Secondary-emission radioisotopic current source

Abstract

SECONDARY-EMISSION RADIOISOTOPIC CURRENT SOURCE V. M. Balebanov, S. S. Moiseev, V. L Karas', I. V. Karas', S. I. Kononenko, V. I. Kolesnik, and V. I. Muratov UDC 533.9Autonomous sources of electrical power are required for solving many scientific and technical problems. The most commonly used sources are chemical cells, employing chemical reactions as the primary source of energy. Historically, such cells were the first ones. Today they are the best-developed, but they have a negligible specific energy capacity, hardly exceeding 0. I kW.h/kg. Radioisotopic sources of electrical energy, based on different physical principles, possess a much higher energy capacity and service life [I, 2]. They form two large classes: thermal and nonthermal radioisotopic converters. In the nonthermal converters, electricity is produced without the use of a fuel cycle. Among such current sources, sources in which electrical charge is collected directly (atomic batteries) are most widely used. In these batteries electrical power is released as a result of collecting c~-and B-particles, emitted by an isotope, by a collector. In such systems, the collector and emitter are electrically insulated from one another by a vacuum gap or dielectric. Such a converter is a current source, and its voltage is determined by the load resistance. The potential difference between the anode and cathode can equal the energy of the particles, but the large internal resistance of the source when a load is connected lowers the voltage and therefore increases the portion of the energy of the charged particles that goes to heating the collector. As a result, the efficiency of the source is substantially diminished [3]. Moreover, there are other drawbacks as well, which decrease the service life of such a source: the need to have an additional voltage source to suppress the secondary electron emission from the collector and the presence of ~-electrons in the o~-particle flux, which substantial decrease the transported current. The high (approximately hundreds of kilovolts) working voltage of atomic batteries requires the use of insulators and high-vacuum conditions, which makes these systems difficult to use.Systems employing the cathode-anode contact potential difference are one type of atomic battery. The space between the anode and cathode is f'dled with gas, which is ionized by the radiation from the radioisotope. The charged particles which are produced accumulate on the cathode and anode, whose work functions are different. The potential difference in this case depends on the work function of the electrode materials and equals -I V. The low efficiency of such a system is related primarily with the small cross section of ionization of the gas atoms by the charged particles. A negligible increase of efficiency is possible by using a mixture of reactive and noble gases at pressures of several atmospheres. However, a high pressure in the atomic battery filled with highly toxic gas is hazardous to service personnel and equipment.One way to convert the energy ...

Energy in the small: micro-scale energy sources

“…The two large classes of the radioisotopic energy converters are thermal and nonthermal [53]. In principle, conversion of the particle energy into heat allows for ∼100% energy collection.…”

<title>Energy spectrum estimates for the ion-electron emission in the radioisotope battery</title>

“…In the material with atomic charge number Z and atom density N , the distribution on energy E of electrons knocked out by the single fast ion from an atom (jer the unit length of the ion path) is described by the following 2Ne/axaE{41tNtZte4Zeff2/mevç(E+J)2 }g(E), (1) where Zeff S the effective charge number of fast ion, vis its velocity, J -is the ionization potential of target atoms. For the suprathermal electron (SE), created with initial energy E at the depth z from the film surface, the probability to arrive at film surface where its energy ( due to the particle slowing down ) will be equal is proportional (see, e.g.…”

Quasi steady-state distributions for particles with power-law interaction potentials

“…We restrict ourselves to the time independent sources with small intensities n S /t S = ε Ӷ 1. Then we go to the new time variable t/ε and obtain ∂f /∂t =Î[f, f ]ε −1 + S for (6). Note that,…”

“…Some experimental data on the emission current from metals irradiated by lasers can be reasonably explained by the mechanism for the formation of NE distributions [4][5][6][7][8]. It was shown [3,6,8] that, for a semiconductor plasma in the energy range E −E F > E F (where E F is the Fermi energy) a power-like distribution with a non-zero flux of energy or particles in momentum space can be established. This NE distribution function is formed both due to collisions with electrons whose energy is in the range E−E F > E F and background (equilibrium) electrons.…”