1. 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” ( 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: 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

2. 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