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1.
Control of population transfer by rapid adiabatic passage has been an established technique wherein the exact amplitude profile
of the shaped pulse is considered to be insignificant. We study the effect of ultrafast shaped pulses for two-level systems,
by density-matrix approach. However, we find that adiabaticity depends simultaneously on pulse profile as well as the frequency
modulation under non-resonant conditions 相似文献
2.
The particle-in-cell (PIC) method is used to simulate the self-consistent accumulation and bunching of space charge in the
trap of a gyrotron electron-optical system. It is shown that it is possible to generate charge bunches that oscillate along
the direction of the magnetic field. The dependence of the characteristics of these oscillations on the magnitude of the electron
current into the trap is determined, along with the effect of the accumulated charge on the velocity distribution of electrons
in the current passing through the magnetic mirror. Satisfactory agreement with the experimental data is obtained.
Zh. Tekh. Fiz. 67, 98–101 (September 1997) 相似文献
3.
L. Krlín 《Czechoslovak Journal of Physics》1972,22(12):1240-1258
Interaction of the trapped beam particles with spectrum is discussed in the paper. In models of particles in two waves and in a spectrum (with given amplitudes) we discuss partly well trapped particles (in the region of harmonic oscillations), partly weakly trapped particles near the separatrix; further, we discuss the range of resonances, the transport of energy and a possibility of transition of the trapped beam into the quasiergodic state. For the case of a discrete spectrum, conditions for the beam diffusion are given and, within the framework of system with mixing, conditions for existence of hf field-beam particles balance are discussed.Nademlýnská 600, Praha 9, Czechoslovakia. 相似文献
4.
Boichenko A. M. Burachenko A. G. Kostyrya I. D. Tarasenko V. F. Tkachev A. N. 《Technical Physics》2011,56(8):1202-1209
The influence of the voltage pulse rise time on the amplitude of a runaway electron beam and X-ray generation in air and nitrogen
under atmospheric pressure is studied experimentally and theoretically. Generalization of the whistle criterion for the case
of a nonuniform field is suggested. It is shown that the maximal energy of beam electrons and the beam current amplitude grow
when the voltage pulse rise time decreases. It is found that the amplitude of the runaway electron current reaches a maximum
at a certain curvature of the cathode. The maximal energy of electrons increases when the radius of curvature of the cathode
exceeds the value at which the beam current amplitude is the highest. If the field is nonuniform, its critical value at which
many electrons run away is more than an order of magnitude lower than in the uniform field. 相似文献
5.
We study the influence of some types of reflections on the oscillatory processes in a gyrotron. The oscillation stability
conditions in the presence of a reflected signal are estimated, the processes in a gyrotron with a fixed structure of the
HF field are simulated numerically, and the enrichment of the signal spectrum in the presence of reflections is studied.
Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novogorod, Russia. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 10, pp. 1348–1357, october 1998. 相似文献
6.
We have succeeded in obtaining the optical model potential for 12C---12C scattering at low incident energies (10 MeV Ecm 20 MeV), by applying the adiabatic approximation to the coupled channels equation. As for this potential inelastic channels of single and mutual excitations of 12C*(2+, 4.43 MeV) make a contribution to the real part and not to the imaginary part. 相似文献
7.
Effect of supply voltage and body-biasing on single-event transient pulse quenching in bulk fin field-effect-transistor process 下载免费PDF全文
Charge sharing is becoming an important topic as the feature size scales down in fin field-effect-transistor(Fin FET)technology. However, the studies of charge sharing induced single-event transient(SET) pulse quenching with bulk Fin FET are reported seldomly. Using three-dimensional technology computer aided design(3DTCAD) mixed-mode simulations,the effects of supply voltage and body-biasing on SET pulse quenching are investigated for the first time in bulk Fin FET process. Research results indicate that due to an enhanced charge sharing effect, the propagating SET pulse width decreases with reducing supply voltage. Moreover, compared with reverse body-biasing(RBB), the circuit with forward body-biasing(FBB) is vulnerable to charge sharing and can effectively mitigate the propagating SET pulse width up to 53% at least.This can provide guidance for radiation-hardened bulk Fin FET technology especially in low power and high performance applications. 相似文献
8.
Englert BG Mielenz M Sommer C Bayerl J Motsch M Pinkse PW Rempe G Zeppenfeld M 《Physical review letters》2011,107(26):263003
We present a versatile electric trap for the exploration of a wide range of quantum phenomena in the interaction between polar molecules. The trap combines tunable fields, homogeneous over most of the trap volume, with steep gradient fields at the trap boundary. An initial sample of up to 10(8), CH(3)F molecules is trapped for as long as 60 s, with a 1/e storage time of 12 s. Adiabatic cooling down to 120 mK is achieved by slowly expanding the trap volume. The trap combines all ingredients for opto-electrical cooling, which, together with the extraordinarily long storage times, brings field-controlled quantum-mechanical collision and reaction experiments within reach. 相似文献
9.
S. V. Nikiforov V. S. Kortov A. A. Nosal E. V. Moiseikin 《Physics of the Solid State》2011,53(10):2141-2146
The effect of deep hole traps on the intensity and shape of the dosimetric peak of thermoluminescence (TL) has been studied at 450 K in anion-defect alumina single crystals. It has been shown that filling of deep hole centers leads to a decrease in the sensitivity to radiation of crystals with a small half-width of the TL peak and has no effect on the sensitivity of crystals with a broadened peak. It has been assumed that traps responsible for the TL dosimetric peak broadening are of hole nature, which can be caused by the presence of Ti3+ ions in the corundum lattice. The results obtained have been interpreted within the modified model of the interactive system of traps. 相似文献
10.
R. Klíma 《Czechoslovak Journal of Physics》1963,13(10):716-724
The adiabatic approximation of motion in the plane perpendicular to the magnetic induction B and the averaged motion in the direction parallel to B are derived from the Hamiltonian transformed to natural coordinates. Certain conservative properties of the field are shown. The conditions derived therefrom for magnetic traps with a cusped field are given.The author would like to thank J. Váa for support and J. atlov and J. Teichmann for criticism of this work. 相似文献
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13.
The ATHENA and ATRAP groups at CERN recently reported the production of weakly bound antihydrogen atoms in a non-neutral positron-antiproton plasma. This Letter derives an equation of motion for weakly bound atoms in the electric and magnetic fields of the plasma and trap. The atoms are polarized by the electric field and can be trapped radially in the edge region of the plasma where the electric field is maximum. 相似文献
14.
Savilov A.V. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(1):36-40
As a method for the realization of the regime of trapping and adiabatic deceleration of particles in relativistic RF electron autooscillators, the scheme of the twystron with a self-exciting input section and an output section where the deceleration of electrons is provided by profiling the parameters of the system is suggested. It is shown that for a wide range of parameters, almost total trapping of the particles and, therefore, high-efficiency stable RF generation, can be achieved 相似文献
15.
We report pulse trapping in passively mode-locked fiber lasers operating in a near-zero dispersion regime. Two polarization components of vector pulses have different central wavelengths while copropagating as a unit in fiber lasers. The vector pulses exhibit smooth Gaussian spectral profile without any sidebands, qualitatively distinct from those observed in net-anomalous and net-normal fiber lasers. Numerical simulations suggest that the pulse trapping depends not only on fiber birefringence and cavity dispersion but also on saturable absorption effect. The experimental observations are in good agreement with the numerical simulations. 相似文献
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17.
《Physics letters. A》2006,353(4):295-299
Entanglement evolution of a degenerate system is studied. It is found that an entangled state becomes unentangled under an adiabatic variation of the system, and vice versa. The amount of entanglement varies with different adiabatic paths. It is concluded that the entanglement of complete set of eigenstates of a system at thermal equilibrium is independent on perturbations, but the entanglement of partial eigenstates may change with adiabatic perturbations. This can help us to control entanglement properties and is very useful in the quantum computations. 相似文献
18.
提出一种基于谐振电路与脉冲变压器结合的高压脉冲实现方案,该方案利用电容与电感的谐振效应,结合脉冲变压器的升压作用,在仅使用一个半导体开关的条件下,实现高压脉冲的输出,其结构简单,成本低,并且可实现零电压关断。并对于电路的运行模式进行了理论分析,搭建了原理样机进行实验。容性负载条件下,实现频率1~ 15 kHz、幅值0~ 10 kV可调的高压脉冲输出,对比分析了续流支路以及续流电阻对于输出高压脉冲波形的影响。利用该脉冲电源进行DBD放电实验,成功驱动介质阻挡放电反应器,验证了该方案的可行性。 相似文献
19.
Jun HE Bao-dong YANG Yong-jie CHENG Tian-cai ZHANG Jun-min WANG 《Frontiers of Physics》2011,6(3):262-270
In our experiment, a single cesium atom prepared in a large-magnetic-gradient magneto–optical trap (MOT) can be efficiently transferred into a 1064-nm far-off-resonance microscopic optical dipole trap (FORT). The efficient transfer of the single atom between the two traps is used to determine the trapping lifetime and the effective temperature of the single atom in FORT. The typical trapping lifetime has been improved from ~ 6.9 s to ~ 130 s by decreasing the background pressure from ~ 1 × 10–10 Torr to ~ 2 × 10–11Torr and applying one-shot 10-ms laser cooling phase. We also theoretically investigate the dependence of trapping lifetimes of a single atom in a FORT on trap parameters based on the FORT beam’s intensity noise induced heating. Numerical simulations show that the heating depends on the FORT beam’s waist size and the trap depth. The trapping time can be predicted based on effective temperature measurement of a single atom in the FORT and the intensity noise spectra of the FORT beam. These experimental results are found to be in agreement with the predictions of the heating model. 相似文献
20.
The adiabatic particle definition of Parker [1] has only been discussed for particular choices of the field variable and time coordinate, referred to here as the choice of a normal-form. It seems to have been implicitly assumed that the associated vacuum is independent of the normal-form chosen; we show that this is indeed the case.NATO Postdoctoral Fellow. 相似文献