Counter Array Research Articles

Development of a novel scintillation-trigger detector for the MTV experiment using aluminum-metallized film tapes

A new type of a trigger-scintillation counter array designed for the MTV experiment at TRIUMF-ISAC has been developed, which uses aluminum-metallized film tape for wrapping to achieve the required assembling precision of ±0.5mm. The MTV experiment uses a cylindrical drift chamber (CDC) as the main electron-tracking detector. The barrel-type trigger counter is placed inside the CDC to generate a trigger signal using 1mm thick, 300mm long thin plastic scintillation counters. Detection efficiency and light attenuation compared with conventional wrapping materials are studied.

X-RAY SPECTRAL STATE EVOLUTION IN IGR J17091–3624 AND COMPARISON OF ITS HEARTBEAT OSCILLATION PROPERTIES WITH THOSE OF GRS 1915+105

In this work, we study the X-ray timing and spectral evolution of the transient low mass X-ray binary IGR J17091-3624 during first 66 days of its 2011 outburst. We present results obtained from observations with two instruments, Rossi X-ray Timing Explorer (RXTE)/Proportional Counter Array (PCA) and SWIFT/X-ray telescope (XRT), between 09 February, 2011 and 15 April, 2011. Using quasi-periodic oscillation classifications, power density spectrum characteristics, time-lag behavior and energy spectral properties, we determine source states and their transitions at different times of the outburst. During the first part of the evolution, the source followed trends usually observed from transient black hole X-ray binaries (BHXBs). Interestingly, a gradual transition is observed in IGR J17091-3624 from the low-variability SIMS, commonly seen in BHXBs, to a high-variability state with regular, repetitive and structured pulsations, seen only from GRS 1915+105 (also known as 'rho' class variability/'heartbeat' oscillations). We study the time evolution of characteristic time-scale, quality factor and rms amplitude of heartbeat oscillations in IGR J17091-3624. We also present a detailed comparison of the timing and spectral properties of heartbeat oscillations and their evolution in IGR J17091-3624 and GRS 1915+105.

Classification and spectral evolution of outbursts of Aql X-1

We present a broad classification of all outbursts detected with the All-Sky Monitor (ASM) on the Rossi X-Ray Timing Explorer (RXTE) and the Monitor of All Sky X-Ray Image (MAXI) of Aql X-1. We identify three types of outbursts; long-high, medium-low, and short-low, based on the duration and maximum flux. We analyse the trends in the "phase-space" of flux-derivative versus flux to demonstrate the differences in the three identified outburst types. We present a spectral analysis of the observations of Aql X-1 performed by the Proportional Counter Array (PCA) onboard RXTE during the 2000 and 2011 outbursts of the long-high class and the 2010 outburst of the medium-low class. We model the source spectrum with a hybrid thermal/non-thermal hot plasma emission model (EQPAIR in XSPEC, Coppi 2000) together with a Gaussian component to model the Fe K_alpha emission line. We construct time histories of the source flux, the optical depth of the corona (tau), the seed photon temperature (kT_bb) and the hard state compactness (l_h) for these three outbursts. We show that the physical parameters of either classes reach the same values throughout the outbursts, the only difference being the maximum flux. We discuss our results in the terms of modes of interaction of the star with the disc and size of the disc kept hot by irradiation. We conclude that irradiation is the dominant physical process leading to the different classes of outbursts.

The cooling rate of neutron stars after thermonuclear shell flashes

Thermonuclear shell flashes on neutron stars are detected as bright X-ray bursts. Traditionally, their decay is modeled with an exponential function. However, this is not what theory predicts. The expected functional form for luminosities below the Eddington limit, at times when there is no significant nuclear burning, is a power law. We tested the exponential and power-law functional forms against the best data available: bursts measured with the high-throughput Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer. We selected a sample of 35 'clean' and ordinary (i.e., shorter than a few minutes) bursts from 14 different neutron stars that 1) show a large dynamic range in luminosity, 2) are the least affected by disturbances by the accretion disk and 3) lack prolonged nuclear burning through the rp-process. We find indeed that for every burst a power law is a better description than an exponential function. We also find that the decay index is steep, 1.8 on average, and different for every burst. This may be explained by contributions from degenerate electrons and photons to the specific heat capacity of the ignited layer and by deviations from the Stefan-Boltzmann law due to changes in the opacity with density and temperature. Detailed verification of this explanation yields inconclusive results. While the values for the decay index are consistent, changes of it with the burst time scale, as a proxy of ignition depth, and with time are not supported by model calculations.

Statistics Counter Architecture for Backbone Network Traffic Analysis and Management

PDF HTML阅读 XML下载 导出引用 引用提醒 面向骨干网流量分析与管理的计数器结构 DOI: 10.3724/SP.J.1001.2013.04365 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏省自然科学基金(BK2010103) Statistics Counter Architecture for Backbone Network Traffic Analysis and Management Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:针对高速骨干网流量分析与流量管理对大规模高速统计计数器的需求,提出了一种简单、高效的主动式计数器结构——DALCA,其新颖之处在于对计数器向量进行分层,除第1 层外,其他各层子计数器向量采用多级哈希表的形式进行组织,获得了良好的空间效率和时间效率.与现有的主动式计数器结构BRICK 相比, DALCA 的空间效率与其接近,但是时间效率明显优于BRICK.采用真实的骨干网流量数据,通过仿真实验对DALCA 的性能进行了评估,结果表明:执行查询操作时,DALCA的访存带宽需求约为BRICK 的1/10;执行更新操作时,DALCA的访存带宽需求约为BRICK 的1/6. Abstract:A simple and efficient active statistics counter architecture named DALCA (direct addressing layered counter array) is presented for high speed network traffic analysis and management. The novelty of DALCA is that the counter vector is split up into multiple layers, and all layers except the first one are organized as multi-level hash tables. This makes DALCA efficient in both from the space and time perspective. DALCA has similar space efficiency and significantly higher time efficiency compared with BRICK;the state-of- the-art active statistics counter architecture. The performance of DALCA is evaluated using real world backbone network traffic traces. Simulation results show that the memory bandwidth demand of DALCA is about 1/10 and 1/6 that of BRICK during query and update operations respectively. 参考文献 相似文献 引证文献

Recent Frequent Item Mining Algorithm in a Data Stream Based on Flexible Counter Windows

In the paper the author introduces FCW_MRFI, which is a streaming data frequent item mining algorithm based on variable window. The FCW_MRFI algorithm can mine frequent item in any window of recent streaming data, whose given length is L. Meanwhile, it divides recent streaming data into several windows of variable length according to m, which is the number of the counter array. This algorithm can achieve smaller query error in recent windows, and can minimize the maximum query error in the whole recent streaming data.

Novel Hamamatsu Multi-Pixel Photon Counter (MPPC) array studies for the GlueX experiment: New results

The novel Hamamatsu Multi-Pixel Photon Counter (MPPC) S12045(X) is an array of 16 individual 3×3mm2 MPPC devices each with 3600 Geiger-mode Avalanche Photodiode pixels of 50×50μm2. Each MPPC in the array operates at a reverse bias of approximately 70V. This paper summarizes our characterization of MPPC arrays used in the GlueX experiment in Hall D at Thomas Jefferson National Accelerator Facility (Jefferson Lab). We studied the main features of each of the 16 MPPC array channels for 2800 MPPC arrays at several different temperatures. Two measurement stations were built to extract gain, breakdown voltage, photon detection efficiency, optical crosstalk and dark rate for each of the 44800 MPPC array channels at each temperature setting. The hardware and the data analysis are described, and new analytical expressions for the mean number of photoelectrons and optical crosstalk are presented, as well as systematic trends of the performance parameters.

A Programmable Controller IC for DC/DC Converter and Power Factor Correction Applications

This paper presents the design of a low-cost programmable controller integrated circuit (IC) for general power electronics applications. The architecture of the programmable controller IC consists of 10-bit ADC and DAC, programmable counter array (PCA), which is configured to function as PWM, and a control unit (processor) for regulation. The processor unit is configured as digital compensator, through fewer program steps to perform accurate compensation on the voltage control loop of the converter system. Limit-cycle oscillation is minimized through inclusion of a sufficiently low integral gain term in the control law. A hybrid control method is first used to control the input voltage and current waveforms to achieve a unity power factor correction. It is observed that the programmable converter achieves the high efficiency power conversion. The conversion efficiency of the digital controlled boost converter is 91% with a 0.8% ripple voltage performance. While in power factor correction (PFC) circuit application, the power factor and output ripple voltage of converter are 0.995 and 0.93%, respectively. The chip is implemented with TSMC 0.25 um CMOS process.

An Improved Hall Vehicle Speed Sensor Detection System

In order to improve the detecting efficiency of the Hall vehicle speed sensor, an improved detection system was presented in this paper. This system was consists of five parts of system manager, A/D converter, D/A converter, voltage comparator, and a high-speed programmable counter array. The quality of Hall vehicle speed sensor online was evaluated, and the statistical result was graphically displayed by PC. Compared with the synchronous detection of digital storage oscilloscope, it is shown that the detecting accuracy of the system can then meet the requirements of industrial production, and will be suitable for mass production.

Four-layer DOI PET detectors using a multi-pixel photon counter array and the light sharing method

Silicon photomultipliers (SiPMs) provide many advantages for PET detectors, such as their high internal gain, high photon detection efficiency and insensitivity to magnetic fields. The number of detectable scintillation photons of SiPMs, however, is limited by the number of microcells. Therefore, pulse height of PET detectors using SiPMs is saturated when large numbers of scintillation photons enter the SiPM pixels. On the other hand, we previously presented a depth-of-interaction (DOI) encoding method that is based on the light sharing method. Since our encoding method detects scintillation photons with multiple readout pixels, the saturation effect can be suppressed. We constructed two prototype four-layer DOI detectors using a SiPM array and evaluated their performances.The two prototype detectors consisted of four layers of a 6×6 array of Lu2(1−x)Y2xSiO5 (LYSO) crystals and a SiPM (multi-pixel photon detector, MPPC, Hamamatsu Photonics K.K.) array of 4×4 pixels. The size of each LYSO crystal element was 1.46mm×1.46mm×4.5mm and all surfaces of the crystal elements were chemically etched. We used two types of MPPCs. The first one had 3600 microcells and high photon detection efficiency (PDE). The other one had 14,400 microcells and lower PDE. In the evaluation experiment, all the crystals of the detector using the MPPC which had the high PDE were clearly identified. The respective energy and timing resolutions of lower than 15% and 1.0ns were achieved for each crystal element. No saturation of output signals was observed in the 511keV energy region due to suppression of the saturation effect by detecting scintillation photons with several MPPC pixels by the light sharing method.

Recent Frequent Item Mining Algorithm in a Data Stream Based on Flexible Counter Windows

In the paper the author introduces FCW_MRFI, which is a streaming data frequent item mining algorithm based on variable window. The FCW_MRFI algorithm can mine frequent item in any window of recent streaming data, whose given length is L. Meanwhile, it divides recent streaming data into several windows of variable length according to m, which is the number of the counter array. This algorithm can achieve smaller query error in recent windows, and can minimize the maximum query error in the whole recent streaming data.

SUPERORBITAL PHASE-RESOLVED ANALYSIS OF SMC X-1

The high-mass X-ray binary SMC X-1 is an eclipsing binary with an orbital period of 3.89 d. This system exhibits a superorbital modulation with a period varying between ~40 d and ~65 d. The instantaneous frequency and the corresponding phase of the superorbital modulation can be obtained by a recently developed time-frequency analysis technique, the Hilbert-Huang transform (HHT). We present a phase-resolved analysis of both the spectra and the orbital profiles with the superorbital phase derived from the HHT. The X-ray spectra observed by the Proportional Counter Array onboard the Rossi X-ray Timing Explorer are fitted well by a blackbody plus a Comptonized component. The plasma optical depth, which is a good indicator of the distribution of material along the line of sight, is significantly anti-correlated with the flux detected at 2.5-25 keV. However, the relationship between the plasma optical depth and the equivalent width of the iron line is not monotonic: there is no significant correlation for fluxes higher than ~35 mCrab but clear positive correlation when the intensity is lower than ~20 mCrab. This indicates that the iron line production is dominated by different regions of this binary system in different superorbital phases. To study the dependence of the orbital profile on the superorbital phase, we obtained the eclipse profiles by folding the All Sky Monitor light curve with the orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip in Her X-1, lying at orbital phase ~0.6-0.85, was discovered during the superorbital transition state. This indicates that the accretion disk has a bulge that absorbs considerable X-ray emission in the stream-disk interaction region. The dip width is anti-correlated with the flux, and this relation can be interpreted by the precessing tilted accretion disk scenario.

Detection of a variable QPO at ∼41 mHz in the Be/X-ray transient pulsar 4U 0115+634

We report the detection of quasi-periodic oscillation (QPO) at ~41 mHz in the transient high-mass Be/X-ray binary pulsar 4U~0115+634 using data from the Rossi X-Ray Timing Explorer (RXTE) observatory. The observations used in the present work were carried out during X-ray outbursts in 1999 March-April, 2004 September-October and 2008 March-April. This frequency of the newly detected QPO was found to vary in 27-46 mHz range. This ~41 mHz QPO was detected in four of the 36 pointed RXTE Proportional Counter Array (PCA) observations during 1999 outburst where as during 2004 and 2008 outbursts, it was detected in four and three times out of 33 and 26 observations, respectively. Though QPOs at ~2 mHz, and ~62 mHz were reported earlier, the ~41 mHz QPO and its first harmonic were detected for the first time in this pulsar. There are three RXTE/PCA observations where multiple QPOs were detected in the power density spectrum of 4U~0115+634. Simultaneous presence of multiple QPOs is rarely seen in accretion powered X-ray pulsars. Spectral analysis of all the pointed RXTE/PCA observations revealed that the 3-30 keV energy spectrum was well described by Negative and Positive Power-law with EXponential cutoff (NPEX) continuum model along with interstellar absorption and cyclotron absorption components. During the three X-ray outbursts, however, no systematic variation in any of the spectral parameters other than the earlier reported anti-correlation between cyclotron absorption energy and luminosity was seen. Presence of any systematic variation of QPO frequency and rms of QPO with source flux were also investigated yielding negative results.

Characterization of novel Hamamatsu Multi Pixel Photon Counter (MPPC) arrays for the GlueX experiment

The novel Hamamatsu Multi Pixel Photon Counter Array S12045(X) is an array of 16 individual MPPCs (3×3mm2) (further in the paper MPPC array channel) each with 3600 G-APD (Geiger-mode Avalanche Photodiodes) pixels (50×50 [μm2]). Each MPPC in the array works with its individual reverse bias voltage mode (around 70V). The paper summarizes the characterization process of MPPC arrays used in GlueX experiment (Hall D, Jefferson Lab). We studied the main features of each MPPC array channel for 2800 MPPC arrays at different temperatures. Two measurement stations were built to extract gain, breakdown voltage, photo detection efficiency (PDE), optical crosstalk and dark rate for each MPPC array channel. The hardware and the data analysis are described, which includes new analytical expressions to obtain the mean number of photo-electrons and optical crosstalk. The dynamical behavior of characterization parameters is presented as well.

An Application of Hilbert-Huang Transform on the Non-Stationary Astronomical Time Series: The Superorbital Modulation of SMC X-1

We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of <TEX>$n_H$</TEX> has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.

GALACTIC ULTRACOMPACT X-RAY BINARIES: EMPIRICAL LUMINOSITIES

Ultracompact X-ray binaries (UCXBs) are thought to have relatively simple binary evolution post-contact, leading to clear predictions of their luminosity function. We test these predictions by studying the long-term behavior of known UCXBs in our Galaxy, principally using data from the MAXI All-Sky Survey and the Galactic bulge scans with RXTE's Proportional Counter Array instrument. Strong luminosity variations are common (and well documented) among persistent UCXBs, which requires an explanation other than the disk instability mechanism. We measure the luminosity function of known UCXBs in the Milky Way, which extends to lower luminosities than some proposed theoretical luminosity functions of UCXBs. The difference between field and globular cluster (GC) X-ray luminosity functions in other galaxies cannot be explained by an increased fraction of UCXBs in GCs. Instead, our measured luminosity function suggests that UCXBs only make up a small fraction of the X-ray binaries above a few × 1036 erg s−1 in both old field populations and GCs.

J-PARC E27 Experiment to Search for a Nuclear Kaon Bound State K − pp

In the J-PARC E27 experiment, we search for a K − pp bound state via the d(π +, K +) reaction at 1.7 GeV/c at the K1.8 beam line. The binding energy and decay width of the K − pp bound state can be obtained in the missing mass measurement with a good energy resolution of 2 MeV/c 2. A range counter array (RCA) was constructed to detect the two high-momentum protons from the K − pp decay and to reduce the background such as quasi-free hyperon production. Recently, we have carried out a pilot run in June, 2012. The d(π +, K +) missing-mass spectrum has been obtained for the first time. In this report, an overview of the E27 experiment and a preliminary result on this pilot run are presented.

3D numerical simulation of a Coulter counter array with analysis of electrokinetic forces

Coulter counters have played an important role in biological cell assays since their introduction decades ago. Several types of high throughput micro-Coulter counters based on lab-on-chip devices have been commercialized recently. In this paper, we propose a highly integrated micro-Coulter counter array working under low DC voltage. The real-time electrical current change, including the pulse amplitude and width, of the micro-Coulter counter with novel structure is systematically investigated numerically. The major types of forces exerted on the particle in the micro-Coulter counter, including hydrodynamic force and electrokinetic force are quantitatively analyzed. The simulation in this study shows the pulse profile, such as width and amplitude, is affected by both particle size and the flow condition. The special cases of multiple particle aggregation and cross-talk between neighboring channels are also considered for their effects on the electric current pulses. This simulation provides critical insight and guidance for developing next new generations of micro-Coulter counter.

Search for serendipitous trans-Neptunian object occultation in X-rays

To study the population properties of small, remote objects beyond Neptune's orbit in the outer Solar system, of kilometre size or smaller, serendipitous occultation search is so far the only way. For hectometre-sized trans-Neptunian objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wavelengths are needed. Here, we report the effort of TNO occultation search in X-rays using Rossi X-ray Timing Explorer/Proportional Counter Array data of Sco X-1 taken from 2007 June to 2011 October. No definite TNO occultation events were found in the 334-ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.

Design of Capacity Loss Tester of Power Transformer

A capacity loss tester for no-load and with-load testing of power transformer has been developed. The tester has the ability of sampling the three-phase voltage and current simultaneously. Programmable counter array (PCA) unit in MPU, which captures zero-crossing of signal by the function of positive and negative edge trigger, is applied to the average phase detection of zero-crossing in bi-direction, in order to acquire the phase difference and period accurately. In terms of software, synchronism sampling method based on real-time parameter self-optimizing is adopted to minimize period truncation error, and the measuring accuracy is improved. The capacity of the power transformer is discriminated by table-look-up method in software, corresponding to different load loss. The testing result is converted from the value under testing temperature to the value under the condition of reference temperature (75°C).