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Application-specific integrated circuits of DIE8 (ATLAS, CERN), NINO (ALICE, CERN), and PADI (CBM, GSI) amplifiers−discriminators have been designed specifically for applications with resistive ...plate chambers, a new type of multichannel detectors. The main development trends formed during the creation of new, large-scale experiments at the Large Hadron Collider (LHC) are shown. The main characteristics of the integrated circuits, the motivation for setting the design task, problems, and application features are compared.
For the full exploitation of the excellent timing properties of the Multigap Resistive Plate Chamber (MRPC), front-end electronics with special characteristics are needed. These are (a) differential ...input, to profit from the differential signal from the MRPC (b) a fast amplifier with less than 1ns peaking time and (c) input charge measurement by Time-Over-Threshold for slewing correction. An 8-channel amplifier and discriminator chip has been developed to match these requirements. This is the NINO ASIC, fabricated with 0.25μm CMOS technology. The power requirement at 40mW/channel is low. Results on the performance of the MRPCs using the NINO ASIC are presented. Typical time resolution σ of the MRPC system is in the 50ps range, with an efficiency of 99.9%.
The time over threshold (TOT) method that uses a pulse sine shaper, which is based on the mathematical function of the raised cosine (FRC), is described. The FRC has an important property for the TOT ...method—the formation of a smooth pulse with the variability of both the smoothing coefficient and the response time. In this case, the shape of the FRC pulse is independent of the input pulse action within a given time range. Thus, on the basis of the FRC, it was possible to create a pulse sine shaper with a preset time response, which provided an unambiguous dependence of the TOT-pulse duration on the input charge, and to improve the accuracy characteristics due to optimal spectral filtering in the FRC. A pulse sine shaper based on the FRC was successfully used in the reading systems of the HADES (GSI, Darmstadt, Germany) and BM&N (JINR, Dubna) experiments. The total number of reading channels was more than 5000; the method has an error of ~0.3%.
Two modules of the AD detector have been studied with the test beam at the T10 facility at CERN. The AD detector is made of scintillator pads read out by wave-length shifters (WLS) coupled to clean ...fibres that carry the produced light to photo-multiplier tubes (PMTs). In ALICE the AD is used to trigger and study the physics of diffractive and ultra-peripheral collisions as well as for a variety of technical tasks like beam-gas background monitoring or as a luminometer. \par The position dependence of the modules' efficiency has been measured and the effect of hits on the WLS or PMTs has been evaluated. The charge deposited by pions and protons has been measured at different momenta of the test beam. The time resolution is determined as a function of the deposited charge. These results are important ingredients to better understand the AD detector, to benchmark the corresponding simulations, and very importantly they served as a baseline for a similar device, the Forward Diffractive Detector (FDD), being currently built and that will be in operation in ALICE during the LHC Runs 3 and 4.
Effect of Zn2+ ions on DNA transition from B-form to a metallized form (m-DNA) in Tris and tetraborate buffers at pH 8.5 has been studied by visible and differential UV-spectroscopy and by thermal ...denaturation. The results have been compared to those obtained at pH 6.5 in cacodylate buffer. It was found that in alkaline solutions Zn2+ ions induced a hypochromicity of the DNA absorption in the whole spectral range monitored, which was attributed to DNA transition from B- to the m-form. Complete metallization occurred only upon heating the DNA solutions containing more than ∼2×10−4M of Zn2+ ions. Phase diagrams of the DNA–zinc complexes at pH 6.5 and 8.5 have been obtained for the first time. The m-DNA form showed higher thermal stability compared to B-DNA.
Dependence of DNA metallization degree during B-DNA transition into the metallized (m) form on DNA concentration has been studied by visible and differential UV-spectroscopy in the presence of Zn2+, ...Co2+ and Ni2+ ions in tetraborate buffer (pH 8.5) with and without ethidium bromide. Constants of Mt2+ binding to double stranded DNA were calculated. The obtained binding constants corresponded to the formation of inter-strand metal bridges stabilizing m-form. Thermodynamic origin of higher efficiency of Zn2+ ions in DNA metallization compared to Co2+ and Ni2+ was revealed. Increase of the DNA helix-coil transition temperature by up to 10°С upon formation of m-form in the presence of Zn2+ ions was observed and rationalized. Furthermore, a strong cooperative decrease (up to 30°С) of the temperature of В→m transition induced by heating in the presence of Zn2+ was found and its nature was explained.
Effect of Zn2+ ions on the conformation of single-stranded polynucleotides polyU and polyC in a wide temperature range at pH 7 was studied by differential UV spectroscopy and by thermal denaturation. ...The atoms coordinating Zn2+ ions were determined (O4 and N3 in polyU and N3 in polyC). A three-dimensional phase diagram and its two-dimensional components were constructed for a polyC–Zn2+ system. The phase diagram revealed a region in which ordered single-stranded structures, stabilized by Zn2+-mediated cross-links involving N3 atom of cytosine, are formed. The phase diagram also demonstrated that the behavior of the polyC–Zn2+ system is similar to the effect of retrograde condensation observed in some binary solutions of simple liquids. A dependence of Zn2+–polyC binding constant on the metal ion concentration was obtained. The reason why zinc-induced transition of the sequences with adenine–uracil (AU) base pairs from A-form geometry to a metallized m-form requires higher pH compared to the sequences comprised of guanine–cytosine (GC) base pairs is explained. This information can be useful for the development of possible technological applications based on m-DNA.
Effect of Zn(2+) ions on the conformation of single-stranded polynucleotides polyU and polyC in a wide temperature range at pH 7 was studied by differential UV spectroscopy and by thermal ...denaturation. The atoms coordinating Zn(2+) ions were determined (O4 and N3 in polyU and N3 in polyC). A three-dimensional phase diagram and its two-dimensional components were constructed for a polyC-Zn(2+) system. The phase diagram revealed a region in which ordered single-stranded structures, stabilized by Zn(2+)-mediated cross-links involving N3 atom of cytosine, are formed. The phase diagram also demonstrated that the behavior of the polyC-Zn(2+) system is similar to the effect of retrograde condensation observed in some binary solutions of simple liquids. A dependence of Zn(2+)-polyC binding constant on the metal ion concentration was obtained. The reason why zinc-induced transition of the sequences with adenine-uracil (AU) base pairs from A-form geometry to a metallized m-form requires higher pH compared to the sequences comprised of guanine-cytosine (GC) base pairs is explained. This information can be useful for the development of possible technological applications based on m-DNA.
An ultrafast front-end preamplifier-discriminator chip called NINO has been developed for use in the ALICE time-of-flight detector. The chip has eight channels. Each channel is designed with an ...amplifier with less than 1-ns peaking time, a discriminator with a minimum detection threshold of 10 fC and an output stage. The output pulse has minimum time jitter (less than 25 ps) on the front edge, and the pulsewidth is dependent of the input signal charge. Each channel consumes 27 mW, and the eight channels fit in a 2/spl times/4 mm/sup 2/ ASIC processed in IBM 0.25-/spl mu/m CMOS technology.
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