SLAC, Menlo Park, California, USA
ANL, Lemont, Illinois, USA
Euclid TechLabs, LLC, Solon, Ohio, USA
MIT/PSFC, Cambridge, Massachusetts, USA
AAI/ANL, Lemont, Illinois, USA
UNIST, Ulsan, Republic of Korea
We present experimental studies of metamaterial (MTM) structures for wakefield acceleration. The MTM structure is an all-metal periodic structure with its period much smaller than the wavelength at X-band. The fundamental TM mode has a negative group velocity, so an electron beam traveling through the structure radiates by reversed Cherenkov radiation. Two experiments have been completed at the Argonne Wakefield Accelerator (AWA), namely the Stage-I and Stage-II experiments. Differences between the two experiments include: (1) Structure length (Stage-I 8 cm, Stage-II 20 cm); (2) Bunch number used to excite the structure (Stage-I up to 2 bunches, Stage-II up to 8 bunches). In the Stage-I experiment, two bunches with a total charge of 85 nC generated 80 MW of RF power in a 2 ns long pulse. In the Stage-II experiment, the highest peak power reached 380 MW in a 10 ns long pulse from a train of 8 bunches with a total charge of 224 nC. Acceleration of a witness bunch has not been demonstrated yet, but the extracted power can be transferred to a separate accelerator for two-beam acceleration or directly applied to a trailing witness bunch in the same structure for collinear acceleration.
MOZBB3
ANL, Lemont, Illinois, USA
Euclid TechLabs, LLC, Solon, Ohio, USA
ANL, Lemont, Illinois, USA
UW-Madison/PD, Madison, Wisconsin, USA
Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail.
[1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)
ANL, Lemont, Illinois, USA
Euclid Beamlabs LLC, Bolingbrook, USA
The RF system of Argonne Wakefield Accelerator (AWA) facility has grown over the years from one RF power station into 4 RF power stations. The demand for RF power keeps growing as the capability of AWA continues to grow. Now the 5th RF station is needed to fulfill the RF power needs of AWA facility. Some details regarding the construction and commissioning of the 5th RF station of AWA facility are documented in this paper.
LANL, Los Alamos, New Mexico, USA
Euclid Beamlabs LLC, Bolingbrook, USA
IIT, Chicago, Illinois, USA
ANL, Lemont, Illinois, USA
Diamond Field Emitter Array (DFEA) cathodes are arbitrarily shaped arrays of sharp (~50 nm tip size) nano-diamond pyramids with bases on the order of 3 to 25 microns and pitches 5 microns and greater. These cathodes have demonstrated very high bunch charge in tests at the L-band RF gun at the Argonne National Laboratory (ANL) Advanced Cathode Test Stand (ACTS). Intrinsically shaped electron beams have a variety of applications, but primarily to achieve high transformer ratios for Dielectric Wakefield Accelerators (DWA) when used in conjunction with Emittance Exchange (EEX) systems. Here we will present results from a number of recent cathode tests including bunch charge and YAG images. We have demonstrated shaped beam transport down the 2.54-meter beamline. In addition we will present emission simulations that demonstrate shielding effects for this geometry.
UCLA, Los Angeles, California, USA
ANL, Lemont, Illinois, USA
UNIST, Ulsan, Republic of Korea
Systematic differences between the linear and nonlinear regimes of plasma wakefield acceleration from electron beams are manifested in the plasma response. Typically, the ratio of peak beam density to nominal plasma density determines operation in the linear or nonlinear regime. Previous reports have shown that a the cross-over into the nonlinear regime is associated with an increase in the wakefield amplitude, as well as sawtooth-like shape. In this paper, we present preliminary measurements of quasi-nonlinear wakefields driven by a linearly ramped beam, with a maximum charge close to the unperturbed plasma density. We also demonstrate nonlinear wakefield behavior in a probe bunch using a single shot, multi-period wakefield measurement and its dependency on plasma density.
ANL, Lemont, Illinois, USA
Euclid Beamlabs LLC, Bolingbrook, USA
Beam position monitor (BPM) is widely used in accelerator facilities worldwide. It is a device which is capable of providing, non-destructively, accurate beam centroid and charge information of a passing charged beam. A typical BPM system contains customized hardware and specialized processing electronics. The cost is often too high for small facilities to afford them. As a small facility, Argonne Wakefield Accelerator (AWA) decided to develop a solution with high cost-efficiency to fit in its budget. Some details about the development are presented in this paper.