Geomagnetically trapped alpha particles

New Evidence for Geomagnetically Trapped Anomalous Cosmic Rays

We report new observations of _> 15 MeV/nuc trapped heavy ions with Z_> 2, made on the polar-orbiting SAMPEX spacecraft in late 1992 and early 1993. A trapped population that includes He, N, O, and Ne is found to be located at L -2. We conclude that the observed N, O, and Ne ions are "anomalous" cosmic rays, trapped by the mechanism proposed by Blake and Friesen. While it is not expected that t...

Physics with Trapped Charged Particles

Exposure of school children to alpha particles

Background: A substantial part of the public’s natural radiation dose is due to the inhalation of radon gas. Most of the exposure occurs indoors where the airborne concentration of radon and its decay products is usually higher than outdoors. Materials and Methods: Radon activity concentration has been measured twice in 50 classrooms in 5 levels (10 each) during summer and winter using solid-st...

Orientation of optically trapped nonspherical birefringent particles.

While the alignment and rotation of microparticles in optical traps have received increased attention recently, one of the earliest examples has been almost totally neglected--the alignment of particles relative to the beam axis, as opposed to about the beam axis. However, since the alignment torques determine how particles align in a trap, they are directly relevant to practical applications. ...

Optical microrheology using rotating laser-trapped particles.

We demonstrate an optical system that can apply and accurately measure the torque exerted by the trapping beam on a rotating birefringent probe particle. This allows the viscosity and surface effects within liquid media to be measured quantitatively on a micron-size scale using a trapped rotating spherical probe particle. We use the system to measure the viscosity inside a prototype cellular st...