Multiple filamentation

Prior to deposition on a moving belt or screen, the molten polymer threads from a spinnerette must be attenuated to orient the molecular chains of the fibers in order to increase fiber strength and decrease extendibiUty. This is accompHshed by hauling the plastic fibers off immediately after they have exited the spinnerette. In practice this is done by accelerating the fibers either mechanically (18) or pneumatically (17,19,20). In most processes, the fibers are pneumatically accelerated in multiple filament bundles however, other arrangements have been described wherein a linearly aligned row(s) of individual filaments is pneumatically accelerated (21,22). 

Pcr, nonlinear effects start to become important and processes set in that give rise to filamentation and temporal splitting. In the very high power regime, when P is hundreds of times larger than Pcr, nonlinear effects dominate the dynamics and a number of complex effects have to be taken cognizance of, like multiple cone formation [24] and multiple filamentation [25]. 

Figure 5.2 shows that the onset of collapse in barium fluoride as the incident power is varied from 110 PCT to 1,200 Pcr. The onset of filamentation, z0f, the filament start position (the arrow in each panel marks the onset position), varies from 4.6 mm inside the crystal at 110 PCI to a position that is located on the incident face of the crystal at 1,200 PCI. Note that the images in Fig. 5.2 indicate that multiple filamentation occurs within the crystal at such high power levels. 

Fig. 5.6. Multiple filamentation in a 5 cm long glass cell containing coumarin dye in ethanol. Control over filamentation was obtained by means of a wire mesh (see text)...

Mach-Zehnder interferometer, 144 Medical applications, 153 Metal-insulator transitions, 52 Monte Carlo procedure, 135 Multi-energy X-ray imaging, 131 Multilayer targets, 131 Multiphoton absorption, 85 Multiphoton ionization, 82 Multiple filamentation, 91, 92 Multipulse techniques, 152... 

M. G. Inghram and W. A. Chupka. Surface Ionization Source Using Multiple Filaments. Rev. Sci. Instrum., 24(1953) 518-520. 

In practice there are few systems in which the S-L model actually describes the ion formation process, since molecular transformations are usually involved in this process. A more typical thermal ion source has a multiple-filament arrangement wherein a neutral molecule volatilizes from a sample filament at a modest temperature, undergoes fragmentation on a much hotter ionizing filament, and... 

Femtosecond Atmospheric Light Strings Multiple Filament Formation... 

This application of the z-UPPE simulator illustrates break-up of a high-power, wide femtosecond pulse into chaotically interacting light filaments. Beams that carry power exceeding the critical self-focusing power many times usually break transversally into multiple filaments. To capture such dynamics, a fully spatially resolved simulator is needed that doesn t impose axial symmetry. 

Below, we illustrate how such multiple filaments are concurrently created at different transverse and longitudinal locations, and how they interact with the low-intensity background. It was first proposed in [15] that such an interaction is crucial for long distance propagation of high-power femtosecond pulses in air. The basic idea is that of dynamic exchange of energy between multiple, essentially unsynchronized and spatially sharply localized filament cores and the low-intensity, spatially wide pedestal of the beam. 

In this wide-beam simulation, the initial condition is a Gaussian pulse with a phase perturbation. The waist of the initially collimated Gaussian was chosen to be 5 mm, the pulse duration is 500 fs, A = 248 nm, and the maximal intensity is 2 x 1014Wm-2. The total pulse energy is approximately 9mJ. A random phase perturbation is imposed on the pulse to initiate the transverse break-up of the pulse into multiple filaments (see Fig 13.3). We adjusted the amplitude of the perturbation such that it results in the filamentation onset after a few meters of propagation. 

G. Fibich, B. Ilan, Deterministic vectorial effect lead to multiple filamentation, Optics Letters 26, 840 (2001)... 

V. P. Kandidov, N. Akozbek, M. Scalora, O. G. Kosareva, A. V. Nyakk, Q. Luo, S. A. Hosseini, S. L. Chin, Towards a control of multiple filamentation by spatial regularization of a high-power femtosecond laser pulse, Applied Physics B 80, 267-275 (2005)... 

S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, S.L. Chin, O.G. Kosareva, N.A. Panov, N. Akozbek, V.P. Kandidov, Competition of multiple filaments during the propagation of intense femtosecond laser pulses, Physical review A 70, 033802 (2004)... 

Figure 12.11 Diagrammatic representation of adhesion between solid surfaces at rest (a) no adhesive layer (b) a viscous liquid at the interface and (c) a semisolid adhesive layer. On separation, the nature of the intervening film is shown (a) no film, (b) a necking filament of liquid, (c) multiple filaments of the semisolid layer...

Scanned Beam Single Linear Filament Multiple Filament... 

The secondary and subsidiary lights can be equipped with an automatic lamp changer or multiple filament bulb. This provides a minimum of one standby lamp or filament which will be automatically activated in the event of a filament failure. Filament failure should produce an alarm in the central control room and the radio room until a defective bulb is replaced. 

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