Belle-II VXD radiation monitoring and beam abort with sCVD diamond sensors Lorenzo Vitale, Belle-II SVD collaboration INFN and Univ. Trieste, ITALY Requirements Measurement of instantaneous dose rates & integrated doses sensitivity O(1 mrad/s = 10 μGy/s), sampling rate O(100 KHz) Beam Abort for excessive beam losses affecting PXD, SVD “Fast” (10-100 μs) “slow” (ms), “very slow” (> 1s) Beam Abort triggers Programmable “intelligent” thresholds, depending on accelerator conditions Conceptual design Based on experience from Belle, BaBar, CDF, LHC Diamond sensors, measurement of currents Typical pCVD sensor (10 × 10 × 0.5) mm3: 1 nA = 7 mrad/s = 70 μGy/s Noise should be limited to a few pA, in current measurements 4 + 4 sensors near PXD 6 + 6 sensors near SVD

First prototypes Characterization Electronics Design In collaboration with Electronics Division of the Elettra Synchrotron light source: current digitizer with FPGAs and additional memory for the digital filtering and beam abort trigger. Selectable current digitization ranges: 0÷50 μA and 0÷2 mA. Several levels of running averages updated every 10μs. First prototypes Characterization Characterization of first prototypes of sCVD with Al or Au electrodes mounted in compact package: I-V current-voltage characteristics; “dark” I-V (<1 pA up to 600V), I-V with light exposure and I-V when irradiated by a β source at a given distance (no saturation observed!). CCE, with single particle from β source (saturation ~100% above 40 V). Long-term stability when irradiated by β source. Current-distance behavior when irradiated by a β source and compared to Fluka simulation. Transient Current Technique (TCT) by α source. Current I vs distance d of 90Sr β source measurement simulation