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    Wyświetlanie 1-13 z 13
    Tytuł:
    Design of a Permanent Magnet Wiggler for a THz Free Electron Laser
    Autorzy:
    Balal, N.
    Magori, E.
    Yahalom, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1401864.pdf
    Data publikacji:
    2015-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    03.50.-z
    07.55.Db
    07.57.Hm
    Opis:
    A THz free electron laser is being built in Ariel University. Upon completion it is intended to become a user facility. The free electron laser is designed to emit radiation between 1 and 5 THz. It is planned to operate in the super radiance regime. The anticipated output of the free electron laser is in excess of 150 kW instantaneous power. An essential part of every free electron laser is a device generating a periodic magnetic field denoting the wiggler. Here we describe a design of a classical Halbach type permanent magnetic wiggler for the THz free electron laser. The main novelty in this paper is the choice of wiggler parameters suitable for operation in the THz frequency range. Considerations such as radiation wave length, wiggler gain and electron optics are taken into account.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 3; 259-263
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Linear Polarized Terahertz Emission under Electrical Breakdown of a Shallow Acceptor in Uniaxially Deformed Germanium
    Autorzy:
    Andrianov, A.
    Zakhar'in, A.
    Yassievich, I.
    Zinov'ev, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813201.pdf
    Data publikacji:
    2008-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.57.Hm
    78.60.Fi
    78.67.De
    Opis:
    We report on polarization spectra of spontaneous terahertz electroluminescence from uniaxially deformed Ge(Ga). At compressive pressure of about 3±0.3 kbar in the [111] direction, near the impurity breakdown threshold, the linear polarization degree attains ≈80-90% for the main lines of the terahertz emission.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 3; 863-867
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Tesla Transformer and a Coaxial Peaking Switch as a UWB Pulse Source
    Autorzy:
    Amal, Y.
    Pecastaing, L.
    Rivaletto, M.
    Reess, T.
    Pignolet, P.
    Cassany, B.
    Ferron, A.
    Courtois, L.
    Merle, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1807938.pdf
    Data publikacji:
    2009-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    84.70.+p
    07.57.Hm
    84.30.Ng
    Opis:
    This paper presents a high voltage pulse source which is able to generate ultra wideband (UWB) pulses during about 1 ns through a 16 antennas array. This UWB source is composed of a 50 kV DC voltage supply, a Tesla transformer to amplify this voltage up to 400 kV, a gaseous pressurized peaking switch and an impedance transformer (50 Ω → 3.125 Ω). This output impedance value corresponds to the input impedance value of a sixteen 50 Ω antennas array. That is why a distributor is needed in order to feed the antenna array. In this paper, the peaking switch and the capacitive line divider used to characterise the generated pulses are particularly described. The peaking switch is based on the principle of a line discharge by means of a high pressure gas switch. It is loaded with a Tesla transformer to obtain a good pulse reproducibility. The main characteristics of the output pulse waveform (amplitude and rise time) are linked to the properties of the gas switch and particularly to the gap distance, the pressure and the nature of the gas used in the switch filling. The aim is to find a good compromise between various parameters as the output pulse amplitude, the rise time and the repetition rate in order to ensure a better efficiency of the UWB source. Classical voltage measurement techniques do not allow us an estimation of the main characteristics of such an output signal. Therefore a voltage probe was designed and realised to measure both the amplitude and the rise time of the pulses delivered by the generator. This device is based on the principle of a capacitive line divider. Calibration tests (transient and frequency tests) were performed and show that the high cut-off frequency, around 2.5 GHz, is consistent with the transient response of the output high voltage waveform. The design, realisation and calibration tests are also presented.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 6; 1115-1117
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Submillimeter-Wave Oscillations in Recessed InGaAs/InAlAs Heterostructures: Origin and Tunability
    Autorzy:
    Pérez, S.
    Mateos, J.
    González, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505462.pdf
    Data publikacji:
    2011-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    85.30.Fg
    07.57.Hm
    73.40.Kp
    Opis:
    By means of an ensemble Monte Carlo simulator, the appeareance of THz oscillations in InAlAs/InGaAs slot diodes is predicted when the applied bias exceeds the threshold for intervalley transfer. Such high frequency is attained by the presence of a Gunn-like effect in the recess-to-drain region of the device channel whose dynamics is controlled by ballistic Γp valley electrons. In this work we explain the mechanism at the origin of this effect and also the influence of the bias conditions, δ-doping, recess-to-drain distance and recess length on the frequency of the ultrafast Gunn-like oscillations. The simulations show that a minimum value for the δ-doping is necessary to have enough carrier concentration under the recess and allow the oscillations to emerge. Finally, we show that shortening the devices (small recess and recess-to-drain lengths) increases the oscillation frequency, so provides an interesting frequency tunability of this THz source.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 2; 111-113
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Development of a Fast Marx Generator for High Power Ultra Wideband Pulse Radiation
    Autorzy:
    Cadilhon, B.
    Pecastaing, L.
    Reess, T.
    de Ferron, A.
    Pignolet, P.
    Brasile, J.
    Andrieu, J.
    Vauchamp, S.
    Bertrand, V.
    Lalande, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1807924.pdf
    Data publikacji:
    2009-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    84.70.+p
    07.57.Hm
    84.30.Ng
    Opis:
    We present in this paper the design and realisation of two autonomous, ultra wideband radiation sources consisting of a high gain broadband antenna driven by two subnanosecond pulsed power sources. Each one is made of a Marx generator and a pulse forming device based on the use of gaseous spark gap. The main pulsed source is a ten stage subnanosecond Marx generator which delivers pulses in the range of 250 kV/1.5 J, with a 300 ps rise time, subnanosecond pulse duration at a pulse repetition frequency of 350 Hz. The antenna combined with the pulsed source is a travelling wave antenna called Valentine antenna. Some mechanical modifications were made to improve the dielectric strength of this radiation element. A 3D model of the antenna, on a time domain electromagnetic software, was first performed to study the influence of these modifications on the main radiating characteristics of the antenna. Its high gain and its capability to radiate short pulses without dispersion allow us to achieve a high measured figure of merit.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 6; 1084-1085
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Low-Temperature MBE Grown GaAs for Pulsed THz Radiation Applications
    Autorzy:
    Adomavičius, R.
    Balakauskas, S.
    Bertulis, K.
    Geižutis, A.
    Molis, G.
    Krotkus, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041645.pdf
    Data publikacji:
    2005-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.65.Re
    07.57.Hm
    78.47.+p
    Opis:
    Attempts to optimize recombination characteristics of low-temperature MBE grown GaAs layers for their use in terahertz radiation devices are described and the characteristics of this material are compared with its alternative - As-ion implanted GaAs crystals.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 1; 128-131
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spontaneous Terahertz Emission under Electrical Breakdown of a Shallow Acceptor in Ge
    Autorzy:
    Andrianov, A. V.
    Zaharin, A. O.
    Yassievich, I. N.
    Zinovev, N. N.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041653.pdf
    Data publikacji:
    2005-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.De
    78.60.Fi
    07.57.Hm
    Opis:
    The spectra of spontaneous terahertz (THz) electroluminescence at the breakdown of shallow Ga acceptor in Ge were observed for the first time and investigated. We found and characterized the emission lines corresponding to the hole transitions between the excited states and the ground state of the impurity center as well as the transitions of the hot holes from the valence band to the impurity and within the valence band. A high quantum yield of the radiative transitions will become an important factor in designing electrically pumped THz emitters for the≈2 THz spectral range.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 1; 142-146
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    THz Reflection Spectra of Different Materials, Including Explosives, Measured at a Distance up to 5 m
    Autorzy:
    Walczakowski, M.
    Palka, N.
    Czerwiński, A.
    Sypek, M.
    Szustakowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398672.pdf
    Data publikacji:
    2015-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    06.60.Ei
    07.57.Hm
    07.57.Kp
    07.57.Pt
    33.20.Ea
    Opis:
    This work presents a terahertz system designed for the reflection spectroscopy of different materials located at a distance up to 5 m. The source of the radiation is a tunable solid-state optical parametric oscillator, which generates a narrow-band nanosecond pulses in the range of 0.7-2.5 THz. The signal is detected with relatively fast and having big sensitivity hot electron bolometer. The detailed description of each device and the functioning of the experimental setup are provided as well as the methodology of the measurement is explained. Investigations were performed in the 0.7-2.2 THz range in free space with relative humidity of about 40%. The experiment was divided into three series, each of which was carried out with different distance between the examined sample and the system - 1 m, 3 m, and 5 m. Obtained spectra of selected materials, including explosives, are similar to the results received from a purged time domain spectroscopy system. The observed small deviations are connected with fluctuations of the laser wavelength and the instability of the bolometer.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 3; 689-692
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Terahertz Emission from Narrow Gap Semiconductors Photoexcited by Femtosecond Laser Pulses
    Autorzy:
    Adomavičius, R.
    Urbanowicz, A.
    Molis, G.
    Krotkus, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041649.pdf
    Data publikacji:
    2005-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.65.Re
    07.57.Hm
    78.47.+p
    72.30.+q
    Opis:
    Large increase in the emitted terahertz power was observed for p-InAs samples with the p-doping levels of approximately 10$\text{}^{16}$-10$\text{}^{17}$ cm$\text{}^{-3}$. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in the layer. Terahertz fields radiated by the samples of all three investigated Cd$\text{}_{x}$Hg$\text{}_{1-x}$Te layers was of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification. Azimuthal angle and magnetic fields emission witness that it is caused by linear photo-Dember type processes.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 1; 132-136
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Pump - Terahertz Probe Measurement of the Electron Dynamics in Ga$\text{}_{1-x}$Mn$\text{}_{x}$As
    Autorzy:
    Šustavičiūtė, R.
    Balakauskas, S.
    Adomavičius, R.
    Krotkus, A.
    Sadowski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047687.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.65.Re
    07.57.Hm
    78.47.+p
    75.50.Pp
    Opis:
    An optical pump - terahertz probe technique was used for measuring electron lifetime in various Ga$\text{}_{1-x}$Mn$\text{}_{x}$As epitaxial layers with the subpicosecond temporal resolution. The measurements were performed on the samples with x up to 2%, which had large resistivities and were transparent in a THz frequency range. It has been found that an induced THz absorption relaxation is the fastest and electron lifetimes are the shortest for the samples with the smallest Mn content. For the samples with x=0.3% and x=2% this relaxation becomes much slower; its rate is comparable to the carrier recombination rate in Ga$\text{}_{1-x}$Mn$\text{}_{x}$As substrate.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 311-314
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermal Microwave Radiation for Subsurface Absolute Temperature Measurement
    Autorzy:
    Susek, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1506860.pdf
    Data publikacji:
    2010-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    87.63.Hg
    44.40.+a
    84.40.Dc
    07.57.Hm
    Opis:
    Problems related to thermal radiation of human bodies in the microwave range are presented in the paper from medical diagnosis point of view. The paper reviews physical principles of thermal radiation measurement at microwave frequencies. A design of a modulation type radiometer with both zero reading and compensation of influence of the reflectivity is presented in the paper. On the base of this design, requirements for absolute temperature measurement conditions in the lossy and homogeneous medium were found. It is worth noting that these demands do not need any limitations for environmental parameters, especially for their stability during measurement (ambient temperature stability). At the end, experimental results of the measurements carried out with the use of the microwave radiometer operating in the 1.5 GHz band are shown.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 6; 1246-1249
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Terahertz Emission from the Surfaces of InAs and Other Narrow-Gap Semiconductors
    Autorzy:
    Adomavičius, R.
    Krotkus, A.
    Molis, G.
    Urbanowicz, A.
    Malevich, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813200.pdf
    Data publikacji:
    2008-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.65.Re
    07.57.Hm
    78.47.-p
    72.30.+q
    Opis:
    THz pulses were used to investigate carrier dynamics in narrow-gap semiconductors. The measurement of the optically induced THz pulse absorption transients provided important insights into electron energy relaxation in the conduction band. In the second set of experiments, THz generation from the surfaces of various semiconductors was studied and compared. It was found that the most efficient THz emitters are semiconductors with a narrow band gap, large intervalley separation in the conduction band, and low nonparabolicity of the main valley.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 3; 859-862
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Noise Radar with Microwave Correlation Receiver
    Autorzy:
    Susek, W.
    Stec, B.
    Rećko, Cz.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505215.pdf
    Data publikacji:
    2011-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.57.Hm
    41.90.+e
    84.40.Ua
    84.40.Xb
    84.40.Dc
    Opis:
    The idea of microwave quadrature correlation as well as the block diagram of the microwave broadband correlation receiver and principle of quadrature correlation detection of noise signals using an analog microwave correlator are presented in the paper. Measurement results for the correlation function of noise signals are shown and application of such solution in the noise radar for precise determination of distance changes and velocity of these changes is also presented. Results for short range noise radar operation are presented both for static and moving. Experimental results using 2.6-3.6 GHz noise like waveform for the signal from a breathing human is presented. Conclusions and future plans for the use of presented detection technique in broad-band noise radars close the paper.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 4; 483-487
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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