Beamstrahlung considerations in laser-plasma-accelerator-based linear colliders

Abstract

Beam-beam interaction constraints modify the basic plasma density scalings for a linear collider based on laser-plasma accelerators. In the quantum beamstrahlung regime, it is shown that operating at low plasma density increases beamstrahlung effects, owing to the higher bunch charge and longer bunch length. At high plasma density, the bunch charge is limited by beam loading, and the required power is proportional to the square root of the plasma density. At low plasma density, the bunch charge is limited by beamstrahlung, which, for fixed luminosity, requires operation at higher laser repetition rate and, hence, higher power requirements, or the use of multibunch trains. If round beams are used in a multibunch train format with fixed beam loading, and the collider is constrained by beamstrahlung, then the required collider power is independent of plasma density.

Laser-plasma-based linear collider using hollow plasma channels

“…For example, 4.2 GeV electron beams have been produced in a 9 cm plasma channel, using a 40 fs laser pulse containing 15 J of laser energy [2]. The rapid experimental progress in LPAs over the last decade has resulted in interest in the development of laser-plasma-based acceleration as a basis for future linear electronpositron colliders [3][4][5][6]. Future colliders based on LPAs will require both high average (or geometric) accelerating gradient to reduce the size of the facility (i.e., reduced construction costs) and low power consumption (i.e., reduced operating costs).…”

Operational plasma density and laser parameters for future colliders based on laser-plasma accelerators

“…[4] under the assumptions of fixed final focusing to the IP, fixed laser efficiency, and a fixed center-of-mass energy and luminosity required for high-energy physics experiments, but independent of limitations due to beam-beam interactions (manifest at low plasma density) [5]. Table 1 shows the basic LPA scalings under these assumptions.…”

“…Multi-bunch trains may be considered for improved efficiency, as discussed in Ref. [5]. Also one may consider reducing the laser intensity such that a 0 1.…”

Staging of laser-plasma accelerators

“…An efficient LPA at such low densities would also require a high bunch charge, increasing beamstrahlung beyond acceptable limits for highenergy physics applications. 4 Hence, LPA staging is critical to the application of LPAs to future colliders. In addition to high-energy physics applications, LPA staging can be important to decelerate electrons after photon production to mitigate shielding needs in compact photon sources.…”