LANL, Los Alamos, New Mexico, USA
We present the simulations and test results for focusing studies performed on diamond field emitter array cathodes. This design utilized a simple variable-focus solenoidal lens in conjunction with a scanning wire technique in order to measure the beam spot size. The spot size was measured by scanning a thin copper wire across the beam in 1 µm increments, with voltage being measured and averaged at each location in order to map the location and intensity of the beam. Scans were taken at different distances away from the magnetic center of the lens, and show good agreement with our simulations of the beam. Ultimately this has allowed us to focus the beam to a spot size of 5.72 µm with an average current of 15.78 µA.
LANL, Los Alamos, New Mexico, USA
Stanford University, Stanford, California, USA
Nanocrystalline diamond is a promising material for electron emission applications, as it combines robustness of diamond and ability to easily conform to a pre-defined shape, even at nano-scale. However, its electron emission properties are yet to be fully understood. Recently, we started to investigate femtosecond-laser-induced strong-field photoemission from nanocrystalline diamond field emitters with very sharp (~10 nm apex) tips. Initial results show that the mechanism of electron emission at ~1010 W/cm2 light intensities in the near UV to near IR range is more complex than in metals. We present our latest experimental results obtained at Stanford University, while LANL’s strong-field photoemission test stand is being commissioned. We show that strong-field photoemission occurs not only at the nano-tip’s apex, but also on flat diamond surfaces (e.g., pyramid sides), that is why extra care needs to be taken to differentiate between emission spots on the chip. Qualitatively, we discuss the models that explain the observed dependences of electron emission on the optical power, polarization of the light, etc.
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.
LANL, Los Alamos, New Mexico, USA
UCLA, Los Angeles, California, USA
This poster will report on the status of the new high gradient C-band accelerator project at LANL. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. Our goal is to use a multi-disciplinary approach that includes accelerator design, molecular dynamics simulations, and advanced manufacturing to develop high gradient, high efficiency RF structures for both compact and facility-size accelerator systems. We considered common operation frequencies for accelerators and identified C-band as the optimal frequency band for high gradient operations based on achievable gradients and means to control wakefields. We are putting together a high gradient C-band test facility that includes a 50 MW Toshiba klystron and cryo-coolers for operating copper NCRF accelerator cavities at long pulse duration. We plan to conduct high gradient testing of the optimized RF structures made of copper and novel copper alloys. LANL modeling capabilities will be used to systematically study the formation of breakdown precursors at high fields to develop basic theoretical understanding of the breakdown.