The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform

A Romanenko - One of the best experts on this subject based on the ideXlab platform.

  • Frequency Dependence of trapped flux sensitivity in srf cavities
    Applied Physics Letters, 2018
    Co-Authors: Mattia Checchin, Martina Martinello, Anna Grassellino, Sebastian Aderhold, Saravan K Chandrasekaran, Oleksandr Melnychuk, S Posen, A Romanenko
    Abstract:

    In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field—sensitivity—is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of the electron mean-free-path, compared to 120 °C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field—sensitivity—is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of the electron mean-free-path, compared to 120 °C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.

  • Frequency Dependence of trapped flux sensitivity in srf cavities
    arXiv: Accelerator Physics, 2017
    Co-Authors: Mattia Checchin, Martina Martinello, Anna Grassellino, Sebastian Aderhold, Saravan K Chandrasekaran, Oleksandr Melnychuk, S Posen, A Romanenko
    Abstract:

    In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field - sensitivity - is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of electron mean-free-path, compared to 120 C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including at frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.

S. K. Morgan Ernest - One of the best experts on this subject based on the ideXlab platform.

  • Do persistent rare species experience stronger negative Frequency Dependence than common species
    Global Ecology and Biogeography, 2017
    Co-Authors: Glenda M. Yenni, Peter B. Adler, S. K. Morgan Ernest
    Abstract:

    Understanding why so many species are rare yet persistent remains a significant challenge for both theoretical and empirical ecologists. Yenni et al. (2012, Ecology, 93, 456–461) proposed that strong negative Frequency Dependence causes species to be rare while simultaneously buffering them against extinction. This hypothesis predicts that, on average, rare species should experience stronger negative Frequency Dependence than common species. However, it is unknown if ecological communities generally show this theoretical pattern. We discuss the implications of this phenomenon for community dynamics, and develop a method to test for a non-random relationship between negative Frequency Dependence and relative abundance using species abundance data from 90 communities across a broad range of environments and taxonomic groups. To account for biases introduced by measurement error, we compared the observed correlation between species relative abundance and the strength of Frequency Dependence against expectations from a randomization procedure. In approximately half of the analysed communities, we found increasingly strong negative Frequency Dependence with decreasing relative abundance: rare species experienced stronger Frequency Dependence than common species. The randomization test never detected stronger negative Frequency Dependence in more common species. Our results suggest that strong negative Frequency Dependence is a signature of persistent, rare species in many communities.

  • Do persistent rare species experience stronger negative Frequency Dependence than common species
    2016
    Co-Authors: Glenda M. Yenni, Peter B. Adler, S. K. Morgan Ernest
    Abstract:

    Understanding why so many species are rare yet persistent remains a significant challenge for both theoretical and empirical ecologists. Yenni, Adler, and Ernest (2012) proposed that strong negative Frequency Dependence causes species to be rare while simultaneously buffering them against extinction. This hypothesis predicts that, on average, rare species should experience stronger negative Frequency Dependence than common species. However, it is unknown if ecological communities generally show this theoretical pattern, or if rarity is primarily determined by other processes that overwhelm the effects of strong negative Frequency Dependence. We discuss the implications of this mechanism for natural communities, and develop a method to test for a non-random relationship between negative Frequency Dependence and relative abundance, using species abundance data from 90 communities across a broad range of environments and taxonomic groups. To account for biases introduced by measurement error, we compared the observed correlation between species relative abundance and the strength of Frequency Dependence against expectations from a randomization procedure. In approximately half of the analyzed communities, rare species showed disproportionately strong negative Frequency Dependence compared to common species. Specifically, we found a pattern of increasingly strong negative Frequency Dependence with decreasing relative abundance. Our results suggest that strong negative Frequency Dependence is a signature of both rarity and persistence for many species in many communities.

Glenda M. Yenni - One of the best experts on this subject based on the ideXlab platform.

  • Do persistent rare species experience stronger negative Frequency Dependence than common species
    Global Ecology and Biogeography, 2017
    Co-Authors: Glenda M. Yenni, Peter B. Adler, S. K. Morgan Ernest
    Abstract:

    Understanding why so many species are rare yet persistent remains a significant challenge for both theoretical and empirical ecologists. Yenni et al. (2012, Ecology, 93, 456–461) proposed that strong negative Frequency Dependence causes species to be rare while simultaneously buffering them against extinction. This hypothesis predicts that, on average, rare species should experience stronger negative Frequency Dependence than common species. However, it is unknown if ecological communities generally show this theoretical pattern. We discuss the implications of this phenomenon for community dynamics, and develop a method to test for a non-random relationship between negative Frequency Dependence and relative abundance using species abundance data from 90 communities across a broad range of environments and taxonomic groups. To account for biases introduced by measurement error, we compared the observed correlation between species relative abundance and the strength of Frequency Dependence against expectations from a randomization procedure. In approximately half of the analysed communities, we found increasingly strong negative Frequency Dependence with decreasing relative abundance: rare species experienced stronger Frequency Dependence than common species. The randomization test never detected stronger negative Frequency Dependence in more common species. Our results suggest that strong negative Frequency Dependence is a signature of persistent, rare species in many communities.

  • Do persistent rare species experience stronger negative Frequency Dependence than common species
    2016
    Co-Authors: Glenda M. Yenni, Peter B. Adler, S. K. Morgan Ernest
    Abstract:

    Understanding why so many species are rare yet persistent remains a significant challenge for both theoretical and empirical ecologists. Yenni, Adler, and Ernest (2012) proposed that strong negative Frequency Dependence causes species to be rare while simultaneously buffering them against extinction. This hypothesis predicts that, on average, rare species should experience stronger negative Frequency Dependence than common species. However, it is unknown if ecological communities generally show this theoretical pattern, or if rarity is primarily determined by other processes that overwhelm the effects of strong negative Frequency Dependence. We discuss the implications of this mechanism for natural communities, and develop a method to test for a non-random relationship between negative Frequency Dependence and relative abundance, using species abundance data from 90 communities across a broad range of environments and taxonomic groups. To account for biases introduced by measurement error, we compared the observed correlation between species relative abundance and the strength of Frequency Dependence against expectations from a randomization procedure. In approximately half of the analyzed communities, rare species showed disproportionately strong negative Frequency Dependence compared to common species. Specifically, we found a pattern of increasingly strong negative Frequency Dependence with decreasing relative abundance. Our results suggest that strong negative Frequency Dependence is a signature of both rarity and persistence for many species in many communities.

B. M. Wood - One of the best experts on this subject based on the ideXlab platform.

  • Octofilar resistors with calculable Frequency Dependence
    Metrologia, 2001
    Co-Authors: J Boh Cek, B. M. Wood
    Abstract:

    The results are presented of calculation of the Frequency Dependence of an octofilar resistor, the resistive element of which is folded in such a way that it forms four long loops connected in series. Magnetic fluxes produced by the loops tend to cancel, similar to the fluxes produced by the two loops of the common quadrifilar reversed resistor. The folded length of the octofilar resistive element is one half of that of a quadrifilar resistor made from the same wire and having the same nominal resistance, and the octofilar resistor has a smaller Frequency Dependence. As an example, a 12906 Ω octofilar resistor is described, for which the Frequency Dependence of its parallel equivalent resistance is more than seven times smaller than that of a previously made 12906 Ω quadrifilar resistor in the Frequency range 500 Hz to 5 kHz.

  • Octofilar resistors with calculable Frequency Dependence
    Conference on Precision Electromagnetic Measurements. Conference Digest. CPEM 2000 (Cat. No.00CH37031), 2000
    Co-Authors: Jan Bohácek, B. M. Wood
    Abstract:

    We present the results of calculations of the Frequency Dependence of resistors consisting of eight parallel resistive elements similar in design to the common reversed quadrifilar resistor. At 12906 /spl Omega/ a commercial octofilar resistor has a smaller Frequency Dependence than a reversed quadrifilar resistor with comparable spacing but twice the element length.

Anna Grassellino - One of the best experts on this subject based on the ideXlab platform.

  • Frequency Dependence of trapped flux sensitivity in srf cavities
    Applied Physics Letters, 2018
    Co-Authors: Mattia Checchin, Martina Martinello, Anna Grassellino, Sebastian Aderhold, Saravan K Chandrasekaran, Oleksandr Melnychuk, S Posen, A Romanenko
    Abstract:

    In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field—sensitivity—is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of the electron mean-free-path, compared to 120 °C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field—sensitivity—is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of the electron mean-free-path, compared to 120 °C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.

  • Frequency Dependence of trapped flux sensitivity in srf cavities
    arXiv: Accelerator Physics, 2017
    Co-Authors: Mattia Checchin, Martina Martinello, Anna Grassellino, Sebastian Aderhold, Saravan K Chandrasekaran, Oleksandr Melnychuk, S Posen, A Romanenko
    Abstract:

    In this letter, we present the Frequency Dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field - sensitivity - is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of electron mean-free-path, compared to 120 C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including at frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the Frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The Frequency Dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.