Patent Number: 
Section: description

The detailed description set forth below in connection with the appended drawings is intended as a description of presently-preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the invention in connection with the illustrated embodiments. However, it is to be understood that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As shown in FIG. 1, the xcex1-voltaic power source 100 uses liquid gallium 102 as a conversion medium for energetic xcex1-particles. The liquid gallium 102 is held between a iridium or other anode 104 and an zirconium or other cathode 106. As used herein, the term xe2x80x9canodexe2x80x9d indicates the electron-accepting electrode while the term xe2x80x9ccathodexe2x80x9d indicates the electron-providing electrode. The anode 104 and cathode 106 may be immersed in the liquid gallium 102. The cathode and anode are placed in such a way that the majority of the liquid gallium 102 is disposed between the anode 104 and cathode 106. The anode lead 112 and the cathode lead 114 may pass through the holding container 110 or otherwise be in communication with the respective anode 104 or cathode 106. Depending upon the work function of the anode 104 and cathode 106, a voltage xcex94V 116 is present between the anode lead 112 and cathode lead 114. This constitutes an electric field in liquid gallium which facilitates the separation of negatively-charged electrons and positively-charged gallium ions. As described in more detail below, where the anode is iridium and the cathode is zirconium, the voltage arising between the anode lead 112 and cathode lead 114 is approximately 1.62 volts which is the difference between the work functions of iridium and zirconium. Elemental gallium is generally a liquid and has a melting point of approximately 30xc2x0 C. (302.9xc2x0 K., 85.8xc2x0 F.). Despite the cold of deep space, deep ocean, or other environments, it is generally a simple task to keep gallium in liquid state as heating can also be accomplished by the dissipation of energy of incoming xcex1-particles, radioisotope heating, or otherwise. Additionally, gallium has a boiling point of approximately 2403xc2x0 C. (2676xc2x0 K., 4357xc2x0 F.). Consequently, if liquid gallium used in the power source 100 of the present invention becomes hot, it will remain a viable xe2x80x9celectrolytexe2x80x9d for the generation and migration of gallium ions and electrons to significantly high temperatures. In order to activate the liquid gallium in order to provide sources of charge and sources of charge absorption, xcex1-particles are used as a result of natural radioactive decay from an xcex1-particle source. Curium-244 may be used as a source of xcex1-particles. Upon emission, the xcex1-particles travel into the liquid gallium 102 and collide with the gallium atoms. When the xcex1-particles collide with the gallium atoms, electrons are liberated from the electron shells of the gallium atoms. These freed electrons are then able to migrate through the liquid gallium over to the iridium or other anode 104. When electrons 132 are free from the originally-neutral gallium atoms 130, positive gallium ions (in the form of Ga+ or otherwise) 134 are created. The gallium ions 134 then migrate to the zirconium or other cathode 106 where they receive electrons to re-form neutral gallium atoms 130. A propitious disposition of the xcex1-source 120 as well as providing a depth of liquid gallium 102 beyond the mean the travel distance of the emitted alpha particles, enables the xcex1-voltaic power source 100 of the present invention to capture a large percentage of emitted xcex1-particles. This enables a large percentage of the a-particle energy to be deposited into the liquid gallium 102 and the creation of electrons 132 and gallium ions 134 in order to create the current 117 and voltage difference 116 across the anode lead 112 and the cathode lead 114. Geometrically, the xcex1-particle source 120 may be disposed centrally in a reservoir of gallium liquid 102. This would allow for omnidirectional xcex1-source emission to quickly encounter the liquid gallium 102. A large number of xcex1-particles will then be captured by the gallium liquid and converted into electrical energy by a liberation of electrons 132 from neutral gallium atoms 130. Contemplated sources of xcex1-particles include curium-244 which emits energetic xcex1-particles with energies of approximately 5.8 MeV. Curium-244 has a half-life of approximately 18 years and so could provide a predictable current 117 across the leads 112, 114 for this half-life period. Typical xcex1-particle activity rates are contemplated as being on the order of approximately 1 Curie (Ci) which is approximately 3.7xc3x971010 xcex1-particles per second. As mentioned above, a voltage of approximately 1.6 volts is generally delivers a current 117 of approximately 10-12 milliamps and a power level of approximately 20 milliwatts. In delivering a voltage, current, and power as indicated, each device is expected to be only approximately 25 mm3 in volume. As with batteries, a series of power sources 100 could be connected serially for greater voltage, in parallel for greater current, or in both series and parallel to deliver greater voltage and current. Other materials may be used in substitution for the gallium liquid so long as they provide for the proper migration of ions and electrons as well as being good targets for xcex1-particle interception. Semimetals are good candidates for such alternative materials, as may be other liquids or fluids. Additionally, while iridium and zirconium have been respectively indicated for anode 104 and cathode 106 plates, additional materials may be used in place of zirconium and iridium to good effect. The resulting voltage 116 would generally be the difference between the work functions of the anode and cathode 104, 106. Furthermore, while a source of xcex1-particles is set forth herein and the use of curium-244 is mentioned with particularity, other sources of xcex1-particles may also be constructively used in the present invention. Other sources of radiation, such as sources of xcex2-rays or xcex3-rays may also provide for generation of electrical power along the lines as described herein. The target liquid 102 generally has to be a liquid semiconductor or a semi-metal with properties generally closer to a semiconductor in order to be a good receiving target for either the xcex3-rays or xcex2-rays and should respond in a manner like that of gallium in its receipt of xcex1-particles and generation of electricity therefrom. The use of the term xe2x80x9cliquidxe2x80x9d as set forth herein encompasses any fluid acting as the atomic/molecular resource from which ions, electrons can be generated by particle collision. While the present invention has been described with regards to particular embodiments, it is recognized that additional variations of the present invention may be devised without departing from the inventive concept.