摘要:

Nuclear and non‐nuclear applications of cineradiography are reviewed, with emphasis on fuel‐motion diagnostic instrumentation that is used for in‐pile nuclear‐reactor safety studies. The primary instrument for this purpose has been the fast‐neutron hodoscope, which achieves quantitative monitoring of time, location, mass, and velocity of fuel movement under the difficult conditions associated with experiments in transient reactors. Nominal 1‐ms, 0.1‐g, 1‐mm resolution have been accomplished during reactor transients of over 104in power. Although alternative diagnostic devices—such as coded apertures, flash radiography, and pinhole imaging—have been developed, they have not matched the performance of the hodoscope; the evaluation of the relevant parameters appears in the paper. Because discriminating detectors can be placed in tandem in hodoscope channels, other test material constituents—such as cladding steel and sodium coolant—can be dynamically distinguished. Material‐motion diagnostic systems can also be used for time‐integrated radiography and direct time‐ and space‐resolved fuel‐pin power monitoring. High‐resolution diagnostic systems are now operating at two reactors, and studies and tests have been carried out for application to several others.

ISSN:0034-6748    

DOI:10.1063/1.1137925

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Arrays of flux detection coils can be used in pulsed relativistic electron beam experiments to Fourier analyze in azimuth the magnetic fields resulting from beam or net currents. In propagation experiments using the beam generated with the IBEX accelerator the displacement perturbations of the initially injected beam were determined using arrays sensitive to the first azimuthal harmonic of the azimuthal magnetic field. These arrays were found to be capable of easily resolving 120‐MHz oscillations of the beam centroid with amplitude less than 0.1 mm.

ISSN:0034-6748    

DOI:10.1063/1.1137926

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Particle dynamics and collimation in the Thomson spectrometer system are discussed. A compact spectrometer which consists of a unique pinhole arrangment, a pair of permanent magnets, and CR‐39 detector is described with a few practical calibration techniques. Applications including analysis of charge‐to‐mass ratio and construction of charge state resolved energy spectra are discussed with experimental examples.

ISSN:0034-6748    

DOI:10.1063/1.1137927

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A low angle x‐ray diffraction camera that is coupled to a nanosecond laser‐produced plasma x‐ray source is described. The system includes a grazing incidence toroidal x‐ray collector, a digital, intensified, television based x‐ray detector, and environmentally controlled sample chamber. The camera is designed for use in time‐resolved x‐ray diffraction studies. Preliminary kinetics x‐ray scattering results from the purple membrane of theHalobacteriumhalobiumare presented.

ISSN:0034-6748    

DOI:10.1063/1.1137928

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A steady‐state discharge device is described suitable for plasma physics experiments requiring relatively large, variable, radial electric fields perpendicular to a static magnetic field. Two independent, coaxial discharge plasmas are produced consisting of a very‐low‐density annular plasma surrounding a denser plasma core. By separately adjusting the potentials of these two plasmas, we have been able to produce plasmas with a radial electric fieldEr≲5 V/cm.

ISSN:0034-6748    

DOI:10.1063/1.1137929

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An attempt has been made to use the pulsed‐laser time‐of‐flight atom probe for a precision measurement of ionic masses and the critical energy deficits, or the appearance energies, of field emitted ions. For this purpose methods for determining accurately the flight‐path constant and the time‐delay constant of the atom probe have been devised. Using 300‐ps laser pulses and a digital electronic timer of 1‐ns resolution and a flight path of slightly over 4 m, ionic masses of pulsed‐laser field desorbed gaseous ions can be measured with an accuracy of better than 0.0005 to 0.003 amu for ions of low to intermediate masses. For multiply charged field evaporated heavy metal ions, the accuracy is not as good due mainly to the very limited number of ions which can be collected at a given low emitter voltage. The accuracy of measuring the critical energy deficit depends on the emitter voltage, and the mass and the charge of the ions. It ranges from ∼0.3 eV for singly charged, heavy gas ions at a low emitter voltage to a few electron volts for multiply charged metal ions at a high emitter voltage. The precision of this instrument in these measurements can be further improved by over a factor of 10 simply by using laser pulses of shorter duration and an electronic timer of better resolution. These units are now commercially available. Using this pulsed‐laser field ion emission technique, those solids which can be formed into a field ion emitter and those gases which can be field adsorbed on an emitter surface can be studied. The technique also has a very high sensitivity.

ISSN:0034-6748    

DOI:10.1063/1.1137930

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We report a new method of measuring fluorescence lifetimes which uses the single‐photon technique and two detection channels with matched impulse response for simultaneous acquisition of fluorescence and excitation (SAFE). This differential arrangement is shown to correct automatically for variations in the optical pulse profile during the measurement, thus eliminating a common source of error. It can be used to improve precision and sensitivity with any pulsed light source such as a flashlamp, laser, or synchrotron. A routing system separates photomultiplier coincidences from the dual detection channels into different memory segments of a multichannel analyzer (MCA) using a single time‐to‐amplitude converter (TAC). Comprehensive data are presented on tuning the single‐photon response of the Philips range of XP2020Q photomultipliers. Results obtained using a coaxial flashlamp to excite a dilute solution of PPO in ethanol give a lifetime of 1.63±0.02 ns in good agreement with that obtained using conventional fluorometry. The method is also useful in the study of dual emissions such as in monomer–excimer systems and in the measurement of time‐resolved emission anisotropy.

ISSN:0034-6748    

DOI:10.1063/1.1137931

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We report a scheme for synchronizing a mode‐locked oscillator–amplifier dye laser with a streak camera detection system. A detailed description of the electronics is given. Operational constraints imposed by existing subcomponents of the apparatus are discussed and directions for future refinement outlined.

ISSN:0034-6748    

DOI:10.1063/1.1137932

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We describe two analog electronic techniques to determine the position of a light spot on a linear photodiode array by detecting its intensity peak or its centroid. The position was detected with an accuracy of 1 and 3.5 &mgr;m by the two methods, respectively, using a 16‐&mgr;m center‐to‐center array. As an example, the displacement of a mirror was measured with a sensitivity of 0.05 &mgr;m.

ISSN:0034-6748    

DOI:10.1063/1.1137914

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The scrambling of the polarization of a light beam by the glass windows of a 25‐kbar hydrostatic Raman cell increases quadratically with the pressure up to 18 kbar, as expected from the theory of the photoelastic effect. When the laser beam passes along the cylinder axis of the window, the degree of scrambling by one window is 0.0022 at 18 kbar, but increases greatly as the laser beam shifts from the center of the window. The theory of the photoelastic effect was specialized to small depolarizations, and from it the mean stress distribution in the window was determined empirically from the degree of scrambling as a function of the radius. The effect of the scrambling on a Raman measurement, which needs a much larger aperture for the exit window than for the exciting laser beam, was estimated for two 90°‐scattering geometries by using the empirical stress distribution. The geometryZ(YZ)Yis particularly suitable because the inlet window produces a weakX‐polarized signal, which is largely rejected by the analyzer, and the strongY‐polarized signal produces no scattering along theYdirection. The calculated degree of scrambling is <10−3at 18 kbar. The depolarization of the symmetric stretching bands of carbon tetrachloride up to 1 kbar and of carbon disulphide up to 10 kbar has been measured and confirms this conclusion.

ISSN:0034-6748    

DOI:10.1063/1.1137915

出版商:AIP    

年代:1984

数据来源: AIP