Scintillation

About: Scintillation is a research topic. Over the lifetime, 14022 publications have been published within this topic receiving 187694 citations.

Development of PET Detectors Using Monolithic Scintillation Crystals Processed With Sub-Surface Laser Engraving Technique

Abstract: New monolithic scintillation detectors for PET have been developed, where the crystals are processed using an internally focused laser processing technique called sub-surface laser engraving (SSLE). When high intensity light pulses of short duration from a laser are focused into a scintillation crystal, they induce multi-photon absorption at the focal point and result in refractive index changes or micro-cracks inside the crystal. By applying the SSLE technique to a monolithic scintillation block, fine segmentation in the crystal can be formed without inter-pixel gaps. We have fabricated 2D segmented arrays by using a Nd:YAG laser to engrave various patterns of micro-cracks inside monolithic LYSO crystal blocks. The processed crystal array, segmented to 12 × 12 with 1.67 mm pitch, has been evaluated by coupling to a position-sensitive photomultiplier tube (PS-PMT). The 2D position histograms were measured for uniform irradiation of gamma rays, and each crystal segment was clearly separated. The average energy resolution was 9.7%, similar to that of the conventional arrays, so the laser-processed LYSO crystals have kept their primary scintillation properties. We have also evaluated the laser-processed crystals by using multi-pixel photon counters (MPPCs) to investigate their possibility as a future PET detector. The results suggest that it is possible to fabricate high performance PET detectors using the SSLE technique.

Scintillation data collecting apparatus and method

Abstract: A scintillation data collecting apparatus and method are provided for a scintillation camera and a data processor. The apparatus comprises a scintillation detector including an adder and an analyzer for detecting the valid scintillations, a plurality of conversion units each including an analog-to-digital converter for converting intensity signals derived from the valid scintillations into high, accuracy digital values, and controllers for controlling operation of each of the analog-to-digital converters of the conversion units. The method comprises steps of adding the intensity signals generated by the scintillation camera and which are indicative of the scintillations, and analyzing the sum of the intensity signals to determine if the detected scintillations are valid. To select only those values involved in a scintillation event for processing and free up ADCs which are uninvolved to convert future intensity signals, the intensity signals may be compared to a threshold value to allow only those ADCs whose corresponding intensity signal is above the threshold to convert, or a rapid determination of which serial ADCs are involved can be done by allowing all serial ADCs to convert, waiting for a first positive MSB from one of the ADCS, and resetting all ADCs determined to be uninvolved in the event. The converted signals derived from the intensity signals are digital value signals indicative of the valid scintillations computable by the data processor to determine spatial locations of the valid scintillations.

Two-scale solution for atmospheric scintillation

Abstract: We demonstrate that a recently derived approximate solution to the fourth-moment equation that was thought to be Valid only for strong scattering is in fact valid for all values of the scattering parameter. We use a modified Kolmogorov spectrum for the index-of-refraction fluctuations and present results in two dimensions for comparison with numerical solutions. We also present results in three dimensions that should represent a quantitatively accurate, theoretical description of the atmospheric-scintillation problem.

Optical diagnostics of random phase objects.

Abstract: Possibilities of optical noncontact diagnostics of random phase objects are studied, based on measurements of transverse coherence function, scintillation index, and amplitude and phase dispersion of the field resulting from interaction with the object. The advantages of these methods are increased speed and accuracy compared with commonly used methods. Interference measurements of second-and higher-order correlation parameters of the field phase is demonstrated which can be used to find the corresponding probability density distribution function for objects with phase statistics differing from Gaussian. The sensitivity threshold of the methods is estimated to be ~0.005 microm when measuring surfaces with slight roughness.