White Paper: Susceptibility of 'Ultracapacitors' to Proton and Gamma Irradiation
By S. Shojah-Ardalan, R. Wilkins, H. U. Machado, B. A. Syed, S. McClure, B. Rax, L. Scheick, M. Weideman, C. Yui, M. Reed and Z. Ahmed
Maxwell Technologies
Abstract
Ultracapacitors are promising components for energy storage, power backup and delivery systems. This study examines the possible effects associated with gamma and proton irradiation in selected samples up to 1200 Farad.
Introduction
The "Ultracapacitor" is a commercial-of-the-shelf (COTS) energy storage component having low internal effective series resistance and high capacitance. The technology is especially suited for applications where a large amount of power is needed for fractions of a second to several minutes. Ultracapacitor can provide high peak currents to loads while the power source provides steady state power. Using the ultracapacitor in this manner will reduce the power source volume and will prolong the power source life. The ultracapacitor can be charged and discharged indefinitely for the life of the system. They are already in use for military applications, hybrid electric vehicles, power generation plants, commercial electric vehicles and racecars. Ultracapacitors are good candidates for space applications in remote or stand-alone systems where the primary power source is provided by a battery, a fuel cell, or solar cell arrays.
The Technologies Assurance group at JSC conducted performance tests on ultracapacitor samples along with electrical and mechanical screening. These tests included visual inspection, fine leak test, accelerated life test, static burn-in, reverse bias test, self heat test via rapid charge-discharge, over voltage pulse, thermal shock and destructive physical analysis. The tests demonstrated that the device was suitable for the intended applications in the ISS electrical portable systems. However, no data is available on the reliability of the component and its performance in an ionizing radiation environment.
We have conducted a series of electrical tests before, during, and after gamma irradiating these devices with a 60 Co source and 60 MeV proton radiation. These tests were performed to characterize the electrical parameters of the ultracapacitors and examine any possible changes in their charge/discharge ability in a radiation environment. This electrolytic capacitor uses an electrolyte consisting of tetraethylammonium tetrafluoroborate, dissolved in acetonitrile solvent. To our knowledge no previously data has been obtained about the interaction of gamma or proton radiation with this electrolyte or individual component.
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