126 research outputs found
Comportamento criogenico di dispositivi optoelettronici per la trasmissione di segnali analogici mediante fibre ottiche
No full textLa trasmissione di un segnale analogico via fibra ottica è tematica di interesse per rivelatori criogenici operanti in strumenti basati a terra oppure imbarcati su satellite. Per meglio comprendere le performance criogeniche dei links ottici analogici, abbiamo investigato il comportamento a bassa temperatura di IR LEDs in AlGaAs, fotodiodi PIN e al Si e di fotodiodi a valanga (APD). I LED al AlGaAs hanno dimostrato un notevole incremento della responsività a 77K e la caratteristica luce-corrente diviene lineare anche se operati a bassa corrente. Al contrario i fotodiodi PIN e al Si mostrano un degrado delle performance quando raffreddati. A 77K, gli APD mostrano invece una responsività pari a quando operati a 300K, ma con una marcata riduzione della tensione di polarizzazione inversa
Cryogenic behaviour of optoelectronic devices for the transmission of analog signals via fiber optics
No full textThe transmission of analog signals via fiber optics is a subject of interest for applications with detectors operating at cryogenic temperature, at ground or on space borne instruments. For those detectors, both thermal and galvanic decoupling shall be required. For a better understanding of the cryogenic performance of cooled optoelectronic devices, we have investigated an infrared AlGaAs LEDs, a Si p-i-n photodiode, a Si photodiode, and an avalanche photodiode (APD). Results of a study related to the photodiode's dark currents at low temperature is presented. In fact, we have clearly measured a strong reduction of the dark current when these devices are cooled dow
Low-noise, transformerless front-end electronics for moderate and high capacitance calorimeters
No full textA charge-sensitive preamplifier showing very low power consumption was developed in two versions: the first using a JFET SNJ903L has a matching capacitance of 310 pF whereas the second one employing a SNJ3600L has 1100 pF. Both versions have a charge sensitivity of 8 μV/e−. The rise time is lower than 200 ns for both low and high capacitance versions at an input capacitance of 1000 and 3000 pF respectively. The low capacitance version has an equivalent noise charge of 220 e− rms at 0 pF for a CR-(RC)2 shaping at 10 μs shaping time. The noise at 1 μs is 510 e− rms at 0 pF and the noise slope is 1.59 e−/pF. The high capacitance version exhibits 400 e− rms at 0 pF and 10 μs shaping time. At 1 μs the equivalent noise charge is 1100 e− rms and the noise slope is 0.91 e−/pF. The second stage uses operational amplifiers of 16 MHz gain-bandwidth product and is prepared to make a differentiation with pole-zero cancellation if required. The final stage provides a differential output with 50 ω output impedance and can drive a 100 ω twisted pair cable loaded with its characteristic impedance. The total power dissipation is 190 mW for the SNJ903L version whereas the SNJ3600L version dissipates 265 mW. Both versions use ±6 V. The circuit is mounted using thick film technology onto a 20×50 mm2 ceramic substrate. The project is complemented with the design of a 3000 V, 24 pF/m coaxial cable for detector biasing and signal transport with minimum contribution to the ENC
The Optically-Coupled Current-Mirror: a Novel Approach for Linear Transmission of Fast Analogue Signals via Fiber Optics
No full textWe report recent improvements in the performance of a novel circuit topology, the optically-coupled current-mirror (OCCM), that includes optical links in its feedback and forward paths. In this way the input-stage remains Galvanically isolated from the rest of the circuit. The input stage consists on a passive dipole composed only by two components: a LED and a photodiode connected back-to-back. When it is cooled down, eventually close to 77 K, the optical power versus LED-current characteristics assumes a perfectly linear law and the open-loop gain increases by a factor at least x 2, due to the increase of the LED responsivity. The input stage can be connected in series with the anode of different types of ionizing detectors. Originally conceived and operated with success for the readout of the DC component of PMTs biased with cathode grounded, the OCCM has now been optimized for the transmission of fast analogue signals. At present the signal bandwidth approaches 32 MHz. The dynamic range can reach large values by connecting two or more input stages in series, each one associated to a single channel with appropriate gain. To be noted that the only semiconductor devices eventually subject to radiation damage are the LED and the photodiode of the input stage. In this paper we describe recent achievements of the OCCM, and discuss the latest results obtained
The baroque stucco plasterer Matteo Camin. The genesis of stucco work in Styria between 1627 and 1673
No full textDie Dissertation behandelt Leben und Werk des Barockstuckateurs Matteo Camin (um 1603-1673), der zwischen 1627 und 1673 einer der bedeutendsten Meister Innerösterreichs war. Einleitend wird die innerösterreichische Hofkunst ab ca. 1580 mit dem Fokus auf den barocken Stuckdekor beleuchtet, weiters wird ein Einblick in die Stucktechnologie gewährt und auf die Genese der frühbarocken Ornamentformen hingewiesen, die sich auch im Schaffen Camins deutlich erkennen lässt. Der nachfolgende Abschnitt widmet sich der Biografie und Werkstatt des Meisters. Den Schwerpunkt der Dissertation bildet die Einteilung von Camins Oeuvre in fünf Rubriken. Zuerst erfolgt die Werkbesprechung der fünf urkundlich gesicherten bzw. überlieferten und erhaltenen Stuckdekorationen. Anhand dieser Werke wird Camins Personalstil ermittelt, der als Basis für die weiteren stilkritischen Untersuchungen dient. Das folgende Kapitel umfasst elf Stuckarbeiten, die stilistisch Camin zugewiesen werden können. Im Anschluss werden neun offene Zuschreibungen behandelt, welche sich nicht eindeutig dem Meister bzw. seiner Werkstatt zuordnen lassen. Drei Stuckaturen werden, entgegen früheren Expertenmeinungen, von der Dissertantin nicht zu Camins Schaffen gezählt, da stilistische Übereinstimmungen mit den gesicherten Werken fehlen. Im Schlusskapitel wird auf drei nicht mehr existierende Stuckdecken eingegangen. Abgesehen von den sieben urkundlich gesicherten bzw. überlieferten Werken, von denen zwei heute nicht mehr existieren, kann das Oeuvre Camins auf achtzehn Stuckausstattungen erweitertet werden. Entgegen dem bisherigen Forschungsstand kommt die Dissertantin zu dem Ergebnis, dass aufgrund der stilkritischen Untersuchungen neun offene Zuschreibungen und drei Abschreibungen vorgenommen werden müssen. Somit kommt es zu einer Neuordnung der Werke Camins.The dissertation examines the life and work of the baroque stucco plasterer Matteo Camin (around 1603-1673), who was one of the most significant Inner Austrian masters in his field between 1627 and 1673. An examination of Inner Austrian court art from around 1580 onwards, with a focus on baroque stucco decoration, as well as an insight into stucco technology are highlighted in the introduction; furthermore, the genesis of early baroque ornamental forms, which are distinctively recognisable in Camin´s work, is discussed in the opening. The subsequent chapter is devoted to the master´s biography and workshop. The emphasis of the dissertation is the classification of Camin´s oeuvre into five categories. At the beginning, the five surviving stucco decorations with documentary evidence are discussed. They serve to define Camin´s personal style, which is the basis for the subsequent style criticism. The next chapter includes eleven stucco works which can be stylistically attributed to Camin and the following chapter discusses nine works whose origin cannot be clearly determined. Three stucco decorations are, as opposed to previous categorisations by experts, not attributed to Camin, since their style does not correspond with the style of the stucco decorations with documentary evidence. In the final section three no longer existent stucco ceilings are discussed. Apart from the seven works with documentary evidence, from which two no longer exist, Camin´s oeuvre can be extended to eighteen stucco decorations. In contrast to previous research done on Matteo Camin the author comes to the conclusion that nine formerly open works have to be added to and three works have to be taken off Camin´s oeuvre. Consequently, this leads to a rearrangement of his works.eingereicht von Susanne Aloisia GinnerAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassungen in dt. und engl. SpracheGraz, Univ., Diss., 2014 1109
Performance of the optically-coupled current-mirror with its input stage cooled to cryogenic temperature
No full textThe Optically-Coupled Current-Mirror (OCCM) is a novel feedback circuit architecture that allows linear transmission of analog signals via optical fibers. Its most distinctive feature is that the input stage is Galvanically isolated and passive, as it consists just on the back-to-back connection of a LED and a photodiode. Only those components are required to be in close contact with the detector, and no power supply is required to be brought to the input stage. All active components are located at a safe distance, therefore saving them from being exposed to radiation, as it is common in most experiments at particle accelerators. We have investigated the properties of the OCCM when its passive input stage is cooled to cryogenic temperatures. Results have been extremely interesting as, for instance, the sharp increase in open-loop gain observed when cooling to 77 K, due to an enhanced LED efficiency. This translates into a higher dynamic range and still better linearity, opening new opportunities for the transmission of current signals generated in cryogenic detectors
Cryogenic ASICs in GaAs for Applications with Particle Detectors
No full textWe present two cryogenic Application Specific Integrated circuits (ASIC's) realized with a GaAs MESFET process. A single-channel differential or double-channel single-ended voltage sensitive preamplifier for 4.2 K operation, to be used with bolometric detectors, was realized and tested. A very simple structure working as a unity gain buffer or as a transconductance amplifier, or even as a shaping filter was tested in view of an application with a fast particle detector operated at liquid Argon temperature
Improvements in dynamic and 1/f noise performances of GaAs MESFETS at cryogenic temperatures by using a monolithic process
No full textLow frequency noise versus temperature spectroscopy of Ge JFETs, Si JFETs and Si MOSFETs
No full textWe have measured low frequency noise in Ge JFETs, Si JFETs and Si MOSFETs. By analyzing the data taken at different temperatures we have been able to determine the energy level and cross sections of traps that give origin to the Lorentzian noise components. To do that we have designed a HW/SW system capable to perform measurements between 4K-300K and to calculate the trap's parameters. Shallow levels have been identified in Ge JFETs. Lorentzian components have been identified in MOS noise spectra
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