Scintillation

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

Simultaneous Rocket-Borne Beacon and In Situ Measurements of Equatorial Spread F - Intermediate Wavelength Results

Abstract: A high-performance rocket carrying a four-frequency, phase-coherent beacon and full complement of in situ diagnostic instrumentation was launched into active equatorial spread F on July 17, 1979. In this paper we report the results of spectrally analyzing the beacon phase-scintillation and Langmuir probe data. By using simultaneous backscatter data from the Altair radar we were able to establish that the scintillation develops in high-density regions adjacent to the prominent plume structures and associated depletions. In these high-density regions the in situ spectra show a pronounced change in the power law slope near a spatial wavelength of 500 m. Larger scale structures admit a systematically varying power law index that is generally less than 2, in good agreement with a large body of Wideband satellite data and recently analyzed Atmospheric Explorer E data. Smaller-scale structures admit a spectral index much larger than 2. A single, overall power law near k−2 was found only in low-density regions that did not contribute significantly to the scintillation. The results presented here and in a companion paper suggest that refinements in the current theories of equatorial spread F near and above the F region peak are needed.

Design of a high-resolution and high-sensitivity scintillation crystal array for PET with nearly complete light collection

Abstract: Spatial resolution improvements in positron emission tomography (PET) can be achieved by developing detector arrays with finer resolution elements. To maintain high sensitivity and image quality, the challenge is to develop a finely pixellated scintillation crystal array with both high detection efficiency and high light collection. High detection efficiency means the crystals must be relatively long and tightly packed. Extracting a high fraction of the available scintillation light from the ends of long and skinny crystals proves to be very difficult and there is a strong variation with light source depth. The result is inadequate energy resolution. To facilitate light collection, the crystals must be highly polished, which significantly increases costs and complexity. In this paper, we examine this poor light collection phenomenon in more detail. We also describe a novel solution we are developing for readout of an array of 1 mm crystals using avalanche photodiodes (APD). We demonstrate through optical photon tracking simulations that the crystal light collection for this new design is nearly perfect (/spl ges/ 95 %) and is independent of the crystal length, width, and surface treatment and origin of the light created.

A new scintillation material: Pure CsI with 10 ns decay time

Abstract: The properties of pure CsI have been studied with respect to its application as a scintillation material.

A study of inter-crystal scatter in small scintillator arrays designed for high resolution PET imaging

Abstract: Inter-crystal scatter causes mispositioning of scintillation events, which is of particular concern in imaging detectors based on small discrete scintillator elements. Because it is difficult to measure the scatter and its effects on detector intrinsic spatial resolution, a Monte Carlo simulation has been used to study inter-crystal scatter effects for evaluating and optimizing the design of a high resolution animal PET detector based on an array of small scintillator crystals. In this simulation, the authors quantitatively assess the mispositioning of events due to inter-crystal scatter as a function of parameters such as different scintillator materials, crystal geometry, /spl gamma/-ray incident angle and applied energy threshold. In analyzing the tradeoff between the detector efficiency and the position detection accuracy, the authors found that the mispositioning is not sensitive to the energy threshold, however it does change rapidly with the crystal length and the gap between crystals. The authors also compared four different crystal positioning algorithms to provide a theoretical estimate of positioning accuracy and to determine the best algorithm to use. To study how inter-crystal scatter affects detector spatial resolution, the authors analyzed the coincidence line spread function with and without inter-crystal scatter and found that the inter-crystal scatter had very little effect on the FWHM and FWTM of the coincidence line spread function.