摘要:

Key components and technologies have been developed for an ultrahigh repetition rate XeCl excimer laser of 5 kHz to be used for industrial applications. A compact axial blower having a revolution rate of up to10 000 min−1and a maximum pressure of 16.2 kPa in air was made with a canned magnetic coupler to circulate a laser gas at a flow velocity of over 150 m/s in a discharge region. Materials constituting a laser chamber were tested to prevent discharge instability by gas contamination to enable long time operation. The dominant cause of the instability was investigated by a simple simulation. For a preionization, a novel sealed-off x-ray tube was developed to compare the suitability in a high repetition rate operation with that of conventional UV preionization. The gas due to the shock and acoustic waves generated by discharge pulses was measured to design the damper, which enabled the suppression of the gas turbulence by around a tenth. To simplify cumbersome laser maintenance, a new power supply provided by a novel fast switching semiconductor device was evaluated by operating the laser. The experimental laser apparatus integrating these key components and technologies was operated to confirm the practical availability for high repetition of up to 5 kHz. Many kinds of basic experiments have been performed to increase repetition rate, average power, and reliability. Though these experimental results have not yet been integrated and performed simultaneously, we have achieved operation up to an average output power of 0.56 kW at 5 kHz. Based on the results and empirical knowledge, the prospect for a practical high repetition rate excimer laser was discussed. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148471

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Diode lasers have been used for ion temperature measurements in ArII plasmas by finding new laser-induced fluorescence (LIF) schemes suited to the present range of available wavelengths. The new LIF schemes require excitation at 664, 669, and 689 nm, all near industry-standard wavelengths. Conventional LIF measurements performed by dye lasers in ArII use 611.66 nm in vacuum, shorter than any commercially available red diode laser line, and depend on the population of the3d′ 2G9/2metastable state. The metastable state density of the conventional LIF scheme was found to be larger than the populations of the other metastable states by an order of magnitude or less. A master oscillator power amplifier diode laser was used both in a Littman–Metcalf cavity and as an optical amplifier for a low power diode laser which was in a Littman–Metcalf cavity. Both systems provided intensity of up to 500 mW, continuously tunable over 10 nm centered at 666 nm, and were used to obtain high resolution ion velocity distribution functions. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148472

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A new type of low cost optomechanical laser-beam shutter without any wearing parts, consisting of a resonantly oscillating piezoelectric element and an optical telescope, is described. In intracavity operation, the 2.5 &mgr;s optical switching time is suitable forQ-switching lasers having long buildup times. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148473

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An in-vacuum minipole (short period) insertion device has been developed in a collaboration between SPring-8 and the National Synchrotron Light Source (NSLS). The magnetic arrays were assembled, field measured, corrected, and vacuum tested by SPring-8 and were installed in an NSLS-developed chamber with mechanical parts in the NSLS X-Ray Ring(E=2.584 GeV)in May 1997 and a successful commissioning of the device was carried out in June 1997. The device is made of permanent magnets with 30.5 periods and a period length of 11 mm. It is designed to produce fundamental radiation at 4.6 keV, and with a modest value of deflection parameter(K=0.7at 3.3& mm gap) enables higher harmonics to be used as well, for a variety of experiments. A detailed description of the mechanical support and vacuum chamber will be reported elsewhere. We describe technical challenges encountered in constructing this type of device, and present an outline of our collaboration. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148871

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present experimental results obtained with a cryogenically cooled, high-resolution x-ray spectrometer based on a141 &mgr;m×141 &mgr;mNb-Al-Al2O3-Al-Nbsuperconducting tunnel junction (STJ) detector in a demonstration experiment. Using monochromatized synchrotron radiation we studied the energy resolution of this energy-dispersive spectrometer for soft x rays with energies between 70 and 700 eV and investigated its performance at count rates up to nearly 60 000 cps. At count rates of several 100 cps we achieved an energy resolution of 5.9 eV (FWHM) and an electronic noise of 4.5 eV for 277 eV x rays (the energy corresponding to CK). Increasing the count rate, the resolution 277 eV remained below 10 eV for count rates up to∼10 000 cpsand then degraded to 13 eV at 23 000 cps and 20 eV at 50 000 cps. These results were achieved using a commercially available spectroscopy amplifier with a baseline restorer. No pile-up rejection was applied in these measurements. Our results show that STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft x rays. Thus STJ detectors may prove very useful in microanalysis, synchrotron x-ray fluorescence (XRF) applications, and XRF analysis of light elements (Klines) and transition elements (Llines). ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148474

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have developed a new submillimeter wave pulsed molecular beam spectrometer with phase stabilized backward wave oscillators (BWOs). In the frequency ranges of 260–380 and 440–630 GHz, the BWOs output power varies between 3 and 60 mW. Part of the radiation was coupled to a novel designed harmonic mixer for submillimeter wavelength operation, which consists of an advanced whiskerless Schottky diode driven by a harmonic of the reference synthesizer and the BWO radiation. The resulting intermediate frequency of 350 MHz passed a low noise high electron mobility transistor amplifier, feeding the phase lock loop (PLL) circuit. The loop parameters of the PLL have been carefully adjusted for low phase noise. The half power bandwidth of the BWO radiation at 330 GHz was determined to be as small as 80 MHz, impressively demonstrating the low phase noise operation of a phase locked BWO. A double modulation technique was employed by combining an 80 Hz pulsed jet modulation and a 10–20 kHz source modulation of the BWO and reaching a minimum detectable fractional absorption of2×10−7.For the first time, a number of pure rotational (Ka=3←2,Ka=4←3) and rovibrational transitions in the van der Waals bending and stretching bands of the Ar–CO complex were recorded. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148475

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A new device, a selective digital integrator (SDI), for the acquisition of modulated polarization spectroscopy (MPS) signals is described. Special attention is given to the accurate measurement of very small signals (ac component of interest<10−3×dccomponent) buried in noise. The polarization of light is altered with fast modulators (modulation frequency∼50 kHz). A SDI connected to a single detector is used to separately and selectively measure the polarization-dependent intensities of electronic transitions. The SDI is a major improvement over the lock-in approach: it has on-the-fly time-resolved data acquisition and integration capability, and a wide gain-switching-free dynamic range (10 orders of magnitude). This design permits a variety of applications that require detection of modulated or pulsed signals. The advantages of the MPS-SDI method are demonstrated on the first Rydberg electronic transitions of (+)-3-methylcyclopentanone. The selectively measured MPS intensities are provided in 3D form (intensity versus both wavelength and light polarization). A discussion of the scattering problems that bedevil measurements at higher optical densities is included, and ways to correct for it are outlined. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148476

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A wide acceptance angle first-order reflectron lens has been incorporated into a three-dimensional atom probe (3DAP) to provide improved mass resolution. This new 3DAP instrument is capable of resolving isotopes in the mass spectrum, with resolutions better thanm/&Dgr;m=500full width at half maximum and 250 full width at 10&percent; maximum. However, use of a reflectron for energy compensation within an imaging system means that improvements in mass resolution result in degradation of the spatial resolution. This article addresses the detailed design of the energy compensated 3DAP, and the minimization and compensation of chromatic aberrations in the imaging performance of the instrument. Some applications of the new instrument are included to illustrate its capabilities in the atomic-scale analysis of engineering alloys. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148477

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The characteristics of a beam generated by a “hollow cathode” gun, intended for electron cooling purposes, are thoroughly investigated. Attention was focused on the details of the current density and temperature distributions across the electron beam. Consequently a high quality beam was obtained, comparable with the beams generated by standard guns. Much insight was gained on the vacuum and alignment conditions for this new configuration. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148478

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A simple, compact, high-current, 2.45 GHz microwave ion source has been built and tested. The source uses permanent magnets rather than electrical solenoids to provide the required magnetic field. Developed from an earlier microwave-driven ion source, the plasma generator volume has been reduced by a factor of 8 with no discernible change in rf efficiency or feed consumption. A hydrogen beam of over 60 mA has been extracted from a single 5 mm diameter aperture with a proton fraction of 80&percent; at a rf power of 450 W and a gas flow of 1.5 sccm. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148479

出版商:AIP    

年代:1998

数据来源: AIP