Beam Tests

With control and monitoring tools to operate devices at the CMS Tracker design temperature of $-10^{\circ}\,\rm C$, a cooling box was built. Three silicon detector modules were constructed at HEPHY including the very first modules with APV6 and APV25S0 readout. A typical MIP signal-to-noise ratio of 17 (corresponding to a noise of about $1300\,\rm e$) has been obtained in beam tests for non-irradiated full-size CMS detector modules when read out by the APV25 in deconvolution mode, which outperforms the previous APV6 version especially in terms of noise. Pre-irradiated silicon detectors were included in these tests, showing a small but not critical degradation of the output signal. During a high-intensity beam period, a radiation induced leakage current increase of $\alpha\approx 8\cdot 10^{-17}\,\rm A\,cm^{-1}$ was observed, which agrees with other measurements. Moreover, a prototype of the analog optical link was successfully tested in the module readout path.

The effects of radiation on both digital and analog sections of the APV25S1 circuitry were measured with $300\,\rm MeV/c$ pions. No permanent damage was observed, and a digital single event upset cross-section of approximately $2\,\cdot 10^{-12}\,\rm cm^2$ has been found, which is compatible to similar measurements performed with heavy ions. From extrapolation of these data, a total upset rate in the order of $100\,\rm SEUs/hour$ is expected for Inner or Outer Barrel parts of the CMS Tracker. Analog upsets appear as a negligible increase in noise background.