专业英语 Radioisotopes.ppt

 Radioisotope Batteries  Zhengyuan Zhao 080730226 Jingang Li 080730223 Zheng Li 080730224 Zheng Huang Introduction Radioisotope batteries provide reliable batteries with high energy density They are valuable when long life is needed and recharging or refueling is difficult they can function in harsh environments They can be very useful as onboard MEMS power sources Comparison Consider 1 mg for power source What is a Radioisotope Battery? Goal: convert energy from radioactive decay to electricity Convertion Options: ? ? Thermal ? ? Non-thermal Radioisotopes and decay Radioisotope Thermoelectric Generators (RTGs)(放射性同位素热电式发电机) Use radoisotope (usually ceramic Pu- 238) to provide heat Electricity produced by thermoelectric RTGS Nuclear Batteries Direct conversion ? ? betavoltaics effect ? ? Contact Potential Difference ? ? Secondary Electrons ? ? The Gamma-Electric Cell ? Indirect conversion Direct charge Direct conversion nuclear battery Direct conversion nuclear battery: collecting charges emitted from radioisotopes with a capacitor to achieve high voltage output(J. H. Coleman, V=Q/C 10-100 kV voltages can be created in vacuum Betavoltaics effect Adding a Dielectric（电解质） introduction ?Early 1950’s ?Source at S ?D is dielectric; C is collector ?Radiation penetrates dielectric ?No need for vacuum ?High voltage ?Prevents secondary electrons from getting back to source ?50 mCiSr-90 ?polystyrene Betavoltaic Microbattereis Contact Potential Difference Secondary Electrons The Gamma-Electric Cell Indirect conversion Indirect Conversion Nuclear Batteries have the following features: Direct charge Static Accumulation ?Early 1950’s ?Source at K ?D is electrical insulator ?Chamber is evacuated （抽真空） ?0.25 CiSr-90 ?365 kV ?About 1 nA ?0.2 mW Pacemakers（心脏起搏器） 3 Ci Pu-238 ?~3 ounces, ~3 inches ?100 mrem/yto patient ?Since supplanted by Li batteries (~10 yr life) Summary Advan