Recently, a remarkable progress has been made in fast ADCs which enables a radiation signal analysis system based on digital waveform processing. Methods and advantages of detailed analysis of pulse waveforms are presented in this system. Example of digital waveform processing in a coaxial Ge detector is also presented using multiple parameters. This technique has a potential possibility to deliver conceiled information in pulse waveform to be used as an advanced signal processing method.

  With great development in the recent digital signal processing techniques, the digital waveform analysis using a fast ADC is becoming applicable to the pulse signals from radiation detectors. In the present work, this digital technique has been applied to pulse shape analysis for a ³He proportional counter. The "wall effects" in the pulse height spectrum has been successfully suppressed through detecting the pulse shape incompleteness which appears in the pulse leading edge region, when analyzing the ionization density on the triton and proton tracks produced by ³He(n,p)T reaction.

  The method of neutron-gamma pulse shape discrimination method studied for large liquid scintillators (NE-213) by the use of digital processing. A flush ADC (Analogue to Digital Converter) was used for recording the output signal of scintillation detectors as a function of time. Investigation was made to confirm the reason for poor characteristics of neutron-gamma separation for liquid scintillators of larger size. The optimum method was found for the neutron-gamma discrimination in the case of measuring neutrons of wide energy range in low intensity circumstances.

  When a resistance of an anode wire of a position-sensitive proportional counter(PSPC) is small, thermal noise and reflection of a signal give a serious influence on position resolution. Digital waveform processing was applied to signals from a PSPC to remove these influences. The rejection of thermal noise was confirmed with an equivalent circuit simulating PSPC. The component of reflection in a PSPC signal was able to compensate. The digital waveform processing could bring the position resolution better than that obtained with a conventional pulse height processing with an analog filter.

  In domestic oil and gas fields, we measured environmental radioactivities by various measuring instruments; survey meters, dosimeters and an in situ γ-ray spectrometer. Very weak radiations were detected only in Higashi-Kashiwazaki gas field and any NORM (Naturally Occurring Radioactive Material) was not measured in other fields.