For deeply penetrating laser wavelengths, such as 1064 nm, the effect of light scattering in the skin leads to a spreading of the beam and consequently a significant reduction in effective fluence for small laser-beam spot sizes. For this reason, the 1064 nm Nd:YAG laser has not been used with fractional handpieces, where pixel beam spot sizes are typically very small. Instead, Nd:YAG fractiona...

This work aims at simulating the time response of a structure damped by viscoelastic materials. The structure is discretised by finite elements and a 4-parameter fractional derivative model is used to describe the frequency-dependency of the mechanical properties of the viscoelastic material. The proposed approach combines a classical Newmark time-integration scheme to solve the semi-discretise...

Connecting a passive electrical network to a structurally attached piezoelectric transducer is referred to as passive shunt damping. Current shunt circuit designs, e.g. a single mode L¡R network, typically require large inductance values of up to thousands of Henries. In practice, discrete inductors are limited in size to around 1 H: By placing an additional capacitance across the terminals of ...

The first generation of strongly HOM-damped RF cavities are now being operated with beam in accelerators with good success. We briefly review these designs and consider some factors in the design of a second generation HOM damped copper RF cavity suitable for use in high current storage rings such as linear collider damping rings, light sources and high luminosity colliders. We consider the pro...

Results from three-dimensional electromagnetic particle simulations of an electron-positron plasma with a relativistic electron beam (y=2) are presented. As part of the initial conditions, a poloidal magnetic field is specified, consistent with the current carried by the beam electrons. The beam undergoes pinching oscillations due to the pressure imbalance. A transverse two-stream instability i...

Work supported by the U.S. Department of Energy under contract No. DE-AC02-76CH03000. [email protected] Abstract Transverse e-p instability in the proton rings could be damped by increase a beam density and the rate of secondary particles generation above a threshold level, corresponded a decrease of the unstable wavelength below a transverse beam size. In high current proton rings as LANSCE PS...

The APS storage ring beam chamber has been storing the beam up to 100 mA successfully. However, in some beam chambers, spurious signals corrupted the BPM outputs. The cause of the unwanted signals was investigated, and it was found that transverse electric (TE) longitudinal harmonic resonances of the beam chamber were responsible. The beam chambers have small height in the area between the oval...