Speaker
Description
Seeding of the drive bunch self-modulation (SM) process is essential when using a long particle bunch (σz>>λpe) to drive wakefields in plasma. Seeding in principle leads to a SM phase reproducible from event-to-event, allowing for deterministic injection of an electron witness bunch to be accelerated.
Since external injection requires generation of an electron bunch in an RF-gun or LWFA, we explore opportunities and challenges related to also using an electron bunch for seeding of the SM process in AWAKE. Seeding with an electron bunch has a number of possible advantages over seeding with a relativistic ionization front: no high-power laser needed, use of a source with pre-formed plasma (helicon, discharge, etc.), effective use of the entire drive bunch to drive wakefields, etc. It may also has have some difficulties: implementation of a plasma density step, evolution of the seed bunch if not matched to the plasma focusing force, energy loss and dephasing of the seed bunch, etc.
