The X-band Laboratory for Accelerators and Beams (X-LAB) at the University of Melbourne enables high-power testing of X-band accelerator technologies, including components for CERN’s Compact Linear Collider (CLIC). At its core is Mel-BOX, a high-gradient test stand rebuilt from CERN’s XBOX3. Two TD24 structures, previously conditioned at CERN, have been successfully re-tested, along with RF windows, SLED-I pulse compressors, and 3D-printed loads. Beam instrumentation at X-LAB includes Faraday cups with high-resolution digitizers to measure dark current and breakdown emissions. Fast time-domain measurements along the waveguide using GHz-bandwidth oscilloscopes allow localization of breakdown events. Optical fibers detect Cherenkov light near the structures, providing complementary pulse-resolved signals. These are cross-referenced with Faraday cup data to study early-stage field emission. X-LAB integrates RF testing and diagnostics to support the development of compact, high-gradient accelerator systems.

Two CLIC TD24 accelerating structures, manufactured by CERN, are undergoing high-power testing on the 12 GHz RF test stand, MelBOX, at the x-Band Laboratory for Accelerators and Beams (XLAB). Installed in late 2024, these are the first devices tested at the facility. The goal is to condition the structures for stable operation at gradients of 100 MV/m. The maximum gradient is limited by electrical breakdown—vacuum arc formation under high electric fields—which interrupts RF transmission and can damage the structure. To study breakdown dynamics and validate models of their initiation, detailed, time-resolved charge measurements are needed. Faraday cups upstream and downstream, combined with high-performance 5 GS/s, 12-bit, 3 GHz FEB digitisers, enable precise characterisation of both dark and breakdown current emissions. Fast digitiser readout allows continuous acquisition at the 400 Hz repetition rate, capturing breakdown events and several hundred preceding pulses. This dataset supports in-depth analysis of precursors. We present initial results from structure conditioning, including breakdown statistics, dark current trends, and preliminary analysis of breakdown behaviour.

Optical beam diagnostics, such as OTR screens and streak cameras, can overcome bandwidth limitations of electronic diagnostics. However, efficient light collection and transport is challenging. At the PEER (Pulsed Energetic Electrons for Research) facility at the Australian Synchrotron (AS), we use Cherenkov radiation (CR) generated in optical fibers to reconstruct longitudinal bunch profiles at ps timescales, using a streak camera. This is enabled by proportionality of emitted CR intensity to incident charge*, when electrons directly impact the fiber. Streak cameras have been used to image CR**, but generating and transporting CR in the same fiber is novel, simplifying detector design and light transport. We present bunch profile measurements using this technique and assess its feasibility. We quantify distortion of CR due to modal and chromatic dispersion in the fiber, survey methods to reduce distortion, and improve signal-to-noise ratio. Bunch profile measurements at ps resolution may enable bunch purity optimisation and detection of microbunching, previously not possible at PEER. This will greatly benefit PEER users, as well as beam quality in the AS booster and storage rings.