共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
I. V. Grekhov A. V. Rozhkov L. S. Kostina A. V. Konovalov Yu. L. Fomenko 《Technical Physics》2011,56(10):1429-1433
High-voltage fast silicon p
+
Nn
+ diodes used in almost all modern electrical energy converters must have a low residual voltage in the conducting state, but
can simultaneously be rapidly switched to the off state with low commutation losses without producing a surge overvoltage.
Such a combination of parameters is usually ensured by producing the profile concentration distribution for recombination
centers in the N base with a peak of the p
+
N junctions. Such a distribution is produced by irradiating the p
+
Nn
+ diode in vacuum by protons or α particles on the side of the p
+
N junctions. We report on the results of testing of diodes in which profile distribution for the centers is obtained using
a simpler and more productive method by electron bombardment in a certain energy range in air. It is shown using the specially
designed devices with a blocked voltage up to 5 kV that all dynamic characteristics of the diodes correspond to the world
standard, and the residual voltage in the conducting state for the working current density is approximately 30% lower. 相似文献
3.
A 2× 2 electro-optic switch is experimentally demonstrated
using the optical structure of a Mach--Zehnder interferometer (MZI) based
on a submicron rib waveguide and the electrical structure of a PIN diode on
silicon-on-insulator (SOI). The switch behaviour is achieved through
the plasma dispersion effect of silicon. The device has a modulation arm
of 1~mm in length and cross-section of 400~nm× 340~nm. The
measurement results show that the switch has a VπLπ
figure of merit of 0.145~V\cdot cm and the extinction ratios of two
output ports and cross talk are 40~dB, 28~dB and -28~dB,
respectively. A 3~dB modulation bandwidth of 90~MHz and a switch
time of 6.8~ns for the rise edge and 2.7~ns for the fall edge are also
demonstrated. 相似文献
4.
Haisheng San Lin Li Gang Li Xuyuan Chen Boxue Feng 《Applied physics. B, Lasers and optics》2007,88(3):411-415
We report on a photoionization scheme for controlled loading of 88Sr+ ions into a radio-frequency (rf) ion trap. The two-step doubly-resonant process drives the 88Sr atom on the 5s2
1
S
0 – 5s5p1
P
1 transition at 461 nm using a frequency-doubled diode laser, and then excites the atom to the autoionizing (4d2+5p2) 1
D
2 state with 405 nm light from a free-running diode laser. This method of trap loading is quantitatively compared to electron
bombardment loading, and shown to reduce the Sr vapour pressure required to load by four orders of magnitude. It also provides
more than an order of magnitude reduction in the day-to-day variation of the voltages required to compensate micromotion.
We additionally introduce a two-step atomic source consisting of an oven and hotplate, which reduces the number of impurities
evaporated towards the trap. This is shown to significantly reduce fluctuations in required micromotion compensation voltages.
The demonstrated reduction in flux and increased source purity are expected to improve the reliability of trap operation for
precision ion-trap experiments.
PACS 32.80.Fb; 32.80.Pj; 39.10.+j 相似文献
5.
The results of a study of the generation of a gigawatt-level pulsed ion beam formed by a diode with an explosive-emission
potential electrode in self-magnetic insulation mode are presented. The experiments have been performed on the TEMP-4M ion
accelerator operating in double-pulse formation mode: the first pulse is negative polarity (300–500 ns, 100–150 kV) and the
second is positive (150 ns, 250–300 kV). The ion current density is 20–40 A/cm2; the beam consists of protons and carbon ions. To increase the efficiency of the ion current generation, a circular geometry
diode is proposed. It is shown that with the new design, the plasma is effectively formed over the entire working surface
of the graphite potential electrode. During ion beam generation, magnetic insulation of the electrons is achieved over the
entire length of the diode (B/B
cr ≥ 3). Because of the high drift velocity, the transit time of electrons in the anode-cathode gap is 3–5 ns, whilst the transit
time of C+ carbon ions exceeds 8 ns. This indicates low efficiency self-magnetic insulation for this geometry of diode. At the same
time, it has been observed experimentally that during ion current generation (the second pulse), the electron component of
the total current is suppressed by a factor of 4–5. A new mechanism of limiting the electron emission, which explains the
decrease in the electron component of the total current in the circular diode with self-magnetic insulation, is proposed. 相似文献
6.
The complete diagonalisation (of energy matrix) method based on the two-spin-orbit-parameter model is applied to unifiedly calculate the spin-Hamiltonian parameters (g factors g//, g⊥ and hyperfine structure constants A//, A⊥) and optical band positions for Ni+ ion in silver gallium selenide (AgGaSe2) crystal. In the model, besides the contribution due to the spin-orbit parameter of central dn ion (i.e., the one-spin-orbit-parameter model in the traditional crystal-field theory), that of ligand ions are taken into account. The calculated results are reasonably consistent with the experimental values. The local structure of Ni+ centre in AgGaSe2 is estimated through the calculation. The complete diagonalisation method based on the one-spin-orbit-parameter model is also applied to calculate these electron paramagnetic resonance and optical data. It is found that although the calculated optical band positions are close to those based on the two-spin-orbit-parameter model and hence to the experimental values, the calculated spin-Hamiltonian parameters (in particular, the g factors) are in disagreement with the experimental values. The latter point is further confirmed from the calculations with the perturbation method. So, for the rational calculations of spin-Hamiltonian parameters of dn clusters with ligand having large spin-orbit parameter, the contributions due to spin-orbit parameters of both the central dn ion and ligand ion should be contained. 相似文献
7.
An Innovative Simple Method for Study of the Characteristics of the Trigatron Plasma Switch 下载免费PDF全文
A simple Semi‐Analytical method used to fit the experimentally recorded current of the closed switch discharge circuit into the free running under damped LC oscillator model and the arc plasma conductivity, electron density of the plasma and efficiency of the spark gap switch energy transfer have been driven from the model by some simple calculations. The charging voltage, switch pressure and the spark gap has been changed between 6 to 15 kV, 1 to 1.5 bar and 1.4 or 2.8 mm, respectively. The obtained values for plasma conductivity and electron density of plasma are (5‐25)(Ω mm)–1, (0.5–3.5)·1024m–3, respectively. The efficiency of the switch is plotted Vs. Pd and E/P which in both cases the peak value has been about 80 present. 相似文献
8.
V. V. Balashov V. K. Dolinov 《The European Physical Journal A - Hadrons and Nuclei》2008,37(1):97-110
An extended set of observables of the nuclear quasi-free (p, dπ+) reaction including the triple differential cross-section for coincidence measurements, its analyzing power in case of polarized
proton beams and, also, the parameters of the polarization of the excited recoil nucleus and the produced deuteron are considered
in the framework of the distorted-wave impulse approximation using the reaction 16O(p, dπ+)15N at a proton energy of 650 MeV as an example. The calculations show a high sensitivity of the differential cross-section
and, especially, of the polarization transfer characteristics of the reaction to the spin-multipole decomposition of the amplitude
of the basic two-body pp → dπ+ process. 相似文献
9.
The electron paramagnetic resonance (EPR) parameters (g-factors g
‖, g
⊥ and zero-field splitting D) of two tetragonal 3d3 impurity centers M3d-VMg and M3d-Li+ (where M3d = Cr3+ or Mn4+, VMg is the Mg2+ vacancy) in M3d-doped MgO crystals are calculated from the high-order perturbation formulas including both the crystal-field (CF) and the
charge-transfer (CT) mechanisms for 3d3 ions in the tetragonal symmetry. The calculated results are in reasonable agreement with the experimental values. From the
calculations, it can be found that the relative importance of the CT mechanism for EPR parameters increases with increasing
valence state of the 3d3 ion. So, for the high-valence 3d
n
ions in crystals, a reasonable explanation of EPR parameters should take into account both CF and CT mechanisms. The defect
structures (characterized by the displacement ΔR of O2− in the intervening M3d and VMg or Li+ at the Mg2+ site) for these tetragonal impurity centers are obtained from the calculations. The results are consistent with the expectations
based on the electrostatic interactions. 相似文献
10.
利用剩余键的思想, 通过数学推导, 建立定量描述金属熔体结构与黏度关系的物理模型, 提出黏度的微观结构变化特性为熔体剩余键结构尺寸d的演变; 应用建立的模型理论计算液相线以上一定温区镁熔体和铝熔体的运动黏度, 得到函数关系式分别为vMg=3.17×10-7+3.04×10-7· d和vAl=1.65×10-7+1.05×10-7·d, 这与采用坩埚扭摆振动法的实验测量结果相符合. 该模型从化学结合键角度揭 示了金属熔体的结构微观不均匀性及其黏度的微观物理本质, 为金属熔体黏度的理论计算提供了一种新的途径. 这对于深入认识液态金属的微观结构及其与宏观物性之间的关系具有重要意义. 相似文献
11.
V. E. Tarasov V. V. Khabarov A. E. Kudryavtsev V. M. Weinberg 《Physics of Atomic Nuclei》2008,71(8):1410-1423
The Kd reactions are considered in the impulse approximationwithNN final-state interactions (FSI) taken into account. Realistic parameters for the KN phase shifts are used. The “quasi-elastic” energy region, in which the elementary KN interaction is predominantly elastic, is considered. The theoretical predictions are compared with the data on the K
+
d → K
+
pn, K
+
d → K0
pp, K
+
d → K
+
d, and K
+
d total cross sections. The NN FSI effect in the reaction K
+
d → K
+
pn has been found to be large. The predictions for the Kd cross sections are also given for slow kaons, produced from ϕ(1020) decays, as the functions of the isoscalar KN scattering length a
0. These predictions can be used to extract the value of a
0 from the data.
The text was submitted by the authors in English. 相似文献
12.
研究了应用于介质壁加速器的小间隙光导开关在大功率激光二极管驱动下的导通特性。激光二极管产生的激光脉冲中心波长为905nm,脉冲宽度(FWHM)约20ns,前沿约3.1ns,抖动小于200ps,峰值功率约90W。所用光导开关为异面电极结构的砷化镓(GaAs)光导开关,电极间隙5mm,偏置电压为15~22kV脉冲高压,工作在非线性(高增益)模式。测得光导开关最小导通电阻4.1Ω,抖动小于1ns,偏置电压在18kV时平均使用寿命约200次。 相似文献
13.
Dynamics of electron-hole plasma in semiconductor opening switches for ultradense currents 总被引:2,自引:0,他引:2
A physicomathematical model for calculating the dynamics of the electron-hole plasma in semiconductor opening switches for
ultradense currents is developed. The model takes account of the real doping profile of a semiconductor p
+-p-n-n
+ structure and the following elementary processes in the electron-hole plasma: current-carrier diffusion and drift in high
electric fields, recombination on deep impurities and Auger recombination, and collisional ionization in a dense plasma. The
electrical pumping circuit of the opening switch is calculated by solving the Kirchhoff equations. The motion of the plasma
in the semiconductor structure is analyzed on the basis of the model. It is shown that for ultrahigh pumping levels the interruption
of the current in the opening switch occurs in the heavily doped regions of the p
+-p-n-n
+ structure and is due to saturation of the particle drift velocity in high electric fields.
Zh. Tekh. Fiz. 67, 64–70 (October 1997) 相似文献
14.
Summary We used polarization spectroscopy to perform a high-resolution investigation of atomic oxygen in the visible and near-infrared
spectral region by means of dye and semiconductor diode lasers. We measured the fine structure of the highly excited 4d
5
D level and resolved the hyperfine structure of the metastable 3s
5
S
2 level of17O. Isotope shift values are also reported for several transitions of the three stable oxygen isotopes (16O,17O,18O). Polarization lineshapes are discussed and compared with those obtained in saturation techniques. 相似文献
15.
A unified calculation of optical band positions and electron paramagnetic resonance (EPR) (or spin-Hamiltonian) parameters for the trigonal Cr3+–Li+ centre in CsMgCl3 crystal is made by using the complete diagonalisation (of energy matrix) method based on the two-spin–orbit-parameter model. In this model, the contributions from the spin–orbit parameter of central dn ion and that of ligand ion are included. From the calculation, the 11 observed optical and EPR data (eight optical band positions and three EPR parameters g//, g⊥, D) are reasonably explained with five adjustable parameters and the defect structure of the Cr3+–Li+ centre (which is consistent with the expectation based on the electrostatic interaction) in CsMgCl3 is acquired. The results are discussed. 相似文献
16.
K. I. Kozlovsky A. S. Martynenko E. D. Vovchenko M. I. Lisovsky A. A. Isaev 《Physics of Atomic Nuclei》2017,80(11):1677-1682
The results of examination of the insulating magnetic field in an accelerating ion diode are presented. This field is produced in order to suppress the electron current and thus enhance the neutron yield of the D(d, n)3He nuclear reaction. The following two designs are discussed: a gas-filled diode with inertial electrostatic confinement of ions and a vacuum diode with a laser-plasma ion source and pulsed magnetic insulation. Although the insulating field of permanent magnets is highly nonuniform, it made it possible to extend the range of accelerating voltages to U = 200 kV and raise the neutron yield to Q = 107 in the first design. The nonuniform field structure is less prominent in the device with pulsed magnetic insulation, which demonstrated efficient deuteron acceleration with currents up to 1 kA at U = 400 kV. The predicted neutron yield is as high as 109 neutrons/pulse. 相似文献
17.
NMR and DFT studies on persistent carbocations derived from benzo[kl]xanthene,dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran,and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran in superacidic media 下载免费PDF全文
Takao Okazaki Madoka Nakagawa Takeshi Futemma Toshikazu Kitagawa 《Journal of Physical Organic Chemistry》2016,29(2):107-111
Persistent carbocations generated by the protonation of hetero‐polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene ( 1 ), dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran ( 2 ), and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran ( 3 ) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO3H‐SbF5 (4:1)/SO2ClF and 3 in FSO3H‐SbF5 (1:1)/SO2ClF ionized to 1aH+ with protonation at C(4) and to 3aH+ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH+ and 3aH+ were the most stable protonated carbocations and that 2 should ionize to 2aH+ with protonation at C(6). According to the changes in 13C chemical shifts (Δδ13C), the positive charge was delocalized into the naphthalene unit for 1aH+ , into one benzo[b,d]furan unit for 2aH+ , and into one benzo[b,d]furan unit for 3aH+ . Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
I. V. Grekhov L. S. Kostina A. V. Rozhkov N. F. Zitta V. I. Matveev 《Technical Physics》2008,53(12):1609-1614
The static parameters of and switching transients in an advanced high-voltage high-speed switching device—a MOSFET-controlled
integrated thyristor—and their dependences on the geometry and electrophysical properties of base layers in the n
+
pnn’p
+ device structure are studied experimentally. It is shown that the residual resistance of the high-voltage (∼2.5 kV) microthyristor
chip in the on-state is much smaller than that of the high-voltage IGBT with the speed of the former kept at a sufficiently
high level. The new device is multifunctional and can operate under different operating conditions. Specifically, it can be
turned off by shunting the n
+
p emitter by an add-on MOSFET, by applying a gate current pulse, and in the cascode turn-off regime. In these regimes, the
ultimate value of the turn-off current noticeably grows. 相似文献
19.
20.
V. Berardi M. Armenante R. Bruzzese F. Esposito S. Solimeno N. Spinelli S. Bakhramov 《Il Nuovo Cimento D》1991,13(4):423-433
The intensity dependence of the multiphoton ionization spectra of Xe atoms has been investigated with an improved accuracy
and well-controlled laser parameters. In particular, we have examined the ionization rates for X3+, X2−, X+ as functions of the laser intensity and the pressure in the target chamber. The apparatus used for these measurements is
characterized by a high-energy resolution (better than 200 meV) and a completely digital acquisition system. The time-of-flight
spectra clearly show the contributions of the different isotopes present in Xe gas. The laser pulses have been characterized
with great accuracy by monitoring the energy, pulse width and divergence shot by shot. The ionization rates of the different
ions have been used for testing the basic assumption of the Geltman theory of multiple ionization based on the single electron
ionization model. We have found that for the small intensity range investigated the quantity (dXe
+/dI)·(dXe
3+/dI)/(dXe
2+/dI)2 appears to be quite close to the value 0.5 predicted by this model. 相似文献