Pepper-pot emittance measurement of laser-plasma wakefield accelerated electrons

The transverse emittance is an important parameter governing the brightness of an electron beam. Here we present the first pepper-pot measurement of the transverse emittance for a mono-energetic electron beam from a laser-plasma wakefield accelerator, carried out on the Advanced Laser-Plasma High Energy Accelerators towards X-Rays (ALPHA-X) beam line. Mono-energetic electrons are passed through an array of 52 mu m diameter holes in a tungsten mask. The pepper-pot results set an upper limit for the normalised emittance at 5.5 +/- 1 pi mm mrad for an 82 MeV beam

Plasma density measurements using chirped pulse broad-band Raman amplification

Stimulated Raman backscattering is used as a non-destructive method to determine the density of plasma media at localized positions in space and time. By colliding two counter-propagating, ultra-short laser pulses with a spectral bandwidth larger than twice the plasma frequency, amplification occurs at the Stokes wavelengths, which results in regions of gain and loss separated by twice the plasma frequency, from which the plasma density can be deduced. By varying the relative delay between the laser pulses, and therefore the position and timing of the interaction, the spatio-temporal distribution of the plasma density can be mapped out

Suitability of Killai backwaters for prawn farming-a preliminary micro level survey

Brackishwater areas have been given much importance for prawn farming. No information was available on the Killai backwaters about factors like water quality, topography, contour, extent of the area, tidal amplitude, seed potential and possibilities of flooding etc. Hence during 1982-'84 Klllai area was thoroughly surveyed on the above aspects and the results have been discussed in this paper. From this it is inferred that a total area of about 155 ha is readily available for undertaking both pond and pen culture in this backwater

Manoeuvring Experiments Using the MUN Explorer AUV

Autonomous Underwater Vehicles (AUVs) are self-propelled robotic platforms that can perform a predetermined mission completely unmanned. A series of manoeuvring experiments were performed using the MUN Explorer AUV during the summer of 2006 and a selection of these experimental results are presented in this paper. The purpose of these experiments was to collect a set of useful data for validating a hydrodynamic model of the dynamic performance of the vehicle. This paper aims at explaining the methods and measures adopted in accomplishing this task. Apart from providing a data set for validation of the hydrodynamic model, the data record also shows the ability of the AUV to perform extreme manoeuvres and the accuracy with which it can follow a pre-planned mission

Manoeuvring Trials with the MUN Explorer AUV: Data Analysis and Observations

Manoeuvring trials are usually performed to determine the manoeuvring characteristics of a marine vehicle. It is through certain standard manoeuvres we evaluate the robustness, performance and limitations of the vehicle control system. A series of open-water manoeuvring trials were performed using the MUN Explorer AUV in the summer of 2006. The actual purpose of these experiments was to collect a set of experimental data in order to validate a hydrodynamic model of the dynamic performance of the vehicle. This paper presents the results and observations from the analysis of a set of manoeuvring trials data: in particular the results from straightline (acceleration – deceleration) tests and turning circles. It outlines briefly the method by which these tests were conducted and discusses the results and observations made. Apart from providing a data set for validation purposes, the results also indicate the ability of the vehicle to follow a pre-planned mission with precision

Chirped pulse Raman amplification in plasma: high gain measurements

High power short pulse lasers are usually based on chirped pulse amplification (CPA), where a frequency chirped and temporarily stretched ``seed'' pulse is amplified by a broad-bandwidth solid state medium, which is usually pumped by a monochromatic ``pump'' laser. Here, we demonstrate the feasibility of using chirped pulse Raman amplification (CPRA) as a means of amplifying short pulses in plasma. In this scheme, a short seed pulse is amplified by a stretched and chirped pump pulse through Raman backscattering in a plasma channel. Unlike conventional CPA, each spectral component of the seed is amplified at different longitudinal positions determined by the resonance of the seed, pump and plasma wave, which excites a density echelon that acts as a "chirped'" mirror and simultaneously backscatters and compresses the pump. Experimental evidence shows that it has potential as an ultra-broad bandwidth linear amplifier which dispenses with the need for large compressor gratings

Noise in Grover's Quantum Search Algorithm

Grover's quantum algorithm improves any classical search algorithm. We show how random Gaussian noise at each step of the algorithm can be modelled easily because of the exact recursion formulas available for computing the quantum amplitude in Grover's algorithm. We study the algorithm's intrinsic robustness when no quantum correction codes are used, and evaluate how much noise the algorithm can bear with, in terms of the size of the phone book and a desired probability of finding the correct result. The algorithm loses efficiency when noise is added, but does not slow down. We also study the maximal noise under which the iterated quantum algorithm is just as slow as the classical algorithm. In all cases, the width of the allowed noise scales with the size of the phone book as N^-2/3.Comment: 17 pages, 2 eps figures. Revised version. To be published in PRA, December 199

Near-threshold electron injection in the laser-plasma wakefield accelerator leading to femtosecond bunches

We gratefully acknowledge the support of the UK EPSRC (grant no. EP/J018171/1), the EU FP7 programmes: the Extreme Light Infrastructure (ELI) project, the Laserlab-Europe (no. 284464), and the EUCARD-2 project (no. 312453).The laser-plasma wakefield accelerator is a compact source of high brightness, ultra-short duration electron bunches. Self-injection occurs when electrons from the background plasma gain sufficient momentum at the back of the bubble-shaped accelerating structure to experience sustained acceleration. The shortest duration and highest brightness electron bunches result from self-injection close to the threshold for injection. Here we show that in this case injection is due to the localized charge density build-up in the sheath crossing region at the rear of the bubble, which has the effect of increasing the accelerating potential to above a critical value. Bunch duration is determined by the dwell time above this critical value, which explains why single or multiple ultra-short electron bunches with little dark current are formed in the first bubble. We confirm experimentally, using coherent optical transition radiation measurements, that single or multiple bunches with femtosecond duration and peak currents of several kiloAmpere, and femtosecond intervals between bunches, emerge from the accelerator.Publisher PDFPeer reviewe

Chirped pulse Raman amplification in plasma

Raman amplification in plasma has been proposed to be a promising method of amplifying short radiation pulses. Here, we investigate chirped pulse Raman amplification (CPRA) where the pump pulse is chirped and leads to spatiotemporal distributed gain, which exhibits superradiant scaling in the linear regime, usually associated with the nonlinear pump depletion and Compton amplification regimes. CPRA has the potential to serve as a high-efficiency high-fidelity amplifier/compressor stage