Radiation spectrometer for RF breakdown detection in THz linear accelerators

RF Breakdown RFBD) is a serious limitation in the performance of high gradient >200 MV/m) accelerators operating in W-band frequency range ~100 GHz). In order to study this phenomena at such high frequency, a special detector is required. Conventional detection instruments and methods, such as Faraday Cups, that are used to detect RFBD at lower frequencies are not capable of distinguishing the RFBD from the current jitter in the 100 GHz frequency range. In response to this problem, it is proposed to design and build a single-shot narrow-band terahertz spectrometer that will be able to detect the radiation spectrum widening due the RF pulse shortening cause by an RFBD. In Phase I, we will design, build and test at SLAC the 8- channel prototype of such spectrometer to prove the principle of concept, and to prepare for a commercial 32-channel design a prototype fabrication in Phase II. The goal of Phase I is to build an instrument that will be immediately used by SLAC National Accelerator Laboratory in their work on improving the performance of high-gradient 100 GHz accelerating structure for CLIC. The strategic goal of the Phase I and II of this project is to build a commercial prototype of the spectrometer that can become a useful and important instrument for a wide spectrum of applications, which include testing the THz sources and amplifiers, light source beamline diagnostics, general THz instrumentation and accelerator diagnostics.