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Nuclear Science, IEEE Transactions on

Issue 6 • Date Dec. 1999

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Displaying Results 1 - 25 of 39
  • A MCM-D-type module for the ATLAS pixel detector

    Page(s): 1861 - 1864
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB)  

    For the ATLAS experiment at the planned Large Hadron Collider (LHC) at CERN hybrid pixel detectors are being built as innermost layers of the inner tracking detector system. Modules are the basic building blocks of the ATLAS pixel detector. A module consists of a sensor tile with an active area of 16.4 mm/spl times/60.4 mm, 16 read out ICs, each serving 24/spl times/160 pixel unit cells, a module controller chip, an optical transceiver and the local signal interconnection and power distribution busses. The dies are attached by flip-chip assembly to the sensor diodes and the local busses. In the following a module based on MCM-D technology will be discussed and prototype results will be presented. View full abstract»

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  • Functional characteristics and radiation tolerance of AToM, the front-end chip of BaBar silicon vertex tracker

    Page(s): 1865 - 1870
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    The readout chip designed to process the microstrip signals in the BaBar Silicon Vertex Tracker (SVT), after being realized twice in a radsoft technology has been transferred into the final radhard process. So far the circuit has gone through four different radhard submissions, one aiming at providing a preliminary insight into the characteristics of the radhard chip, the other ones constituting pre-production and production runs. Chips from these submissions have undergone a thorough set of tests addressing functional aspects, noise parameters and effects of radiation on signal and noise behavior. The present paper discusses the results of these tests and describes the final version of the circuit which has been proven to successfully meet the experiment requirements. View full abstract»

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  • ASD IC for the thin gap chambers in the LHC Atlas Experiment

    Page(s): 1871 - 1875
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    An amplifier-shaper-discriminator (ASD) chip was designed and built for Thin Gap Chambers in the forward muon trigger system of the LHC Atlas experiment. The ASD IC uses SONY Analog Master Slice bipolar technology. The IC contains 4 channels in a QFP48 package. The gain of its first stage (preamplifier) is approximately 0.8 V/pC and output from the preamplifier is received by a shaper (main-amplifier) with a gain of 7. The baseline restoration circuit is incorporated in the main-amplifier. The threshold voltage for discriminator section is common to the 4 channels and their digital output level is LVDS-compatible. The IC also has analog output of the preamplifier. The equivalent noise charge at input capacitance of 150 pF is around 7500 electrons. The power dissipation with LDVS outputs (100 /spl Omega/ load) is 59 mW/ch. View full abstract»

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  • Noise analysis of a pulse processor using SPICE

    Page(s): 1876 - 1879
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    We describe a technique, simpler than earlier ones, for using SPICE in the computation of the 1/f, step, and delta noise indices of linear and time-valiant filters. The method is based on obtaining a weighting function from the results of simulation and is demonstrated for triangular and trapezoidal shapers. The results are compared with those obtained by direct calculation. The greatest discrepancies occur when the method is applied to gated integrators, but the errors are probably due to artifacts not related to the basic method described here. View full abstract»

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  • A compact readout system for multi-pixel hybrid photodiodes

    Page(s): 1880 - 1883
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    The excellent properties of the recently developed multi-pixel hybrid photodiodes (M-HPD) will be easier to exploit following the development of the new hybrid read-out circuits described in this paper. This system will enable all of the required read-out functions to be accommodated on a single board into which the M-HPD is plugged. The design and performance of a versatile system is described in which a trigger-signal, derived from the common-side of the silicon anode in the M-HPD, is used to trigger the readout of the 61-anode pixels in the M-HPD. The multi-channel amplifier section is based on the use of a new, commercial VLSI chip, whilst the read-out sequencer uses a chip of our own design. The common anode signal is processed by a fast amplifier and discriminator to provide a trigger signal when a single event is detected. In the prototype version, the serial analogue output data-stream is processed using a PC-mounted, high speed ADC. Results obtained using the new read-out system in a compact gamma-camera and with a small muon tracking-chamber demonstrate the low-noise performance of the system. The application of this read-out system in other position-sensitive or multi-anode photomultiplier tube applications are also described. View full abstract»

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  • Measurement of dose rate dependence of radiation induced damage to the current gain in bipolar transistors

    Page(s): 1884 - 1890
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    We report the study of radiation induced change in the current gain of bipolar transistors for three different gamma dose rates. The dose rates differed by a factor of 60 with the lowest dose to that anticipated for the LHC, and the highest at a rate we have been routinely using for radiation damage tests. The maximum dose attained was 200 kRad, which is high enough to compare with other measurements. The importance of annealing high dose rate data is demonstrated. View full abstract»

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  • Fast peak detector stretchers for use in XAFS applications

    Page(s): 1891 - 1893
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    In this paper we present two different design approaches to the implementation of fast peak detector-stretchers for X-ray absorption fine structure fluorescence applications (XAFS). After describing the motivations for using peak detector-stretchers in high rate applications, we discuss in detail the design and benefits of their use in a modern nuclear spectroscopy system. View full abstract»

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  • MICROMEGAS: high rate and radiation hardness results

    Page(s): 1894 - 1897
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    In this report, we present results of gain studies using various gas mixtures in a novel structure of a gaseous detector called MICROMEGAS which is under development at Saclay. We in particular studied the maximum of gain achievable with MICROMEGAS before the discharge. We tried various gas mixtures (argon, neon, CF/sub 4/) with various proportions of quencher (isobutane, cyclohexane, DME). We also studied the radiation hardness of MICROMEGAS using argon-isobutane and CF/sub 4/-isobutane mixtures. View full abstract»

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  • Absorption of electrons in xenon for energies up to 200 keV: a Monte Carlo simulation study

    Page(s): 1898 - 1900
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB)  

    Gas proportional scintillation counters are room-temperature, general-purpose X-ray detectors, which are used in many applications due to their good energy resolution, which can be better than standard proportional counters by a factor of /spl sim/2. However, for energies higher than /spl sim/20 keV, the experimentally measured energy resolution is found to deviate from the usual 1//spl radic/E law. Under these circumstances, it is of great interest to understand the mechanisms involved in the detection of higher energy X-rays. Since the photoelectrons will then carry most of the absorbed energy, we study in this work the response of xenon detectors to electrons with energies up to /spl sim/200 keV, using a Monte Carlo simulation technique. Distributions of the number of primary (subionization) electrons produced per parent electrons with energy E/sub e/ are calculated, and results are presented for the Fano factor, the w-value and the intrinsic energy resolution as a function of E/sub e/ in the range 20-200 keV. The influence of an applied reduced electric field on the results is assessed, showing that for 200 keV electrons an increase in the field from 0.1 to 0.8 Td causes an increase as high as 35% in the intrinsic energy resolution. View full abstract»

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  • Development of hybrid photon detectors with integrated silicon pixel readout for the RICH counters of LHCb

    Page(s): 1901 - 1906
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    We report on the ongoing work towards a hybrid photon detector with integrated silicon pixel readout for the ring imaging Cherenkov detectors of the LHCb experiment at the Large Hadron Collider at CERN. The photon detector is based on a cross-focussed image intensifier tube geometry where the image is demagnified by a factor of 4. The anode consists of a silicon pixel array, bump-bonded to a fast, binary readout chip with matching pixel electronics. The developments and tests of full-scale prototypes with 80% active area are presented. Specific requirements for pixel front-end and readout electronics in LHCb are outlined, and recent results obtained from pixel chips applicable to hybrid photon detector design are summarized. View full abstract»

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  • Neutron response functions for superheated droplet detectors

    Page(s): 1907 - 1912
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    Neutron response functions for superheated droplet detectors have been analyzed from threshold up to 2 MeV incident energy, taking into account a gradual threshold function, in terms of temperature and incident energy. A method for obtaining fitted parameters is described. Detection mechanisms up to 14 MeV are discussed. View full abstract»

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  • CAFNA/sup (R)/, coded aperture fast neutron analysis for contraband detection: preliminary results

    Page(s): 1913 - 1915
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    We have developed a near field coded aperture imaging system for use with fast neutron techniques as a tool for the detection of contraband and hidden explosives through nuclear elemental analysis. The technique relies on the prompt gamma rays produced by fast neutron interactions with the object being examined. The position of the nuclear elements is determined by the location of the gamma emitters. For existing fast neutron techniques, in pulsed fast neutron analysis (PFNA), neutrons are used with very low efficiency; in fast neutron analysis (FNA), the sensitivity for detection of the signature gamma rays is very low. For the coded aperture fast neutron analysis (CAFNA/sup (R)/) we have developed, the efficiency for both using the probing fast neutrons and detecting the prompt gamma rays is high. View full abstract»

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  • A new thermal neutron detector for protein crystallography

    Page(s): 1916 - 1919
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB)  

    A new position-sensitive detector is being developed for protein crystallography studies at a spallation source. Based on eight, independent, wire proportional chamber segments housed in a curved pressure vessel, the device covers a scattering angle of 120 degrees, and has a collecting area of 1.5 m by 20 cm. The position resolution will be about 1.3 mm FWHM, with a total counting rate in excess of one million per second. Timing resolution, essential for a spallation source application, is of order 1 /spl mu/s and provides neutron energy determination that is well suited for crystallography. Advanced features of this device include a digital centroid finding scheme, a seamless readout between segments, and a wire array design that minimizes anode modulation. Details of the mechanical design are given, together with digital centroid measurements that illustrate accurate, uniform response. View full abstract»

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  • Results from the SIFTER (Scintillating Fiber Telescope for Energetic Radiation) beam test apparatus

    Page(s): 1920 - 1924
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB)  

    The Scintillating Fiber Telescope for Energetic Radiation (SIFTER) is a large-area instrument concept for high-energy (E>10 MeV) gamma-ray astronomy. It takes advantage of the technology of fine (/spl sim/1 mm/sup 2/) plastic scintillating fibers in the context of a pair tracker/calorimeter telescope. In our on-going SIFTER research, we have developed a small test apparatus, consisting of 12 fiber planes, each with a potential active area of 10 cm/spl times/10 cm covered with a thin tantalum foil converter. This apparatus was tested in July, 1998 with high-energy photons (/spl sim/0.5-1.6 GeV) at the Thomas Jefferson National Accelerator Laboratory Hall B tagged gamma-ray facility. We report on results of the beam test, concentrating on comparisons with detailed Monte Carlo simulations of the instrument performance, including track reconstruction, angular resolution and detection efficiency. View full abstract»

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  • Scintillation light emission studies of LSO scintillators

    Page(s): 1925 - 1928
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    UV and /spl gamma/-ray excited luminescence and nuclear spectroscopy were used to study the relationship between the scintillation mechanisms of LSO and the spectroscopic characteristics obtained with PMT and APD readouts at room temperature. No correlation was found between scintillation decay time and light output. Like other investigators, we observed the existence of two distinct luminescence centers, Ce1 and Ce2, that mainly give rise to short (420 nm) and long (440 nm) emission wavelengths. Our measurements showed that different LSO crystals excited by /spl gamma/-rays have emission spectra with largely different shapes and maxima depending on the relative population and luminescence efficiency of these centers. It was also found that the poor energy resolution of LSO and YSO scintillators is well correlated with the coexistence of the two competing luminescence mechanisms. The prevalence of either Ce1 or Ce2 luminescence tends to reduce the variance of light emission and, thus, to improve energy resolution. Inversely, the coexistence of the two centers increases variance and degrades energy resolution. View full abstract»

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  • Development of a real-time radon monitoring system for simultaneous measurements in multiple sites

    Page(s): 1929 - 1933
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    A real-time radon monitoring system that can simultaneously measure radon concentrations in multiple sites was developed and tested. The system consists of maximum of four radon detectors, optical fiber cables and a data acquisition personal computer. The radon detector uses a plastic scintillation counter that collects radon daughters in the chamber electrostatically. The applied voltage on the photocathode for the photomultiplier tube (PMT) acts as an electrode for radon daughters. The thickness of the plastic scintillator was thin, 50 /spl mu/m, so as to minimize the background counts due to the environmental gamma rays or beta particles. The energy discriminated signals from the radon detectors are fed to the data acquisition personal computer via optical fiber cables. The system made it possible to measure the radon concentrations in multiple sites simultaneously. View full abstract»

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  • Temperature characteristics of the radiation detector using the TlBr crystals

    Page(s): 1934 - 1937
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (313 KB)  

    The radiation detector was fabricated from the TlBr crystals grown by the TMZ (travelling molten zone) method and the FWHM and transit time of electrons and holes were measured as a function of temperature. The TlBr radiation detector shows the best response characteristics at about 313 K (3.19 K/sup -1/) in cases where holes mainly contributed to the output pulses. However, for temperatures higher than 300 K (3.33 K/sup -1/), the FWHM for /sup 241/Am /spl alpha/-particles (5.48 MeV) becomes worse. An activation energy of about 0.90 eV has been deduced from the resistivity measurement. View full abstract»

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  • Moisture proof columnar cesium iodide (CsI) layers for gas avalanche microdetectors

    Page(s): 1938 - 1942
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    Cesium iodide columnar layers having a diameter of /spl ap/3 /spl mu/m, and wall spacing of /spl ap/1 /spl mu/m act as secondary electron emitters and can be used for detection of radiation: charged particles, X-rays and gamma rays. With a large enough electric field across the columnar layers, /spl ap/400 /spl mu/m in thickness, gas avalanche gain is evident when placed in a suitable gas, such as P10 or argon-ethane mixtures. The cesium iodide columns are damaged by ambient moisture. This damage can be prevented by evaporating protective layers of insoluble, low boiling point inorganic materials, such as mercuric iodide. Columnar layers with 20 nm coatings of mercuric iodide yield more than 30000 electrons on average when traversed by electrons from a /sup 90/Sr beta source. View full abstract»

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  • Analysis and characterisation of the confining mechanism of the controlled-drift detector

    Page(s): 1943 - 1947
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (441 KB)  

    The controlled-drift detector is a recently designed position-sensing X-ray detector. It operates by switching between integration and drift mode. The basic idea is to generate potential wells within the otherwise linear drift potential. During the integration mode signal electrons are being accumulated within these wells. The removal of the barriers in an externally controlled way restores a uniform drift field that sweeps the electrons towards the readout anodes. The height of the confining barrier depends on the drift field and on the amplitude of the potential perturbation at the surface. An experimental study of the charge handling capability has been carried out as a function of the amplitude of the surface perturbation (up to 2.1 V) and as a function of the drift field (250-400 V/cm). The study provides a sensitive measurement of the actual potential barrier of the integration well in different operating conditions. A detailed analysis and characterisation of the mechanisms to confine the signal electrons in the 3D well is presented. For a drift field of 300 V/cm, storage of more than 10/sup 5/ electrons in 180/spl times/180 /spl mu/m/sup 2/ pixels has been achieved with 1.67 V surface perturbation. View full abstract»

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  • Thin photodiodes for a scintillator-silicon well detector

    Page(s): 1948 - 1951
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    In developing position sensitive radiation sensors, e.g. for medical imaging, low-gain silicon well sensors were made for the detection of scintillation light. The 3/spl times/3 arrays include N/sup ++/NP diodes, processed in the /spl sim/12 /spl mu/m thick membranes that remain after thinning of 530 /spl mu/m thick [100] silicon wafers by means of a potassium hydroxide (KOH) solution. A comparison is made for the light detection efficiency of these diodes with that of a 500 /spl mu/m thick PIN photodiode. View full abstract»

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  • Development of an imaging plate as a heavy-nuclide detector

    Page(s): 1952 - 1956
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    It is very important for the study of nucleo-synthesis in supernova explosion to be able to measure the abundance of heavy nuclides in cosmic rays. Though a large-area detector is necessary for measurements of the abundance, it takes very long time to analyze the data for large-area detectors such as emulsion chamber. To address this need, we are developing a new type of heavy nuclide detector using an imaging plate which is manufactured by Fuji Film Co. Ltd. This film has a position resolution of 25 /spl mu/m and a sensitivity 1000 times higher than X-ray film. Moreover it is easy to enlarge since the area of one plate can be 20/spl times/25 cm/sup 2/, and the accumulated cosmic-ray-interaction information can be read out in about 10 minutes. To measure the characteristics of the imaging plate for heavy nuclides, we irradiated it with several kinds of nuclides using an accelerator in the National Institute of Radiological Sciences. These tests demonstrated that using an imaging plate, carbon, silicon, and argon nuclides can be distinguished. View full abstract»

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  • Evaluation of radiation damaged p-in-n and n-in-n silicon microstrip detectors

    Page(s): 1957 - 1963
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    Two p-in-n and one n-in-n silicon microstrip detectors were radiation-damaged and tested in a beam. A comparison was made between the p-in-n and the n-in-n in high resistivity wafers, and the p-in-n in a low and a high resistivity wafer. The charge collection showed a clear difference in the n-in-n and the p-in-n detectors, which suggested that the signals were shared between strips more in the irradiated p-in-n detectors. Although a difference of the low and the high resistivity wafers was observed in the body capacitance measurement, little difference was observed in the beam test results. View full abstract»

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  • Depletion voltage and charge collection for highly irradiated silicon microstrip detectors with various initial resistivities

    Page(s): 1964 - 1968
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    We have irradiated p-on-n silicon microstrip detectors of initial bulk resistivity between 0.2 and 2.7 k/spl Omega/-cm with 55 MeV protons to fluences of 0.7, 2 and 11/spl times/10/sup 13/ p/cm/sup 2/ (equivalent to twice the fluence in high energy protons), and have measured the depletion voltage before and after irradiation using C-V methods. In addition, we have measured the charge collection of minimum ionization on a single strip with a fast amplifier as a function of bias voltage. We compare the depletion voltage deduced from both methods for samples with different initial resistivities. View full abstract»

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  • Ab-initio cluster calculations of hole formation and trapping in PbF/sub 2/ and PbF/sub 4/ [scintillation]

    Page(s): 1969 - 1973
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    We have used ab-initio quantum chemistry computer codes to model the formation of holes and the energy barriers for their diffusion in two lead fluoride hosts of potential interest for scintillation-PbF/sub 2/ and PbF/sub 4/. The crystals were modeled by Pb/sub 24/F/sub 48/ and Pb/sub 14/F/sub 56/ atomic clusters embedded in arrays of several thousand point charges to reproduce the Madelung potential to an accuracy of several mV throughout the cluster. Cubic PbF/sub 2/ has the same crystal structure as CaF/sub 2/, however their electronic structures are different. It is known experimentally that in CaF/sub 2/ holes travel easily along rows of F atoms which accounts for the high luminous efficiency of the scintillator CaF/sub 2/:Eu. In contrast, these calculations show that in PbF/sub 2/ holes are trapped on the Pb atoms by an energy barrier of /spl sim/1 eV. This result is consistent with the failure of PbF/sub 2/ as an activated scintillator. Similar calculations on the experimentally unexplored crystal PbF/sub 4/ predict that the holes are trapped on F atoms with an energy barrier of /spl sim/1 eV and is therefore not a promising host for an activated scintillator. These computational techniques can be applied to other crystals to find those with mobile holes for new heavy-atom scintillators and solid-state detectors. View full abstract»

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  • Stability in the parallel signal transfer mode from a silicon strip focal plane detector

    Page(s): 1974 - 1978
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    A parallel signal-transfer method is used for the front-end readout of a silicon strip focal plane detector. This paper focuses on the system stability, in particular the prevention of resonant oscillations using a time-variant method. A similar analysis can be applied to other detector systems that have large numbers of parallel readout channels. View full abstract»

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