIONThe ILC Beam Delivery System (BDS) is responsible for transporting the e + /e − beams from the exit of the high energy linacs, focusing them to the sizes required to meet the ILC luminosity goals (σ * x = 639 nm, σ * y = 5.7 nm in the nominal parameters), bringing them into collision, and transporting the spent beams to the main beam dumps. In addition, the BDS must measure the linac beam and match it into the final focus (FF); protect the beamline and detector against mis-steered beams from the main linacs; remove any large amplitude particles (beam-halo) from the linac to minimize background in the detectors; measure and monitor the key physics parameters such as energy and polarization before and after the collisions. The BDS must provide sufficient instrumentation, diagnostics and feedback systems to achieve these goals.The main subsystems of the beam delivery starting from the exit of the main linacs are the diagnostics region, fast extraction and tuneup beamline, betatron and energy collimation, final focus, interaction region (IR) and extraction line. The layout of the beam delivery system is shown in Figs. 1 can be upgraded to 1 TeV with additional magnets. There is a single collision point with a 14 mrad crossing angle. The beam delivery systems are in line with the linacs and the linacs are also oriented at a 14 mrad angle. Two detectors in a common IR hall alternately occupy the single collision point, in a so-called "push-pull" configuration. The detectors are pre-assembled on the surface and then lowered into the IR hall in large subsections once the hall is ready for occupancy.The initial part of the BDS is responsible for measuring and correcting the properties of the beam before it enters the collimation and FF. In addition, errant beams must be detected here and safely extracted in order to protect the downstream systems. Starting at the exit of the main linac, the system includes the machine protection system (MPS) collimation, skew correction section, emittance diagnostic section, polarimeter with energy diagnostics, fast extraction/tuning system and beta matching section.At the exit of the main linac is a short 90• FODO lattice, composed of large bore quadrupoles, which contains a set of sacrificial collimators of decreasing aperture. This section also contains kickers and BPMs for inter-and intratrain trajectory feedback.

Superconducting Magnets for Particle Accelerators

“…The ILC final focus (FF) at the IR requires a compact superconducting quadrupole magnet system for the incoming and outgoing beam lines, as close as possible to the beam interaction point (IP), as shown in Fig. 25, in order to minimize the beam size and to maximize the beam interactions at the IP [107], [112]. The ILC interaction region is complicated, since even with a 14 mrad crossing angle configuration the incoming/outgoing beams are in very close proximity.…”

The superconducting magnets of the ILC beam delivery system

“…But QDEX1 has a larger clear aperture to minimize energy deposition from the outgoing beam. At present three QD0 L*s, 3.5, 4.0 and 4.5 m, are studied and different QDEX1 designs exist for three different extraction line starting points [3].…”

Compact IR Quadrupoles for Linear Colliders Based on Rutherford-Type Cable

“…Each doublet consists of two small-aperture superconducting (SC) quadrupoles QD0 and QF1 and multipole correctors (see Fig.1). The two outgoing disrupted beams are channeled into extraction beam lines by two larger aperture SC quadrupoles QDEX1 and QFEX2 [1]. QD0 with its corrector and QDEX1 are placed in the same cryostat and installed inside the detector.…”