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1.
Laser-produced plasma helium-like titanium Kα x-ray source and its application to Rayleigh-Taylor instability study 下载免费PDF全文
Several experiments are performed on the ShenGuang-II laser facility to investigate an x-ray source and test radiography concepts.X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources.By using a time-integrated space-resolved keV spectroscope and pinhole camera,potential helium-like titanium Kα x-ray backlighting (radiography) line source is studied as a function of laser wavelength,ratio of pre-pulse intensity to main pulse intensity,and laser intensity (from 7.25 to~11.3×10 15 W/cm 2).One-dimensional radiography using a grid consisting of 5 μm Au wires on 16 μm period and the pinhole-assisted point projection is tested.The measurements show that the size of the helium-like titanium Kα source from a simple foil target is larger than 100 μm,and relative x-ray line emission conversion efficiency ξ x from the incident laser light energy to heliumlike titanium K-shell spectrum increases significantly with pre-pulse intensity increasing,increases rapidly with laser wavelength decreasing,and increases moderately with main laser intensity increasing.It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast.It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments. 相似文献
2.
Y B S R Prasad V K Senecha H C Pant M P Kamath G S Solanki P K Tripathi A P Kulkarni S Gupta R Pareek A S Joshi N Sreedhar Sameer Nigam C P Navathe 《Pramana》2000,55(5-6):797-802
The x-ray emission from slab targets of copper irradiated by Nd:glass laser (1.054 μm, 5 and 15 ns) at intensities between 1012 and 1011W/cm2 has been studied. The x-ray emissions were monitored with the help of high quantum efficiency x-ray silicon photo diodes
and vacuum photo diodes, all covered with aluminium filters of different thickness. The x-ray intensity vs the laser intensity
has a scaling factor of (1.2–1.92). The relative x-ray conversion efficiency follows an empirical relationship which is in
close agreement with the one reported by Babonneau et al. The ion velocities were monitored using Langmuir probes placed at different angles and radial distances from the target
position. The variation of the ion velocity with the laser intensity follows a scaling of the form Φ
β
where β ∼0.22 which is in good agreement with the reported scaling factor values. The results on the x-ray emission from Cu plasma
are reported. 相似文献
3.
V K Senecha Y B S R Prasad M P Kamath A S Joshi G S Solanki A P Kulkarni S Gupta R Pareek H C Pant 《Pramana》2000,55(5-6):789-795
An investigation of x-ray emission from Cu plasma produced by 1.054 μm Nd:glass laser pulses of 5 ns duration, at 2 × 1012 − 2 × 1013 W cm−2 is reported. The x-ray emission has been studied as a function of target position with respect to the laser beam focus position.
It has been observed that x-ray emissions from ns duration plasma show a volume effect similar to subnanosecond plasmas. Due
to this effect the x-ray yield increases when target is moved away relative to the best focal plane of the laser beam. This
result supports the theoretical model of Tallents and has also been testified independently using suitably modified theoretical
model for our experimental conditions. While above result is in good agreement with similar experimental results obtained
for sub-nanosecond laser produced plasmas, it differs from result claiming filamentation rather than pure geometrical effect
leading to x-ray enhancement for ns plasmas. 相似文献
4.
Through the use of time and space integrated kiloelectronvolt (keV) spectroscopy, we investigate the thermal emission of plasma, which produces strong line emission from the titanium K shell (He-a at 4.7 keV and H-α at 4.9 keV), created by laser. In order to optimize the conversion efficiency enhancement on titanium foils, the experiment is conducted under a variety of laser-driven intensity conditions. The X-ray emission intensity at 4.7 keV is measured and compared with prediction. The experimental result demonstrates that the solid Ti target laser-produced plasma (LPP) source has X-ray emission at 4.7 keV, which are all generated from electronic transitions in Ti ions at pulse width of 2.1 ns or 30 ps, the crudely evaluated He-α X-ray intensity appears to slightly increase with laser intensity enhancement, and the pre- pulse effect increases the conversion efficiency of the He-α X-ray. In addition, a 90-μm-thick Ti foil as a filter is used to transmit He-α X-ray at near 4.7 keV, creating a quasi-monochromatic transmission and greatly reducing the lower- and higher-energy background. 相似文献
5.
A method of studying a non-equilibrium x-ray laser plasma is
developed by extending the existing one-dimensional similarity
equations to the case of two-dimensional plasma study in the
directions perpendicular to the slab and along a focal line. With this
method the characteristics of pre-plasma are optimized for transient
neon-like Cr x-ray laser. It is found that when the duration and the
intensity of 1.053μm pre-pulse are 1.2ns and
6.5 TW/cm2 respectively with a delay time of 1.5ns, the
temperature and the temperature discrepancy each approach a proper
state, which will provide a uniform distribution of properly ionized
neon-like Cr ions before the arrival of pumping pulse. 相似文献
6.
S. Tresch P. Ackerbauer M. Augsburger W.H. Breunlich M. Cargnelli D. Chatellard J.-P. Egger T. von Egidy B. Gartner F.J. Hartmann R. Jacot-Guillarmod E. Jeannet R. King B. Lauss J. Marton M. Mühlbauer F. Mulhauser C. Petitjean C. Piller W. Prymas L.A. Schaller L. Schellenberg H. Schneuwly W. Schott Y.-A. Thalmann A. Werthmüller J. Zmeskal 《Hyperfine Interactions》1999,119(1-4):109-114
The transfer reaction of negative muons from muonic protium to 3 and 4 in binary and triple gas mixtures was studied. In the binary mixtures the transfer rates to the two helium isotopes were
determined from the time distribution of the 7-keV X-rays of the intermediate muonic molecule (pμHe)*. The experimental transfer rate to 4 is in good agreement with theoretical predictions, whereas the rate to 3 is a factor 2 to 3 smaller than the predicted ones. Radiative branching ratios of the (pμHe)8 molecular decay were obtained. Muon transfer from excited states of muonic protium gives the main contribution to the
total intensity of the μHe Lyman series in the binary mixtures. Values of q
1s
He
are determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
An experiment on a transient nickel-like Mo x-ray laser in the extreme light Ⅲ (XL Ⅲ) laser facility is analyzed, based on the two-dimensional hydrodynamic evolutions of a plasma under a non-uniform incident laser. Influences of the pulse duration and intensity on plasma scale length, electron density, temperature, as well as their distributions are investigated, based on which the pre-pulse character and delay time are determined according to the parameters of laser line focus on XLⅢ. It is found that the optimal intensity of the pre-pulse is 1.0 TW/cm^2 with a duration of 500ps; a well modified pre-plasma can be obtained after 1.6ns under low quality line focus in the lab. 相似文献
8.
An intense laser radiation (1012 to 1011 W/cm−2) focused on the solid target creates a hot (≥1 keV) and dense plasma having high ionization state. The multiple charged ions
with high current densities produced during laser matter interaction have potential application in accelerators as an ion
source. This paper presents generation and detection of highly stripped titanium ions (Ti) in laser produced plasma. An Nd:glass
laser (KAMETRON) delivering 50 J energy (λ=0.53 μm) in 2.5 ns was focused onto a titanium target to produce plasma. This plasma
was allowed to drift across a space of ∼3 m through a diagnostic hole in the focusing mirror before ions are finally detected
with the help of electrostatic ion analyzer. Maximum current density was detected for the charge states of +16 and +17 of
Ti ions for laser intensity of ∼1011 W/cm−2. 相似文献
9.
boldmath Broadband water window supercontinuum generation with a ω+3ω/2 multicycle two-colour pulse 下载免费PDF全文
We propose a method to generate a high-efficiency broadband water window supercontinuum with a ω+3ω/2 multicycle two-colour pulse. Our results reveal that the 3ω/2 laser pulse can simultaneously modulate the acceleration step and the ionization step, which not only broadens the bandwidth but also enhances the yield of the generated supercontinuum. An ultra-broadband supercontinuum from 290 eV to 555 eV covering the whole water window is generated. Using this method, we expect that an isolated 62-as pulse with a minor pre-pulse can be directly obtained. 相似文献
10.
Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG), a scaling law of HHG is established. The scaling law states that when the atomic binding energy Eb, the wavelength λ and the intensity I of the laser field change simultaneously to kEb, λ/k, and k3I, respectively. The characteristics of the HHG spectrum remain unchanged, while the harmonic yield is enhanced k3 times. That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms. The variation of integrated harmonic yields is also discussed. 相似文献
11.
N. G. Borisenko A. A. Akunets A. M. Khalenkov D. Klir V. Kmetik E. Krousky J. Limpouch K. Masek Yu. A. Merkuliev M. Pfeifer V. G. Pimenov J. Ullschmied 《Journal of Russian Laser Research》2007,28(6):548-566
The velocities of energy transport in an undercritical plasma of polymer aerogel with and without copper nanoparticles were
measured. Transmission of the laser light through targets of different thicknesses such as submicron three-dimensional polymer
networks with densities below the critical value (0.13–0.52 N
cr) for a wavelength of 0.438 μm and intensity of (3–7)·1014 W/cm2 at a half-height pulse duration of 0.32 ns was studied. The transfer of a heating laser radiation was registered on the rear
side of the target. It ranged from a level of ∼0.5% for the thickness of a low-density layer of 400 μm and density of 9 mg/cm3 (mass per unit square of 0.36 mg/cm2) up to 50–60% for a thickness of 100 μm and density of 2.25 mg/cm3 (mass per unit square of 0.02 mg/cm2). The time dependences of the optical emission from the rear side of the targets were measured. They appear to be indicative
of the plasma dynamics in two-layer targets (polymer foam on Al foil) and enable the estimation of the absorption depth for
the laser light in an undercritical plasma.
__________
Translated from Preprint No. 8 of the P. N. Lebedev Physical Institute, Moscow (2007). 相似文献
12.
D. A. Zatsepin E. S. Yanenkova É. Z. Kurmaev V. M. Cherkashenko S. N. Shamin S. O. Cholakh 《Physics of the Solid State》2006,48(2):218-223
X-ray emission spectroscopy (Si L
2, 3 spectra, 3d3s → 2p electronic transition) was employed to study p-and n-type silicon samples implanted with Fe+ ions in a pulse mode (the implantation energy was 30 keV, the pulse current was varied up to 0.5 A, the pulse duration was
400 μs, and the ion irradiation doses ranged from 1014 to 1017 cm−2). The x-ray emission spectra were found to be dependent on the ion irradiation dose and the electron-accelerating voltage
that was used in the x-ray studies. By comparing the Si L spectra with the spectra of reference materials and by modeling the former spectra, it was revealed that, as the ion-irradiation
dose increases, there occur disordering of the structure, partial amorphization of the sample in a surface layer approximately
7200-? thick, and its subsequent recrystallization (under high irradiation doses). It was shown that this effect is most pronounced
in a layer at a depth of ∼1000 ? and is not associated with the formation of iron silicide FeSi in the bulk of the sample
but rather is due to the breakage of Si-Si bonds caused by ion implantation under the irradiation doses used.
Original Russian Text ? D.A. Zatsepin, E.S. Yanenkova, é.Z. Kurmaev, V.M. Cherkashenko, S.N. Shamin, S.O. Cholakh, 2006, published
in Fizika Tverdogo Tela, 2006, Vol. 48, No. 2, pp. 204–209. 相似文献
13.
Using a pulsed capilary discharge through helium as a light source fluorescence within the Lyman bands (transitionX
1 ∑
g
+
→B
1 ∑
u
+
of molecular hydrogen and deuterium has been investigated. Selecting a narrow spectral range (width ≈ 8 ?) from the continuum
radiation with a spectrometer, lines in the wavelength range from 1060 ? to 1110 ? have been excited having a vibrational
quantum number υ″=0 in the lower state, and ≦υ′≦4 in the upper state. The fluorescence intensity has been measured as a function
of υ′ and of the hydrogen density. Agreement with calculations has been found to be within ±30%. The method at present allows
the determination of densities between 1010 and 1015 molecules per cm3 with a temporal resolution of 1μs and with a spacial resolution of 0.1 cm3 相似文献
14.
A. I. Kupchishin A. D. Muradov Zh. A. Omarbekova B. G. Taipova 《Russian Physics Journal》2007,50(2):153-160
Joint effect of high-energy electrons, mechanical loads, and temperature on polyimide films of thicknesses in the range 30–130
μm is investigated. The films were preliminary irradiated by electrons in air using an éLU-6 linear accelerator with energy
of 2 MeV and doses D = 1, 5, 10, 20, 30, 40, and 100 MGy and then subjected to uniaxial mechanical tension at temperatures
(T) from 293 to 593 K. It is established that at T = 293–450 K and D = 20–40 MGy, the mechanical load causes almost the same
deformations (εl max) of nonirradiated and irradiated samples; at T = 450–550 K, deformations of films sharply increase, and the character of
their dependence changes. The εl max value of the initial sample increases almost linearly with temperature by a factor of 10, whereas the character of changing
εl max(T) of the irradiated films is more complex, and its value increases approximately by a factor of 4. For T > 500 K, the deformation
reaches limiting values. Irradiation increases the intensity of IR-spectra by 2–6 times and essentially increases the widths
of absorption bands at 720, 1380, and 1775 cm−1, which is caused by the formation of hydrogen bonds and cycles with nitrogen as well as by the formation of nitrogen oxides.
External loading applied to film rupture causes an increase in the EPR signal amplitude from 3·103 to 5·103, which is connected with an increased concentration of radicals =N-H and-NH
2. The electron irradiation of the polyimide films with their subsequent mechanical loading causes the spectrum lines to displace
from 3475.0 to 3512.5 cm−1 with simultaneous reduction of the signal amplitude from 6·103 to 4·103.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 52–58, February, 2007. 相似文献
15.
The influence of the width of a lattice-matched Al0.82In0.18N/GaN single quantum well (SQW) on the absorption coefficients and wavelength of the intersubband transition (ISBT) has been investigated by solving the Schrödinger and Poisson equations self-consistently. The wavelength of 1—2 ISBT increases with L, the thickness of the single quantum well, ranging from 2.88 μm to 3.59 μm. The absorption coefficients of 1—2 ISBT increase with L at first and then decrease with L, with a maximum when L is equal to 2.6 nm. The wavelength of 1—3 ISBT decreases with L at first and then increases with L, with a minimum when L is equal to 4 nm, ranging from approximately 2.03 μm to near 2.11 μm. The absorption coefficients of 1—3 ISBT decrease with L. The results indicate that mid-infrared can be realized by the Al0.82In0.18N/GaN SQW. In addition, the wavelength and absorption coefficients of ISBT can be adjusted by changing the width of the SQW. 相似文献
16.
A new method of cylindrical cumulation of fast ions undergoing ponderomotive acceleration at the focus of a high-power subpicosecond
laser is proposed. When a laser beam is focused in a preionized gas at a ring focus, radial acceleration of ions by the ponderomotive
force occurs. The ions accelerated from the inner side of the ring form a cylindrical shock wave converging toward the axis.
As the shock wave cumulates, the ion density increases rapidly and the ion-ion collision probability increases along with
it. A numerical simulation for a ~100 TW subpicosecond laser pulse predicts the generation of up to 200 keV ions and up to
100-fold volume compression of the plasma in a cylinder ~1 μm in diameter. The lifetime of the dense plasma filament over
the length of the laser caustic is several picoseconds. It is suggested that laser cumulation of ions be used for the production
of a bright and compact subpicosecond source of fast neutrons, media for x-and γ-ray lasers, and multiply-charged ions and for the initiation of nuclear reactions.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 20–25 (10 January 1999) 相似文献
17.
B. K. Kardashev O. A. Plaksin V. A. Stepanov V. M. Chernov 《Physics of the Solid State》2004,46(8):1449-1455
The behavior of Young’s modulus E and the decrement of ultrasonic vibrations δ in a V-4Ti-4Cr alloy is studied during proton (8-MeV protons, dose rate 104 Gy/s) or IR laser (YAG: Nd3+ laser, wavelength 1.06 μm, intensity up to 102 W/cm2) irradiation. Measurements are performed using the method of a composite piezoelectric oscillator (longitudinal 100-kHz resonance
vibrations). The sizes of the irradiated surface regions of a sample in the proton and laser experiments are the same in order
to provide the same thermal conditions in the sample-quartz transducer system. The amplitude, time, and temperature dependences
of E and δ are measured before and after preliminary plastic deformation, as well as before, during, and after irradiation of
a sample. The process of postdeformation aging (the kinetics of recovery of internal friction after deformation) during proton
irradiation is shown to differ substantially from that during laser irradiation. The specific features detected can be explained
by the more intense evolution of the defect structure during proton irradiation. Analysis shows that radiation annealing is
related to the ionizing component of proton irradiation, which excites the electronic subsystem of the metallic alloy and,
thus, creates hot electrons and plasmons. The electron excitations relax at lattice defects (dislocations) and increase the
dislocation mobility; this results in a relatively rapid decrease in the dislocation density and in a more significant (as
compared to the laser irradiation) decrease in the level of internal stresses in the material.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 8, 2004, pp. 1409–1415.
Original Russian Text Copyright ? 2004 by Kardashev, Plaksin, Stepanov, Chernov. 相似文献
18.
There are two physical phenomena in a strong laser intensity. One is the high-order harmonic emission; the other is x-ray emission from optical-field ionized plasmas. The experiment of conversion from high-order harmonics to x-ray emissions was given with a 105fs Ti:sapphire laser by adjusting laser intensities. The ingredient in plasma was investigated by the numerical simulations.Our experimental results suggested that the free electrons have detrimental effects on harmonic generation but are favourable for x-ray emission from optical-field ionized plasmas. If we want to obtain more intense harmonic signals as a coherent light source in the soft x-ray region, we must avoid the production of free electrons in plasmas. At the same time, if we want to observe x-rays for the development of high-repetition-rate table-top soft x-ray lasers, we should strip all atoms in the plasmas to a necessary ionized stage by the optical-field-ionization in the field of a high-intensity laser pulse. 相似文献
19.
Mitigation of energetic ion debris from Gd plasma using dual laser pulses and the combined effect with ambient gas 下载免费PDF全文
For the next-generation beyond extreme ultraviolet lithography(EUVL) sources, gadolinium(Gd) plasma with emission wavelength at 6.7 nm seems to be the leading candidate. Similar to the Sn target 13.5 nm light source, ion debris mitigation is one of the most important tasks in the laser-produced Gd plasma EUV source development. In this paper,a dual-laser-pulse scheme, which uses a low energy pulse to produce a pre-plasma and a main pulse after a time delay to shoot the pre-plasma, is employed to mitigate the energetic ion generation from the source. Optimal conditions(such as pre-pulse energy and wavelength, and the time delay between the pre-pulse and the main pulse for mitigating the ion energy) are experimentally obtained, and with the optimal conditions, the peak of the ion energy is found to be reduced to1/18 of that of a single laser pulse case. Moreover, the combined effect by applying ambient gas to the dual-pulse scheme for ion debris mitigation is demonstrated, and the result shows that the yield of Gd ions is further reduced to around 1/9 of the value for the case with dual laser pulses. 相似文献
20.
A reduced surface electric field in AlGaN/GaN high electron mobility transistor (HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas (2-DEG) channel as an electric field shaping layer. The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions. Compared with the HEMTs with conventional source-connected field plate and double field plate, the HEMT with Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge. By optimizing both the length of Mg-doped layer, Lm, and the doping concentration, a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure, respectively. In a device with VGS=-5 V, Lm=1.5 μm, a peak Mg doping concentration of 8× 1017 cm-3 and a drift region length of 10 μm, the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty. 相似文献