R. Malchow

Particle‐ and photoinduced conductivity in type‐IIa diamonds

Electrical characteristics associated with radiation detection were measured on single‐crystal natural type‐IIa diamond using two techniques: charged particle‐induced conductivity and time‐resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle‐induced conductivity technique measures the product of the carrier mobility μ and lifetime τ throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micrometers of the material surface. For each technique, the μτ product was determined by integration of the respective signals. The collection distance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surface electrical properties was performed. The data from these two techniques are in agreement, indicating no difference in the electrical properties between the bulk and the surface of the ...

Performance of a diamond-tungsten sampling calorimeter

We report here the first measurements of a diamond-tungsten sampling calorimeter. The calorimeter consisted of twenty layers of diamond with one radiation length of tungsten per layer. The diamond layers were grown by chemical vapor deposition and were 3.0 × 3.0 cm2 wafers with an average thickness of 500 μm. We measured the energy response and resolution (σE/E) of this calorimeter in 0.5–5.0 GeV electron beams and compared the results with those from a silicon calorimeter of similar construction. Our energy resolution is σE/E = (4.7 ± 2.7)%/E≍(19.13±0.86)%/√E≍(2.3±1.8)% for the diamond-tungsten calorimeter, where ⊕ indicates addition in quadrature. This is in good agreement with our result for the silicon-tungsten calorimeter of σE/E = (3.89 ± 0.87)%/E ≍ (19.73±0.19)%/√E ≍(0.0 ± 1.6)%. We also compare our data with EGS simulations.

Diamond detectors for high energy physics

We have constructed charged particle detectors using high quality CVD diamond. We report here the measurements of a diamond-tungsten sampling calorimeter and a diamond mustrip detector. The energy response and resolution (σEE) of the calorimeter were measured using an electron beam of energy 0.5 to 5.0 GeV, and compared with those from a silicon calorimeter of similar construction. We find σEE = (4.7 ± 2.7)%/E ⊕ (19.13 ± 0.86)%/√E ⊕ (2.3 ± 1.8)% for the diamond-tungsten calorimeter, where ⊕ indicates addition in quadrature, which is in good agreement with our result of σE/E = (3.89 ± 0.87)%/E ⊕ (19.73 ± 0.19)%/√E ⊕ (0.0 ± 1.6)% for the silicon-tungsten calorimeter. The CVD diamond mustrip detector consists of 50 μm wide strips on 100 μm centers. A signal-to-noise ratio of 6: 1 and a position resolution of 25 μm was observed during recent accelerator tests.

Diamond Detectors for the SSC

Diamond is well suited as a particle detector in the high rate and high radiation environment of the SSC. The use of diamond is made possible by recent developments in the chemical vapor deposition (CVD) growth process. CVD diamonds have been studied using radioactive sources and test beams. The measured charge collection distance of CVD diamonds now exceeds that of natural diamond. No degradation of signal is observed up to a rate of 104 particles cm-2s-1. Exposure to stopping 5 MeV α particles shows no radiation damage with a dose of up to 1013 particles cm-2. Prototype diamond/tungsten and silicon/tungsten calorimeters have been constructed and tested in an electron beam at KEK. The energy resolution of the diamond/tungsten detector is comparable to the silicon/tungsten calorimeter.

Two-body Ds+ decays to , , , , and +

We have made measurements of several {ital D}{sub {ital s}} branching ratios, relative to the {phi}{pi}{sup +} mode. We have observed two previously unseen two-body hadronic decays of the {ital D}{sub {ital s}}{sup +}, namely {eta}{rho}{sup +} and {eta}{prime}{rho}{sup +}, and measured relative branching ratios of 2.86{plus minus}0.38{sub {minus}0.38}{sup +0.36} and 3.44{plus minus}0.62{sub {minus}0.46}{sup +0.44}, respectively. We have determined the relative branching ratio for the decay into {phi}{rho}{sup +} to be 1.86{plus minus}0.26{sub {minus}0.40}{sup +0.29}. In addition, we have measured relative branching ratios for the {eta}{pi}{sup +} and {eta}{prime}{pi}{sup +} states, for which there had previously been conflicting measurements; our results are 0.54{plus minus}0.09{plus minus}0.06 and 1.20{plus minus}0.15{plus minus}0.11, respectively. Combining these new measurements with previous results and using (3.7{plus minus}1.2)% for the value of {ital scrB}({ital D}{sub {ital s}}{r arrow}{phi}{pi}{sup +}), we can account for {approx}(79{plus minus}26)% of all {ital D}{sub {ital s}}{sup +} decays. In addition we have also measured relative branching ratios or set upper limits on {ital D}{sup +} decays to all of the above-mentioned final states.