A quality survey on different shielding configurations of gamma ray detector used with a portable PGNAA system

• A series of shielding sets has been studies for use in a portable PGNAA system.
• An241Am–Be source has been used for shielding properties measurement.
• The radiation field components absorbed in shielding material have been measured.
• The best shielding choice has been presented for a portable PGNAA measurement.
• The effect of different HPGe shieldings on the peak areas has been studied.

The appropriate gamma-ray detector shielding configuration is critical for a precise prompt gamma neutron activation analysis (PGNAA) measurement. The shielding material has to prevent the radiation damage to the detector crystal and it must produce less activation gamma rays, whether prompt or delayed, which may interfere the gamma ray spectrum of the sample. In this research, using common shielding materials, a number of combinations have been studies to form a 50 cm long shield for portable PGNAA system against both fast and slow neutrons as well as gamma rays emitted by 20Ci Am–Be source. The measurement results show that in contrast with conventional shadow cone in which the shielding material starts with 20 cm heavy metals such as iron and ends with 30 cm polymer materials, in portable PGNAA systems, the shielding material gives better results if it starts with about 40 cm borated polymer material and ends with an appropriate thickness (7 cm to 10 cm) of heavy metal such as tungsten.