Radioisotopic High-Potential, 
Low-Current Sources 
Batteries using an Sr’’-Y" source and a polystyrene insulator provide up to 
7,000-volt charging potential at 40uya. 
Smaller, lighter, and less expensive to 
operate than chemical batteries, they offer long life under extreme conditions 
By JOHN H. COLEMAN 
Radiation Research Corporation, West Palm Beach, Florida 
GENERATION OF ELECTRIC ENERGY by 
collecting the beta particles emitted 
from a radioactive source with an elec- 
trode that is insulated from the source 
by asolid dielectric has been found fea- 
sible with polystyrene as the insulator. 
The principle of operation of direct- 
conversion devices in general can be 
illustrated by generators utilizing a 
vacuum dielectric (1-5). Two of these 
devices will be described preliminary to 
a discussion of models incorporating 
solid dielectrics. 
Vacuum-Dielectric Devices 
As early as 1918, Moseley (1) at- 
tained a high electric potential by 
collecting the beta particles emitted 
Vacuum 
exhaust 
~>>~+- Electrometer 
---Collector 
-} -lsotope 
~*~ Quartz 
bulb 
~>~Quartz rod 
FIG. 1. 
Moseley’s vacuum generator 
from a radioactive source suspended in 
a vacuum. Moseley’s apparatus, Fig. 
1, consisted of two concentric spheres 
with a vacuum connection to the outer 
sphere for evacuation. The center 
sphere or source electrode was a quartz 
bulb containing approximately 20 
millicuries of radium. The wall of the 
bulb was sufficiently thin to enable 
penetration of the emitted beta par- 
ticles but thick enough to absorb the 
alphas. 
This source of beta electrons was 
supported by a thin insulating quartz 
rod attached to the inside wall of the 
outer sphere that collected the elec- 
trons. The inner and outer sphere 
were covered with a conducting coating 
of silver, forming the anode and 
cathode, respectively. Any potential 
difference between the electrodes was 
measured by an attractive disk-type 
electrometer located in the mouth of 
the vacuum connection. 
On evacuation of the interelectrode 
space, Moseley repeatedly measured 
around 150 kv on the source electrode 
before internal flashover discharged 
the device. A simple capacity-charg- 
ing relationship was noted after each 
discharge for a beta charging current 
of about 1071! ampere. 
In 1952, Linder (2) published results 
on two vacuum devices similar to 
Moseley’s, using a Sr°%-Y°% fission- 
product source. In one device, with 
— 
Specifications of Solid-Dielectric Batteries 
Battery model 
B-50 D-50 
Source 10-me Sr°°-Y % 10-me Sr?°-Y 9° 
Insulator Polystyrene Polystyrene 
Collector Aluminum Aluminum 
Shield Lead Lead 
Potting compound Biwax Polystyrene 
Output current (uua) at zero voltage 40 40 
Current-collector efficiency 33% 33% 
Maximum charging voltage (volts) 6,000 (after 2 months) 7,000 (after 2 weeks) 
Total volume (in.%) 4 1 
i  ——————————————— 
137 
