Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question

Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5-10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30-60 degree hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators

Wide-angle electron beams from laser-wakefield accelerators

Advances in laser technology have driven the development of laser-wakefield accelerators, compact devices that are capable of accelerating electrons to GeV energies over centimetre distances by exploiting the strong electric field gradients arising from the interaction of intense laser pulses with an underdense plasma. A side-effect of this acceleration mechanism is the production of high-charge, low-energy electron beams at wide angles. Here we present an experimental and numerical study of the properties of these wide-angle electron beams, and show that they carry off a significant fraction of the energy transferred from the laser to the plasma. These high-charge, wide-angle beams can also cause damage to laser-wakefield accelerators based on capillaries, as well as become source of unwanted bremsstrahlung radiation

Coherent radiation sources based on laser driven plasma waves

Here we explore ways of converting laser radiation into coherent electromagnetic radiation using laser-driven plasma waves. Several schemes are presented, including colliding laser pulses in magnetized plasma and utilizing ultra-short electron bunches from laser wakefield accelerators to produce intense single-cycle pulses through coherent transition radiation and few-cycle coherent synchrotron radiation in undulators and plasma channels. These sources rely on high current electron bunches with femtosecond durations, which can result in radiation over a broad range of frequencies from 1 to 105 THz

Degradation Kinetics of Protein Digestibility and Available Lysine During Thermal Processing of Tuna

3 pages, 2 figures, 1 tableChanges in available lysine and protein digestibility which take place during thermal processing of canned white tuna with olive oil were evaluated using a steady-state procedure. Kinetic parameters were then calculated by means of weighted nonlinear regression and the jac!+ procedures. Good agreement was found between predicted and observed values. The resulting kinetic equations can be used to evaluate, design and optimize thermal processing of tuna in oil.This work was supported by a research grant from the Comisión Interministerial de Ciencia Y Tecnología (ALI88-0145-C02-02. Spain)Peer reviewe

Silicon vertex detector upgrade in the ALPHA experiment

The Silicon Vertex Detector (SVD) is the main diagnostic tool in the ALPHA-experiment. It provides precise spatial and timing information of antiproton (antihydrogen) annihilation events (vertices), and most importantly, the SVD is capable of directly identifying and analysing single annihilation events, thereby forming the basis of ALPHA's analysis. This paper describes the ALPHA SVD and its upgrade, installed in the ALPHA's new neutral atom trap