Vol. 23, No. 1 (1974)
1974-01-05
CONTENT
1974, 23 (1): 1-16.
doi: 10.7498/aps.23.1
Abstract +
The plasma electron density, shape and instability of the 23 kJ θ-pinch have been studied through the use of a Mach-Zehnder interferometer with a giant pulsed ruby laser illumination. The axial interferograms in the range of 45-120 m Torr deuterium pressures gave two-dimensional electron density distributions for the dicharge and established peak plasma electron densities in the range of 6-1016-2.3·1017 cm-3 for the plasma at peak pinch. The time of the peak pinch was about 1/3 of the first half-cycle of the main compressive magnetic field. The plasma characteristic time of containment (time required for the number of particles to be reduced to 1/e) close to peak pinch was 1.8-4.3μs. The interferograms with reverse bias magnetic field showed that the bias magnetic field was trapped in the plasma, and revealed that radial hydromagnetic oscillation of the plasma occurred between the trapped magnetic field and the main compressive magnetic field. The interferograms also showed that the plasma is essentially stable during the first half-cycle of the main compressive magnetic field in the range 45-80 m Torr deuterium pressures.
1974, 23 (1): 17-26.
doi: 10.7498/aps.23.17
Abstract +
Modulation of air stream is an efficient method of sound production. Man's speech organs, sirens, electro-pneumatic loudspeakers as well as common whistles are all based on this principle. The features of air stream sound sources are their high efficiency and possibility of high power outputs, which afford them practical value. The sound production by modulating air streams were discussed by previous authors and theories-given, but some were oversimplified and others too involved to allow practical computations. In this paper, air flow vs pressure characteristics of air stream sources are derived from the basic theory of gasdynamics and graphical method is presented for the estimation of sound radiation under given conditions of plenum pressure and nozzle-to-horn throat area ratio. It is established that although the air flow characteristics as well as the radiation relations are nonlinear, the radiated sound power is determined mainly by the radiation of the fundamental, and approximations give rise to simple expressions for the radiated sound power, the air stream yield and efficiency, with an error less than 1 dB from exact results. Charts are given to facilitate design and question of optimum condition is discussed.
1974, 23 (1): 27-37.
doi: 10.7498/aps.23.27
Abstract +
In this paper, the equivalent circuit method is used in analysing the performance of the vibrating system of an electropneumatic loudspeaker, and results are given for the input impedance and displacement amplitude as functions of frequency, and applied to typical designs of this kind of loudspeakers, illustrating the value of equivalent circuit analysis in guiding its practical design. The electrical driving power required for the vibrating system is proportional to the fourth power of the mechanical resonance frequency, which is the upper limit of the frequency range of the electro-pneumatic loudspeaker. Thus the high frequency performance is poor. The optimum condition is found for a flat frequency response below the mechanical resonance frequency. Experiments show that under the optimum condition the high frequency response improves slightly with increase of the magnetic induction in the gap of the magnetic structure. Experimental results agree well with theory, and sound pressure levels up to 181 or 184.8 dB re 2×10-5N/m2 under different conditions were obtained in the horn thoat of the loudspeaker.
1974, 23 (1): 38-45.
doi: 10.7498/aps.23.38
Abstract +
The probability distribution of prompt neutron number from the spontaneous fission of Pu240 has been measured by use of a spherical liquid scintillation detector 60 em in diameter. The experimental distribution can be well represented by a Gaussian distribution with σ=1.08. This result was compared with the experimental results of B. C. Diven, A. Hicks and J. W. Boldeman, and is in agreement with the semi-emperical theoretical distribution given by J. Terrel. The absolute efficiency of the detector for the fission neutron of Pu240 has been found to be 0.759 ± 0.011, based on the average number of prompt neutrons per fission for spontaneous fission of Pu240 v=2.154±0.028[5].
1974, 23 (1): 46-51.
doi: 10.7498/aps.23.46
Abstract +
The distribution of prompt neutron numbers (Pv) in the spontaneous fission of uranium-238 was measured using a cadmium-loaded liquid scintillation detector. The experimental results show, that σv, the width of Pv distribution, is equal to 0.90± 0.09, wbich is smaller them the corresponding values of other even-even heavy nuclei (Pu, Cm, Cf and Fm). It was found also, that the average neutron number v= 1.96 ± 0.05, which is in agreement with previous results.
1974, 23 (1): 52-62.
doi: 10.7498/aps.23.52
Abstract +
A new-type charged particle spectrograph has been proposed and built up. It combines the property of the small magnet which can analyse the particle momentum with that of the semiconductor detector which has a higher energy resolution. As a result, the particle identification and the analysis of energy spectrum can be obtained simultaneously. In this paper, the design and structure of this spectrograph are described, some experimental results of using it in nuclear reaction studies are given, and its applications and characteristics are discussed. This kind of spectrograph is more simple and facile but possesses rather better performances.
1974, 23 (1): 63-68.
doi: 10.7498/aps.23.63
Abstract +
The dynamical origin of the mass relations and the interaction between stra-tons inside the hadrons are discussed. Assuming that the wave functions describing the internal structures of the hadrons obey SU(6) symmetry. We rederive the GMO relations and other well-known mass relations. Furthermore, three new relations among the masses of the baryons and the mesons are obtained, namely: (ρ-π)/(K*-K)=(△-N)/(Σ*-Σ), 4(∧-N)=3(K*-ρ)+(K-π), (ρ-π)/(△-N)=((φ-ρ)-2(K-π))/(2(Ω-△)-3/2(K-π)-9/4(φ-ρ)). The connection between these relations and the symmetry properties of the straton interaction is discussed.
1974, 23 (1): 69-76.
doi: 10.7498/aps.23.69
Abstract +
In this paper, the results of creep and stress-rupture tests on Ni3Al base γ′ monocrystals are presented. The results show that the steady state creep rate εs conforms to the relationship: εs=Cσmexp(-Qc′/RT). The exponent m depends only on temperature. m(850℃)=3.95, m(950℃) = 3.62. The apparent activation energy of creep Qc′ amounts to 88 k cal/g-at. for Ni3Al crystals. All of the alloying elements studied Ti, Nb and W raise Qc′, the effect of Nb being the greatest, while W proves to be most effective in improving the creep strength. The orientation of crystals has a marked influence on εs. oriented crystals have the lowest εs and the longest stress-rupture life tr. tr≥ 100 hr for T= 1050℃ and σ= 5 kg/mm2. The Monkman-Grant relation tr(εs)p=const. holds likewise for Ni3Al single crystals, with p = 0.82.The glide system of γ′ crystals in creep appears to be {111} .
