摘要:

Microwave resonant cavities running at 2.45 GHz are now being investigated for use in the high power remote plasma processings. The present paper deals with the design of two coupling devices, e.g., one coaxial cavity and one TM012mode cylindrical cavity, using an antenna coupling. Their main attractive feature is the ability to run at powers as high as 3 and 6 kW, respectively. A basic model used to describe the wave–plasma interaction is developed and leads to the main consequences for the cavities conception thanks to the deduced equivalent electrical circuits. Their high efficiency is experimentally demonstrated for nitrogen, oxygen, air, and argon.

ISSN:0034-6748    

DOI:10.1063/1.1144519

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A new method for the diagnostics of charged particle beams by employing localized space‐charge waves is presented. The propagation of space‐charge waves in the form of localized perturbations can be measured easily and accurately in experiments. The results carry valuable information about many beam parameters such as the wave speed, the geometry factorgfor the longitudinal space‐charge field, the beam radius, the beam impedance under longitudinal perturbations, etc. The principle of this technique and an experimental example are given in this article.

ISSN:0034-6748    

DOI:10.1063/1.1144520

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The experimentally measured modulation characteristics of a planar Cs–Ba plasma switch (tacitron) are presented and discussed. Tests are performed that focus on characterizing the operation capabilities of a planar Cs–Ba tacitron. Results show that the operation characteristics of the device are independent of geometry (cylindrical or planar). The forward voltage drop decreases as either the grid‐collector (GC) gap size and/or the Cs pressure increases. Also, stable current modulation is easier to sustain when the grid is placed closer to the collector, at the expense of increasing the forward voltage drop across the device.

ISSN:0034-6748    

DOI:10.1063/1.1144521

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The velocity of a gadolinium atomic beam produced by electron beam heating was found to range from 700 to 1000 m/s by measuring the drift velocity of the plasma, which is produced by ionizing atoms in the atomic beam with pulsed dye lasers and using Langmuir probes. The measured atomic beam velocity spread agrees with that determined by the microbalance method.

ISSN:0034-6748    

DOI:10.1063/1.1144522

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A mass selective electron‐impact ionization detector for use in energy resolved thermal He scattering experiments is presented. The detector combines a short effective ionization region (approximately 3 mm FWHM) with a high detection efficiency of 10−5at 2 mA electron emission. An efficiency of 10−4at 10 mA emission current can be achieved if time resolution below 20 &mgr;s is dispensable. The design is discussed and measurements of detection efficiency and time resolution are presented. The ionizer can likewise be employed for an efficient detection of other types of atoms or molecules.

ISSN:0034-6748    

DOI:10.1063/1.1144523

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We describe an instrument designed for studying the electronic structure of bulk, surface, and deep solid–solid interface. The analysis is made by soft‐x‐ray emission spectroscopy induced by electron bombardment. The target is placed under ultrahigh vacuum and can be prepared and treatedinsitu. High resolution is achieved both as concerns the photon energy and the electron‐beam energy. Tests have been made in the dispersive mode and in the characteristic isochromat mode. In both cases experimental resolution is in good agreement with the expected one.

ISSN:0034-6748    

DOI:10.1063/1.1144524

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The retrapping of highly charged Xe44+and Th68+,72+ions extracted from an ‘‘electron‐beam ion trap’’ (EBIT) is demonstrated after injection of the ions into RETRAP, a cryogenic Penning trap (up to 6 T magnetic field) currently with an open cylinder design. Ion extraction in a short pulse (5–20 &mgr;s) from EBIT, essential for efficient retrapping, is employed. The ions are slowed down upon entering a deceleration tube mounted above the trap within the magnetic field. The potential is then rapidly (100 ns) decreased, enabling low‐energy ions to enter the trap. Capture efficiencies up to 25% are observed via detection of the delayed ion release pulse with a detector below the trap. Signal voltages induced in a tuned circuit due to single and multiple ions have been observed by tuning the ion resonant axial oscillation frequencies for different ions. Results from transporting and retrapping of the ions, as well as their detection, are described and the trapping efficiency is discussed. The motivation for these studies is to cool the trapped very highly charged ions to low temperatures (<4 K) in order to perform ultrahigh‐resolution precision spectroscopy, collision studies at ultralow energies, and to observe phase transitions in Coulomb clusters of highly charged ions.

ISSN:0034-6748    

DOI:10.1063/1.1144525

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An experiment using a wire simulating an electron beam was carried out in atmosphere to find organic particles (5‐&mgr;m thickness collected from an ion pump) trapped in a low electric field. It was found that these needlelike charged flakes stood upright at the bottom surface of the beam chamber without applied electric field. In spite of large adhesive action between the particle and the inner chamber surface in air, it was also found that the sample microparticles were trapped at the low electric field of 2525 V/m. Furthermore, the measured charge on the samples ranged from 1×10−13C to 3×10−13C. Our new theoretical analyses for the samples show that the electric field acting on the needlelike microparticles is enhanced approximately 104times from the results of the atmospheric experiment, and that the charged particles in vacuum can be trapped at a lower electric field of 70 V/m in the TRISTAN accumulation ring (time average electric field at the beam current of 30 mA) because of weak adhesion between the particles and an inner chamber surface rather than that in atmosphere. Therefore, microparticle trapping phenomena can be caused by such a charged particle coming from an ion pump or a distributed ion pump used in an electron accelerator.

ISSN:0034-6748    

DOI:10.1063/1.1144526

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An all metal multistage low frequency vibration isolator for a laser interferometer gravitational wave detector has been built and tested with a very sensitive accelerometer. Curved cantilever springs are used to form a low frequency compact form of isolation element. Near center of mass suspension of the isolation stages reduces cross coupling between orthogonal directions. The isolator has a low‐pass corner frequency of 6.5 Hz vertically and 1.8 Hz horizontally. The system shows low temperature coefficients and absence of creep. Results demonstrate that steel curved springs near their elastic limit do not generate broadband acoustic noise at the 10−15m /&sqrt;Hz level.

ISSN:0034-6748    

DOI:10.1063/1.1145218

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An expansion of the capabilities of high‐speed, multichannel spectroscopic ellipsometry (SE) is described that involves simultaneous measurement of the reflectance spectrum along with the two spectra in the ellipsometric angles (&psgr;, &Dgr;). Previously, a novel rotating‐polarizer spectroscopic ellipsometer has been perfected that employs a photodiode array detector for high‐speed acquisition of (&psgr;, &Dgr;) spectra, designed for real‐time studies of thin‐film growth. For a polarizer angular rotation frequency of &ohgr;0, the (&psgr;, &Dgr;) values at a given photon energy are deduced from the 2&ohgr;0Fourier components of the detector irradiance, normalized by the dc component. Athirdparameter, the weighted reflectanceRA, can be obtained from the dc component and from a calibration based on the known optical properties of the substrate measured prior to film growth. With (&ohgr;0/2&pgr;)=12.5 Hz, three‐parameter data sets, [&psgr;(h&ngr;), &Dgr;(h&ngr;),RA(h&ngr;); 1.5≤h&ngr;≤4.5 eV], can be acquired with a time resolution as short as 40 ms. AlthoughRAprovides complementary information to (&psgr;, &Dgr;), it has yet to be exploited in conjunction with real‐time SE until this study. A resilient analysis approach, based on mathematical inversion and least‐squares fitting of the real‐time three‐parameter data sets, is designed to yield the film dielectric functions and thicknesses independently at each time during the early stages of thin‐film growth. The three‐parameter approach has been applied successfully in studies of amorphous silicon (a‐Si:H) thin films prepared by plasma‐enhanced chemical vapor deposition, and aluminum and silver films prepared by physical vapor deposition. For thea‐Si:H films,RA(h&ngr;) exhibits deviations as large as ∼3% from that predicted in modeling (&psgr;, &Dgr;) alone. The deviations result from light scattering by plasma particulates, and we show how additional information can be extracted from the spectral dependence of the scattering loss.

ISSN:0034-6748    

DOI:10.1063/1.1144527

出版商:AIP    

年代:1994

数据来源: AIP