The Secondary Electron Emission Photocathode Characteristics for Time Resolved X-Ray Spectroscopy

Thin carbon foils have become integral parts of low-energy particle detectors in forthcoming space experiments. In these devices, the foil acts as electron source for signal generation. Since 10–20-eV photons can also generate electrons from these foils and since intense HLα and He i resonance lines prevail in space environment, forward photoemission yield in carbon foils must be investigated. Crabon foils of 2.0, 7.0, and 14.0 μg cm−2 thickness (density 1.35 g cm−3) are subjected to 121.6-nm or 10.2-eV photons and 58.4-nm or 21.2-eV photons and the corresonding forward photoemission yield and transmittance are obtained. Energy distributions of photoemitted electrons are also measured.

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Extreme ultraviolet induced forward photoemission from thin carbon foils

Hsieh

Keppler

Schmidtke

1980

Journal of Applied Physics

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The characterization of x-ray photocathodes in the 0.1–10-keV photon energy region

Henke

Knauer

Premaratne

1981

Journal of Applied Physics

326

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A method and an instrument are described for the measurement of the absolute quantum yield for front-surface and transmission photocathodes in the 0.1–10-keV photon energy region. The total and the secondary electron photoemission yields have been measured for the Al, Au, CuI, and CsI photocathodes as required for the absolute calibration of the x-ray diode detectors and for the x-ray streak cameras. The relative secondary electron yields have also been measured for the same photocathodes by high resolution electron spectroscopy of the secondary electron energy distributions, which are in good agreement with the absolute yield measurements. The secondary electron yield of CsI is ten to one-hundred times higher than that for Au in the 0.1–10-keV region and with a secondary energy distribution that is appreciably sharper. For these reasons, CsI should be an effective photocathode for sensitive, time-resolved spectroscopy into the picosecond region. It is verified experimentally that the secondary electron quantum yield varies approximately as Em(E), with E as the photon energy and m(E) as the photoionization cross section, and that the primary (fast) electron quantum yield is a small fraction of the total yield and varies approximately as E2m(E). A simple model for x-ray photoemission is described which leads to semiempirical equations for front- and back-surface secondary electron photoemission as based upon an escape depth parameter that may be obtained from yield-versus-photocathode thickness data. The model predictions are in good agreement with experiment.

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Theoretical study on temporal and spatial performance of magnetic solenoid used in dilation x-ray imager

Wang

Cao

Chen

et al. 2020

Review of Scientific Instruments

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In the Dilation X-ray Imager (DIXI), which is characterized by an ultra-short gating time, a magnetic solenoid is used to keep the photoelectrons from defocusing during the drift process. The performance of the magnetic solenoid has an important influence on the performance of the DIXI. We present in this paper the efforts on studying the spatial and temporal performance of the magnetic solenoid used in the DIXI by tracking the photoelectrons with the particle-in-cell method. The initial parameters of the photoelectrons of the Au cathode were sampled with a Monte Carlo code. A novel magnetic solenoid with a shielding shell made of soft iron was proposed. We compared the performance of this solenoid with a normal solenoid. The simulation results of magnetic field distribution, spatial resolution, transit time spread, and temporal distortion were presented in detail to demonstrate that the performance of the DIXI can be significantly improved by using the magnetic solenoid with the proposed iron shell.

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The Secondary Electron Emission Photocathode Characteristics for Time Resolved X-Ray Spectroscopy

Cited by 4 publications

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Extreme ultraviolet induced forward photoemission from thin carbon foils

Extreme ultraviolet induced forward photoemission from thin carbon foils

The characterization of x-ray photocathodes in the 0.1–10-keV photon energy region

Theoretical study on temporal and spatial performance of magnetic solenoid used in dilation x-ray imager

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