Variation Of Pulse Height Research Articles

Longitudinal phase-space diagnostics using a stripline-type beam-timing monitor at the KEKB injector linac

Abstract A new beam-timing monitor (BTM) has been developed to analyze the longitudinal beam dynamics and bunching characteristics at the pre-injector of the KEKB injector linear accelerator (linac). The BTM is a conventional stripline-type beam monitor with two pickup electrodes. It measures the relative time delay between the arrival time of the beam signal and 1st-zero-cross time of the fundamental accelerating radio frequency (rf) signal (2856 MHz) immediately after the detection of the beam signal. The beam tests were performed to evaluate the performance and characteristics of the BTM for primary single-bunched electron beams with high bunch charges of ∼ 8 nC for positron production. It was found that the results show that the resolution in the delay-time measurement is σ ∼ 1.2 ps in one standard deviation. This report describes the basic design of the BTM system, the beam tests, and results in detail, to investigate the sensitivity and stability of the beam timing based on the longitudinal phase-space parameters at the pre-injector and location A1 of the injector linac, along with the calibration method in the pulse-height variation of the BTM signal.

Evaluation of the health status of six volunteers from the Mars 500 project using pulse analysis.

To comprehensively evaluate the health status of 6 volunteers from the Mars 500 Project through analyzing their pulse graphs and determining the changes in cardiovascular function, degree of fatigue and autonomic nervous function. Six volunteers were recruited; all were male aged 26-38 years (average 31.83±4.96 years). Characteristic parameters reflflecting the status of cardiovascular functions were extracted, which included left ventricular contraction, vascular elasticity and peripheral resistance. The degree of fatigue was determined depending on the difference between the calendar age and biological age, which was calculated through the analysis of blood pressure value and characteristic parameters. Based on the values of pulse height variation and pulse time variation on a 30-s pulse graph, autonomic nervous function was evaluated. All parameters examined were marked on an equilateral polygon to form an irregular polygon of the actual fifigure, then health status was evaluated based on the coverage area of the actual fifigure. The results demonstrated: (1) volunteers developed weakened pulse power, increased vascular tension and peripheral resistance, and slight decreased ventricular systolic function; (2) the degree of fatigue was basically mild or moderate; and (3) autonomic nervous function was excited but generally balanced. These volunteers were in the state of sub-health. According to Chinese medicine theories, such symptoms are mainly caused by the weakening of healthy qi, Gan (Liver) failing in free coursing, and disharmony between Gan and Wei (Stomach), which manifests as a weak and string-like pulse.

Progress Towards Improved Analysis of TES X-ray Data Using Principal Component Analysis

The traditional method of applying a digital optimal filter to measure X-ray pulses from transition-edge sensor (TES) devices does not achieve the best energy resolution when the signals have a highly non-linear response to energy, or the noise is non-stationary during the pulse. We present an implementation of a method to analyze X-ray data from TESs, which is based upon principal component analysis (PCA). Our method separates the X-ray signal pulse into orthogonal components that have the largest variance. We typically recover pulse height, arrival time, differences in pulse shape, and the variation of pulse height with detector temperature. These components can then be combined to form a representation of pulse energy. An added value of this method is that by reporting information on more descriptive parameters (as opposed to a single number representing energy), we generate a much more complete picture of the pulse received. Here we report on progress in developing this technique for future implementation on X-ray telescopes. We used an $$^{55}$$ Fe source to characterize Mo/Au TESs. On the same dataset, the PCA method recovers a spectral resolution that is better by a factor of two than achievable with digital optimal filters.

The TORCH PMT: a close packing, multi-anode, long life MCP-PMT for Cherenkov applications

Photek (U.K.) and the TORCH collaboration are undertaking a three year development program to produce a novel square MCP-PMT for single photon detection. The TORCH detector aims to provide particle identification in the 2–10 GeV/c momentum range, using a Time-of-Flight method based on Cherenkov light. It is a stand-alone R&D project with possible application in LHCb, and has been proposed for the LHCb Upgrade. The Microchannel Plate (MCP) detector will provide a single photon timing accuracy of 40 ps, and its development will include the following properties: (i) Long lifetime up to at least 5 C/cm2; (ii) Multi-anode output with a spatial resolution of 6 mm and 0.4 mm respectively in the horizontal and vertical directions, incorporating a novel charge-sharing technique; (iii) Close packing on two opposing sides with an active area fill factor of 88% in the horizontal direction. Results from simulations modelling the MCP detector performance factoring in the pulse height variation from the detector, NINO threshold levels and potential charge sharing techniques that enhance the position resolution beyond the physical pitch of the pixel layout will be discussed. Also, a novel method of coupling the MCP-PMT output pads using Anisotropic Conductive Film (ACF) will be described. This minimises parasitic input capacitance by allowing very close proximity between the frontend electronics and the MCP detector.

K-mean clustering algorithm for processing signals from compound semiconductor detectors

Abstract The K-mean clustering algorithm was employed for processing signal waveforms from TlBr detectors. The signal waveforms were classified based on its shape reflecting the charge collection process in the detector. The classified signal waveforms were processed individually to suppress the pulse height variation of signals due to the charge collection loss. The obtained energy resolution of a 137 Cs spectrum measured with a 0.5 mm thick TlBr detector was 1.3% FWHM by employing 500 clusters.

Correction for pulse height variability reduces physiological noise in functional MRI when studying spontaneous brain activity

EEG correlated functional MRI (EEG-fMRI) allows the delineation of the areas corresponding to spontaneous brain activity, such as epileptiform spikes or alpha rhythm. A major problem of fMRI analysis in general is that spurious correlations may occur because fMRI signals are not only correlated with the phenomena of interest, but also with physiological processes, like cardiac and respiratory functions. The aim of this study was to reduce the number of falsely detected activated areas by taking the variation in physiological functioning into account in the general linear model (GLM). We used the photoplethysmogram (PPG), since this signal is based on a linear combination of oxy- and deoxyhemoglobin in the arterial blood, which is also the basis of fMRI. We derived a regressor from the variation in pulse height (VIPH) of PPG and added this regressor to the GLM. When this regressor was used as predictor it appeared that VIPH explained a large part of the variance of fMRI signals acquired from five epilepsy patients and thirteen healthy volunteers. As a confounder VIPH reduced the number of activated voxels by 30% for the healthy volunteers, when studying the generators of the alpha rhythm. Although for the patients the number of activated voxels either decreased or increased, the identification of the epileptogenic zone was substantially enhanced in one out of five patients, whereas for the other patients the effects were smaller. In conclusion, applying VIPH as a confounder diminishes physiological noise and allows a more reliable interpretation of fMRI results.

Performance evaluation for 120 four-layer DOI block detectors of the jPET-D4

The jPET-D4 is a brain positron emission tomography (PET) scanner that we have developed to meet user demands for high sensitivity and high spatial resolution. For this scanner, we developed a four-layer depth-of-interaction (DOI) detector. The four-layer DOI detector is a key component for the jPET-D4, its performance has great influence on the overall system performance. Previously, we reported the original technique for encoding four-layer DOI. Here, we introduce the final design of the jPET-D4 detector and present the results of an investigation on uniformity in performance of the detector. The performance evaluation was done over the 120 DOI crystal blocks for the detectors, which are to be assembled into the jPET-D4 scanner. We also introduce the crystal assembly method, which is simple enough, even though each DOI crystal block is composed of 1,024 crystal elements. The jPET-D4 detector consists of four layers of 16 x 16 Gd(2)SiO(5) (GSO) crystals and a 256-channel flat-panel position-sensitive photomultiplier tube (256ch FP-PMT). To identify scintillated crystals in the four-layer DOI detector, we use pulse shape discrimination and position discrimination on the two-dimensional (2D) position histogram. For pulse shape discrimination, two kinds of GSO crystals that show different scintillation decay time constants are used in the upper two and lower two layers, respectively. Proper reflector arrangement in the crystal block then allows the scintillated crystals to be identified in these two-layer groupings with two 2D position histograms. We produced the 120 DOI crystal blocks for the jPET-D4 system, and measured their characteristics such as the accuracy of pulse shape discrimination, energy resolution, and the pulse height of the full energy peak. The results show a satisfactory and uniform performance of the four-layer DOI crystal blocks; for example, misidentification rate in each GSO layer is <5% based on pulse shape discrimination, the averaged energy resolutions for the central four crystals of the first (farthest from the FP-PMT), second, third, and 4th layers are 15.7 +/- 1.0, 15.8 +/- 0.6, 17.7 +/- 1.2, and 17.3 +/- 1.4%, respectively, and variation in pulse height of the full energy peak among the four layers is <5% on average.

Synthesis and morphological investigation of pulsed current formed nano-structured lead dioxide

An electro-forming method was used for the preparation of nano-structured lead dioxide on lead substrate in 4.8 M H 2SO 4. A two electrode system composed of two similarly prepared lead electrodes was employed. A constant current was applied between two electrodes for a short time, followed by a relaxation period. A dark oxidation film of suitable stability and homogeneity was formed on the anode electrode. Different parameters including pulse height, pulse time ( t on) and relaxation time ( t off) were optimized. A change in morphology of lead dioxide from globular to nanofibriliar was observed when the pulse time and relaxation time varied from 0.01 to 10 and 0.1 to 5 s, respectively, at a pulse height of 25 mA cm −2. A variation in pulse height caused a variation in diameter and length of nanofibers formed at a pulsed time of 0.1 s and relaxation time of 5 s. The scanning electron microscopy (SEM) showed that lead dioxide particles obtained under these conditions have nanofibriliar morphology with an average diameter in the range between 20 and 50 nm and length of 500–1000 nm.

DLTS measurements on CuInS 2 solar cells

Deep-level transient spectroscopy (DLTS) was used in this work to reveal information about deep defect levels in CuInS 2 based solar cells. A strong variation of the defect spectrum from sample to sample was found. A minority carrier trap at 0.25 eV and a majority carrier trap at 0.35 eV were identified as bulk traps by variation of pulse height. Two majority carrier traps at 0.24 and 0.8 eV were confirmed as interface traps.

Design considerations and initial performance of a 1.2 cm/sup 2/ beta imaging intra-operative probe

A novel small area beta (/spl beta//sup /spl plusmn//) detector is under development for nuclear emission imaging of surgically exposed, radiolabeled tumor beds. The imaging device front-end consists of a 0.5 mm thick by 1.25 cm diameter CaF/sub 2/(Eu) scintillator disk coupled to a rigid bundle of 2 mm diameter double clad optical fibers through a polystyrene light diffuser. The detector area (1.2 cm/sup 2/) was determined by the requirement of introducing the probe into small cavities, e.g. during neuro-surgical lesion resection, but large enough to produce images of clinical significance. Flexible back-end optical fibers (1.9 m long) were coupled to the front-end components allowing /spl sim/75 photo-electrons to be detected for mean beta energies of 250 keV, indicating that sufficient signal can be obtained with clinical beta emitters (e.g. /sup 18/F, /sup 131/I). The long flexible fibers guide the scintillation light to a Philips XP1700 series, fiber optic faceplate, Multi-Channel PMT. The parallel MC-PMT outputs are fed into a variable gain, charge divider network and an i-V pre-amplifier/line driver network, whose resulting four outputs are digitized and histogrammed with standard Anger positioning logic. The various components in the imaging chain were evaluated and optimized by both simulations and measurements. Line spread functions measured in the 10.8 mm FOV were 0.50 mm /spl plusmn/0.038 mm and 0.55 mm /spl plusmn/0.065 mm FWHM in X and Y, respectively. A 20% variation in pulse height and minimal variation in spatial resolution was observed. The differential image uniformity was measured to be /spl plusmn/15.6% with /spl sim/150 cts/pixel. Preliminary images show excellent reproduction of phantom activity distributions.

Speed properties of the hybrid photodiode tube

The Hybrid PhotoDiode (HPD) tube, a non-multiplicative photon detector with a gain of a few thousand, has been proposed in recent years for the replacement of photomultiplier tubes. Recent developments of the silicon chip (the active element in this detector) allowed it to perform with sub-nanosecond rise times for electrostatically focused versions and between less than one and a few ns rise times (depending on the working conditions and on the chip's active surface) for proximity focused, magnetic field insensitive models. The negligible electron time of flight fluctuations and of photoelectron to photoelectron pulse height variations, make the HPD an ideal tool for photon timing. Timing precision below 100 ps was easily achieved.

Integrating and differentiating channels in digital tape recording

The waveform at an inductive reproduce head of a digital magnetic recording system is a differentiated representation of the magnetic transition. Detection of the transition can be by zero-crossing detection when the head waveform is either further differentiated, or integrated to approximate the original flux pattern. For an integrating channel d.c. equalization is also required. The effect of pulse slimming, d.c. equalization, noise and pulse height variation is examined for both systems, from which it is concluded that an integrating channel has advantages provided that pulse height variations are small.

Fast photoconductors for synchrotron radiation research

We report on measurements of the response of InP doped with Fe in the energy range 200 eV to 3 keV. The experiments were performed on the lithography beam line at SSRL. The detector had a response time (fwhm) of 180 ps and had an active area of 1 mm × 1 mm. An array of filters (carbon, magnesium and beryllium) was used to unfold the energy response of the detector. Direct measurements of the time structure of the ring bunches were limited by the bandwidth of the real time recording system (400 MHz), but individual ring pulses were easily recorded with a pulse amplitude of 65 mV for the unfiltered beam. With the ring operating in a four bunch mode, the variation of pulse height with ring bunch was also observed.

Microwave Diagnostic of the Pulsed Plasma Generation in the Hollow-Cathode Glow Discharge

Abstract The radius and speed of the cylindric ionization front that expands during the application of a high-voltage pulse upon a double-plate hollow-cathode, is measured by reflection of 8 mm-microwaves. By comparing the number of transported electrons and their ionizing action, ionization by single electron collisions is shown to be impossible. In the "normal regime" below a certain voltage threshold, a pulse height variation has only an influence on the final plasma radius but not on the local speed of the cut-off surface during recombination.

Simple scheme for light collection from large-area plastic scintillators

The design and performance of a large-area veto counter which has no light guide are described. A novel reflector scheme is used to increase the light collection efficiency. Principal features of the design are mechanical simplicity, low cost, and substantial variation of pulse height across the counter.

Noise characteristics of a microchannel plate x-ray image intensifier.

The noise performance of an experimental microchannel plate x-ray image intensifier has been evaluated. The intensifier, constructed for use with photons of energies between 20 and 150 keV, uses an MCP as the photon-to-electron converter. The influence of noise was determined by analysis of the optical-density fluctuations of a photograph of the viewing screen of the intensifier when the conversion layer was exposed to between 1 and 60 mR. Additionally, the contrast-detail performance of the experimental device was determined. The influence of both stochastic noise, due to quantum mottle and pulse-height variations, and structural noise, due to fluctuations in inherent gain from point to point, have been considered by using a model that adds these components.

Walk-free fast timing for a heavy-ion time-of-flight telescope

An intrinsic time resolution of 68 ps between two surface barrier detectors has been achieved. The timing walk associated with pulse height variations is reduced by means of computer correction to below 30 ps.

Neutron scintillating glasses: Part 1: Activation by external charged particles and thermal neutrons

A synopsis of the development of amorphous glass scintillators for thermal neutron detection via the 6Li(n, α) is given. The complete, available, range of commercial scintillators have been tested under neutron, alpha and beta excitation. For all the radiation sources, the variation in pulse height with glass composition follows a common pattern, related in the paper to the degree of divergence from the composition of a related polycrystalline X-ray phosphor. For external particle excitation, the count rate at the peak of the pulse height distribution relates directly to the pulse height patterns. For neutron excitation, the count rate follows the 6Li concentration, but not exactly. Calculations on ionisation densities, atomic spacings and glass species densities are reported and correlated with the experimental results. A detailed analysis of pulse height spectrum at the peak of the 6Li(n, α) indicates the superior performance of the low lithium content, enriched 6Li glasses, in respect of pulse height statistics and energy discrimination. Further experiments to be reported soon are described in respect of their contribution to the understanding of energy transfer processes in these scintillators. Attention is drawn to the observed deviations between measured lithium content and content based on compositional data. Non-uniform lithium distribution of 10% has been observed and is reported.

Method permitting continuous measurement of pulse height variations

A method is described which provides a dc voltage corresponding to the average pulse height of input pulses with a Gaussian pulse height distribution and thereby permits accurate and successive measurements of pulse height variations by the use of a digital voltmeter and associated equipment.

Billet expansion as a mechanism for noise production in impact forming machines

In this paper a new mechanism for the production of impulsive noise in impact forming machines is proposed; namely the sudden radial expansion of the billet at the instant of impact. First of all a mathematical model of a forging machine is described which, though simplified in order to render it amenable to calculation, contains the essential features necessary for a realistic calculation of the sound pulse. A theory then is developed which enables the sound pulse to be computed given the rate of expansion of the billet surface. It is shown that the main part of the pulse from this source is produced during the first few microseconds of impact, the remaining few milliseconds of impact time producing a relatively small pulse. It being assumed, then, that the acceleration of the billet surface is essentially a delta function, the sound pulse produced by such an acceleration is computed and shown to constitute a significant part of the peak pressure measured. Finally the variation of pulse height with billet dimensions and impact velocity are given.