Method of measurement of both gamma radiation and neutrons with energies above 500keV - fast neutrons - for the use in homeland security applications, preferably in portable handheld devices, utilizing a scintillation crystal, said scintillation crystal having a first light decay time (T 1) following the interaction of a gamma quant with the scintillation crystal and a second and shorter light decay time following the interaction of a fast neutron with the scintillation crystal, a glass window and a photo detector together with an amplifier, as well as sampling Analog to Digital Converters - ADC - and a digital signal processing device including a Multi-Channel-Analyzer, said devices configured to perform a pulse shape discrimination, configured to distinguish light decay times of a few nanoseconds up to several microseconds, and to process count rates of more than 10 counts per second for interactions of gamma quanta and of more than 1 count per second for interactions of neutrons with the scintillation crystal, comprising the steps of • allowing gamma quanta and neutrons to interact with the scintillation crystal, • collecting the light, emitted by the scintillation crystal, guiding it to the glass window optically coupled to the scintillation crystal and letting that light interact with the photo detector, • amplifying the signal output from the photo detector with the amplifier, wherein the photo detector with the amplifier preferably is a photomultiplier tube - PMT - thus generating an amplifier output signal, characterized in that said scintillation crystal comprises one of NaI(Tl) or CsI as scintillation material and the method comprising the following further steps of • digitizing and sampling the amplifier output signal at a constant rate, producing a time series of integer values, • whereby said time series of integer values starts with the detection of the first photo electron above the noise threshold and ends when the amplifier output signal has decayed to a fraction of its maximum height, • determining the pulse shape from this time series of integer values, • determining the light decay time of the scintillator from said pulse shape for each interaction measured, • separating the signals with a first decay time from those with a second decay time, • determining the total charge collected for each signal with a first decay time, that total charge being a measure for the energy deposed in the scintillation crystal, • sorting said total charge signals in a spectrum, i.e. by using the Multi-Channel-Analyzer, said spectrum representing the energy distribution of the gamma quants having deposed at least 10 keV and therefore at least a part of their energy in the scintillation crystal, • counting the signals with a second decay time and determining the count-rate, that is the number of signals per given time interval, that count rate being a measure for the number of neutrons having deposed at least part of their energy in the scintillation crystal. • allowing gamma quanta and neutrons to interact with the scintillation crystal, • collecting the light, emitted by the scintillation crystal, guiding it to the glass window optically coupled to the scintillation crystal and letting that light interact with the photo detector, • amplifying the signal output from the photo detector with the amplifier, wherein the photo detector with the amplifier preferably is a photomultiplier tube - PMT - thus generating an amplifier output signal, characterized in that said scintillation crystal comprises one of NaI(Tl) or CsI as scintillation material and the method comprising the following further steps of • digitizing and sampling the amplifier output signal at a constant rate, producing a time series of integer values, • whereby said time series of integer values starts with the detection of the first photo electron above the noise threshold and ends when the amplifier output signal has decayed to a fraction of its maximum height, • determining the pulse shape from this time series of integer values, • determining the light decay time of the scintillator from said pulse shape for each interaction measured, • separating the signals with a first decay time from those with a second decay time, • determining the total charge collected for each signal with a first decay time, that total charge being a measure for the energy deposed in the scintillation crystal, • sorting said total charge signals in a spectrum, i.e. by using the Multi-Channel-Analyzer, said spectrum representing the energy distribution of the gamma quants having deposed at least 10 keV and therefore at least a part of their energy in the scintillation crystal, • counting the signals with a second decay time and determining the count-rate, that is the number of signals per given time interval, that count rate being a measure for the number of neutrons having deposed at least part of their energy in the scintillation crystal.