A wakefield experiment at the Argonne Wakefield Accelerator (AWA) facility utilizes flat electron beams with highly asymmetric transverse emittances to drive plasma wakefields in the underdense regime. These beams create elliptical blowout structures, producing asymmetric transverse focusing forces. The experiment utilizes a compact 4-cm-long capillary discharge plasma source developed at UCLA. Analytic models of blowout ellipticity and matching conditions, supported by particle-in-cell simulations, guide the experiment's design. Engineering preparations including the use of windows for vacuum-gas separation, beam transport and diagnostics are discussed along with the first beam runs which involve flat beam generation and transport. The theory of flat beam plasma wakefield interaction will also be discussed

The emittance exchange (EEX) beamline at the Argonne Wakefield Accelerator (AWA) is designed to transfer properties of an electron beam phase space between the transverse and longitudinal planes. Recently, it has been proposed this beamline could be used to convert a microscale transverse modulation created by a TEM grid into a microbunch train in the longitudinal plane. Such a technique would be useful for obtaining nano-scale microbunching that does not rely on the sensitive process of FEL gain. This new approach has been proposed to enable development of a compact free-electron laser at Arizona State, greatly reducing size and cost compared with existing short wavelength FELs. To perform an exploratory demonstration of this concept at AWA, this experiment requires low normalized emittance (~50 nm·rad), low charge (~1pC) electron bunches, and transverse diagnostics with high-resolution (1-3 microns) and high-light-collection to resolve the modulation on the electron beam. This report will give a progress update on preparing the necessary beams and diagnostics at AWA for an emittance exchange experiment that would produce 100s of nm scale microbunches.

Multileaf collimators (MLC) are versatile tools for beam shaping, both transversely or, when used in conjunction with an emittance exchange (EEX) beamline, longitudinally. The requirement for ultra-high vacuum compatibility introduces significant constraints on the design of a MLC. Here, we present a novel design for a MLC based on stacks of rotors with angularly dependent radii. The use of tabs and slots allow dozens of these rotors to be positioned using a single vacuum feedthrough, dramatically reducing complexity over independently positioned leaves. We discuss other design elements and also the considerations arising from having a volumetric rather than planar beam mask.

A wakefield experiment at the Argonne Wakefield Accelerator (AWA) facility utilizes flat electron beams with highly asymmetric transverse emittances to drive plasma wakefields in the underdense regime. These beams create elliptical blowout structures, producing asymmetric transverse focusing forces. The experiment utilizes a compact 4-cm-long capillary discharge plasma source developed at UCLA. Analytic models of blowout ellipticity and matching conditions, supported by particle-in-cell simulations, guide the experiment's design. Engineering preparations including the use of windows for vacuum-gas separation, beam transport and diagnostics are discussed along with the first beam runs which involve flat beam generation and transport. The theory of flat beam plasma wakefield interaction will also be discussed

Positrons and electrons can be generated by impinging a relativistic electron beam onto a solid converter, sometimes referred to as a non-neutral fireball beam. Depending on the scenario, a substantial fraction of the incoming driver bunch may still have sufficient quality to drive high gradient (~GV/m) accelerating wakefields in a dielectric structure. Here we consider the design of a dielectric loaded waveguide, positron converter, and electron driver bunch structure to realize capture and GV/m dielectric wakefield acceleration of positrons at SLAC FACET-II.

Recent simulation work has indicated that next generation photoinjectors will be capable of delivering beams with emittances below 100 nm for bunch charges of a few hundred pico-Coulombs. Experimentally validating these results by measuring such emittances is challenging due to the high resolution required. Additionally, in some cases it is desirable for these characterization measurements to be non-destructive, and to have the capability of selecting subsets of the beam. One technique that has been considered is the use of inverse Compton scattering (ICS) spectra to measure the emittance. Here we present simulation results on the use of ICS to measure 50 nm – 500 nm emittances for a 250 pC bunch charge electron beam.

At Los Alamos National Laboratory, we finalized the design of a 1.6-cell C-band RF photoinjector cavity for the Cathodes And Radiofrequency Interactions in Extremes (CARIE) project. The photoinjector cavity is intended to operate at 5.712 GHz, with an intense electric field on the photocathode up to 240 MV/m, producing 250-pC electron bunches at room temperature. The photoinjector cavity design focused on minimizing the peak electric and magnetic fields. The distributed RF coupling waveguide network design was optimized for achieving minimized vacuum pressure at the photocathode plug emitting surface. We report the RF simulation and vacuum simulation results of the photoinjector cavity. We also discuss the mechanical design considerations related to photocathode plug alignment, laser pipes, and baking out. The designed photoinjector cavity is currently under fabrication.

Wigglers are periodic arrays of magnets with myriad applications in accelerator physics. Generally though, they are only tunable by adjusting the gap between jaws. Here, we present a wiggler based on diametrically magnetized cylindrical magnets with independently adjustable angle. This allows the realization of arbitrary (bandwidth constrained) magnetic configurations. We illustrate its application to the recently proposed "transverse wiggler" concept for transverse phase space control.