摘要:

A real time digital spectral analysis system, applicable to broad band plasma fluctuations, is presented. The system digitally records plasma potential fluctuations on a pair of matched electrostatic probes, and subsequently outputs the cross power spectral density and phase via an on‐line computer graphics display. The spectral analysis system and its experimental accuracy are discussed. Using the Lawrence Berkeley Laboratory ten amp neutral beam ion source, several examples demonstrating the systems application to plasma wave detection are given.

ISSN:0034-6748    

DOI:10.1063/1.1136397

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An electron distribution function measurement system, applicable to noisy plasma environments, is presented. The system is based on the harmonic differentiation technique, which utilizes the nonlinearity of the probe current‐voltage characteristic to infer distribution function structure. Measurements couple low noise, phase sensitive detection with digital data acquisistion and analysis, resulting in fast and accurate measurement in noisy environments where active electronic differentiation may prove untenable. The accuracy of the experimental technique and measurement system is discussed. Using a high power arc plasma, an example demonstrating the experimental system is given.

ISSN:0034-6748    

DOI:10.1063/1.1136398

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Beam power transmission and grid loading characteristics of a two‐stage neutral beam source are presented. The dependence of power deposition on the target, the grids, and the gas cell was studied over a wide range of extraction perveance values with the accel‐to‐extraction gap field ratio as the other parameter. The results show that the power transmission improves remarkably with increasing field ratio. For sufficiently large field ratios (≈2.5), more than 80% of the input IV power was collected on a target located 4 m downstream and subtending 2 ° half angle to the source. The sum of the grid loading is approximately double that of single‐stage accelerators; the plasma grid loading is the highest, followed by ground grid, accel grid, and extraction grid in that order.

ISSN:0034-6748    

DOI:10.1063/1.1136399

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An apparatus has been constructed to produce well‐characterized fast beams of rare gas metastable atoms for subsequent scattering experiments. Optical pumping by a collinear laser beam can be used to selectively remove either of the two metastable components from the beam. Laser‐induced‐fluorescence (LIF) techniques can be used to determine the original beam composition and to monitor composition changes resulting from optical absorption. These techniques have been successfully applied to a metastable neon beam produced by near‐resonant charge transfer of Ne+in Na. A simple model has been developed which accurately reproduces the observed LIF lineshape generated by tuning the laser throught the optical transition frequency.

ISSN:0034-6748    

DOI:10.1063/1.1136400

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Techniques developed to measure the amplitude, wavelength and azimuthal mode structure of high frequency (a few hundred MHz) waves impressed on an intense relativistic electron beam are described. The details of a wave probe array, two different signal processing schemes and data reduction methods are discussed. Sample data illustrating the use of these techniques, including a multi‐probe wavelength measurement made on a single machine firing are presented.

ISSN:0034-6748    

DOI:10.1063/1.1136401

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An optically isolated electronic trigger system for a pulsed Van de Graaff electron accelerator, producing an external pretrigger pulse 75 ns before arrival of the electron pulse at the target, is described. The total time jitter between trigger signal and electron pulse is 50 ps. The measurement of optical and electrical transients on a subnanosecond time scale with a sequential sampling oscilloscope is demonstrated. The contribution of various parts of the equipment to the total jitter is discussed. Those contributions to the jitter due to the electron transit time fluctuations in the accelerator assuming a constant acceleration voltage gradient and to the shot noise in the photomultiplier detector of the trigger system are calculated to be 5 ps and 12 to 21 ps respectively. Comparison with the experimental results leads to the conclusion that a considerable part of the total jitter may be attributed to acceleration voltage gradient fluctuations, to accelerator vibrations and possibly to density fluctuations in the insulation gas. Possible improvements of the trigger system are discussed. The apparatus is used for pulse radiolysis experiments with subnanosecond time resolution down to 100 ps in combination with subnanosecond time duration electron pulses.

ISSN:0034-6748    

DOI:10.1063/1.1136402

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An electric field‐jump apparatus is constructed, with a synchronized Xe flash lamp for photometric monitoring of chemical relaxations. The instrument is especially useful for the investigation of linear macromolecules, where the analyzing light beam must be linearly polarized. A video amplifier is used in conjunction with the photomultiplier, providing for fast rise time and low noise of the detection system.

ISSN:0034-6748    

DOI:10.1063/1.1136403

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A reliable Ho:YLF laser system has been successfully developed. Problems encountered in laser‐rod and support‐system design were unique and most difficult to solve. These problems include holding a fragile laser rod having nonisotropic thermal expantion with vacuum tight seals which can be thermally cycled. Experimentally proven solutions are described which should help others in developing new solid‐state laser systems.

ISSN:0034-6748    

DOI:10.1063/1.1136393

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A method of measurement of the absorption coefficient of a material is presented using a CO2optically pumped far infrared waveguide laser which has been specially developed for this purpose. This method permits the elimination of the instability effects due to the basic design concept of the laser. It is used to measure the absorption coefficient of a few mesogeneous substances in order to deduce their order parameters.

ISSN:0034-6748    

DOI:10.1063/1.1136394

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An instrument is described which measures the spectral dependence of the radiometric (photophoretic) force on a micron‐sized particle in a static configuration. This spectrometer consists of a servo‐stabilized Millikan chamber which can be used as a photophoretic balance over the spectral range from 200 nm to 1000 nm. Spectra may be taken in a vacuum as small as 10−4torr. The action spectrum of the photophoretic force on a crystallite of CdS is used as an example. The pressure dependence of the force at 500 nm is consistant with a radiometric mechanism.

ISSN:0034-6748    

DOI:10.1063/1.1136395

出版商:AIP    

年代:1980

数据来源: AIP