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Vol. 32, No. 10 (1983)

1983-05-20
CONTENT
THEORETICAL ANALYSIS OF ELECTRON CYCLOTRON RESONANCE AMPLIFIER
LI ZHUANG, XU CHENG-HE
1983, 32 (10): 1237-1246. doi: 10.7498/aps.32.1237
Abstract +
In this paper, the kinetic power theorem is used for solving the problem of interaction between a relativistic electron beam moving in a static magnetic field and a travelling electromagnetic wave. The electron bunching function suggested here is specially suitable for analyzing the electron bunching process in this amplifier. By using numerical calculation, the whole process of energy exchange between the gyrating electrons and waves in the interaction region is analysed. The results of calculation show that the imaginary part of the axial wa-venumber is not a constant, so that the gain characteristics is nonlinear. Under the situation of high efficiency and high power output operation, very high stability is required for the static magnetic field. By adjusting the operation parameters to lower the output power, the high stability requirement may be somewhat.relaxed By analysing the electron bunching process, these properties of this amplifier can be well explained.
THEORY OF ELECTRON CYCLOTRON RESONANCE AMPLIFIER WITH A TAPERED WAVEGUIDE
LI ZHUANG, XU CHENG-HE
1983, 32 (10): 1247-1254. doi: 10.7498/aps.32.1247
Abstract +
In this paper the wave approach is used for analysing the ECR amplifier, its dispersion relation is derived, but it is suitable only for the small signal regime. Then by using kinetic power conservation theorem, a theoretical analysis is employed to treat this amplifier, it can be applied beyond the small signal regime to calculate the saturated output power and efficiency of this device. For a concrete waveguide form, the performence of the amplifier has been calculated numerically. The theoretical results show that the amplifiers of this type exhibit an obvious advantage, i.e. the variation of static magnetic field has less influence on its output power, besides, in comparison with the amplifier with a regular waveguide under the condition of same output powers and gains, this amplifier has a wider bandwidth and its interaction length is somewhat shortened.
ON THE FRACTURE TOUGHNESS OF METALS
XING XIU-SAN
1983, 32 (10): 1255-1262. doi: 10.7498/aps.32.1255
Abstract +
According to stochastic evolution process of microcracks and the mechanism of microc-rack growth which requires the gliding of pile-up group of dislocations continuously in order to force the leading dislocation into microcrack, the crack-extension force and fracture toughness and its statistical distribution function are derived and a discussion affecting factors are given.
THEORY OF T2 SYMMETRIC DEEP LEVEL WAVE FUNCTIONS IN Si
REN SHANG-YUAN, MAO DE-QIANG, LI MING-FU
1983, 32 (10): 1263-1272. doi: 10.7498/aps.32.1263
Abstract +
A systematic investigation and numerical results of calculation of T2 symmetric deep level wave function induced by short range defect potential in Si are described, based on a recently developement on site defect potential Green's function method. [5,6] Such a complete information of T2 symmetric wave functions in Si is presented for the first time. The occupation probability P1 of the wave function located around four nearest neighbour sites of the defect center has a peak exceeding 50%. This part of wave function could be described by T2 symmetric combination of four hybrid orbital quasi dangling bonds located at four nearest neighbour sites and pointing toward the defect center. The total occupation probability of wave function located on the 0,1,2 shells arround the defect center is about 70%. The rest part of the wave function extends diversely over a wide range of space. The characteristics of the wave function are insensitive to the defect energy over most part of the energy range in the gap. Only when the defect energy level approaches very closely to the band edge of either conduction (Ec) or valence (Ev) band, the aforementioned peak P1 disappears and the wave function extends smoothly all over the space. A T2 symmetric deep level due to ideal vacancy is found at 0.51 eV up to the Ev.
ONE-DIMENSIONAL PERCOLATION PROBLEM WITH FURTHER NEIGHBOUR BONDS——REAL-SPACE RENORMALIZATION GROUP METHOD
LI TIE-CHENG, ZHANG ZHAO-QING, PU FU-CHO
1983, 32 (10): 1273-1280. doi: 10.7498/aps.32.1273
Abstract +
One-dimensional site and bond percolation problems with bonds connecting Lth nearest neighbors are studied by using real-space renormalization group method. Exact thermal-like and field-like scaling powers are found. Using the scaling relations we obtain all the critical exponents. For the site percolation, we have ap= 2-L, βp=0,γp= L, δp= ∞, ηp = 1 and vp = L which are consistent with the results obtained by using generating function method. For the bond percolation, we have ap = 2-(L(L+1))/2,βp= 0, γp= L, δp =∞, ηp= 1 and vp= L where the "thermal" exponents are consistent with the results obtained by using transfer matrix method. Magnetic exponents found here are new results. Suzuki's renormalized ex-ponents are φ≡(2-α)/v = 1, β≡β/v = 0, γ≡γ/v = 1, δ≡δ=∞ and η≡η=1 which are independent of both L and site or bond percolations.
THE NUMBER OF PERMISSIBLE PHASES IN ISING LATTICE SYSTEM
LIU JIAN-MIN, GONG CHANG-DE
1983, 32 (10): 1281-1291. doi: 10.7498/aps.32.1281
Abstract +
Catastrophe theory is applied to investigate the number of permissible phases in Ising lattice system. It is shown that the system with d=3 can contain three phases at least.
SOFT PHONON AND ITS RAMAN SCATTERING IN A CHARGE-DENSITY-WAVE SUPERCONDUCTOR
LEI XIAO-LIN
1983, 32 (10): 1292-1301. doi: 10.7498/aps.32.1292
Abstract +
Following the idea put forward by Balseiro and Falicov, we have calculated the renor-malized spectral function A (ω) of the amplitude mode of Charge-Density-wave (CDW) phonon by electron-phonon interaction in a model system with coexisting CDW and superconductivity. The A(ω) obtained shows a havily weighted peak of delta-function type at the frequency ω≤2G, where G is the CDW band gap, and a relatively broad continuous spectrum in the region ω>2(G2十△2)1/2, where △ is the superconducting energy gap. Under the condition of fixed G, as △ decreases the intensity of the peak decreases considerably with only a small shift in its position, while the weight of the continuous spectrum raises. These characteristics are in agreement with the behavior of the Raman-active gap modes found by Sooryakumar and Klein in CDW superconductor 2H-NbSe2.
THE GROWTH HABITS OF ALEXANDRITE CRYSTAL
LU JIA-JIN, MA XIAO-SHAN, QIAN ZHEN-YING
1983, 32 (10): 1302-1310. doi: 10.7498/aps.32.1302
Abstract +
The a, b and c axis alexandrite crystals have been grown by Czochralski technique. We have determined the orientations of all developing facets in the crystals by means of x-ray and optical methods, and hence determined their Miller indices. According to the PBG theory, we explained the relations between morphology of alexandrite crystal and its structure.
A STUDY ON CdS/CdTe/LIQUID-CRYSTAL NONCOHERENT-COHERENT IMAGE CONVERTER
ZHONG QI-MING, ZHAO HUAN-QING, JIA YU-RUN, ZHANG ZHI-MING
1983, 32 (10): 1311-1318. doi: 10.7498/aps.32.1311
Abstract +
The fabrication of an optical image converter composed of CdS/CdTe photo-sensitive heterojunction film and nematic liquid crystal film is investigated. Its performance is described in this paper. The CdS film and the CdTe film is vacuum evaporated under careful monitoring in order to obtain high photo-sensitivity and high electrical reactance. The correlation between the optical and electrical parameters of these composing films and the performance of the device is discussed. It is shown that these properties dopend not only on the parameters of each individual film but also on the matching between different films under optimization.
BRIEF REPORT
ION-ION STREAMING INSTABILITY IN A HIGH BETA PLASMA
C. S. WU, ZHOU YU-MEI
1983, 32 (10): 1319-1322. doi: 10.7498/aps.32.1319
Abstract +
The criterion Vd/VAe)1/2 for instability mentioned in the existing theories is based on the assumption βi《 1. The present study investigates the effects of finite βe and βi on the ion-ion streaming instability. It is found that within the domains under investigation in the parameter space the growth rate increases with the increase of βe. Moreover, the unstable region, as a function of the streaming velocity Vd/VA, becomes broader. On the other hand, when βi increases (for a given βe) the unstable region in the Vd/VA space becomes narrower.
THE THEORETICAL LIMIT OF ISOLATION DEGREE OF A QUASI-OPTICAL RECEIVING SYSTEM
WANG ZHAO-SHEN, CAO YONG-JUN
1983, 32 (10): 1323-1327. doi: 10.7498/aps.32.1323
Abstract +
In this paper, we discussed the problem on the theoretical limit of isolation degree of a quasi-optical receiving system used for plasma diagnostics. We deduced a formula which predicts the approximate value of the isolation degree for a receiving system which is weekly coupled with a vacuum chamber.
AN INVESTIGATION OF Al/GaAs INTERFACE REACTION BY XPS
DAI DAO-XUAN, TANG HOU-SHUN, NI YU-HONG, YU XI-TONG
1983, 32 (10): 1328-1332. doi: 10.7498/aps.32.1328
Abstract +
After deposition of a layer of super-thin A film on a clean disordered GaAs surface, the Al/GaAs interface reaction is studied by XPS. The results show that the Al atom can penetrate into GaAs substrate to form AlAs with freed Ga left on GaAs substrate surface by Al-Ga replacement reaction. A Ga/AlAs + GaAs/GaAs three layer model is proposed.
THE SURFACE FEATURES OF THE POISONING OF LATHANIUM RICH MIXED RARE EARTH-NICKEL HYDROGEN STORAGE MATERIAL BY CO,O2 AND H2O
YU XIN-NAN, ZHANG QING-ZHE, XIE KAN, QI SHANG-XUE, KANG JIN, LIN ZHANG-DA
1983, 32 (10): 1333-1338. doi: 10.7498/aps.32.1333
Abstract +
In this paper, we report the study on the poisoning of hydrogen storage material MlNi5 (Ml = La, Ce, Pr, Nd) by CO, O2, H2O using x-ray and ultra violet photoeletron Spectro-scopy (XPS and UPS), With increasing of the poisoning gas exposure, peak a (0.3eV) and peak b (1.2 eV) below EF in UPS show evident change, they decayed shift toward the higher BE side and form a shoulder gradually: While the peak c (6eV) and peak d (9.5 eV) shifted increase with gas exposure. The chemical states of poisoned material were identified by XPS technique.The MINi5 poisoned by oxygen was restcred by hydrogen at 300 ℃ and after regenerating we observed from UPS the increasing of a, b intensities.Similar results were obtained in MlNi5 material peisoned by carbon monoxide and water vapor and then heated in UHV and etched by Ar+.These results were further demonstrated by XPS. The experiment results provide information on the Charge-transfer between d-electron of transition metal nickel in MINi5 and free molecular orbital of poisoning gases. It is a base for understanding of poisoning and re-generating of surface catalysis in practical use.
THE UPS STUDY OF GaAs(1OO) SURFACE (4×1) STRUCTURE
DONG GUO-SHENG, DING XUN-MIN, YANG SHU, WANG XUN, XU YA-BUO
1983, 32 (10): 1339-1343. doi: 10.7498/aps.32.1339
Abstract +
The ultraviolet photoelectron spectroscopy of GaAs (100) surface (4×1) structure has been measured by using a polarized UV light source. From the differential spectra between the UPS of the clean surface and the surface with adsorbed oxygen, the surface state peak located within 2eV below valence band maximum could be identified. According to the spectra obtained with s- and p-polarized light and the selection rule of electron transition, it could be shown that this surface state cosists of three peaks: the peak at 0.5eV below valence band maximum corresponding to the bridge bond states of surface Ga atoms, the peak at 0.7eV resulting from the bridge bond states of surface As atoms, and the peak at 1.3eV related to the dangling bond states.
A NEW TYPE OF PULSED ELECTRON AND ION SOURCE WITH A DURATION OF NANOSECONDS
JIANG XING-LIU, CHEN KE-FAN, PIAO YU-BO
1983, 32 (10): 1344-1348. doi: 10.7498/aps.32.1344
Abstract +
This paper describes a new type of electron and ion source under low gas pressure. Pulsed electron beams with a current density greater than 106A/cm2 with total current up to several hundred amperes and pulsed ion beams of the order of amperes were produced by this device. A model of the field escalation effect is proposed to explain the discharge mechanism in the multiplate chamber. It is expected that this device may have a lot of applications .
ON THE PROBLEIM OF DETAILED BALANCE UNDER NONEQUILIBRIUM STATIONARY STATE IN THE CHEMICAL REACTIONS
MAO KE-XIN
1983, 32 (10): 1349-1356. doi: 10.7498/aps.32.1349
Abstract +
The formation mechanism of stationary state far from equilibrium in the chemical reactions is investigated. It is proved that there may exist detailed balance under nonequilibri-um stationary state in two-variable chemical reactions, but this stationary state is unstable.
DEMONSTRATION FOR A GRIN FIBER ARRAY AS A PSEUDO-CONJUGATOR
WANG SHAO-MIN, ZHOU GUO-SHENG, WU MEI-YING, PENG LIAN-HUI, TIAN LI-JUAN
1983, 32 (10): 1357-1360. doi: 10.7498/aps.32.1357
Abstract +
In this article, we describe a new type of pseudo-Conjugator, it can be used for Compensating the wave front distorsion due to index inhomogeneities.