Plasma Energy Transfer to Metal Surfaces Irradiated by Pulsed Lasers

Pirri, A. N.; Root, Robert G.; Wu, Peter

doi:10.2514/3.61046

Cited by 124 publications

(28 citation statements)

References 8 publications

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“…The drawback with this is the presence of strong plasma screening. The over-dense plasma decouples the target from the laser due to the generation of a laser-supported detonation wave (LSD) [16]. This wave absorbs the incoming radiation and shields the target.…”

Section: Discussionmentioning

confidence: 99%

Enhanced drilling using a dual-pulse Nd:YAG laser

Lehane

Kwok

2001

Appl Phys A

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Abstract.A new method for improving the efficiency of laser drilling has been developed. Two synchronized free-running laser pulses from a tandem-head Nd:YAG laser are capable of drilling through 1/8-in-thick stainless-steel targets at a standoff distance of 1 m without gas-assist. The combination of a high-energy laser pulse for melting with a properly tailored high-intensity laser pulse for liquid expulsion results in the efficient drilling of metal targets. We argue that the improvement in drilling is due to the recoil pressure generated by rapid evaporation of the molten material by the second laser pulse. PACS: ; ;CE aLaser drilling and cutting of metals are established industrial processes. They are applied in many different production lines. There have been some attempts to understand the laser-material interaction process with the aim of improving the efficiency of laser drilling and cutting [1][2][3][4]. It has been found that material is removed in both the vapor and the liquid states. The intense laser energy used for laser drilling is sufficient to melt and subsequently vaporize the material. This vaporization process creates a recoil pressure, which is responsible for expelling the liquid. The amount of material ejected in the liquid state has a direct effect on the laser drilling/cutting efficiency due to the fact that the material is removed without the loss of additional energy required for vaporization. Many theoretical models have been developed in an attempt to characterize the dynamics of the laser drilling process [5][6][7][8][9].In most instances, a gas jet is used to assist the drilling/ cutting of the material. In the case of stand-off drilling/cutting at a distance without gas-assist, the efficiency is rather low. The problem is due to resolidification of the molten pool. Increasing the laser power does not work well. Several novel methods for improving the efficiency of material removal in laser drilling have been developed. Fox [10] combined a cw CO 2 laser with Q-switched Nd:glass laser pulses to * Corresponding author. (E-mail: eekwok@usthk.ust.hk) achieve a factor of two increase in the drilling efficiency of carbon steel. The Q-switched pulse was responsible for the ejection of liquid metal, which had not yet consumed the latent heat of vaporization, resulting in a higher drilling efficiency. This experiment was theoretically modeled by Robin and Nordin [11] and Towle et al. [12]. Another novel technique was reported by Kim et al. [13]. They reported that the laser penetration efficiency was enhanced by amplitudemodulating a free-running Nd:YAG laser. They attributed this improvement to a reduction in the plasma screening effect due to the repetitive chopping of the laser beam, along with possible acoustic resonance effects of the molten metal.In this paper, we propose and demonstrate a new method for increasing laser drilling efficiency using two synchronized free-running Nd:YAG laser pulses. We show that a Qswitched pulse is not necessary for explosive liquid expulsion. In fact, ...

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Section: Discussionmentioning

confidence: 99%

Enhanced drilling using a dual-pulse Nd:YAG laser

Lehane

Kwok

2001

Appl Phys A

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“…The classic analysis of high-intensity laser interaction with materials divides into two regimes: laser supported combustion (LSC) and laser supported detonation (LSD) [Pirri 1973;Pirri, Root and Wu, 1978;Raizer 1977]. Although the analysis was originally developed by aerodynamicists for interactions in air, these concepts can (5) also apply to a solid target in vacuum.…”

Section: Inducing Shock In Targetsmentioning

confidence: 99%

Overview of laser applications: the state of the art and the future trend

Phipps

2003

SPIE Proceedings

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The range and maturity of commercially useful laser applications are illustrated by selected examples. Macroscopic applications (commercialized or potentially so in the near future) include cutting, machining and welding metals, cutting fabrics, shock hardening of steels, nitrogenization of iron, and laser drilling through rock. Microscopic applications include drilling micro-holes for cooling of jet engine turbine blades, thin film growth, precision machining of structures inside transparent materials and inertially-confined deuterium-tritium fusion. To be commercially useful, these applications take advantage of the special properties of laser light, such as monochromaticity, high brightness, high pulse energy or intensity, wavelength range from soft xray to far infrared and pulse duration from femtoseconds to CW. This talk will be divided into three sections: (a) summary of the theory of laser-materials interactions with examples from published laser impulse production studies, (b) macroscopic applications, (c) microscopic applications and (d) exotic and futuristic applications, including a diode-laser-driven .tN thruster for micro-and nano-satellites, and proposals to use lasers to clean hundreds of thousands of small but hazardous space debris from near-Earth space and to launch 5kg payloads into near-Earth orbit.

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“…As a result of material vaporization and plasma formation, target erosion appears in the form of craters on the sample surface. The theoretical considerations on plasma production and heating by means of laser beams have been proposed by several workers [25][26][27][28]. The initiation of plasma formation over a target surface begins in the hot target vapor.…”

Section: Processes In Laser Produced Plasmamentioning

confidence: 99%