摘要:

A conically tapered resistive disk with a single conducting hemisphere is used to effect the same energy selection as a pair of concentric hemispheres. The combination of this energy filter with a quadrupole mass spectrometer produces a secondary ion mass spectrometry (SIMS) instrument with a high total transmission attributable to its open geometry and lack of restricting apertures. An approximate form for the energy filter‐mass spectrometer combined transmission function is constructed for operating conditions pertaining experimentally, and the theory and experiment are shown to be in good agreement. For a primary beam spot large compared with the electrical entrance aperture of the quadrupole, the energy bandwidth increases linearly with the spot diameter, and the transmission increases quadratically with the mass bandwidth and inverse quadratically with the spot diameter. The overall transmission (absolute sensitivity) is typically on the order of 5×10−4in the static mode, and would be much higher (∼12% for typical applications) in the dynamic mode with small spot rastering. Static mode ion transmissions are measured for Cu+, Al+, Si+, and Ni+at the peak of the kinetic energy distribution with an energy bandwidth of less than 3 eV. The instrument is used to study the copper surface in the static mode at current densities as low as 1.5×10−9A/cm2, using 90° incidence for the primary ions, with energies as low as 500 eV. The kinetic distribution of Cu+ions is only weakly dependent upon primary ion energy over the range 500 eV to 3 keV. The Cu+distributions show a 13‐eV halfwidth and a maximum at 10 eV, while the Cu2+ion kinetic energy distribution has a 10‐eV halfwidth and a maximum at 7 eV. Molecular ions ejected from a copper surface after a plasma oxidation are CuOH+,Cu2O+Cu2OH+, and Cu2(C2H2)+. These ions have kinetic energy distributions with ∼7 eV half‐widths and peaks at ∼5 eV. The aforementioned measurements are made with an energy resolution of less than 3 eV, which is compatible with a mass resolution equal to the mass number of at least 250 amu.

ISSN:0034-6748    

DOI:10.1063/1.1136506

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Energy dispersive diffraction from high‐pressure specimens with a synchrotron radiation source is described. A remote‐controlled diffraction stage which has greatly facilitated alignment of the high‐pressure sample in the radiation beam is discussed. An experimental diffraction pattern and theoretical relative intensities are compared.

ISSN:0034-6748    

DOI:10.1063/1.1136507

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Experimental comparison is made of four plasma grids, each with a specific aperture geometry, in an attempt to improve the ion optics of a multiple aperture ion source. It is clearly shown that a simple notch geometry outperforms the other candidates with a high transmission efficiency (∼68%) to a 2° target at high perveance (∼9.6 &mgr;perv).

ISSN:0034-6748    

DOI:10.1063/1.1136508

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A cold electron plasma has been produced, with a greater latitude in neutral pressure and plasma density than previously, by drifting plasma through an improved magnetic cusp cage. The motion across this cage has been characterized as a two‐step process. First, the plasma between the cusps cools off as it loses contact with the primary ionizing electrons which are confined at the cusps and, second, the cold plasma electrons experience a ∇B×B drift across the cage barrier magnetic field. Large ambipolar fields are also seen across the region. A two‐component, positive ion (Ar+)–negative ion (SF6−) plasma was created with the ratio of electron density (ne) to positive ion density (n+) continuously variable from 10−3<ne/n+<1.

ISSN:0034-6748    

DOI:10.1063/1.1136509

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A method is presented for determining the two‐dimensional (2‐D) spatial distribution of the volume emission intensity [E=f(r,&Vthgr;)] in a plasma from line integral data obtained by arrays of collimated detectors looking through the plasma along different chords. Subject to the assumption thatEcan be represented byJm [fm(r)cos m&Vthgr; +gm(r)sin m&Vthgr;] with only a few termsm, expressions are developed that separate harmonic contributions to the line integrals, a numerical procedure is outlined for inversion of these contributions to obtain the factorsfm(r) andgm(r), and the formulas that result are presented form= 0 throughm= 5. This method was developed for application to data from arrays of soft x‐ray detectors on the Impurity Study Experiment (ISX‐B) tokamak. One use would be comparison of the soft x‐ray volume emission contours with other measures of plasma shape. Simulations of these shape determinations were performed, using as input, a pressure profile representing a calculated MHD equilibrium for a D‐shaped plasma in ISX‐B. The results of these simulations are shown and the determination of the poloidal structure of MHD perturbations in the plasma is also illustrated.

ISSN:0034-6748    

DOI:10.1063/1.1136510

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A simple device using a Phase‐Locked Loop is described which allows automatic recording of the frequency and the quality factor of a rf cavity used to study a nonstationary dielectric medium.

ISSN:0034-6748    

DOI:10.1063/1.1136511

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

To meet specific fuel filling requirements, it is important to know the buckling properties of microspheres used in laser fusion targets. A visual technique for determining the room temperature elastic buckling strength of microspheres is described.

ISSN:0034-6748    

DOI:10.1063/1.1136512

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A low voltage (50 kV), low energy (3 J) x‐ray preionization source has been developed specifically for avalanche discharge laser preionization. The new device uses a single stage high‐voltage capacitor switched by a gradient grid hydrogen thyratron that drives a cold‐cathode electron beam. Intense x‐ray emission is produced by allowing theebeam to impact a high Z target foil. The entire system can operate up to 35 Hz repetition rate and produce an electron preionization density of ∼108 cm−3in most rare‐gas/halide laser gas mixtures.

ISSN:0034-6748    

DOI:10.1063/1.1136500

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A system is described for the recovery of xenon from XeCl lasers and variants for other rare gas halide (RGH) combinations are presented. The batch recovery systems discussed are simple and cost effective and lead to no degradation of laser performance. The added cost associated with continuous gas processing seems difficult to justify at the present time for a system of this size.

ISSN:0034-6748    

DOI:10.1063/1.1136501

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The construction of an inexpensive 50‐ps rise‐time photodiode is discussed. The temporal response of the photodiode is made insensitive to the quality of focus of the incoming light through a relatively simple procedure. Quantum efficiencies of up to 5.9% at 514 nm were measured.

ISSN:0034-6748    

DOI:10.1063/1.1136502

出版商:AIP    

年代:1981

数据来源: AIP