Microprocessing by intense pulsed electron beam

Generation of intense electron beams by superposing two discharges, namely, a low-pressure dc glow discharge and a high-current pulsed discharge at pressures and voltages very similar to that of the pseudospark gap devices, has been studied. The small beam diameter, high peak current, and short pulse length are the characteristics of the electron beam generated using this technique. This technique does not require high vacuum facilities, and applications such as microprocessing, X-ray generation, and preionization for high-power lasers are feasible. The electron beam current is in the range of 10-30 A. Microprocessing as drilling tenths of microns diameter holes in different materials such as copper, titanium, and, tantalum has been performed. The microstructure of the irradiated materials has been investigated by means of scanning electron microsope (SEM) and atomic force microscope (AFM). Currently, the possibility of processing a matrix of holes is being considered

Micro processing by intense fast electron beam

Generation of intense electron beams by superposing two discharges, namely a low pressure do glow discharge and a high current pulsed discharge at pressures and voltages very similar to that of the pseudo-spark gap devices, has been reported previously [1, 2]. The small diameter, high peak current and short pulse length are the characteristics of the electron beam generated using this technique. In this technique, no high vacuum facilities are necessary, and many applications such as micro processing, X-rays generation, pre-ionization for high-power lasers are feasible. The electron beam current is in the range of 10-30 A. A full characterization of the electron beam that is utilized in this work has been given in a previous work [3]. In this work it is reported that the most energetic part of the electron beam is about 5-nanosecond pulse duration. The beam is magnetically deflected to the specific point. The pulse repetition rate is up to 100 Hz. Micro-processing as drilling tenths of microns diameter holes in different materials such as copper, titanium, tantalum has been performed. The microstructure of the irradiated materials has been investigated by means of SEM and AFM. Currently, the possibility of processing a matrix of holes is being considered

High Voltage Design Guidelines: A Timely Update

The evolving state of high voltage systems and their increasing use in the space program have called for a revision of the High Voltage Design Guidelines, Marshall Space Flight Center technical document MSFC-STD-531, originally issued September 1978 (previously 50 M05189b, October 1972). These guidelines deal in depth with issues relating to the specification of materials, particularly electrical insulation, as well as design practices and test methods. Emphasis is on corona and Paschen breakdown as well as plasma effects for Low Earth Orbiting systems. We will briefly review the history of these guidelines as well as their immediate predecessors and discuss their range of applicability. In addition, this document has served as the basis for several derived works that became focused, program-specific HV guidelines. We will briefly review two examples, guidelines prepared for the X-33 program and for the Space Shuttle Electric Auxiliary Power Unit (EAPU) upgrade

The electron beam and pinch effect characteristics of double discharge pulsed electron beam generator

The double discharge pulsed electron beam generator (DDPEBG) is a device that generates an intense filamentary electron beam by superposing two discharges namely a low pressure dc glow discharge and a high current pulsed discharge. The characteristics of this electron beam are: small beam diameter (8 μm), high peak current (20 A), and short pulse length (30 ns). The filling gas is helium, argon or nitrogen at approximately 0.1 Torr pressure, and the discharge chamber does not require a high vacuum system. The absence of a high vacuum system and the capability to generate ultra short, intense electron beams are the major advantages of this device and, might be useful in many applications. In this work, further results on operating characteristics of the DDPEBG, such as pinch effects and electron density measurements are given. The beam diameter is measured experimentally by utilizing the interaction of a single pulse with diffrent metal foils targets. These foils are then examined by a scanning electron microscope (SEM) and the measured diameters are compared with the beam diameter values resulted from the pinch effect calculations of the filamentary discharge. The electron density is determined from the beam diameter and current intensity

Towards a Constructional Approach of L2 Morphological Processing

International audienceFollowing Silva & Clahsen seminal work, psycholinguistic research on L2 morphological processing has mainly adopted a morpheme-based, decompo-sitional dual route approach suggesting that L2 learners have a limited access to morphological representation during processing and consequently rely more on lexical storage (Clahsen H, Felser C, Neubauer K, Sato M, Silva R, Lang Learn 60:21-43, 2010; Clahsen and Felser, 2017). Therefore, experimental research, which largely used the masked priming paradigm, mainly focused on the distinction between storage and computation as two alternative, mutually exclusive and competing mechanisms. In this paper, we claim that a word-based approach, which considers morphology in terms of constructional schemas, allows us to overcome the rule vs. list fallacy and therefore reshapes the dichotomy between L1 and L2 processing mechanisms. Although a consistent proposal is still out of reach, given that data on L2 processing are limited, we will discuss the advantages of a model which jointly considers formal and semantic similarities, as well as paradigmatic proprieties