LIVIVO - Das Suchportal für Lebenswissenschaften

switch to English language
Zurück zur letzten Suche Suchhistorie
Erweiterte Suche

Ihre letzten Suchen

  1. AU="Karkare, Siddharth"
  2. AU="Corrêa, Diogo G"
  3. AU="Choi, Sun Ha"

Suchergebnis

Treffer 1 - 8 von insgesamt 8

Suchoptionen

  1. Artikel ; Online: A cryogenically cooled 200 kV DC photoemission electron gun for ultralow emittance photocathodes.

    Gevorkyan, Gevork / Sarabia-Cardenas, Carlos / Kachwala, Alimohammad / Knill, Christopher / Hanks, Tatum J / Bhattacharyya, Priyadarshini / Li, William H / Cultrera, Luca / Galdi, Alice / Bazarov, Ivan / Maxson, Jared / Karkare, Siddharth

    The Review of scientific instruments

    2023  Band 94, Heft 9

    Abstract: Novel photocathode materials like ordered surfaces of single crystal metals, epitaxially grown high quantum efficiency thin films, and topologically non-trivial materials with dirac cones show great promise for generating brighter electron beams for ... ...

    Abstract Novel photocathode materials like ordered surfaces of single crystal metals, epitaxially grown high quantum efficiency thin films, and topologically non-trivial materials with dirac cones show great promise for generating brighter electron beams for various accelerator and ultrafast electron scattering applications. Despite several materials being identified as brighter photocathodes, none of them have been tested in electron guns to extract electron beams due to technical and logistical challenges. In this paper, we present the design and commissioning of a cryocooled 200 kV DC electron gun that is capable of testing a wide variety of novel photocathode materials over a broad range of temperatures from 298 to 35 K for bright electron beam generation. This gun is designed to enable easy transfer of the photocathode to various standard ultra-high-vacuum surface diagnostics and preparation techniques, allowing a full characterization of the dependence of beam brightness on the photocathode material and surface properties. We demonstrate the development of such a high-voltage, high-gradient gun using materials and equipment that are easily available in any standard university lab, making the development of such 200 kV electron guns more accessible.
    Sprache Englisch
    Erscheinungsdatum 2023-09-14
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/5.0160818
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 46/112: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  2. Artikel ; Online: Ultracold Electrons via Near-Threshold Photoemission from Single-Crystal Cu(100).

    Karkare, Siddharth / Adhikari, Gowri / Schroeder, W Andreas / Nangoi, J Kevin / Arias, Tomas / Maxson, Jared / Padmore, Howard

    Physical review letters

    2020  Band 125, Heft 5, Seite(n) 54801

    Abstract: Achieving a low mean transverse energy or temperature of electrons emitted from the photocathode-based electron sources is critical to the development of next-generation and compact x-ray free electron lasers and ultrafast electron diffraction, ... ...

    Abstract Achieving a low mean transverse energy or temperature of electrons emitted from the photocathode-based electron sources is critical to the development of next-generation and compact x-ray free electron lasers and ultrafast electron diffraction, spectroscopy, and microscopy experiments. In this Letter, we demonstrate a record low mean transverse energy of 5 meV from the cryo-cooled (100) surface of copper using near-threshold photoemission. Further, we also show that the electron energy spread obtained from such a surface is less than 11.5 meV, making it the smallest energy spread electron source known to date: more than an order of magnitude smaller than any existing photoemission, field emission, or thermionic emission based electron source. Our measurements also shed light on the physics of electron emission and show how the energy spread at few meV scale energies is limited by both the temperature and the vacuum density of states.
    Sprache Englisch
    Erscheinungsdatum 2020-08-14
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.054801
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 58/153: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  3. Buch ; Online: Ab initio many-body photoemission theory of transverse energy distribution of photoelectrons

    Nangoi, J. Kevin / Karkare, Siddharth / Sundararaman, Ravishankar / Padmore, Howard A. / Arias, T. A.

    PbTe(111) as a case study with experimental comparisons

    2020  

    Abstract: This manuscript presents, to our knowledge, the first fully ab initio many-body photoemission framework to predict the transverse momentum distributions and the mean transverse energies (MTEs) of photoelectrons from single-crystal photocathodes. The need ...

    Abstract This manuscript presents, to our knowledge, the first fully ab initio many-body photoemission framework to predict the transverse momentum distributions and the mean transverse energies (MTEs) of photoelectrons from single-crystal photocathodes. The need to develop such a theory stems from the lack of studies that provide complete understanding of the underlying fundamental processes governing the transverse momentum distribution of photoelectrons emitted from single crystals. For example, initial predictions based on density-functional theory calculations of effective electron masses suggested that the (111) surface of PbTe would produce very small MTEs ($\leq$ 15 meV), whereas our experiments yielded MTEs ten to twenty times larger than these predictions, and also exhibited a lower photoemission threshold than predicted. The ab initio framework presented in this manuscript correctly reproduces the magnitude of the MTEs from our measurements in PbTe(111) and also the observed photoemission below the predicted threshold. Our results show that photoexcitations into bulk-like states and coherent, many-body electron-photon-phonon scattering processes, both of which initial predictions ignored, indeed play important roles in photoemission from PbTe(111). Finally, from the lessons learned, we recommend a procedure for rapid computational screening of potential single-crystal photocathodes for applications in next-generation ultrafast electron diffraction and X-ray free-electron lasers, which will enable new, significant advances in condensed matter research.

    Comment: Submitting to Physical Review B
    Schlagwörter Condensed Matter - Materials Science ; Physics - Accelerator Physics ; Physics - Computational Physics
    Thema/Rubrik (Code) 541
    Erscheinungsdatum 2020-06-21
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Volltext online

    Zusatzmaterialien

    Kategorien

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  4. Buch ; Online: Effect of nano-scale surface roughness on transverse energy spread from GaAs photocathodes

    Karkare, Siddharth / Bazarov, Ivan

    2011  

    Abstract: High quantum yield, low transverse energy spread and prompt response time make GaAs activated to negative electron affnity, an ideal candidate for a photocathode in high brightness photoinjectors. Even after decades of investigation, the exact mechanism ... ...

    Abstract High quantum yield, low transverse energy spread and prompt response time make GaAs activated to negative electron affnity, an ideal candidate for a photocathode in high brightness photoinjectors. Even after decades of investigation, the exact mechanism of electron emission from GaAs is not well understood. We show that a nanoscale surface roughness can affect the transverse electron spread from GaAs by nearly an order of magnitude and explain the seemingly controversial experimental results obtained so far. This model can also explain the measured dependence of transverse energy spread on the wavelength of incident light.

    Comment: 3pages, 3figures
    Schlagwörter Physics - Accelerator Physics ; Condensed Matter - Materials Science
    Erscheinungsdatum 2011-02-23
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Volltext online

    Zusatzmaterialien

    Kategorien

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  5. Artikel ; Online: Review and demonstration of ultra-low-emittance photocathode measurements.

    Lee, Hyeri / Karkare, Siddharth / Cultrera, Luca / Kim, Andrew / Bazarov, Ivan V

    The Review of scientific instruments

    2015  Band 86, Heft 7, Seite(n) 73309

    Abstract: This paper reports the development of a simple and reliable apparatus for measuring ultra-low emittance, or equivalently the mean transverse energy from cryogenically cooled photocathodes. The existing methods to measure ultra-low emittance from ... ...

    Abstract This paper reports the development of a simple and reliable apparatus for measuring ultra-low emittance, or equivalently the mean transverse energy from cryogenically cooled photocathodes. The existing methods to measure ultra-low emittance from photocathodes are reviewed. Inspired by the available techniques, we have implemented two complementary methods, the waist scan and voltage scan, in one system giving consistent results. Additionally, this system is capable of measuring the emittance at electric fields comparable to those obtained in DC photoinjectors.
    Sprache Englisch
    Erscheinungsdatum 2015-07
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/1.4927381
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 46/112: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  6. Artikel ; Online: 2-D energy analyzer for low energy electrons.

    Karkare, Siddharth / Cultrera, Luca / Hwang, Yoon-Woo / Merluzzi, Richard / Bazarov, Ivan

    The Review of scientific instruments

    2015  Band 86, Heft 3, Seite(n) 33301

    Abstract: A 2-D electron energy analyzer is designed and constructed to measure the transverse and longitudinal energy distribution of low energy (<1 eV) electrons. The analyzer operates on the principle of adiabatic invariance and motion of low energy electrons ... ...

    Abstract A 2-D electron energy analyzer is designed and constructed to measure the transverse and longitudinal energy distribution of low energy (<1 eV) electrons. The analyzer operates on the principle of adiabatic invariance and motion of low energy electrons in a strong longitudinal magnetic field. The operation of the analyzer is studied in detail and a design to optimize the energy resolution, signal to noise ratio, and physical size is presented. An energy resolution better than 6 meV has been demonstrated. Such an analyzer is a powerful tool to study the process of photoemission which limits the beam quality in modern accelerators.
    Sprache Englisch
    Erscheinungsdatum 2015-03
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/1.4913655
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 46/112: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  7. Artikel ; Online: Reduction of Intrinsic Electron Emittance from Photocathodes Using Ordered Crystalline Surfaces.

    Karkare, Siddharth / Feng, Jun / Chen, Xumin / Wan, Weishi / Palomares, F Javier / Chiang, T-C / Padmore, Howard A

    Physical review letters

    2017  Band 118, Heft 16, Seite(n) 164802

    Abstract: The generation of intense electron beams with low emittance is key to both the production of coherent x rays from free electron lasers, and electron pulses with large transverse coherence length used in ultrafast electron diffraction. These beams are ... ...

    Abstract The generation of intense electron beams with low emittance is key to both the production of coherent x rays from free electron lasers, and electron pulses with large transverse coherence length used in ultrafast electron diffraction. These beams are generated today by photoemission from disordered polycrystalline surfaces. We show that the use of single crystal surfaces with appropriate electronic structures allows us to effectively utilize the physics of photoemission to generate highly directed electron emission, thus reducing the emittance of the electron beam being generated.
    Sprache Englisch
    Erscheinungsdatum 2017-04-21
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.118.164802
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 58/153: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  8. Artikel ; Online: Ultrabright and ultrafast III-V semiconductor photocathodes.

    Karkare, Siddharth / Boulet, Laurent / Cultrera, Luca / Dunham, Bruce / Liu, Xianghong / Schaff, William / Bazarov, Ivan

    Physical review letters

    2014  Band 112, Heft 9, Seite(n) 97601

    Abstract: Crucial photoemission properties of layered III-V semiconductor cathodes are predicted using Monte Carlo simulations. Using this modeling, a layered GaAs structure is designed to reduce simultaneously the transverse energy and response time of the ... ...

    Abstract Crucial photoemission properties of layered III-V semiconductor cathodes are predicted using Monte Carlo simulations. Using this modeling, a layered GaAs structure is designed to reduce simultaneously the transverse energy and response time of the emitted electrons. This structure, grown by molecular beam epitaxy and activated to negative electron affinity, is characterized. The measured values of quantum efficiency and transverse energy are found to agree well with the simulations. Such advanced layered structures will allow generation of short electron bunches from photoinjectors with superior beam brightness.
    Sprache Englisch
    Erscheinungsdatum 2014-03-07
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.112.097601
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 58/153: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

Zum Seitenanfang