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1.
Summary A microwave coherent backscattering experiment has been carried out on Mirabelle, a weakly ionised plasma device, with the
objective of measuring the electron density fluctuation level. The experiment is a preliminary step in order to prepare the
detection system for a microwave stimulated backscattering experiment. The incident electromagnetic wave is focused in front
of a plane grid which excites ion acoustic or electron Bernstein waves inducing fluctuations in the plasma. The backscattering
signal is collected by the launching circuit and detected by homodyne mixing. The typical ratio of the scattered power to
the incident power is about 10−12 and the relative density fluctuations are of the order of δn
e/n
e=10−3 against a background electron density ofn
e=1–5·109 cm−3. The backscattering measurement is compared with Langmuir probe measurements. The spectral width of the backscattered signal
has also been studied, by taking into account effects due to the incident wave focusing and plasma wave damping.
The authors of this paper have agreed to not receive the proofs for correction 相似文献
2.
V. I. Tsebro O. E. Omel’yanovskii E. F. Kukovitskii N. A. Sainov N. A. Kiselev D. N. Zakharov 《Journal of Experimental and Theoretical Physics》1998,86(6):1216-1219
Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport
measurements, were prepared by compressing under high pressure (∼25 kbar) a nanotube precursor synthesized through thermal
decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2–100 K) the electric resistance of the samples changes
according to the law ln R ∝ (T
0/T)1/3, where T
0∼7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between
the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the
density of electron states at the Fermi level of about 5×1021 eV−1 cm−3.
Zh. éksp. Teor. Fiz. 113, 2221–2228 (June 1998) 相似文献
3.
H. Heinrich M. Essig J. Geiger 《Applied Physics A: Materials Science & Processing》1977,12(2):197-202
An electron gun system with post-acceleration is described suitable to operation with a carbon fibre field-emission tip. The
system was tested in an electron optical bench with a vacuum pressure of about 10−6 torr. The electron current was most stable if the current to the extraction electrode was minimized. The half width of the
energy distribution of the electrons accelerated up to 30 keV was 215 meV for small currents (≈10−9A). The half width of the distribution increases with growing emission current. This increase may be attributed to instabilities
in the surface structure due to ion bombardment and to the circumstance that more than one emission centre contributes to
the electron current. 相似文献
4.
The effects of uranium and its progeny radium are known to be harmful and their measurements in drinking water are necessary
for careful monitoring. Fast and accurate methods for determination of uranium and radium in water samples with various salinity
and activities concentrations have been developed. High Resolution Inductively Coupled Plasma Mass Spectrometry is used for
direct measurement of uranium. Calibration is performed with 238U standards and 209Bi is used as internal standard to correct the matrix effects and plasma instability. The radium is determined by photon electron
rejected alpha liquid spectrometry after a chemical separation procedure that includes co-precipitation of radium with barium
sulphate, transformation of the sulphate to carbonate and extraction of radium in the scintillation cocktail. The minimal
detectable activities of 3.5×10−8 Bq kg−1 for uranium and 2.3×10−4 Bq kg−1 for radium are obtained. 相似文献
5.
R Rajesh B Ramesh Kumar S K Varshney Manoj Kumar Chhaya Chavda Aruna Thakkar N C Patel Ajai Kumar Aditya Team 《Pramana》2000,55(5-6):733-740
Thomson scattering technique based on high power laser has already proved its superoirity in measuring the electron temperature
(T
e and density (n
e) in fusion plasma devices like tokamaks. The method is a direct and unambiguous one, widely used for the localised and simultaneous
measurements of the above parameters. In Thomson scattering experiment, the light scattered by the plasma electrons is used
for the measurements. The plasma electron temperature is measured from the Doppler shifted scattered spectrum and density
from the total scattered intensity. A single point Thomson scattering system involving a Q-switched ruby laser and PMTs as the detector is deployed in ADITYA tokamak to give the plasma electron parameters. The system
is capable of providing the parameters T
e from 30 eV to 1 keV and n
e from 5 × 1012cm−3−5 × 1013cm−3. The system is also able to give the parameter profile from the plasma center (Z=0 cm) to a vertical position of Z=+22 cm to Z=−14 cm, with a spatial resolution of 1 cm on shot to shot basis. This paper discusses the initial measurements of the plasma
temperature from ADITYA. 相似文献
6.
The present paper reports that triboluminescence (TBL) does not appear at the instant of impact of the load but a certain
time lag is required for its appearance which depends on the value of the stress applied to the crystal. Since TBL appears
in sugar crystals during the creation of new surfaces, the fracture-initiation time of the crystal has been taken to be the
delay time in observing TBL pulse after the application of stress. The dependence of fracture-initiation time,t
f
σ
, of crystals on the stress, σ, may be expressed ast
f
σ
=t
o exp (− ασ), wheret
o and α are constants. The values of the lattice energy, and the change in lattice energy per unit stress, of sugar crystals
have been calculated from TBL measurements and they have been found to be 21·2 kcal mole−1 and 0·41 × 10−8 kcal mole−1 dyne−1 cm2 respectively. 相似文献
7.
M. K. El-Mansy M. M. El-Zaidia E. Abo El-Hassan A. A. Ammar 《Il Nuovo Cimento D》1995,17(10):1121-1130
Summary Thick layers of GeTeSe chalcogenide glass have been prepared and subjected to conduction measurements under the effect of
both temperature and pressure. The results of theI–V characteristics exhibit transition from high-resistance state to differential negative resistance state through a turnover
point. The application of uniaxial pressure shows the similar effect of temperature on that behaviour. Both current and voltage
at the turnover point depend on pressure and ambient temperature. The rise of temperature in the conduction path due to joule
heating and application of uniaxial pressure as well as the reduction in the energy gap width (β=2.87·10−12eV/N m−2) are estimated and discussed at the turnover point. This behaviour is explained according to the orientation of dipoles randomly
dispersed in viscous amorphous matrix. 相似文献
8.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
9.
R. Bernabei P. Belli F. Cappella R. Cerulli C. J. Dai A. d’Angelo H. L. He A. Incicchitti H. H. Kuang X. H. Ma F. Montecchia F. Nozzoli D. Prosperi X. D. Sheng Z. P. Ye 《The European Physical Journal C - Particles and Fields》2009,62(2):327-332
In this paper a new search for non-Paulian nuclear processes, i.e. processes normally forbidden by the Pauli Exclusion Principle
(PEP), is presented. It has been carried out at the Gran Sasso National Laboratory of the INFN by means of the highly radiopure
DAMA/LIBRA set-up (sensitive mass of about 250 kg highly radiopure NaI(Tl)). In particular, a new improved upper limit for
the spontaneous non-Paulian emission rate of protons with energy E
p
≥ 10 MeV in 23Na and 127I has been obtained: 1.63 × 10−33 s−1 (90% C.L.). The corresponding limit on the relative strength (δ
2) for the searched non-Paulian transition is δ
2≲(3–4)×10−55 (90% C.L.). Moreover, PEP-violating electron transitions in iodine atoms have also been investigated. Lifetimes shorter than
4.7×1030 s are excluded at 90% C.L.; this allows us to derive the limit δ
e
2<1.28×10−47 (90% C.L.). This latter limit can also be related to a possible finite size of the electron in composite models of quarks
and leptons providing superficial violation of the PEP; the obtained upper limit on the electron size is r
0<5.7×10−18 cm (energy scale of E≳3.5 TeV). 相似文献
10.
We used the spin-Hamiltonian method for the analysis of the electron paramagnetic resonance (EPR) spectrum of Fe3+ as a probe ion in (NH4)2AlF5·H2O single crystalline basic material. The theoretical expressions for the magnetic field (at which the fine structure transition lines appear) versus the angle between the magnetic field and the axis of symmetry of the magnetic complex are also given. These values were calculated by applying the perturbation theory to the second-order terms. From the experimental results (at 300 K and 9.21 GHz), the spin-Hamiltonian parameters were deduced:D=(668±10)·10−4 T,E=(−56±10)·10−4 T,a=(−54±10)·10−4 T,F=(30±10)·10−4 T. An isotropic superhyperfine structure was evidenced for the five fluorine ions. The obtained EPR data were used to determine the local symmetry of the Al3+ ion. A good agreement with X-ray diffraction measurements was found. 相似文献
11.
The luminescence kinetics of the Cd II ion at a wavelength of 441.6 nm has been studied experi-mentally in a high-pressure
He-Cd mixture in the presence of Ar, Ne, Xe, and CCl4 impurities. Cadmium ions were excited through the bombardment of a cadmium foil heated up to 240°C by a pulsed electron beam
with an electron energy of 150 keV, a pulse duration of 3 ns, and a current of 500 A. The constants of collisional quenching
of the Cd II 5s
2
2
D
5/2 level by Ar, Ne, and Xe atoms and CCl4 molecules and the integral luminescence quenching constants of this level in the helium medium by these impurity gases have
been determined. The constants of collisional quenching appeared to be 8.1 × 10−12 (Ar), 1.2 × 10−12 (Xe), 1.5 × 10−13 (Ne), and 1.8 × 10−10 cm3/s (CCl4, for λ = 325 nm), while the integral constants were found to be, respectively, 4.1 × 10−11, 3.4 × 10−11, 9.5 × 10−12, 1.4 × 10−9 cm3/s for Ar, Ne, Xe, and CCl4 at a buffer gas pressure of 1 atm.
Original Russian Text ? A.I. Miskevich, Liu Tao, 2009, published in Optika i Spektroskopiya, 2009, Vol. 107, No. 1, pp. 45–49. 相似文献
12.
Masayoshi Senba Alicia C. Gonzalez James R. Kempton Donald J. Arseneau James J. Pan Alexandra Tempelmann Donald G. Fleming 《Hyperfine Interactions》1991,65(1-4):979-986
The addition reaction Mu+NO+M→MuNO+M and the spin exchange reaction Mu(↑) +MO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal
field μSR at room temperature in the presence of up to 58 atm of N2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λc) demostrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate
constant has been determined ask
0,Mu
=(1.10±0.25)×10−32 cm6 molecules−2 s−1, almost 4 times smaller than the corresponding H atom reactionk
0,H=3.90×10−32 cm6 molecules−2 s−1 [I.M. Campbell et al., J. Chem. Soc. Faraday Trans. 1.71 (1975) 2097]. The average value of the spin exchange rate constants
in the 2.5–58 atm pressure range,k
SE=(3.16±0.06)×10−10 cm3 molecule−1 s−1, is in good agreement with previous values obtained by transverse field μSR [D.G. Fleming et al., J. Chem. Phys. 73 (1980)
2751]. 相似文献
13.
E. H. Baksht M. I. Lomaev D. V. Rybka D. A. Sorokin V. F. Tarasenko 《Technical Physics》2008,53(12):1560-1564
The parameters of an electron beam generated in helium in the pressure range p = 10−4−12 atm are studied. Nanosecond high-voltage pulses are applied to a gap between a tubular cathode and planar anode, which
is made of 45-μm-thick AlBe foil. Behind the anode, an electron beam is detected at a helium pressure of 12 atm. The pressure
dependence of the beam current amplitude shows three peaks at p ≈ 0.01, ≈ 0.07, and ≈ 3 atm. The beam-induced glow of a luminescent film placed behind the foil and the discharge glow at
different helium pressures in the gas-filled diode are photographed. 相似文献
14.
K. Mettler 《Applied Physics A: Materials Science & Processing》1977,12(1):75-82
Electronic surface parameters of GaAs have been determined from a qualitative and quantitative analysis of the relative photoluminescence
intensity at 300 K. Characteristics of etched (100) surfaces ofn- andp-type liquid phase epitaxial GaAs have been found to be governed by negative surface charges. A density of charged surface
states of about 1012 cm−2 and a band bending of 0.59 eV have been found forn-type material with an electron concentration of 1.1×1017 cm−3. Forp-type samples with hole densities ranging from 6×1015 to 4.3×1018 cm−3 the estimated density of negatively charged surface states was below 2×1011 cm−2, and the band bending was not more than a few kT. 相似文献
15.
S. I. Nanobashvili Z. R. Beria L. R. Gakheladze G. V. Gelashvili G. E. Gogiashvili M. O. Mdivnishvili I. S. Nanobashvili G. I. Rostomashvili 《Czechoslovak Journal of Physics》1999,49(6):999-1004
The properties of plasma injected into an open magnetic trap of uniform field from an independent UHF source have been investigated.
Plasma is created in the UHF source at the frequency of 2400 MHz (power input 150 W) in the electron cyclotron resonance (ECR)
regime at the pressure of neutral argon (10−5−10−2) torr. It is established that a rather quiescent target plasma with controlled density within the range of (2 × 108−2 × 1012) cm−3 and temperature 2–3eV is accumulated in the trap. It turned out that plasma lifetime in the trap is determined by a classical
mechanism of particle escape at the expense of collisions, at fixed value of magnetic field in the trap it practically is
not changed with the variation of neutral gas pressure and reaches the value ≈ 4×10−3 s at the magnetic field strength in the trap equal 1600 Oe. 相似文献
16.
A. Yu. Buki I. S. Timchenko N. G. Shevchenko 《The European Physical Journal A - Hadrons and Nuclei》2012,48(2):17
The Coulomb sums S
L(q) of the 6Li nucleus have been obtained from electron scattering measurements at 3-momentum transfers q = 1.125–1.625 fm−1. It is found that at q > 1.35 fm−1 the Coulomb sum of the nucleus becomes saturated: S
L(q) = 1 . 相似文献
17.
《The European Physical Journal C - Particles and Fields》2009,62(4):625-658
Measurements of the neutral current cross sections for deep inelastic scattering in e
−
p collisions at HERA with a longitudinally polarised electron beam are presented. The single-differential cross-sections d
σ/dQ
2, d
σ/dx and d
σ/dy and the double-differential cross sections in Q
2 and x are measured in the kinematic region y<0.9 and Q
2>185 GeV
2 for both positively and negatively polarised electron beams and for each polarisation state separately. The measurements
are based on an integrated luminosity of 169.9 pb
−1 taken with the ZEUS detector in 2005 and 2006 at a centre-of-mass energy of 318 GeV. The structure functions
and xF
3
γ
Z
are determined by combining the e
−
p results presented in this paper with previously measured e
+
p neutral current data. The asymmetry parameter A
− is used to demonstrate the parity violating effects of electroweak interactions at large spacelike photon virtuality. The
measurements agree well with the predictions of the Standard Model. 相似文献
18.
V. V. Vecheslavov B. V. Chirikov 《Journal of Experimental and Theoretical Physics》1998,87(4):823-831
We present the results of numerical modeling and a theoretical analysis of the splitting of a nonlinear-resonance separatrix
in the intermediate asymptotic region for the standard-map model. Direct measurements of the splitting angle α(K), where K is the small parameter of the system, have been carried out over a huge range, 0.1≳α≳10−208 (1⩾K⩾0.0004), with a relative accuracy greater than one part in 10−25 and an average accuracy of roughly one part in 10−30. This made it possible to compare in detail our results with those of the existing asymptotic theory and to detect a number
of new effects. We find a relatively simple empirical expression for the α vs. K dependence in the intermediate asymptotic region, and this region proves to be surprisingly broad: K≲10−2. We also study the effect of noise, in particular, errors in measuring the angle, which proved to be much more significant
and complicated than expected. Finally, we point out unresolved questions and possible directions of research involving this
problem.
Zh. éksp. Teor. Fiz. 114, 1516–1531 (October 1998) 相似文献
19.
B. Cagnac 《Hyperfine Interactions》1987,38(1-4):499-514
We recall the principle and the general features of Doppler-free multiphotonic absorption. We discuss problems of lineshape
and light shift, which are determinant for very high resolution measurements.
We describe the recent application of the method on hydrogen atoms or deuterium atoms in an atomic beam experiment. The high
precision obtained, of the order of 10−9, permits to confirm preceding measurements of the ratioM
p
/M
e
of the masses of proton and electron, and to deduce a new value of the Rydberg’s constant. Improvements of the experiment
are in progress for the precision 10−10. 相似文献
20.
Silviu Olariu Agata Olariu Diana Martin Anastase Niculescu 《Hyperfine Interactions》2001,135(1-4):71-81
In this paper we study the nuclear transitions induced by incident electrons having an energy of several MeV's. We measured
the cross sections for the excitation of isomeric nuclear states by 7.7 MeV electrons. The cross sections were 1.2 μb for
111m
Cd, 5.5 μb for 113m
In and 7.0 μb for 115m
In. The peak activation rates were 1.8×10−12 s−1 for 111m
Cd, 8.1×10−12 s−1 for 113m
In and 1.0×10−11 s−1 for 115m
In, for a peak power of the electron beam of 1.8×106 W cm−2. Then we describe for the first time the results of a series of experiments in which samples containing the isomeric nuclei
166m
Ho and 186m
Re have been irradiated with MeV electron beams. An upper limit of 17 mb has been determined for the cross section of electron-induced
γ-emission from 166m
Ho and an upper limit of 2.2 mb has been determined for the cross section of electron-induced γ-emission from 186m
Re.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献