Pulse shape discrimination

Pulse-shape discrimination (PSD) is the name given to a process that differentiates pulses produced by different types of particles in the same detector. Although PSD has found many applications, its most common use is to discriminate between pulses generated by neutrons and gammas in organic scintillators (see also Chap. 14), and it is this type of PSD that will be discussed. 

Many different methods have been proposed and used for successful PSD. One method doubly differentiates the detector pulse, either using CR circuits or a delay line, and bases the PSD on the time interval between the beginning of the pulse and the zero crossing point. This time interval, which is 

There are three basic types of preamplifiers charge-sensitive, current-sensitive, and voltage-sensitive. The voltage-sensitive preamplifier is not used in spectroscopy because its gain depends on the detector capacitance, which in turn depends on the detector bias. The charge-sensitive preamplifier is the most 

The detector sees the FET stage as a large capacitor of magnitude ACp As long as AC Ci, where C, is the total input capacitance consisting of the detector capacitance C, the cable capacitance, etc., the voltage at the output of the preamplifier is equal to 

The noise of the charge-sensitive preamplifier depends on three parameters the noise of the input FET, the input capacitance C , and the resistance connected to the input. The noise can be determined by injecting a charge Q, equivalent to E, into the preamplifier and measuring the amplitude of the generated pulse. Commercial preamplifiers are provided with a test input for that purpose. In general, the noise expressed as the width (keV) of a Gaussian distribution increases as input capacitance increases (Fig. 10.36). 

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Rutherford, W. M., Evans, J., Currie, L. A., The Application of Isotopic Enrichment and Pulse Shape Discrimination to the Measurement of Atmospheric 37Ar, Anal. Chem., 48, 607 (1976). 

Since the fast centrifuge system SISAK is equipped with liquid scintillation counting LSC [12,58], it is in principle capable of investigating short-lived a-decaying nuclides of the transactinides, p/y pulses and a pulses are distinguished by pulse-shape discrimination PSD and pile-up pulses are rejected by a pile-up rejection system PUR. This analog electronics proved to result in insufficient background suppression. Thus, two new approaches... 

If the last extractant is also a scintillator such as ETRAC s STRONEX, the equilibrated organic phase can be counted directly in a beta-liquid-scintillation counter or in a PERALS spectrometer. The carboxylic acid is not colored and does not quench. The PERALS spectrometer provides better beta-energy resolution and has only slightly lower counting efficiency for betas and thus may offer some advantage if both Sr and Sr are required in the same sample. The PERALS spectrometer will provide better separation of the 0.546 MeV Sr, the 1.48 MeV Sr, and the 2.28 MeV Y. In addition, if radium is present, the pulse shape discrimination feature of the PERALS spectrometer can be used to reject the contribution from radium alphas. 

The term timing refers to the determination of the time of arrival of a pulse. Timing experiments are used in measurement of the time development of an event (e.g., measurement of the decay of a radioactive species), measurement of true coincident events out of a large group of events, and discrimination of different types of particles based on the different time characteristics of their pulse (pulse-shape discrimination). 

Since the signal separation from the prime and rear detector primarily depends on the pulse shape discrimination and the expected event rate in the shield detector is much larger both due to large area and the higher detection efficiency, an ultra-fast RTD system is essential for a very low dead-time. We have developed... 

Bertrand GHV, Hamel M, Normand S, Sguerra F (2015) Pulse shape discrimination between (fast or thermal) neutrons and gamma rays with plastic scintillators state of the art. Nucl Instmm Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip 776 114-128... 

PULSE SHAPE DISCRIMINATION (PSD) Electronic methods for separating pulses of differing shape, thus enabling pulses from one type of radiation to be separated from those of another. For example in neutron detectors, neutrons may be separated from gammas by PSD. Same as pulse shape analysis, PSA. 

Interference of ionizing radiation with infrared detectors is a potential source of problems. However, use can he made of the large difference in the charge deposit rate and therefore the rise time of the pulse caused hy an ionizing particle as compared to the response to an infrared source. Using electronic pulse shape discrimination techniques it will he possible to limit the disturbance caused hy particle hits to a small fraction of the total observing time. 

Where it is required to measure neutrons in the presence of a significant y-ray background, it is possible to make use of the properties of certain scintillators to distinguish the pulses produced by neutrons from those due to y rays. This is known as a pulse-shape discrimination (PSD) system. In stilbene and some organic liquid scintillators, the pulse rise time for the fluorescence caused by the secondary electrons from a y-ray interaction is considerably shorter than that due to the recoil protons produced by neutron scattering. By the use of fast timing discriminators, it is possible to separate the pulses caused by neutrons from those due to the y rays. 

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