摘要:

Experimental techniques and instrumentation for space plasma imaging in fluxes of energetic neutral atoms (ENAs) are reviewed. ENAs are born in charge exchange collisions between space plasma energetic ions and background neutral gas. ENAs are ubiquitous in the space environment and their energies are in the range from a few eV up to100 keV.Contrary to charged particles, ENAs can travel large distances through space with minimal disturbance, and by recording ENA fluxes as a function of observational direction, one can reconstruct a global image of a planetary magnetosphere or the heliosphere. Plasma ion energy distribution and ion composition can be remotely established by measuring ENA energies and masses. ENA imaging opens a new window on various phenomena in space plasmas with a promise to qualitatively improve our understanding of global magnetospheric and heliospheric processes. At first we review ENA fluxes in space and their properties, and present a brief history of ENA experimental studies and the evolution of experimental approaches. The concepts of ENA imaging and particle identification are considered and followed by comparison with corpuscular diagnostics of fusion plasmas. Basic ENA techniques and instrument components are then described in detail and critically evaluated; performance characteristics, limitations, and requirements to key instrumental elements are discussed. And finally, representative ENA instruments are shown, and promising instrumental approaches are identified. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148389

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on several complementary methods for improving the stability of a free running diode laser. We were primarily concerned with: (a) the construction of a stable power supply to reduce the main frequency and rf noise, and (b) long term drift of the laser frequency, for which we have developed a lock-in amplifier to be combined with a simple proportional-integrating circuit. While we have kept everything simple and inexpensive to construct, the stability is comparable with that of far more expensive, commercially available systems. Development and testing of our stabilization scheme was done on the distributed Bragg reflector diode lasers for use in a range of atomic collision and atom optics experiments, but it is applicable to all diode lasers, and can be used in a large range of atomic physics experiments. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148008

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The construction of He-Ne-I2stabilized laser electronics with digital control by a PC computer is presented in this contribution. This system has been developed to work with a compact laser head as a wavelength standard for metrology of lengths. Due to its compact construction and portability it can be used in calibrations of laser interferometers in mechanical engineering and microelectronics. A novel approach to the design of a control is presented. Sensitive analog circuits are opto-coupled to a digital control communicating with a PC. All functions are accessible from keyboard, iodine spectrum and system diagnostic data are currently displayed. User friendly graphic interface allows easy hyperfine line selection and locking. The system was compared to the BIPM laser and showed a very good reproducibility. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148004

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A commercial high numerical-aperture microscope objective is designed in terms of the sine condition which is needed for two-dimensional space-invariant imaging. The axial trapping efficiency generated by an objective obeying the sine condition is found to be approximately up to 50&percent; smaller than the prediction for an objective obeying the tangent condition which has been currently used in the ray optics theory for trapping force calculations. Our result is in good agreement with the measured value of the trapping efficiency. ©1997 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1148009

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have constructed a quasimonolithic crystal consisting of two offset, parallel-mounted quartz (101¯0) crystals for determining the wavelengths of x-ray transitions on an absolute scale without the need for reference lines. The design and organization of the quasimonolith crystal device, as well as the determination of the relevant parameters and their corresponding uncertainties are discussed. A calibration chain is established that enables linking any wavelength measurement directly to optical wavelength standards and thus to SI units. Our analysis shows that absolute wavelength measurements with an uncertainty of one part per million are in principle possible with the device. Implementation of the quartz quasimonolith in a high-resolution vacuum spectrometer used to study x-ray line emission from an electron beam ion trap is described. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148010

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A generalized hard x-ray detection model for microchannel plate (MCP) detectors has been developed. This model includes all geometrical and compositional parameters of an MCP and the energy of a detected x-ray. An analytical investigation and numerical calculation of the detection efficiency were carried out; data obtained were compared with experimental results. A square and hexagonal channel MCP were considered in addition to a traditional circular channel MCP. Moreover, it is shown that the first ones have advantages as x-ray detectors. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148011

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

One of the promising radiation detection devices for various practical applications is the series-connected superconducting tunnel junction (STJ) detector. In this article, interesting topics of the detectors are described since our previous work: e.g., more than two order higher detection efficiency compared with single STJ detectors, high count rate detection, and position resolution. Detectors were cooled to 0.35–0.4 K by means of a convenient3Hecryostat. The 5.9 and 6.5 keV x rays from55Feare separated by a detector specially designed for x-ray detection. The possible count rate of the series-junction detector estimated from the shaping-time constant applied in the measurements is high, e.g., over104counts per second. A series-junction detector equipped with a position sensing mechanism has shown a position resolution of about 35 &mgr;m in a sensing area with a radius of 1.1 mm. The position resolution of series junctions improves the energy resolution. A new type series-connected STJ detector is also proposed, i.e., the dispersed multitrap series-junction detector, for further improvement of detection efficiency and energy resolution. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148012

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new apparatus has been constructed to eliminate the self-absorption effect from dispersed emission spectra. Droplets of solution smaller than 5 &mgr;m in diameter were generated by ultrasonic vibration from bulk solution, and irradiated with a laser to observe dispersed emission spectra. Effective suppression of self-absorption was demonstrated using ethanol droplets containing rhodamine 640 dye. A slight increase in the ambient temperature—less than 10°—gave rise to a release of solvent molecules from droplets, and consequently, the size of the droplets drastically decreased. Emission spectra over a wide range of concentrations were observed by the method of solvent release. The change of the ratio between monomer/excimer fluorescence from pyrene was clearly shown using droplets generated from solution with single concentration. Effective concentrations and the sizes of droplets at different temperatures were determined from comparison to the results obtained by droplets with different concentrations. The concentration of droplets warmed up to 305 K and was 29 times that of droplets at 297 K. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148013

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new detector for state analysis of multicharged ions, excited in high Rydberg states, at kinetic energies of the order of keV is described. It is composed of a field-ionizing lens system (FILS), associated with two electrostatic spectrometers; the first one, in front of the FILS, selects theq-times charged excited ions of interest, and the second one, behind the FILS, analyzes the(q+1)-times charged ions resulting from field ionization according to their kinetic energy. The principle of the FILS is to generate a linearly increasing electric field, colinear with the excited ion beam, that the excited multicharged ions experience until they are field ionized. This detector has been successfully used to detect for the first time the distributions of very high Rydbergnstates in the domainn=67–100produced inKr7+*(n)ions by electron capture intoKr8+from laser-excitedRb*(nip)atoms. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148448

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new method is described that combines the production of ions by laser ablation with a reflection time-of-flight mass spectrometer for charge-transfer cross section measurements. This method allows a specific charge-transfer channel of an ion-neutral pair to be measured at energies of about 0.1 keV/amu. The metastable state ion fraction in the laser ablation ion beam is shown to be negligible. The charge-transfer cross section is determined by measuring the intensity ratio of the product ions to the parent ions after the charge-transfer reactions occur in the reflection drift tube. Verification on the apparatus is demonstrated through investigation of a single electron charge transfer of ground stateC2+ions andH2with the incident energy ofC2+at 3045.6(&sgr;=12.4) eV. Our measured cross section of6.90(±0.78)×10−16 cm−2is consistent with ground state measurements reported previously. Because of the versatility of the pulsed laser ablation ion source, this facility can be used to examine the cross sections of a variety of multiply charged ions from refractory or gaseous elements. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148014

出版商:AIP    

年代:1997

数据来源: AIP