| Autor: |
Jensen, Kevin L., Connelly, Joseph M., Petillo, John J., Harris, John R., Ovtchinnikov, Serguei, Jensen, Aaron J., Burke, John, Cahay, Marc, Ludwick, J., Tripathi, G., Sanchez-Roddy, Jacob, Puentes, Daniel |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 3/7/2021, Vol. 129 Issue 9, p1-15, 15p |
| Abstrakt: |
Carbon fibers passing current are subject to resistive heating. When failure occurs, this is related to their local temperature. The failure temperature and its location are estimated. The temperature variation is calculated using analytical models for electrical and thermal conductivities based on the temperature dependent electron–phonon relaxation time. In the absence of radiative heat loss, an analytic expression of temperature along the fiber is given from which a maximum possible emission current is derived and is governed by a single introduced parameter ω o. A method of treating the radiative heat loss is developed and is governed by a second parameter γ , which allows a rapid numerical means to calculate the correction to the analytic form. Heat variation along a thick carbon fiber is contrasted to that along a multi-walled carbon nanotube (MWNT): it is shown that the relative magnitude of ω o compared to γ determines that the analytical formula is a good approximation for MWNTs but requires numerical correction for fibers. Furthermore, it is shown that the analytical form of ω o specified a maximum current beyond which the carbon emitter fails due to thermal runaway. The theoretical models are used to interpret observed behavior of field emission from carbon fibers and the resulting damage they endure when the extracted field-emission current is high. Results from implementing the developed temperature variation model into the MICHELLE beam optics simulation code are presented, with an example application predicting the conditions for stable equilibrium operation as well as for the onset of fiber failure. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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