Search results for "width [beam]"
showing 10 items of 168 documents
Detector blockbased on arrays of 144 SiPMs and monolithic scintillators: A performane study
2015
[EN] We have developed a detector block composed by a monolithic LYSO scintillator coupled to a custom made 12 12 SiPMs array. The design is mainly focused to applications such as Positron Emission Tomography. The readout electronics is based on 3 identical and scalable Application Specific Integrated Circuits (ASIC). We have determined the main performance of the detector block namely spatial, energy, and time resolution but also the system capability to determine the photon depth of interaction, for different crystal surface treatments. Intrinsic detector spatial resolution values as good as 1.7 mm FWHM and energies of 15% for black painted crystals were measured. & 2014 Elsevier B.V. All…
High-resolution positron lifetime spectrometer with BaF2 scintillators
1987
In this communication we report on a design of a fast coincidence positron lifetime spectrometer, which is based on single crystal barium fluoride (BaF2) scintillators. A good time resolution (190ps, FWHM), combined with a high efficiency, has been obtained in the normal experimental set-up (with cathode earthed in the photo multipliers). The pile-up effect is observed to disturbe the measured lifetimes in the 180 degree geometry due to the high detection efficiency of the BaF2 scintillator.
Improving the performance of CdZnTe detectors using infrared stimulation
2011
The influence of monochromatic optical stimulation with wavelengths from 400 nm to 1100 on characteristics of the CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light of wavelengths (870–900 nm) close to the absorption edge of the CdZnTe significantly improves the detectors performance at room temperature. Improvement can be achieved with low-intensity IR illumination of about 1–10 µW. The higher intensity illumination leads to degradation of the detector spectrometric characteristics. Infrared radiation penetrates into the detector sensitive volume, change the balance equilibrium between free and trapped carriers, leading to improve char…
A walk-free centroid method for lifetime measurements with pulsed beams
1978
Abstract A delayed-coincidence lifetime measurement method based on a comparison of walk-free centroids of time spectra is presented. The time is measured between the cyclotron rf signal and the pulse from a plastic scintillation detector followed by a fixed energy selection. The events to be time-analyzed are selected from the associated charge-particle spectrum of a silicon detector which is operated in coincidence with the scintillator, i.e. independently of the formation of the signal containing the time information. With this technique, with the micropulse fwhm of typically 500 to 700 ps, half-lives down to the 10 ps region can be measured. The following half-lives are obtained with th…
Control of the speed of a DC motor by employeeing pulse width modulation (PWM) technique
2009
This paper is mainly focused on the technique of pulse width modulation for controlling the speed of a 12 volt DC motor more efficiently. A potentiometer was used to generate a wide variety of pulses. The output of the controlling circuit (Pulse Width) was connected to the second circuit as input for direction control. Here a single push switch was used to change the state (stopforward-stop-reverse) of the DC motor. These two circuits were combined into one for ease of use. Third circuit was designed to measure the speed of the motor by employing an opto-electronic sensor, an amplifier and a two blade fan to interrupt the signal transmission of the sensor. Finally, the output of the sensor …
Towards direct measurements of remitted photon path lengths in skin: kinetic studies in the range 520-800 nm
2019
Skin-remitted picosecond laser pulses have been detected at variable input-output fiber distances (8 … 20 mm) in the spectral range 520-800 nm, with subsequent analysis of the pulse shape changes. Transfer functions representing the temporal responses of remitted photons to infinitely narrow δ-pulse excitation have been calculated. Parameters related to the photon path length in skin – input-output pulse peak delays, pulse FWHM, travel times of the “initial” photons and distributions of the remitted photon path lengths – are presented and analyzed. The measurement results are in general agreement with the photon propagation model expectations
Perturber's charge effect on Stark broadened hydrogen lines in helium plasmas
2002
Abstract The Stark line profiles for hydrogen Ly α , Ly β , Hα, and Hβ are calculated using the computer simulation method for helium plasmas in the range of electron concentration from 1018 to 10 19 cm −3 at increasing temperature values kT from 7 to 10 eV , according to the experimental measurements in dense plasmas (Bochum experiment). The calculation was carried out at two limiting assumptions about the perturbers: (a) in the helium plasma only singly ionized helium ions occur, and (b) in the plasma the doubly ionized ions exclusively exist. In the paper the ratio of the calculated full half-widths, FWHM(b)/FWHM(a), for these lines are presented. The ratio equals about to 1.1 for Lyβ an…
A three-colour scheme to generate isolated attosecond pulses
2009
We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 × 1014 W cm−2 and of wavelength λ = 820 nm, and two properly chosen weak lasers with wavelengths 1.5λ and 0.5λ. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.
Reconfigurable RF waveform generation using optical incoherent sources
2008
An RF waveform generator operating with incoherent broadband light is successfully implemented. Complex RF ~10 GHz bandwidth waveforms are generated by means of incoherent wavelength-to-time mapping. Our technique can be scaled to the mm-wave range.
Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors
2007
A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm x 1.4 mm pads arranged in a 32 x 16 array. The silicon detector…