Background: High-purity germanium(HPGe) detector need to be calibrate detection efficiency for the measured sample using radioactivity standard sources.However

if a great variety of samples which have different materials

densities or geometries need calibrating

the standard sources used will be very expensive and are not beneficial to environmental protection.Purpose: To study a new Full-energy peak(FEP) efficiency calibration method without artificial standard sources for the high purity germanium detector using 82Br

160Tb produced by neutron activation and 40K.Methods: A HPGe detector(diameter 76 mm) with relative efficiency of 42% and two soil samples(φ70 mm×66 mm) were used in the experiments.The ratios relative to 554.3 keV of FEP counting rates

εBr(Ei)

for different γ energies

Ei

of 82Br were used to fit relative efficiency function

fBr(E).The ratios relative to 1271.8 keV

uj

of those for γ-energy

Ej

of 86.7

197.0

215.6

298.6 and 392.5 keV of 160Tb were calculated

and transformed into normalized relative efficiencies to γ-energy of 554.3 keV of 82Br by using the formula εBr(Ej) = uj.fBr(E1271).Then the data of εBr(Ei) and εBr(Ej) were fitted to normalized relative efficiency function f(E).The absolute efficiency K of 40K γ energy(EK=1460.8 keV)

resulting from KCl

which is mixed homogeneously with the sample can be determined.Thus

those of other any energy

E

can also be determined by using the formula

ε(E) =εK.f(E)/ f(EK).Results: The experiments showed that change of fBr(E) is no significant when the sample-detector distance is more than 3 cm.In order to verify the new method

the activity in two soil samples(φ70 mm×66 mm) were measured(sample-detector distance =3.1 cm) and the results were compared with γ-γ coincidence method.The results of the activity concentration of seven radionuclides including 226Ra

235U

232Th

40K

134Cs

137Cs and 60Co in each sample were in good agreement within uncertainties between two methods

respectively.Conclusions: This method is very useful

special for environmental samples with certain volumes

because it doesn’t need to use artificial radioactive standard sources and takes into account the self-absorption of photons in the sample.