Specialized - Radiation Counter ·GeigerMullerCounter
Self-quenching Geiger-Müller counter for beta and gamma radiation detection and measurement. Its gas-filled pulse-counting operation suits general radiation survey, monitoring, and laboratory instruments.
The 1B68 (also designated as the 1B68/VG-13) is a self-quenched Geiger-Mueller counter tube designed for the detection of beta and gamma radiation. Registered under RMA release number 705 on October 28, 1948, the device was manufactured by The Victoreen Instrument Company of Cleveland, Ohio. It is engineered to provide highly efficient radiation detection within a robust, specialized physical envelope.
The 1B68 features a cylindrical construction optimized for radiation sensitivity and physical integration into detection equipment. The tube is terminated with flexible wire leads rather than a standard pin base, facilitating direct soldering or custom mounting configurations.
The physical dimensions and construction details of the tube include:
The thin wall thickness of 30 mg/cm² is critical to its function, allowing beta particles to penetrate the active volume of the tube while maintaining structural integrity.
The 1B68 operates in the Geiger-Mueller region, utilizing a self-quenching gas mixture to terminate the ionization discharge after each detection event. The electrical and performance parameters under standard operating conditions are specified as follows:
| Parameter | Specification |
|---|---|
| Nominal Operating Voltage | 900 VDC |
| Maximum Geiger Threshold Voltage | 850 VDC |
| Minimum Plateau Length | 200 V |
| Maximum Relative Plateau Slope | 3.0% per 100 V |
| Nominal Background Count Rate | 35 counts/min (at operating voltage) |
| Nominal Recovery Time | 100 µs |
| Beta Detection Efficiency | 99.8% |
| Static Electrode Capacitance | 2.2 µµF |
The low static electrode capacitance of 2.2 µµF helps minimize the pulse rise time and overall charge per pulse. The nominal recovery time of 100 µs defines the resolving time limitations of the tube during high-count-rate applications. The plateau characteristics ensure stable operation, with a slope of no more than 3.0% per 100 V over a minimum range of 200 V above the threshold.
The 1B68 is rated for operation across a defined thermal range. The maximum ratings specify that the ambient temperature must be maintained within the following limits:
Operating the tube outside of this 0 to 100 °C range may affect the quenching gas characteristics, plateau stability, or overall detection reliability.
The 1B68 is a specialized, self-quenched counter tube designed by The Victoreen Instrument Company for beta and gamma radiation detection. Characterized by its nominal 900 VDC operating voltage, high beta efficiency of 99.8%, and a low background count rate of 35 counts per minute, the tube provides reliable performance in radiation measurement applications. Its physical design features a 30 mg/cm² wall, a minimum 3-inch active length, and 3-1/2 inch wire leads for anode and cathode connections, making it a distinct and highly optimized component of mid-twentieth-century radiation detection technology.
General specifications
Properties common to every published source and operating point.
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
1 physical section, each with unique specifications.
Section 0
No fixed ratings are recorded for this section.
Source-dependent data
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 01
Published operating points and test conditions from this source.
GeigerThresholdVoltage
850 V
Max
Operating Voltage
900 V
Nominal
PlateauLength
200 V
Minimum
RelativePlateauSlope
3 %/100V
Maximum
Background
105 counts/min
Max
ElectrodeCapacitance
2.2 pF