摘要:

A brief review is presented of the ‘‘Raduga’’ 1–4 repetitively pulsed metal vapor vacuum arc ion sources. Their operation principles and functional ranges are described. The Raduga ion sources provide single‐ and multi‐element implantation. These advantages are achieved by using not only pure single‐element or mixed ion fluxes, but also pulsed beam sequences with controllable composition and energy of each ion species. Another feature of the ion sources is their ability to generate a sequence of ion beam and plasma stream pulses. Switching between ion irradiation and plasma deposition can be done from pulse to pulse, within each pulse, or after accumulation of a required dose. Some specific features of the emission properties of broad beam metal vapor vacuum arc ion sources are described.

ISSN:0034-6748    

DOI:10.1063/1.1144766

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

This article briefly summarizes the work of the author in the field of vacuum arc ion sources from the first version made in 1984, which generated metal ion beams of 20 cm diam with ion current up to 1 A at an accelerating voltage up to 130 kV, pulse duration of 300 &mgr;s, and repetition rate up to 50 Hz, for doing high dose implantation, to the creation in 1987 of the Technological Accelerator of Metal ions and Electron Kit (TAMEK) source which can produce, without switching off the source, the regimes of high‐dose implantation, ion deposition, ion‐beam mixing, and ion‐beam‐assisted deposition of the same metal ions, as well as the generation of electron beams with the same time and energy parameters and current up to 10 A. Sources with a vacuum arc current of several amperes (Iarc≳2 A,Ii≳0.1 A for a copper cathode) and milliseconds duration, and with a vacuum arc current up to 100 kA (Ii=1–10 kA) and microseconds duration, are described. Application of TAMEK sources for improving the properties of surface layers of metal and dielectric materials are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1144767

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We have constructed a self‐starting Kerr‐lens mode‐locked Ti:sapphire laser pumped synchronously by a mode‐locked, LBO‐doubled Nd:YAG laser. Using a home‐built beam‐pointing stabilizer, beam wander of the 532 nm pump is reduced by a factor of 25, thus enabling long term operation of TEM00nearly transform limited pulses with amplitude, repetition rate, and pulsewidth fluctuations comparable to or better than those of Ar‐pumped Ti:Al2O3lasers. Interferometric autocorrelation using second harmonic in reflection from GaAs yielded a pulse width of 30 fs, limited by the dispersion of wide bandwidth cavity optics which permit tunability from 0.7 to 1.0 &mgr;m.

ISSN:0034-6748    

DOI:10.1063/1.1144768

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A KrF‐laser‐based ozone lidar system is described which operates in the wide vertical range between 0.1 and 12 km. The wavelengths used for the measurements are generated by efficient stimulated Raman scattering which is optimized by using a KrF laser in an oscillator‐amplifier configuration. Two receiving telescopes are used to divide the considerable dynamic range of the backscattered signal which covers more than eight orders of magnitude. The ozone density errors are smaller than 7.5×1016m−3(i.e., 3.1 ppbv near the ground) which is comparable to those of standard ozone monitors. A further improved performance is expected in the future. A first annual series with about 580 individual measurements was carried out in 1991 and is briefly discussed.

ISSN:0034-6748    

DOI:10.1063/1.1144769

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We describe sources of error in a breadboard, low‐cost, time‐of‐flight laser rangefinder. The rangefinder deduces the range of a retroreflecting target by directing an intensity‐modulated laser beam at the target and measuring the phase difference between the returned and transmitted modulation envelopes. The phase measurement is performed by a combination of heterodyning and digital signal processing. We present an equation for the standard deviation of statistical errors generated by quantization in the digital signal processing. We show how both electrical crosstalk and stray light give rise to errors which are cyclic with target range, and we describe how these errors can be reduced. We demonstrate the importance of errors caused by the dependence of the photodiode’s propagation delay upon the intensity and placement of the light spot incident upon its surface, and discuss how the instrument’s optical components can be arranged to minimize such errors. Finally, we show that our rangefinder, using a modulation frequency of 140 MHz, has rms nonlinearity less than 85 &mgr;m.

ISSN:0034-6748    

DOI:10.1063/1.1144545

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present a particle detector for intermediate monitoring of beams of ion bunches (e.g., in time‐of‐flight mass analyzers). Its principle is secondary electron emission from a thin wire whose cross section is small (i.e., <5%) compared with the cross section of the primary ion beam. By means of a special experimental setup, anionic, cationic, or neutral particle beams can be formed; in addition, a tandem arrangement of our transit detector and a second detector at the end of the ion flight region allows us to test this transit detector. The influence on mass resolution, reliability of ion peak heights, dependence on kinetic energy and charge of the primary particles, and linearity have been investigated. This new detector may be useful for tandem mass spectrometric experiments, e.g., in time‐of‐flight analyzers with secondary excitation by collisions or photon absorption.

ISSN:0034-6748    

DOI:10.1063/1.1144546

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A coincidence data acquisition system, incorporating a position sensitive detector and a custom‐built data acquisition card installed in an IBM‐PC 486 computer, has been implemented in a coincidence experiment in which scattered electrons and Auger electrons are detected in coincidence. Three analog‐to‐digital converters (ADCs) are used to digitize all the timing and energy information, and custom‐designed and written control software is used to accumulate the data, display it in real time, and store it in expanded memory. The new system has ben used to measure the energy and angular distribution of Auger electrons ejected from argon after electron impact ionization.

ISSN:0034-6748    

DOI:10.1063/1.1144547

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A review of electron optical bench literature is presented, and the designs of two optical benches used by the authors are described. One bench was designed for testing individual electrostatic electron lenses and in‐line optical systems, for example, emission electron microscopes and transmission electron microscopes. It has been in operation for many years. The second electron optical bench is new. It is a branched system designed for several purposes: to study correction of spherical and chromatic aberration with an electron mirror, and to gain experience with low energy electron microscopy (LEEM) optics. The alignment of the electron optical support structure is independent of the vacuum housing, and the bench is designed to be operated either horizontally or vertically. As a demonstration of the performance of the new bench in the horizontal mode, a test pattern on a silicon surface was imaged with LEEM optics.

ISSN:0034-6748    

DOI:10.1063/1.1144548

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

To get ultrahigh stability of the dc high‐voltage (HV) output, we propose a novel compensation method for reducing the periodic ripple included in the output of a Cockcroft–Walton (CW) generator circuit. A compensating signal is injected into the circuit via the ground end to compensate various ripple harmonics at the HV end. Considering the nonlinearity of a CW circuit, we first compose the signal with the linear superposition of harmonics minimizing individual ripple spectral components, and then reduce the deviation due to the nonlinearity through the fine adjustment on the synthesized signal. An experiment testing the method has been carried out in an ultrahigh‐voltage electron microscope, compensating the ripple components from the fundamental to the ninth higher harmonics. Ripple has been decreased by above one order of magnitude, resulting in a percent ripple of less than 1×10−6.

ISSN:0034-6748    

DOI:10.1063/1.1144549

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An instrument that incorporates a scanning electron microscope (SEM) and a scanning tunneling microscope (STM) in an ultrahigh vacuum environment was designed to address the specific difficulties of imaging heterogeneous surfaces. A sample may be mounted in the STM for simultaneous STM and SEM imaging, or transferred to a manipulator where other surface analytical tools may be utilized. The STM is based on a viton‐stainless‐steel stack design and the SEM employs a 5 kV, electrostatic‐lens electron gun. The sample mount is fixed, while the tip can be positioned in three orthogonal directions. Macroscopic positioning of the tip is accomplished using two orthogonal linear piezoelectric ‘‘inchworm’’ motors and a stepper motor, whereas microscopic positioning is accomplished with a piezoelectric tube scanner

ISSN:0034-6748    

DOI:10.1063/1.1144550

出版商:AIP    

年代:1994

数据来源: AIP