Simulation and experimental qualification of the response of microstrip detectors to ion beams
In the framework of the construction of a novel Femtoscope Array for Correlation and Spectroscopy, named FARCOS, aiming at the identification in charge and mass even of particles stopping in the first detection layer, we are performing a thorough characterization of the silicon detector layers in terms of the collection properties as a function of the point of incidence. We have experimental evidence - as previously observed also in the literature for other strip detectors - that interstrip incidence alters the signal shape not only for the trivial effect of charge sharing but also because of induction effects on neighbor strips. In order to clarify this issue we developed a custom simulation suite of the electron-hole transport and signal formation able to properly describe 3-D Coulomb interaction and thermal diffusion in semiconductor detectors. We ran a batch of significant and representative simulations presenting the qualitative correct interpretation and the quantitative validation as proved by the comparison of the simulation results with the experimental data.
The high resolution array (HiRA) for rare isotope beam experiments
Abstract The High Resolution Array (HiRA) is a large solid-angle array of silicon strip-detectors that has been developed for use in a variety of nuclear structure, nuclear astrophysics and nuclear reaction experiments with short lived beta-unstable beams. It consists of 20 identical telescopes each composed of a thin ( 65 μ m ) single-sided silicon strip-detector, a thick (1.5 mm) double-sided silicon strip-detector, and four CsI(Tl) crystals read out by photodiodes. The array can be easily configured to meet the detection requirements of specific experiments. To process the signals from the 1920 strips in the array, an Application Specific Integrated Circuit (ASIC) was developed. The design and performance characteristics of HiRA are described.
Development of an Analytical Method for Explosive Residues in Soil
Abstract : An analytical method was developed to determine the concentrations of HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT in soil. The method involves extracting a 2-g sample with 50 mL of acetonitrile using an ultrasonic bath procedure for 18 hr. A 10-mL portion of the extract is diluted with 10 mL of water, filtered through a 0.45-micrometer Millex SR filter, and analyzed by RP-HPLC using a fixed 254-nm UV detector. Separations were obtained on an LC-18 column eluted with 50:50 water-methanol. Retention times were 2.55, 3.82, 5.16, 6.25, 7.04, 8.47 and 10.15 min for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT, respectively. Confirmation of analyte identities is recommended by RP-HPLC on an LC-CN column using 50:50 water-methanol. Kinetic studies using naturally contaminated soil indicated that equilibrium was achieved within 24 hr for the majority of soils and analytes studied. The method provides linear calibration curves over a wide range of concentrations. Reporting limits were conservatively estimated at 1.6, 1.8, 1.5, 0.5, 5.5, 0.8 and 0.8 micro grams/g for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT. Analytical precision was estimated at + or - 0.44, 0.51, 0.43, 0.13, 1.24, 0.27 and 0.20 micro grams/g, respectively, in the range of homogeneous variance near the detection limits. At higher concentrations the relative standard deviation was constant at 2% for HMX, RDX, DNB and TNB, 3% for TNT and 2,4-DNT, and 6% for Tetryl.