100C — Radiation Counter Tube
A permanent sensitivity, self-quenched radiation counter tube designed for the detection and measurement of beta radiation and X-rays.
Overview
The 100C is a specialized radiation counter tube designed for scientific and industrial radiation detection applications, specifically targeting beta particles and X-rays. It features a robust construction with a stainless steel cathode and a thin mica window that allows low-energy radiation to enter the active volume.
The tube is filled with an argon gas mixture combined with a quenching admixture, enabling self-quenching operation. It operates at a nominal high voltage of 1200 V D.C. and offers an unlimited operational life expectancy under normal use. The device is rated to operate reliably across a wide temperature range from -55°C to +75°C.
Construction and Physical Dimensions
The 100C is engineered with a cylindrical geometry to optimize detection efficiency. Its physical and mechanical specifications include:
- Cathode Material: Stainless steel, which provides excellent durability and stable performance over time.
- Mica Window Thickness: 0.0005 inches (equivalent to a density thickness of 3.5 mg/cm² or a physical thickness of 12.70 microns). This thin window is critical for minimizing the attenuation of incoming beta particles and X-rays.
- Effective Window Diameter: 1-3/32 inches.
- Effective Cathode Dimensions: 1-1/2 inches long by 1-3/16 inches outer diameter (O.D.), with a wall thickness of 3/32 inches.
- Maximum Overall Tube Dimensions: 1-1/2 inches diameter by 3-3/4 inches length.
Unlike some related variants, the standard 100C does not feature an integrated multi-pin base, allowing for direct connection or custom mounting configurations within its 1-1/2 x 3-3/4 inch envelope.
Electrical and Operating Characteristics
The 100C is a high-voltage gas-discharge detector. Its performance is defined by several key electrical parameters:
The wide plateau (exceeding 300 V) ensures that the counting rate remains highly stable even if there are minor fluctuations in the high-voltage power supply. The plateau slope of 5% to 10% per 100 V indicates a well-controlled discharge characteristic. The dead time of approximately 200 microseconds defines the recovery period after an ionization event, during which the tube cannot register subsequent events. For low-level radiation measurements, the background count is kept to a maximum of 50 counts per minute when the tube is housed in a standard 2-inch lead shield.
Related Designations and Comparisons
The 100C is part of a broader family of radiation counter tubes that share physical dimensions but differ in their gas fillings, electrical ratings, or basing styles:
- 100CB: This variant is electrically and physically identical to the 100C, utilizing the same argon and quenching admixture filling, 1200 V D.C. operating voltage, and 0.0005-inch mica window. However, it is equipped with a 4-pin base, which increases its maximum overall dimensions to 1-3/8 inches diameter by 4-11/32 inches length.
- 100N: This tube shares the physical dimensions and window specifications of the 100C but is filled with a neon and quenching admixture. Consequently, it operates at a lower nominal voltage of 700 V D.C. (with a plateau in excess of 200 V) and is designated strictly for beta detection, omitting the X-ray application of the argon-filled 100C.
- 100NB: The 4-pin based version of the neon-filled 100N, sharing the 700 V D.C. operating voltage and the 1-3/8 x 4-11/32 inch physical envelope of the 100CB.
Technical Summary
The 100C is an argon-filled, self-quenched radiation counter tube featuring a stainless steel cathode and a 1-3/32-inch diameter mica window (0.0005 inches thick). Designed for beta and X-ray detection, it operates at 1200 V D.C. with a plateau exceeding 300 volts and a slope of 5% to 10% per 100 volts. With an approximate dead time of 200 microseconds, a maximum shielded background of 50 counts per minute, and an unlimited operational life, the 100C provides reliable radiation detection across a temperature range of -55°C to +75°C.
