Related Experiment Video
Updated: Jun 12, 2026

Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator
Published on: May 9, 2014
Precision measurement of ionization current from a long half-life radioactive source
Stephen P Giblin1, Giuseppe Lorusso1,2
1National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom.
None:
We present precision measurements of the ionization current produced by a sample of carbon-14. Using specialized ammeters with a gain uncertainty of less than a part per million (ppm), the decay of the ∼400 pA ionization current, ∼1 fA/week, is resolved by the measurement system for experimental runs of 50 days. When the apparatus is temperature controlled to ±0.05 °C, fluctuations in instrumental offsets are suppressed, and the random uncertainty is limited by Poisson noise, reaching ∼2.5 ppm of the ionization current for 24 h of data integration. We discuss the possibility of a measurement of the carbon-14 half-life by directly observing the decay in the ionization current.
Related Concept Videos
Radioactive Decay and Radiometric Dating
Atomic Emission Spectroscopy: Lab
Inductively Coupled Plasma Atomic Emission Spectroscopy: Principle
The ions and electrons produced interact with the fluctuating magnetic field created by a water-cooled...
Inductively Coupled Plasma–Mass Spectrometry (ICP–MS): Overview
Atomic Emission Spectroscopy: Instrumentation
Mass Analyzers: Common Types

