Atmospheric turbulence can cause significant performance degradation in free space optical (FSO) communication system. Major effects on the beam such as beam wander and beam scintillation degrades the performance at the receiver. We investigate the impact of diversity technique and aperture averaging technique on the performance of FSO system. Performance evaluation is made in terms of average ...

We present a new technique developed for the measurement of the scintillation efficiency of nuclear recoils in solid scintillators. Using this technique we measured the quenching of the scintillation efficiency for the various recoiling nuclei in CaWO4 crystals which are used in direct Dark Matter searches.

Deep and frequent Global Positioning System (GPS) signal fading due to strong ionospheric scintillation is a major concern for GPSguided aviation in equatorial areas during high solar activity. A GPS aviation receiver may lose carrier tracking lock under deep fading, and a lost channel cannot be used for position calculation until lock is reestablished. Hence, frequent loss of lock due to frequ...

We are exploring the possibility of using PIN photodiodes to readout the scintillation crystals used in Positron Emission Tomography (PET) detector designs. Semiconductor photodetectors typically have a lower signal to noise ratio than photomultiplier tubes (PMTs). However, they have the advantage of compactness, and, thus, scintillation crystal readout schemes not available to PMTs because of ...

A first comparison has been made between the pulse-shape discrimination characteristics of a novel He-based pressurized scintillation detector and a NE-213 liquid-scintillator reference detector using an Am/Be mixed-field neutron and gamma-ray source and a high-resolution scintillation-pulse digitizer. In particular, the capabilities of the two fast neutron detectors to discriminate between neu...

A Global Positioning System (GPS) receiver may lose carrier tracking lock to the GPS signal under deep and frequent fades due to ionospheric scintillation. The frequent loss of lock observed during a strong scintillation period from the past solar maximum can significantly reduce GPS aviation availability. However, the frequency diversity (L1 and L5 frequencies) from the future GPS is expected ...

The earth’s ionosphere can cause serious problems for many radio applications: DOD C31 and navigation systems and commercial applications such as communications, radio astronomy and navigation. They can all be seriously affected by ionospheric disturbances. Disturbance effects such as amplitude fading and phase scintillation limit the ability to coherently integrate weak signals. One solution, ...

The scintillation yield and decay time of LaBr3 doped with 0.2%, 0.5%, and 5% cerium were studied between 80 K and 600 K. LaBr3 :5%Ce 3+ on a photomultiplier tube shows at 300 K a very high scintillation yield of 22 800 photoelectrons per MeV 64 000 photons per MeV with a decay time of 16 ns. At 600 K the yield decreases by 15%. The scintillation yield of LaBr3 :0.2%Ce3+ is 19 800 photoelectron...

We study three quasar radio sources (B1257-326, B1519-273, and J1819+385) that show large amplitude intraday and annual scintillation variability produced by the Earth’s motion relative to turbulent-scattering screens located within a few parsecs of the Sun. We find that the lines of sight to these sources pass through the edges of partially ionized warm interstellar clouds where two or more cl...

Pacific Northwest National Laboratory has recently opened a shallow underground laboratory intended for measurement of low-concentration levels of radioactive isotopes in samples collected from the environment. The development of a low-background liquid scintillation counter is currently underway to further augment the measurement capabilities within this underground laboratory. Liquid scintill...