In recent years, plasma accelerators have advanced significantly toward producing beams suitable for colliders, aiming to replace conventional MV/m RF fields with GV/m fields of nonlinear plasma waves. Realizing a plasma-based collider requires electron bunches with high charge (hundreds of pC), low normalized emittance (~100 nm), and energy spread below 1%. Minimizing energy spread during acceleration involves flattening the accelerating field, which is achievable with a trapezoidal charge distribution. We present a plasma photoinjector concept that enables collider-quality electron bunch generation using two-color ionization injection. The spatiotemporal control over the ionizing laser creates a moving ionization front inside a nonlinear plasma wave, generating an electron bunch with a current profile that flattens the accelerating field. Particle-in-cell (PIC) simulations of the ionization stage show the formation of an electron bunch with 220 pC charge and low emittance ($\epsilon_x = 171$ nm-rad, $\epsilon_y = 76$ nm-rad). Quasistatic PIC simulations of the acceleration stage show that this bunch is efficiently accelerated to 20 GeV over 2-meters with an energy spread below 1% and emittances of $\epsilon_x = 177$ nm-rad and $\epsilon_y = 82$ nm-rad. This high-quality electron bunch meets Snowmass collider requirements and establishes the feasibility of plasma photoinjectors for future collider applications.

To compete with conventional accelerators, collider and light source applications based on plasma wakefield acceleration need to be able to handle 10s of Joules of energy transfer between the drive beam, plasma, and witness beam at repetition rates exceeding 100 Hz. Scaling up to these parameters is challenging due to the large amount of heat deposited in the plasma source. To begin approaching this regime, we developed a laser ionized plasma source using a pair of diffractive optics to produce a meter-scale Bessel focus with a tailored axial intensity profile. Using this source, we demonstrate multi-Joule energy transfer in the plasma accelerator at SLAC’s FACET-II facility with strong deceleration of the drive bunch and acceleration of a witness bunch.