Published online by Cambridge University Press: 18 July 2016
Systematic treatment of the data recorded by our guard counters and corrections introduced for meteorological factors has allowed observations on solar events clearly manifested in the readings. Examples are the solar flares of March 1989 and especially of June 1991, which caused a ca. 10% decrease in the cosmic radiation flux reaching the counters. A sinusoidal variation in the cosmic-ray flux with a period of one year is also clearly manifested in the data. The observation that the background in the 14C measurements depends on the intensity of the cosmic radiation has led to the use of monthly correlations for the determination of the best background value to be used in the age calculations. This reduces the error significantly. However, various factors such as random statistical fluctuations of the background measurements may affect the slope of the correlations and consequently the calculated age of the samples. Long-term observations of the relation between background values and coincidence counts have led to constraints in the slope of the correlation. A simple extension of the fitting procedure is explored, which maintains the physically meaningful range of the slopes, but is flexible to adjust for the seasonally varying contributions to the variations of the cosmic-ray flux.