Using all available multi-component radio pulse profiles for pulsars with medium to long periods and good polarisation data, we have constructed a two-dimensional image of the mean radio beamshape. This shows a peak near the centre of the beam but is otherwise relatively uniform with only mild enhancements in a few regions. This result supports the patchy-beam model for emission beams in which ...

The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. Results of the study of a beam-ion instability [1,2] are presented for a multi-bunch train taking into account the decoherence of ion oscillations due to the ion frequency spread and spatial variation of the ion frequency. ...

We report the results of experiments on a “fast beam-ion instability”[1] at the Advanced Light Source (ALS). This ion instability, which can arise even when the ions are not trapped over multiple beam passages, will likely be important for many future accelerators. In our experiments, we filled the ALS storage ring with helium gas, raising the pressure approximately two orders of magnitude abov...

Ultrasonic phased arrays are an emerging technology in nondestructive evaluation (NDE) applications. A phased array is a multi-element piezo-electric device whose elements are individually excited by electric pulses at programmed delay times [1]. Such a delay scheme allows electronically controlled dynamic beam control. One of the advantages of using phased arrays in NDE applications over conve...

During automatic speech recognition selecting the best hypothesis over a combinatorially huge hypothesis space is a very hard task, so selecting fast and efficient heuristics is a reasonable strategy. In this paper a general purpose heuristic, the multi-stack decoding method, was refined in several ways. For comparison, these improved methods were tested along with the well-known Viterbi beam s...

This paper describes the synthesis of digitally excited pencil/flat top dual beams simultaneously in a linear antenna array constructed of isotropic elements. The objective is to generate a pencil/flat top beam pair using the excitations generated by the evolutionary algorithms. Both the beams share common variable discrete amplitude excitations and differ in variable discrete phase excitations...

The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. A beam-ion instability is studied for a multi-bunch train taking into account the decoherence of ion oscillations due to the ion frequency spread. It is shown that while the decoherence does not completely suppress the inst...

Compensation of multi-bunch beam loading is of great importance in the main linac of the Compact Linear Collider (CLIC). The bunch-to-bunch energy variation has to stay below 1 part in 10. In CLIC, the RF power is obtained by decelerating a drive beam which is formed by merging a number of short bunch trains. A promising scheme for tackling beam loading in the main linac is based on varying the...

We experimentally show that two-photon path-entangled states can be coherently manipulated by multi-mode interference in multi-mode waveguides. By measuring the output two-photon spatial correlation function versus the phase of the input state, we show that multi-mode waveguides perform as nearly-ideal multi-port beam splitters at the quantum level, creating a large variety of entangled and sep...

Hydrogen negative ion beams of 486 keV, 2.8A and 507 keV, 1A have been successfully produced in the JT-60U negative ion source with multi aperture, multi grid accelerator of three stages. This is the first accomplishment of the H beam acceleration up to 500 keV at high-current of > 1 A. These successful productions of the high-energy beams at high current have been achieved by overcoming a poor...