SLAC, Menlo Park, California, USA
We have measured the THz near-field in order to inform the design of improved THz-frequency accelerating structures. THz-frequency accelerating structures could provide the accelerating gradients needed for next generation particle accelerators with compact, GV/m-scale devices. One of the most promising THz generation techniques for accelerator applications is optical rectification in lithium niobate using the tilted pulse front method. However, accelerator applications are limited by significant losses during transport of THz radiation from the generating nonlinear crystal to the acceleration structure. In addition, the spectral properties of high-field THz sources make it difficult to couple THz radiation into accelerating structures. A better understanding of the THz near-field source properties is necessary for the optimization of THz transport and coupling. We have developed a technique for detailed measurement of the THz near-fields and used it to reconstruct the full temporal 3D THz near-field close to the LN emission face. Analysis of the results from this measurement will inform designs of novel structures for use in THz particle acceleration.
TUOZGD3
SLAC, Menlo Park, California, USA
UCSF, San Francisco, California, USA
Northwestern University, Northwester Medicine Proton Center, Warrenville, Illinois, USA
LLU, Loma Linda, USA
We report on the development of a 2.856 GHz accelerator system to provide energy modulation and RF-based steering for rapid 3-D beam scanning for proton therapy. Designs for the accelerator and deflector cavities have been modeled in ANSYS-HFSS and used to produce prototype structures. We present high power test results for a single cell energy modulator prototype and a three cell deflector prototype. Using General Particle Tracer, we simulate proton beam transport through the fully rendered accelerator and deflector beamline. System performance is optimized for the case of sub-relativistic protons with 230 MeV kinetic energy and covers an energy modulation range of ±30 MeV. We present simulated beam profile data after energy modulation and lateral steering, achieved using a combination of dynamic RF deflector cavities and static permanent magnet quadrupoles.
LANL, Los Alamos, New Mexico, USA
Michigan State University, East Lansing, Michigan, USA
SLAC, Menlo Park, California, USA
MSU, East Lansing, Michigan, USA
This work presents the results of high gradient testing of the two C-band (5.712 GHz) normal conducting ß=0.5 accelerating cavities. The first cavity was made of copper and second was made of copper-silver alloy with 0.08% silver concentration. The tests were conducted at the C-Band Engineering Research Facility of New Mexico (CERF-NM) located at Los Alamos National Laboratory Both cavities achieved gradients in excess of 200 MV/m and surface electric fields in excess of 300 MV/m. The breakdown rates were mapped as functions of the gradient and peak surface fields. The gradients and peak surface fields observed in the copper-silver cavity were about 20% higher than those in the pure copper cavity with the same breakdown rate. It was concluded that the dominant breakdown mechanism in these cavities was not the pulse heating but the breakdown due to very high surface electric fields.
SLAC, Menlo Park, California, USA
UCSC, Santa Cruz, California, USA
We report on the design of mm-wave accelerator structures operating near 100 GHz. Simulations of the cavity geometry and RF coupling are performed in ANSYS-HFSS and using SLAC’s parallel electromagnetic code suite ACE3P. We present experimental results for structures fabricated from copper, niobium, and copper plated with NbTiNi. We report on techniques for tuning these high frequency structures, as well as preliminary brazing results. A mm-wave accelerator cavity enables not only a high achievable gradient due to higher breakdown thresholds, but also reduced fill times which decrease pulsed heating and allow for higher repetition rates. We discuss the potential advantages and challenges for applications requiring ultra-compact structures.