We investigate the difference between analytic predictions, numerical simulations, and experiments measuring the transmission of energy through subwavelength, periodically arranged holes in a metal film. At normal incidence, theory predicts a sharp transmission minimum when the wavelength is equal to the periodicity, and sharp transmission maxima at one or more nearby wavelengths. In experiment...

Introduction. The aim of this study was to discuss the radiation doses associated with plain radiographs, cone-beam computed tomography (CBCT), and conventional computed tomography (CT) in dentistry, with a special focus on orthodontics. Methods. A systematic search for articles was realized by MEDLINE from 1997-March 2011. Results. Twenty-seven articles met the established criteria. The data o...

The Next Linear Collider (NLC) requires a substantial system of beam collimators to minimize the halo-related backgrounds at the interaction point, provide machine protection against errant pulses, and limit radiation doses throughout the accelerator. In particular, the NLC design contains a complete 5-dimensional (x,x’,y,y’,energy) collimation system at the entrance and exit of the main linac;...

The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10 halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impa...

Three-dimensional (3D) hybrid PIC simulations are presented to study electron energy transport and deposition in a full-scale fast ignition configuration. Multi-prong core heating close to ignition is found when a few GA, few PW beam is injected. Resistive beam filamentation in the corona seeds the 3D current pattern that penetrates the core. Ohmic heating is important in the low-density corona...

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H− injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electroncloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressin...

In the Beam Delivery Systems (BDS) for linear colliders that have been designed or built, collimators (or scrapers) are used to suppress backgrounds due to the beam halo. Off-energy and off-axis particles are stopped on the collimator jaws, physically limiting the acceptance of the system. This concept does not scale well to higher beam energy, higher intensity or lower emittance. The increased...

Using channeling in a 5-mm crystal with bending angle of 0.65 mrad, a record high efficiency, over 60%, of particle extraction from accelerator was achieved. The extracted beam intensity was up to 5.2×10 11 protons per spill of ∼0.5 s duration. Also, the first proof-of-principle experiment on 'crystal collimation' was performed where crystal-serving as a scraper-has reduced the radiation level ...

Influence of volume capture on a process of volume reflection of ultrarelativistic particles moving in bent single crystals was considered analytically. Relations describing various distributions of particles involving in the process, the probability of volume capture and behavior of channeling and dechanneling fractions of a beam were obtained. Results of study will be useful at creation of mu...