Detector Sensitive Area Research Articles

AUTOMATED DESIGN OF KORSCH ORTHOSCOPIC ASPHERICAL MIRROR TELESCOPES FOR NANOSATELLITES

This study presents the results of an automated parametric synthesis of a series of orthoscopic aspheric optical systems of mirror telescopes with different focal lengths, built according to the Korsch scheme. In order to ensure compactness of the design, these systems consist of three second-order aspheric mirrors and three folded flat mirrors. The obtained optical systems have a focal length ranging from 480 mm to 960 mm, an angular field of view ranging from 1.2° to 2.4°, an aperture number ranging from 6 to 12, an entrance aperture with a diameter of 80 mm, and an axial length of no more than 170 mm, which is within the dimensions of a 2U CubeSat. The maximum linear size of the image detector's sensitive area is 20 mm in all considered systems. The mirror telescopes do not have chromatic aberrations, enabling the capture of images within the visible spectrum and multiple infrared sub-bands. The provided aberration analysis demonstrates the high image quality of the considered optical systems. Specifically, for a wavelength of 0.546 μm, thediffraction modulation transfer function values both in the meridional and sagittal planes across the entire field exceed 0.53 for a spatial frequency of 30 mm-1, and 0.3 for a spatial frequency of 50 mm-1. The maximum relative distortion in the designed systems is 0.005%, corresponding to an absolute displacement of 0.5 μm. The presented telescopes are capable of covering an observation band of Earth's surface with linear dimensions ranging from 12.6 km to 25.1 km when a satellite track height is 600 km. By applying multi-element image detectors with a pixel size of 5 μm and achieving diffraction-limited image quality in the optical systems, both the geometric and diffraction resolution limits on Earth's surface will not exceed 10 m.

Superconducting photon counter for nanophotonics applications

We develop large area superconducting single-photon detector SSPD with a micron-wide strip suitable for free-space coupling or packaging with multi-mode optical fibres. The detector sensitive area is 20 μm in diameter. In near infrared (1330 nm wavelength) our SSPD exhibits above 30% detection efficiency with low dark counts and 45 ps timing jitter.

Achieving a large detector sensitive area of short magnetic focusing pulse-dilation framing tube using a combination lens

A modified short magnetic focusing pulse-dilation framing tube was developed base on imaging characteristic of solenoid lens and short magnetic lens, by which a combination lens composed of two magnetic lenses with a soft iron shield. The spatial performance is simulated by Runge–Kutta method and the imaging distribution of electrons. The detector sensitive area and spatial resolution is measured using Au photocathode with a UV-ray mask and ultraviolet source. When the magnetic field strengths on the axis close to photocathode and microchannel plate were 31 and 56 G, respectively, and the electron image had 2:1 demagnification, the measured detector sensitive area is Φ45 mm and the spatial resolution is about 207 μm. The spatial performance parameter was satisfied the ICF requirement.

A method to calculate the gamma ray detection efficiency of a cylindrical NaI (Tl) crystal

Given a wide range application of NaI(Tl) detector in industrial and medical sectors, computation of the related detection efficiency in different distances of a radioactive source, especially for calibration purposes, is the subject of radiation detection studies. In this work, a 2in both in radius and height cylindrical NaI (Tl) scintillator was used, and by changing the radial, axial, and diagonal positions of an isotropic 137Cs point source relative to the detector, the solid angles and the interaction probabilities of gamma photons with the detector's sensitive area have been calculated. The calculations present the geometric and intrinsic efficiency as the functions of detector's dimensions and the position of the source. The calculation model is in good agreement with experiment, and MCNPX simulation.

Operation of the triple-GEM detectors in the tagging system of the KEDR experiment on the VEPP-4M collider

The tagging system (TS) of the KEDR detector is designed for study of two-photon interactions on the VEPP-4M electron-positron collider. The upgrade of the TS was completed and 8 triple-GEM detectors were added to the system with a single detector sensitive area up to 250*100 mm2, a spatial resolution in the beam orbit plane close to 70 μm and a small angle stereo readout providing a resolution of around 200 μm in perpendicular direction. The triple-GEM detectors were included into the KEDR DAQ system, and since the beginning of the 2010-2011 season they have demonstrated stable operation at a gas gain of 20000–40000 and efficiency of 95–97%. The new detectors will allow performing background suppression and improving the energy resolution of the system.

Development of a multiwire position sensitive proportional counter

Preliminary measurements in a proportional counter with two independently counting wires have shown that counting rates up to 106 counts/s per wire can be reached without critical loss in the ?true versus measured? linearity relation. In this paper, a gas-flow multiwire proportional counter designed and constructed in Iran, is presented. Results obtained with a fabricated detector, containing 32 Ni-chromic anode wires, are shown. Each wire is associated with a fast pre-amplifier and a discriminator channel. Counting rates of over 107 events per second are measured. The diameter, length, and resistance per unit length of anode wires are 35 ?m, 3 cm and 10 ?/m, respectively. The cathode is constructed of two fiber glass printed sheets of 4 x 12cm2 dimensions. In this detector, P10 gas (10% of methane and 90% of argon) is used. The volume of the detector sensitive area is 24 cm3. Detector signals are analyzed carefully through data acquisition systems (MCA, amplifier and preamplifier). Our study indicates that the present detector is a position sensitive detector and that the obtained position sensitivity resolution of this instrument is 3.5 mm.

A prototype coordinate detector based on granulated thin-walled drift tubes

A prototype detector based on thin-walled segmented tubes has been developed and its parameters have been studied. The detector contains 360 registration channels with a straw diameter of 4 mm. The prototype’ granularity is 4 сm 2 and the length of insensitive region due to straw internal elements is less than 5% of its full sensitive area. Deterioration of the spatial resolution near these elements is observed for 1.0% of the detector sensitive area. The time and spatial parameters of the detector do not differ from those of conventional tracking detectors based on drift tubes.

Signal transmission lines for large-size segmented straw detectors

Lines for transmitting the signals of high-granulated coordinate straw detectors from the detector sensitive area to the remote readout electronics are simulated, and samples of these lines are investigated. The possibility of transmitting the signals using lines with a length of up to 2 m without distortions is shown. These lines can also be used to supply a high voltage of up to 3 kV to the straw segments with negligible leakage currents.

The CMS Silicon Strip Tracker

The CMS strip tracker is the first large scale tracker entirely based on silicon detector technology. It consists of 198 m 2 of detector sensitive area instrumenting the inner region of the experiment with a pseudo-rapidity coverage of | η | < 2.5 . This instrument, together with a silicon pixel system, is expected to perform robust tracking and detailed vertex reconstruction while embedded in the LHC high radiation and high luminosity environment. The project is in a well advanced construction phase: the detector module production is completed, the integration of the single components into large sub-detector units is underway and the full tracker commissioning is about to start. In this paper, after a description of the tracker layout, detector modules production overview and a summary of the integration procedures for the inner barrel part of the tracker will be reported.

Fast X-ray/γ-ray imaging using electron multiplying CCD-based detector

Abstract New designs of electron multiplying charge coupled devices (EMCCDs) combine superior spatial resolution and low noise of a conventional CCD with the internal gain of an avalanche photodiode (APD). The presence of internal gain not only enhances the device sensitivity, but virtually eliminates the read noise associated with current CCDs, even when the device is read at very high frame rates of 100 frames per second or higher. Thus, the EMCCDs can simultaneously provide very high sensitivity and a high signal-to-noise ratio (SNR). At RMD we are exploiting these properties of EMCCD for use in radionuclide and X-ray imaging. Specifically, we have developed a system that makes use of an EMCCD with 512 × 512, 16 × 16 μm pixels. Special fiberoptic reducers have been designed to enhance the detector sensitive area. The system gain is software selectable and may be varied from 1 to 1000. This paper describes the detector design along with its γ-ray/X-ray imaging performance.

Real time /spl beta/-imaging with silicon hybrid pixel detectors: kinetic measurements with C-14 amino acids and P-32 nucleotides

We present some additional results obtained with the BETAview system, a digital system for real time /spl beta/-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. We describe the system assembled with a Si detector, 300-/spl mu/m thick, segmented into 64 /spl times/64 square pixels with 170-/spl mu/m pitch. The solid-state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1 Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e/sup -/ (corresponding about 5 keV in Si), and contains a 15-bit counter. The detector sensitive area is about 1 cm/sup 2/, but several detectors could be assembled in arrays. The measured background counts were about 3.5/spl times/10/sup -2/ cps/cm/sup 2/, which implies a very high sensitivity of the device. The detection threshold used in this experiment was /spl sim/15 keV. We show the results obtained in the real-time monitoring of two biological dynamic processes: an amino acid uptake by living cells and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([/sup 14/C]L-Leucine) into Octopus vulgaris eggs cells. The results, described in Section III-B, show that after about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. In Sections III-C and III-D, we also describe the successful performance of the /spl beta/-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different /sup 32/P-radiolabeled nucleotides.

KPIX: a pixel detector imaging chip

We present a VLSI custom device, named KPIX, developed in a 0.6 μm CMOS technology. The circuit is dedicated to readout solid-state detectors covering large areas (on the order of square centimetre) and featuring very small currents. KPIX integrates 1024 channels (current amplifiers) and 8 ADCs on a 15.5×4 mm 2 area. Both an analogue and digital readout are allowed, with a 10 bit amplitude resolution. Amplifiers are organized in 8 columns of 128 rows. When choosing the digital or the analogue readout, the complete set of channels can be read out in about 30 ms. The specific design of the amplification cells allows to measure very small input current levels, on the order of fractions of pico-ampere. Power consumption has also been kept at the level of 80 μW per cell and 150 mW (peak value) in total. The specific chip architecture and geometry allow use of many KPIX circuits together in order to serve a large detector sensitive area. The KPIX structure is presented along with some measurements characterizing its performance.

The CMS silicon strip tracker

Abstract The CMS strip tracker is the first large scale tracker entirely based on silicon detector technology. It consists of 198 m 2 of detector sensitive area instrumenting the inner region of the experiment with a pseudo-rapidity coverage of | η | 2.5 . This instrument, together with a silicon pixel system, is expected to perform robust tracking and detailed vertex reconstruction while embedded in the LHC high radiation and high luminosity environment. The project is in a well advanced construction phase: the detector module production is completed, the integration of the single components into large sub-detector units is underway and the full tracker commissioning is about to start. In this paper, after a description of the tracker layout, detector modules production overview and a summary of the integration procedures for the inner barrel part of the tracker will be reported.

The application of the curved-grid technique to a gas proportional scintillation counter with a small-diameter photo-multiplier tube

The curved-grid technique was developed to maintain the superior performance of large-area gas proportional scintillation counters (GPSCs) without resorting to complex and bulky focusing systems or large photomultiplier tubes (PMTs) for applications in energy-dispersive X-ray fluorescence analysis. The technique is a simple method to compensate for the variation in solid angle viewed by the PMT as a function of the radial distance from the cylindrical axis of the detector. The feasibility of the technique is demonstrated in a GPSC, by measuring the energy resolution as a function of entrance window diameter. With a properly shaped curved grid, no degradation in detector energy resolution is observed even when the effective detector sensitive area is increased approximately six-fold. The maximum ratio of detector entrance window to PMT diameter achieved thus far is approximately 0.75.

The optical/UV filters for the EPIC experiment

EPIC, the European Photon Imaging Cameras is an experiment based on cooled CCDs on board the ESA X-ray Multi Mirrors satellite due to be launched in 1999. Since CCD's are sensitive to radiation other than X-rays, namely Optical and UV light, filters are necessary to prevent this radiation from reaching the detector sensitive area. Three types of filters were developed, to be used alternatively depending on target source. Here we report on the medium and thin filters developed by MOXTEK Inc. in Orem, Utah, while the thick ones, developed at the Max-Planck-Institut fur Extraterrestrische Physik (MPE, Germany) have been described elsewhere. The two filters, described here, have a 1600 /spl Aring/ Polyimide substrate coated with 400 /spl Aring/ and 800 /spl Aring/ aluminium for the thin and medium filter, respectively. After manufacturing, the filters have been submitted to an intensive qualification and calibration programme at MOXTEK. Further calibrations, transmission measurements and performance stability, have been carried out or are in progress at one of the EPIC Institutes (Osservatorio Astronomico di Palermo).

Two-dimensional position-sensing PVDF dust detectors for measurement of dust particle trajectory, velocity, and mass

We have extended our development of polyvinylidene fluoride (PVDF) dust detectors to include the capability for determination of the x, y coordinates of particle entry into the PVDF detector. The two-dimensional position-sensing PVDF dust detectors ( x, y detectors) we have developed employ resistive charge division, and have a set of conducting strips on the front surface and an orthogonal set on the back surface. Our earlier measurements on PVDF x, y detectors made use of a laser to simulate dust particle impacts. These measurements have recently been extended to include impacts from accelerated dust particles. Two 6 μm thick 58 cm 2 PVDF x, y detectors were placed in a telescope arrangement for measurement of particle time-of-flight, trajectory and fragmentation. We present the dust particle results and show that dust particle impact coordinates are measured by the PVDF x, y detectors with typical errors of −1−3 mm for x and y (over most of the detector sensitive area), confirming the results obtained with the laser. We also show that the model we developed earlier to describe signal pulse generation and the occurrence of anomalous currents (i.e., polarity reversal with time) in Si x, y detectors responding to energetic charged nuclei also applies to PVDF x, y detectors responding to hypervelocity dust particles. Finally, we show that even if particle fragmentation occurs upon penetration of the first x, y detector, particle trajectory is still measured, but with a larger position error (∼ 4–6 mm) in the second x, y detector due to the spread of fragment impact positions on the second x, y detector.

Forum

Spectral characteristics of bulk extrinsic photo-conductive detectors have been measured under conditions that only partially illuminated the photo-sensitive areas. The data presented were obtained at background photon flux levels of 10" to 10" photons/sec-cm'. The geometry of the detectors was such that the applied electric field was perpendicular to the incident radiation. Substantial changes in spectral responsivity have have been measured. These changes are dependent upon which portion of the detector's sensitive area is illuminated.