Beam-halo measurements in high-current proton beams.

We present results from an experimental study of the beam halo in a high-current 6.7-MeV proton beam propagating through a 52-quadrupole periodic-focusing channel. The gradients of the first four quadrupoles were independently adjusted to match or mismatch the injected beam. Emittances and beamwidths were obtained from measured profiles for comparisons with maximum emittance-growth predictions of a free-energy model and maximum halo-amplitude predictions of a particle-core model. The experimental results support both models and the present theoretical picture of halo formation.

Electro-optic measurement of the wake fields of a relativistic electron beam.

When a relativistic electron bunch traverses a structure, strong electromagnetic fields are induced in its wake. For a 12 nC bunch of duration 4.2 ps FWHM, the peak field is measured >0.5 MV/m. Time resolution of approximately 5 ps is achieved using electro-optic sampling with a lithium tantalate (LiTaO3) crystal and a short-pulse infrared laser synchronized to the beam. We present measurements for both the longitudinal and radial components of the field and relate them to the wall impedance.

Ultradense reproducible Z-pinch suitable for CO2 laser-pellet simulation experiments.

The design and operating characteristics of a unique reproducible linear, high-density (> 10(19) e(-)/cm(3)), low-temperature (17