Pulse configurations

Fig. 11. Comparison of laser-induced breakdown spectroscopy (LIBS) spectra of RDX using die double-pulse configuration and the single-pulse configuration. Two 160-mJ pulses were separated by 2jjls for die doublepulse spectrum. One 320-mJ pulse was used to collect die single-pulse spectrum. The O to N intensity ratio for die double pulse and the single pulse is 4 and 2, respectively.

A variety of STIRAP pulse configurations and generalizations of STIRAP have jf f been studied. For example, and of interest below, is when one or more of the levels is i either part of the continuum [292, 308] or a resonant state [309, 310] (i.e., a bound Instate coupled to the continuum). 

Numerical studies allow us to explore aspects of these models for a number df molecular continua and pulse configurations. Consider first the effect of the puUe intensity on transition probabilities to a slowly varying continuum by considering continuum composed of single broad Lorentzian [Eq. (10.21)] of wid r, = 2000 cm-1, excited by a 120 cm-1 wide pulse (i.e., a pulse of 80fs durp tion). The central frequency of the pulse is tuned to the center of the continuutfi) (A, = 0) and the pulse peaks at t = 0. 

Note that the approach introduced below relies exclusively on the computatir nbfi material matrix elements, as in the wealc-field domain. As a result, one need Ms compute these matrix elements once in order to obtain dissociation rates anu ifohj abilities for a variety of pulse configurations and field strengths. i I % ... 

Fig. 1 Pulse configuration for a fifth-order experiment. The system interacts with two pairs of pulses at different time t =...

A wide variety of signal manipulations analogous to those that are known from NMR [20], and field polarization conditions that are better known from multiple-pulse high-frequency spectroscopy [74-76] have been explored with IR pulse configurations. The basic concepts of 2D-IR spectroscopy have been frequently reviewed [11, 19, 43], and very recently there was another excellent survey of the methodology of 2D spectroscopy [77]. 

Niehaus L., Meyer B.U., and Weyh T. Influence of pulse configuration and direction of coil current on excitatory effects of magnetic motor cortex and nerve stimulation. Clin. Neurophysiol. 2000 111 ... 

Line side Twin ARU Active Rectifier Units, 12 pulse configuration... 

For siitplicity we analyse these modulated echoes in the parallel pulse configuration setting k I I k and K=K =0. The lasers are tuned at... 

Employ pulse configurations that are biphasic with the cathodic phase first. 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

Fig. 4 Testing configurations of the pump-probe system (a) pulse-echo configuration, (b) split...

Then, the weld depths penetration are controlled in a pulse-echo configuration because the weld bead (of width 2 mm) disturbs the detection when the pump and the probe beams are shifted of 2.2 mm. The results are presented in figure 8 (identical experimental parameters as in figure 7). The slow propagation velocities for gold-nickel alloy involve that the thermal component does not overlap the ultrasonic components, in particular for the echo due to the interaction with a lack of weld penetration. The acoustic response (V shape) is still well observed both for the slot of height 1.7 mm and for a weld depth penetration of 0.8 mm (lack of weld penetration of 1.7 mm), even with the weld bead. This is hopeful with regard to the difficulties encountered by conventional ultrasound in the case of the weld depths penetration. 

Fig. 8 B-scan views of the artificial slot of height 1.7 mm (left image) and of the lack of weld penetration 1.7 mm (right image) in a pulse-echo configuration for gold-nickel alloy.

The Champ-Sons model is a most effieient tool allowing quantitative predictions of the field radiated by arbitrary transducers and possibly complex interfaces. It allows one to easily define the complete set of transducer characteristics (shape of the piezoelectric element, planar or focused lens, contact or immersion, single or multi-element), the excitation pulse (possibly an experimentally measured signal), to define the characteristics of the testing configuration (geometry of the piece, transducer position relatively to the piece, characteristics of both the coupling medium and the piece), and finally to define the calculation to run (field-points position, acoustical quantity considered). 

The light source for excitation of Nd YAG lasers may be a pulsed flashlamp for pulsed operation, a continuous-arc lamp for continuous operation, or a semiconductor laser diode, for either pulsed or continuous operation. The use of semiconductor laser diodes as the pump source for sohd-state lasers became common in the early 1990s. A variety of commercial diode-pumped lasers are available. One possible configuration is shown in Figure 8. The output of the diode is adjusted by composition and temperature to be near 810 nm, ie, near the peak of the neodymium absorption. The diode lasers are themselves relatively efficient and the output is absorbed better by the Nd YAG than the light from flashlamps or arc lamps. Thus diode-pumped sohd-state lasers have much higher efficiency than conventionally pumped devices. Correspondingly, there is less heat to remove. Thus diode-pumped sohd-state lasers represent a laser class that is much more compact and efficient than eadier devices. 

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