A Counter System for High-Precision 14C Dating

TLDR

A multicounter radiocarbon dating system was developed, building on experience from a prior one‑channel low‑level counting facility. The system uses nine identical electrolytic copper proportional counters (0.35–0.7 dm³) filled with high‑pressure methane or CO₂, surrounded by a propane‑filled anticoincidence shield, with signals processed by integrated amplifiers, discriminators, and a microprocessor‑controlled data unit, and software written in BASIC with assembler sub‑routines. The overall precision for modern carbon samples using high‑pressure methane counters is better than 4 % after seven days of counting.

Abstract

A multicounter radiocarbon dating system was developed applying the experiences of the previous one-channel low-level counting facility. The counter system consists of nine electrolytic copper proportional counters of identical diameters with sensitive volumes of 0.35–0.7dm 3 and filled with either methane at high pressure (6 bar) or CO 2 at 1 bar. The inner counters are surrounded by an anticoincidence shield consisting of five multiwire proportional flat counters filled with propane. The pulses of the detectors are handled by integrated amplifiers, discriminators and anticoincidence units interfaced to a microprocessor-controlled data evaluation unit. Software is written in BASIC using ASSEMBLER sub-routines. The overall precision of the system for modern carbon samples using high-pressure methane-filled counters (B ≍ 0.7 cpm, S ≍ 14 cpm) is better than 4 after a counting period of seven days.