114 research outputs found

    A Monitor of the Focusing Strength of Plasma Lenses Using MeV Synchrotron Radiation

    Get PDF
    The focusing strength of plasma lenses used with high energy electron or positron beams can give rise to synchrotron radiation with critical energies in the MeV range. A method is described for measuring the characteristic energy of this radiation as a way of monitoring the strength of the focus. The principle has been implemented in a plasma lens experiment with a 28.5 GeV positron beam

    Inductive and Electrostatic Acceleration in Relativistic Jet-Plasma Interactions

    Full text link
    We report on the observation of rapid particle acceleration in numerical simulations of relativistic jet-plasma interactions and discuss the underlying mechanisms. The dynamics of a charge-neutral, narrow, electron-positron jet propagating through an unmagnetized electron-ion plasma was investigated using a three-dimensional, electromagnetic, particle-in-cell computer code. The interaction excited magnetic filamentation as well as electrostatic plasma instabilities. In some cases, the longitudinal electric fields generated inductively and electrostatically reached the cold plasma wave-breaking limit, and the longitudinal momentum of about half the positrons increased by 50% with a maximum gain exceeding a factor of 2 during the simulation period. Particle acceleration via these mechanisms occurred when the criteria for Weibel instability were satisfied.Comment: Revised for Phys. Rev. Lett. Please see publised version for best graphic

    Code phase assignment DS/CDMA communications for indoor wireless Rician multipath fading channels

    Get PDF
    The technique of using a single basic signature sequence for the DS/CDMA system was investigated. All users have their sequences differed by cyclic phase shifts from a basic signature sequence. It is called Code Phase Assignment (CPA). In [1], it has been shown that the CPA DS/CDMA technique yielded better performance over conventional DS/CDMA communications by substantial reduction of the multiple access interference (MAI) and the multipath interference (MI) for a simplified channel model. This paper further investigates its performance in the indoor Rician multipath fading channel. Comparison with conventional DS/CDMA system will be made and the effect on the change of system parameters will be investigated. Higher multiple access capacity over conventional DS/CDMA will be demonstrated. Lastly, CPA could reduce the effort of exhaustive search for sequences which makes it suitable for indoor applications.published_or_final_versio

    Error probabilities of synchronous DS/CDMA communications over multipath Rayleigh fading channels

    Get PDF
    This paper derives error probabilities for BPSK synchronous DS/CDMA communications over multipath Rayleigh fading WSSUS channels using a RAKE receiver. Both cases of perfectly and approximately synchronized signal transmission are considered. Numerical results are presented.published_or_final_versio

    Some Results On Spectrum And Energy Of Graphs With Loops

    Full text link
    Let GSG_S be a graph with loops obtained from a graph GG of order nn and loops at S⊆V(G)S \subseteq V(G). In this paper, we establish a neccesary and sufficient condition on the bipartititeness of a connected graph GG and the spectrum Spec(GSG_S) and Spec(GV(G)\SG_{V(G)\backslash S}). We also prove that for every S⊆V(G)S \subseteq V(G), E(GS)≥E(G)E(G_S) \geq E(G) when GG is bipartite. Moreover, we provide an identification of the spectrum of complete graphs KnK_n and complete bipartite graphs Km,nK_{m,n} with loops. We characterize any graphs with loops of order n whose eigenvalues are all positive or non-negative, and also any graphs with a few distinct eigenvalues. Finally, we provide some bounds related to GSG_S.Comment: 16 pages, published versio

    Global Incidence and mortality of oesophageal cancer and their correlation with socioeconomic indicators temporal patterns and trends in 41 countries

    Get PDF
    Oesophageal cancers (adenocarcinomas [AC] and squamous cell carcinomas [SCC]) are characterized by high incidence/mortality in many countries. We aimed to delineate its global incidence and mortality, and studied whether socioeconomic development and its incidence rate were correlated. The age-standardized rates (ASRs) of incidence and mortality of this medical condition in 2012 for 184 nations from the GLOBOCAN database; national databases capturing incidence rates, and the WHO mortality database were examined. Their correlations with two indicators of socioeconomic development were evaluated. Joinpoint regression analysis was used to generate trends. The ratio between the ASR of AC and SCC was strongly correlated with HDI (r = 0.535 [men]; r = 0.661 [women]) and GDP (r = 0.594 [men]; r = 0.550 [women], both p < 0.001). Countries that reported the largest reduction in incidence in male included Poland (Average Annual Percent Change [AAPC] = −7.1, 95%C.I. = −12,−1.9) and Singapore (AAPC = −5.8, 95%C.I. = −9.5,−1.9), whereas for women the greatest decline was seen in Singapore (AAPC = −12.3, 95%C.I. = −17.3,−6.9) and China (AAPC = −5.6, 95%C.I. = −7.6,−3.4). The Philippines (AAPC = 4.3, 95%C.I. = 2,6.6) and Bulgaria (AAPC = 2.8, 95%C.I. = 0.5,5.1) had a significant mortality increase in men; whilst Columbia (AAPC = −6.1, 95%C.I. = −7.5,−4.6) and Slovenia (AAPC = −4.6, 95%C.I. = −7.9,−1.3) reported mortality decline in women. These findings inform individuals at increased risk for primary prevention

    High Power Amplifier and Power Supply

    Get PDF
    A document discusses the creation of a high-voltage power supply (HVPS) that is able to contain voltages up to -20 kV, keep electrical field strengths to below 200 V/mil (approximately equal to 7.87 kV/mm), and can provide a 200-nanosecond rise/fall time focus modulator swinging between cathode potential of 16.3 kV and -19.3 kV. This HVPS can protect the 95-GHz, pulsed extended interaction klystron (EIK) from arcs/discharges from all sources, including those from within the EIK fs vacuum envelope. This innovation has a multi-winding pulse transformer design, which uses new winding techniques to provide the same delays and rise/fall times (less than 10 nanoseconds) at different potential levels ranging from -20 kV to -16 kV. Another feature involves a high-voltage printed-wiring board that was corona-free at -20 kV DC with a 3- kV AC swing. The corona-free multilayer high-voltage board is used to simulate fields of less than 200 V/mil (approximately equal to 7.87 kV/mm) at 20 kV DC. Drive techniques for the modulator FETs (field-effect transistors) (four to 10 in a series) were created to change states (3,000-V swing) without abrupt steps, while still maintaining required delays and transition times. The packing scheme includes a potting mold to house a ten-stage modulator in the space that, in the past, only housed a four-stage modulator. Problems keeping heat down were solved using aluminum oxide substrate in the high-voltage section to limit temperature rise to less than 10 while withstanding -20 kV DC voltage and remaining corona-free

    Characteristics of P-Channel Polysilicon Conductivity Modulated Thin-Film Transistors

    Get PDF
    Abstract-A p-channel polysilicon conductivity modulated thinfilm transistor (CMTFT) is demonstrated and experimentally characterized. The transistor uses the concept of conductivity modulation in the offset region to obtain a significant reduction in on-state resistance. The conductivity modulation is achieved by injecting minority carriers (electrons) into the offset region through a diode added to the drain. Experimental results show that the conductivity modulation in the p-channel device is as effective as that in the n-channel device. This structure can provide 1.5 to 2 orders of magnitude higher on-state current than that of the conventional offset drainthin-film transistor (TFT) at drain voltage ranging from 015 V to 05 V while still maintaining low leakage current and simplicity in device operation. The pchannel CMTFT can be combined with the n-channel CMTFT to form CMOS high-voltage drivers, which is very suitable for use in fully integrated large-area electronic applications
    • …
    corecore