01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Elsevier AMS Job code: LRN Ch05-N51734 5-6-2007 4:47 p.m. Page:113 Trim:165×240 MM TS: Integra Font: Times Size:10/12 pt Margins:Top:13 MM Gutter:20MM T.Area:125mm X 198mm 4 Color COP: Recto Floats: Inline Chapter 5 Instrumentation for Laser-Induced Breakdown Spectroscopy V. N. Rai a and S. N. Thakur b a Laser Plasma Division, Centre for Advanced Technology P. O. CAT, Indore 452 013, INDIA b Laser and Spectroscopy Laboratory, Department of Physics Banaras Hindu University, Varanasi- 221 005, INDIA 1. INTRODUCTION Laser-induced breakdown spectroscopy (LIBS) is a laser diagnostics, where a laser beam is focused onto a material generates transient high density plasma as the laser intensity exceeds the breakdown threshold of the material (∼1–10 MW/cm 2 ). The UV and visible emission from the plasma can be spectrally resolved and recorded for qualitative and quantitative analysis of the sample. LIBS was first used for the determination of elemental composition of materials in the form of gases, liquids and solids during 1960’s [1,2]. Research on LIBS continued to grow and reached a peak around 1970 and field-portable instruments capable of in-situ and real time analysis of samples have been developed in recent years with the availability of reliable, smaller and less costly laser systems along with sensitive optical detectors, such as the intensified charge-coupled device (ICCD). Several review articles have been published on this topic [3–14]. A short duration laser pulse of sufficient energy focused onto the surface of a material sample instantly increases its temperature above the vaporization temperature, regardless of the type of material. Compared with the rate of energy delivery from the laser pulse, the energy dissipation through vaporization is relatively slow and the underlying layer of material reaches critical temperatures and pressures before the surface layer vaporizes, which forces the surface to explode. Generally material ablation and plasma formation take place during the initial period of the laser pulse, whereas rest of the laser energy is absorbed by the ablated material to form luminous plasma. The temperature of the plasma emitting UV and visible radiation is in the range of 10 4 − 10 5 0 K, whereas the electron number density ranges from 10 15 to 10 19 cm −3 and the plasma- plume may last from microseconds to milliseconds. The laser-induced plasma may be coupled with various detection systems, such as mass spectrometry (MS), atomic emission spectrometry (AES), atomic absorption spectrometry (AAS), and laser excited atomic fluorescence spectrometry (LEAFS). In some experiments laser-induced plasma