Atomic Cluster Application

So far, we have concentrated on the explosions of individual clusters that have been studied in experiments with low density cluster beams and described theoretically in terms of the nanoplasma model. Now we turn to applications which are carried out in extended (i.e. typically a cylinder of length ~1 mm as set by the gas jet length and diameter around 50 µm corresponding to the laser focal spot size), high density cluster media (see Section 2.2) where the density of clusters is ~106 times greater. Extremely high laser absorption (up to 90%) has been observed in such targets [58] – a remarkable result considering the target has the average density of a gas (at about atmospheric pressure) and is completely transparent to low intensity light. The deposition of almost all the laser pulse energy (a large fraction of a Joule in [58]) into a focal volume of typically ~5 x 10-6 cm-3 leads to the production of a very high energy density plasma that emits copious quantities of X-rays in the 0.1–10 keV range and can provide an environment for nuclear fusion, as we see below.

X-ray generation
X-ray generation is currently the most important application of the laser–cluster interaction. The main attractions of this source, particularly for photolithographic applications, are that it produces very little debris, in contrast to solid targets (which is very important since expensive X-ray collection optics must be positioned close to the target), and that it can be operated at a very high repetition rate. In fact, so attractive is the source that several large microchip manufactures are funding research to investigate it as an XUV photolithographic source for microchip production [59]. On a less commercial note, the prompt (likely to be <1 ps in duration) X-rays emitted by the cluster nanoplasmas immediately after heating by the laser allow the investigation of high-density plasmas through spectroscopic means [60], in the absence of significant absorption and re-emission of radiation that plagues such measurement of solid target laser plasmas. (underline see Principle of Regeneration)

In addition to a prompt X-ray component, time resolution of the X-ray emission using an X-ray streak-camera has shown that the most of the emission (around 99%) is emitted on a nanosecond timescale [15,61]. This implies that it is coming from the hot, underdense (ne < ncrit) plasma that is formed after the individual clusters have exploded and expanded to form a uniform, bulk plasma. The plasma emission is dominated by line emission from the resonance lines of highly charged ions in the plasma, which are populated initially by collisions with hot electrons, and then, after the plasma has cooled, via three body recombination [15]. Conversion of up to 10% of the incident laser energy into X-rays in the 17–30 nm range (e.g. 4p–3d in Kr10+) in Ar clusters was reported in [15] using 30 mJ, 130 fs laser pulses. This is comparable with the yields from solid targets. Many experiments have studied the yields and parameter scaling of the X-ray emission with a view to applications [62,56,63–65]. This continues to be an active area of research. One area of controversy is the scaling of the X-ray signal with the laser wavelength, with some groups claiming a very strong scaling, favouring shorter wavelength lasers such as KrF lasers at 248 nm [66], while others finding evidence of a much weaker scaling [67,79]. However, no systematic study has been carried out over a wide range of wavelengths ensuring identical focusing conditions and using exactly the same cluster source.

See Also

13.04 - Atomic Subdivision
3.14 - Vortex Theory of Atomic Motions
7B.05 - Rotating Triplets
15.08 - Dissociating Water with X-Rays - Radiolysis
Atomic Cluster Charge build-up
Atomic Cluster Expansion
Atomic Cluster Experimental Apparatus
Atomic Cluster Heating
Atomic Cluster Ionization
Atomic Cluster X-Ray Emission
Atomic Clusters
Atomic Force
atomic mass
atomic number
atomic theory
atomic triplet
atomic weight
Clustered Water
Dynasphere Applications
Figure 1.9 - Keelys Molecular Morphology
Figure 4.12 - Keelys Formative Structural Dynamic Morphology
Figure 4.14 - Feynmans Triplet Structures of the Proton and Neutron
Figure 7.6 - Keelys Triune Morphology
Figure 7.7 - Keelys Morphology - Infinite Subdivision of Matter
Figure 7.13 - Keelys Chart showing how Molecules are made of three Atoms
Figure 7B.05 - Triplet Forming a Unity
Figure 7B.06 - Rotating Triplets Animation
Figure 9.8 - Triple Centers
Figure 13.06 - Atomic Subdivision
Formation of Atomic Clusters
Ion Energies from Atomic Cluster Explosions
Laser Cluster Interactions
Law of Atomic Dissociation
Law of Atomic Pitch
Law of Oscillating Atomic Substances
Law of Pitch of Atomic Oscillation
Law of Variation of Atomic Oscillation by Electricity
Law of Variation of Atomic Oscillation by Sono-thermism
Law of Variation of Atomic Oscillation by Temperature
Law of Variation of Atomic Pitch by Electricity and Magnetism
Law of Variation of Atomic Pitch by Rad-energy
Law of Variation of Atomic Pitch by Temperature
Law of Variation of Pitch of Atomic Oscillation by Pressure
Models of Laser Cluster Interactions
Numerical Simulation of an Atomic Cluster Explosion

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