Standard methods of measuring the transverse beam profile are not adaptable for sufficiently high-intensity beams. Therefore, the development of non-invasive techniques for extracting beam parameters is necessary. Here we present experimental progress on developing a transverse profile diagnostic that reconstructs beam parameters based on images of an ion distribution generated by beam-induced ionization. Laser-based ionization is used as an initial step to validate the electrostatic column focusing characteristics, and different modalities, including velocity map imaging. This paper focuses on measurements of the ion imaging performance, as well as the dependence of Ion intensity on gas density and incident beam current for low-energy electron beams (<10 MeV).

New R\&D concepts for particle acceleration, generation, and focusing at ultra high acceleration gradients (GeV/m and beyond) have the potential to enable future e+e- and $\gamma - \gamma$ colliders to and beyond 15 TeV energies. In addition to proven high gradient and ultra-bright beam generation, these systems have the potential to increase luminosity per unit beam power via short beams, for practical energy recovery to extend the reach of high energy physics, and for fast cooling. They hence have potential to reduce the dimensions, CO$_2$ footprint, and costs of future colliders, with added potential to reduce power consumption. The last decade has seen tremendous experimental progress in performance, together with development of concepts to address potential collider issues. Conceptual parameter sets for colliders have been developed for e+e- and $\gamma \gamma$ colliders at a range of energies, which present potentially competitive options with prospects for future cost reduction. In addition to a strengthened ongoing R$\&$D program, continuing to develop these collider concepts in interaction with the collider and high energy physics communities, starting with an integrated set of parameters, is important; as is development of technologies through nearer-term applications. Progress in these concepts, next steps, and results of Snowmass Accelerator Frontier topical group # 6, Advanced Accelerator Concepts (https://doi.org/10.48550/arXiv.2208.13279) will be discussed.

RadiaBeam, in collaboration with UCLA and Fermilab, is developing a strongly tapered helical undulator system for the Tapering Enhanced Stimulated Superradiant Amplification experiment at 515 nm (TESSA-515). The experiment will be carried out at the FAST facility at Fermilab as a Gamma-Ray high Efficiency ENhanced Source (FAST-GREENS). The undulator system was designed by UCLA, engineered by RadiaBeam, and will be installed on the beamline at Fermilab. The design is based on a permanent magnet Halbach scheme of four 1-meter long undulator sections; two of which have been completed and installed. The undulator period is fixed at 32 mm and the magnetic field amplitude can be tapered by tuning the gap along the interaction. Each magnet can be individually adjusted by 1 mm, offering up to 25% magnetic field tunability with a minimum gap of 5.58 mm. This paper discusses the design and engineering of the undulator system and the stage 0 installation status.

The FAST Injector at Fermilab has been the focus of a number of recent experimental efforts as 1) the driver of a novel FEL experiment, 2) as the injector for IOTA, and 3) as a test-bed for novel machine learning algorithms to reconstruct phase space measurements. Here we present our recent work to simulate the FAST injector and perform realistic comparisons of simulated beam distributions to measured beam distributions using a multi-slit emittance diagnostic. We also present studies on using laser pulse stacking to shape the beam distribution for creating optimal current distributions for FEL experiments.

Standard methods of measuring the transverse beam profile are not adaptable for sufficiently high-intensity beams. Therefore, the development of non-invasive techniques for extracting beam parameters is necessary. Here we present experimental progress on developing a transverse profile diagnostic that reconstructs beam parameters based on images of an ion distribution generated by beam-induced ionization. Laser-based ionization is used as an initial step to validate the electrostatic column focusing characteristics, and different modalities, including velocity map imaging. This paper focuses on measurements of the ion imaging performance, as well as the dependence of Ion intensity on gas density and incident beam current for low-energy electron beams (<10 MeV).