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Ivan Bazarov - One of the best experts on this subject based on the ideXlab platform.

  • advances in bright Electron Sources
    2018
    Co-Authors: P Musumeci, Giner J Navarro, J B Rosenzweig, Luca Cultrera, Ivan Bazarov, Jared Maxson, Siddharth Karkare, Howard A Padmore
    Abstract:

    Abstract In this paper, we review the status of bright Electron Sources. High peak current (up to kA) low emittance ( 1  mm rad) Electron beams have been one of the critical components in the development of XFELs. The outlook for the field is even more promising as progress in the understanding of photoemission physics, development of novel photocathode materials, gun and laser technology, enable further progress in advanced light Sources as well as novel applications such as ultrafast Electron diffraction and microscopy. We outline here the more recent research trends which pave the way for potentially orders of magnitude brightness improvements with respect to the current state-of-the-art.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Jai Kwan Bae, Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.

Niels De Jonge - One of the best experts on this subject based on the ideXlab platform.

  • carbon nanotube Electron Sources for Electron microscopes
    2009
    Co-Authors: Niels De Jonge
    Abstract:

    Publisher Summary Electron Sources were constructed from individual multi walled carbon nanotubes with closed caps and thoroughly cleaned surfaces. Nanotubes from both chemical vapor deposition growth and arc discharge growth were investigated. These emitters provide a highly stable emission current up to a threshold current of a few microamperes. At too-large currents several processes occurs such as splitting, breaking, and cap closing. The emission process is field emission for a work function of 5eV. The Electron optical performance is highly beneficial for use of carbon nanotubes as high-brightness point Sources in Electron microscopes and advantageous with respect to state-of-the-art Electron Sources. The industrial process is needed to mount a closed-cap carbon nanotube inside an Electron miroscope so that it provides an Electron beam with a cone around the optical axis of the microscope. This requires not only that the carbon nanotube is mounted in a direction parallel to the optical axis, but also that the cap structure is defined such that the Electrons are emitted primarily in a forward direction.

  • low noise and stable emission from carbon nanotube Electron Sources
    2005
    Co-Authors: Niels De Jonge, Kenneth B. K. Teo, Myriam Allioux, Jim T Oostveen, W I Milne
    Abstract:

    Remarkably stable and low noise field-emission Electron Sources have been obtained using individual carbon nanotubes. The maximum current fluctuation observed over 1h was merely 0.5% and the emission frequency spectrum exhibited 1∕f behavior over a bandwidth of 0.1–25Hz, above which the shot-noise limit was reached. The average noise percentage was determined to be 0.08% (i.e., a signal-to-noise ratio of 1250) for seven CNT emitters operated at several current levels. The influence of the vacuum level was also investigated.

  • optical performance of carbon nanotube Electron Sources
    2005
    Co-Authors: Niels De Jonge, Kenneth B. K. Teo, Myriam Allioux, Jim T Oostveen, W I Milne
    Abstract:

    The figure of merit for the Electron optical performance of carbon-nanotube (CNT) Electron Sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT Electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art Electron point Sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter.

  • carbon nanotube Electron Sources and applications
    2004
    Co-Authors: Niels De Jonge, J M Bonard
    Abstract:

    In this review we give an overview of the present status of research on carbon nanotube (CNT) field emitters and their applications. Several different construction principles of field-emission devices with CNTs are summarized. The emission mechanism is introduced and a detailed overview is given of the measured emission properties and related topics of CNT Electron Sources. We give also several examples of field-emission devices with CNT Electron emitters that are presently being investigated in the academic world as well as in industry. Carbon nanotube Electron Sources clearly have interesting properties, such as low voltage operation, good stability, long lifetime and high brightness. The most promising applications are the field-emission display and high-resolution Electron-beam instruments. But several hurdles remain, such as the manufacture of an Electron source or an array of Electron Sources with exactly the desired properties in a reproducible manner.

  • brightness of carbon nanotube Electron Sources
    2004
    Co-Authors: Niels De Jonge
    Abstract:

    The virtual source sizes of individual multiwalled carbon nanotube Electron emitters were investigated with a point projection microscope. The average radius of the virtual source size was found to be 2.6 nm, which does not correspond to the standard model of a field emitter. Instead, a model based on a flattened cap or an open cap seems to provide a more realistic description. The broadening effect of Coulomb interactions on the virtual source was calculated. The reduced angular current density was measured at the maximum current at which stable emission was obtained and arrived at an average of 30 nA sr−1 V−1. The reduced brightness values obtained for two emitters were (2.5±1)×109 and (1.3±0.5)×109 A m−2 sr−1 V−1, respectively. These values are an order of magnitude larger than the values of state-of-the-art commercial Sources.

Luca Cultrera - One of the best experts on this subject based on the ideXlab platform.

  • advances in bright Electron Sources
    2018
    Co-Authors: P Musumeci, Giner J Navarro, J B Rosenzweig, Luca Cultrera, Ivan Bazarov, Jared Maxson, Siddharth Karkare, Howard A Padmore
    Abstract:

    Abstract In this paper, we review the status of bright Electron Sources. High peak current (up to kA) low emittance ( 1  mm rad) Electron beams have been one of the critical components in the development of XFELs. The outlook for the field is even more promising as progress in the understanding of photoemission physics, development of novel photocathode materials, gun and laser technology, enable further progress in advanced light Sources as well as novel applications such as ultrafast Electron diffraction and microscopy. We outline here the more recent research trends which pave the way for potentially orders of magnitude brightness improvements with respect to the current state-of-the-art.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Jai Kwan Bae, Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.

W I Milne - One of the best experts on this subject based on the ideXlab platform.

  • parametrically optimized carbon nanotube coated cold cathode spindt arrays
    2017
    Co-Authors: Xuesong Yuan, Matthew T Cole, Yu Zhang, W I Milne, Yang Yan
    Abstract:

    Here, we investigate, through parametrically optimized macroscale simulations, the field Electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum Electron devices. The present study builds on empirical data gleaned from our recent experimental findings on the room temperature Electron emission from large area CNT Electron Sources. We determine the field emission current of the present microstructures directly using particle in cell (PIC) software and present a new CNT cold cathode array variant which has been geometrically optimized to provide maximal emission current density, with current densities of up to 11.5 A/cm2 at low operational electric fields of 5.0 V/μm.

  • carbon nanotubes as Electron Sources
    2006
    Co-Authors: W I Milne, Pierre Legagneux, Kenneth B. K. Teo, G A J Amaratunga, Myriam Allioux, Jim T Oostveen, M Mann, N De Jonge, Eric Minoux
    Abstract:

    Carbon nanotubes (CNTs) are a unique form of carbon filament/fiber in which the graphene walls roll up to form tubes. They can exhibit either metallic-like or semiconductor-like properties. With the graphene walls parallel to the filament axis, nanotubes (single wall metallic-type or multi-wall) exhibit high electrical conductivity at room temperature. This high electrical conductivity allied to their remarkable thermal stability has made CNTs one of the most intensely studied material systems for field emission (FE) applications. In this paper we will describe the growth of multiwall CNTs and their application in a range of field emission based systems including their use in SEM Sources, emitters for use in microwave amplifiers and as emitters in field emission based displays (FEDs).

  • low noise and stable emission from carbon nanotube Electron Sources
    2005
    Co-Authors: Niels De Jonge, Kenneth B. K. Teo, Myriam Allioux, Jim T Oostveen, W I Milne
    Abstract:

    Remarkably stable and low noise field-emission Electron Sources have been obtained using individual carbon nanotubes. The maximum current fluctuation observed over 1h was merely 0.5% and the emission frequency spectrum exhibited 1∕f behavior over a bandwidth of 0.1–25Hz, above which the shot-noise limit was reached. The average noise percentage was determined to be 0.08% (i.e., a signal-to-noise ratio of 1250) for seven CNT emitters operated at several current levels. The influence of the vacuum level was also investigated.

  • optical performance of carbon nanotube Electron Sources
    2005
    Co-Authors: Niels De Jonge, Kenneth B. K. Teo, Myriam Allioux, Jim T Oostveen, W I Milne
    Abstract:

    The figure of merit for the Electron optical performance of carbon-nanotube (CNT) Electron Sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT Electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art Electron point Sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter.

  • carbon nanotubes as field emission Sources
    2004
    Co-Authors: W I Milne, Pierre Legagneux, Jean-philippe Schnell, Kenneth B. K. Teo, G A J Amaratunga, L Gangloff, V Semet, Thien V Binh, Oliver Groening
    Abstract:

    Micro and nano-structurally rich carbon materials are alternatives to conventional metal/silicon tips for field emission Sources. In particular, carbon nanotubes exhibit extraordinary field emission properties because of their high electrical conductivity, their high aspect ratio “whisker-like” shape for optimum geometrical field enhancement, and remarkable thermal stability. This paper will review the PECVD growth process, and the microfabrication techniques needed to produce well defined carbon nanotube based micro-Electron Sources for use in novel parallel e-beam lithography and high frequency microwave amplifier systems.

Philip Digiacomo - One of the best experts on this subject based on the ideXlab platform.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.

  • rugged spin polarized Electron Sources based on negative Electron affinity gaas photocathode with robust cs2te coating
    2018
    Co-Authors: Jai Kwan Bae, Luca Cultrera, Philip Digiacomo, Ivan Bazarov
    Abstract:

    Photocathodes capable of providing high intensity and highly spin-polarized Electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoElectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized Electron Sources employing photocathodes with robust coatings.