Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Studies of the Response Speed of Silicon Surface Barrier Detectors, When Irradiated with Different Particles

Abstract: The rise time of produced surface barrier detectors fort?-particles, fission fragments and conversion electrons was measured with and without over-voltage and compared with calculations. The detectors were produced from n-type silicon with resistivities in the range, 250?cm to 9000 ?cm. The best rise times, ?(0-63%), obtained up to now, are ?0.8 ns for alphas (241Am) and 1.4 ns for fission fragments (252Cf) at high fields (system rise time, ??0.6 ns included). The contribution of the plasma time, ?p, due to the erosion of the ionisation tracks with their high carrier density by the field was studied in some more detail. ?p vs. Em (effective field), derived from the rise time measurements, seems to be a relatively pure exponential dependence, ?p ? k Em-n, Por a given detector at fields greater than 500 V/cm (0.7 < n < 1.3). 'k' is a constant, dependent on particle type. With fission fragments from 252Cf the time jitter of correlated fragments in selected energy ranges was measured by irradiating two detectors in a wide angle (sandwich counter). A minimum jitter (F.W.H.M.) of 90 ps was reached for threshold detection. Zero crossing circuitry was also used for time detection to have an idea of the probable pulse shape jitter from fragments irradiating a detector under different angles. (Different orientation of the particle track with respect to the field). Such jitter seems to exist, also at relatively high fields.

Ultra-fast all-optical 2-to-4 decoder based on a photonic crystal structure

Abstract: In this paper, a photonic crystal structure based on nonlinear cavities has been proposed to improve the time response of a 2-to-4 decoder. The structure includes an array of chalcogenide rods with an air gap in which the spatial period of rods is 500 nm. The radius of the fundamental rods is assumed to be 125 nm, which results in a photonic bandgap of 1092–1724 nm at TM mode. Three cavities, including the nonlinear rods with a Kerr coefficient of 10−14m2/W, drop the incoming waves concerning the amount of optical intensity. The finite-difference time-domain method was used to calculate the components of the electric and magnetic fields throughout the structure. The time analysis of the device shows the rise time is equal to 200 fs, which is less than one for the previous structures. The area of 110µm2 and the margins of 4% and 88% for logics 0 and 1 are other advantages of the proposed structure. Based on the obtained results, it was proven that the performance of the 2-to-4 photonic crystal-based decoder has been improved by this work.

All-optical analog to digital converter based on nonlinear photonic crystal ring resonators

Abstract: Optical analog to digital conversion is very important for implementing all-optical data processing systems. In this study, we designed an all-optical analog to digital converter using photonic crystal nonlinear ring resonators. The main goal of this study was to design an optical analog to digital converter with no upper limit for the input optical intensity when generating “11” codes at the output ports. Simulation results showed that the maximum rise time for the proposed structure is about 1.5 ps

A high-speed low-noise CMOS 16-channel charge-sensitive preamplifier ASIC for APD-based PET detectors

Abstract: A high-speed low-noise 16-channel amplifier integrated circuit (IC) has been fabricated in a 0.5 /spl mu/m CMOS process. It is a prototype for use with a PET detector that uses a 4/spl times/4 avalanche photodiode (APD) array having 3 pF of capacitance and 75 nA of leakage current per pixel. The preamplifier must have a fast rise time (a few ns) in order to generate an accurate timing signal, low noise in order to accurately measure the energy of the incident gamma radiation, and high density in order to read out 2-D arrays of small (2 mm) pixels. A single channel consists of a charge-sensitive preamplifier followed by a pad-driving buffer. The preamplifier is reset by an NMOS transistor in the triode region which is controlled by an externally supplied current. The IC has 16 different gain settings ranging from 2.1 mV/fC to 10.7 mV/fC. The gain is determined by four switched capacitors in the feedback loop. The switch state is set using a 64-bit shift register. A preamplifier 10%-90% rise time as low as 2.7 ns, with no external input load and 3.6 ns with a load of 5.8 pF was achieved. For the maximum gain setting and purely capacitive (5.8 pF) input load, the amplifier had 400 electrons root mean square (rms) noise at a peaking time of 0.7 /spl mu/s. When loaded with an APD pixel (/spl sim/3 pF capacitance, 125 nA leakage current), a noise minimum of 1550 electrons rms at a peaking time of 0.1 /spl mu/s is achieved. The IC is powered by a +3.3 V supply drawing 60 mA.

High-speed long-wavelength optical modulation in InGaAs/InAlAs multiple quantum wells

Abstract: A long-wavelength optical modulator has been fabricated which makes use of an electroabsorption effect in multiple quantum wells (MQWs). Here, InGaAs/InAlAs MQWs are prepared in a PIN configuration using molecular beam epitaxy (MBE). The rise time of the detected pulse modulation signal has been measured at 190 ps. This response level has been attributed to the detecting system response and RC time constant, and not to such intrinsic effects as carrier lifetime.