Development of Single-Crystal CVD-Diamond Detectors

Single-Crystal CVD-Diamond Detectors (SC-DD) of ~ 300μm thickness have been tested in Cave A with proton beams of Ep > 1AGeV as start detectors for minimum ionizing particles. Fast charge-sensitive amplifiers developed at GSI and Bucharest were used. At particle rates up to 1MHz, stable operation and detection efficiency of ~100% are observed. The measured time resolution of σ ≥ 330ps is not satisfying. The next step will be the test of ‘sandwich’ detectors providing shorter rise time at higher S/N ratio. In FRS [1] experiments, the energy-loss (ΔE) and the Z-resolution of three SC-DD of 400μm thickness, a size of 4x4mm and an active area of 3mm in diameter were measured using Xe projectiles of different energies: 334 AMeV, 740 AMeV and 1.2 AGeV, respectively. The fragments produced on a Be target of 4g/cm were identified via Bρ, ToF measured with lucite scintillators between S2 and S4, and ΔE into two MUSIC detectors placed at S4 in front and behind the diamonds. Even for the primary xenon beams the beam spot onto the diamonds was larger than the size of the active detector area. Due to ‘boarder’ events of different timing and shape, low-energetic tails appear in the raw energy spectra. However, for all three projectile energies the preliminary online data analysis shows an unexpected good ΔE/E resolution of 1%-2%, which is comparable to the resolution of the ionization chambers. In fragmentation spectra (Fig. 1) all particles are clearly identified with a ΔZ/Z ≤ 1.