Introduction
Chapter 2 included a broad summary of the LIBS approach. The framework that was used in the experimental setting is briefly described in this chapter.
Instrumentation of LIBS
The major elements of a typical LIBS configuration are a laser, a focusing lens, a detecting device to determine the spectral resolution of the light gathered, and a computer for signal analysis and information storage. The LIBS applications determine each key component’s requirements.
Laser System
For LIBS instruments, the Q-switched Nd: YAG laser system is the most used solid-state laser source. This flashlamp-pumped laser has a fundamental wavelength of 1064 nm and typical pulse width in the range of 6 to 15 ns. A pulsed Nd: YAG laser operating at a wavelength of 532 nm with a pulse duration of 6–10 ns and a repetition rate of 10 Hz was utilized in each SP-LIBS experiment. The SP-LIBS and DP-LIBS studies generated blistering impulses from a frequency-doubled Nd: YAG output (532 nm). By lengthening their optical paths, reheat impulses set to 506 nm were optically delayed by 10 ns, and the pulse energy was kept constant at 7 MJ across all trials.
Sample Holder
The known distance between the lens and the LTSD sample is one of the crucial factors determining the precision and accuracy of the LIBS measurement. Small modifications have a big impact on the ablation mass, the intensity of the emission lines, and plasma properties, including plasma temperature. LTSD influences the intensity of radiation at the sample surface. A unique sample holder was created to prevent or reduce LTSD fluctuation. When assessing anti-diabetic tables using the calibration curve approach, the sample holder’s major issue was to keep the ITS value constant. A range of tablets with different thicknesses has been created for this specific use. Multiple exposures may be performed at various spots on the plate surface thanks to the sample holder’s mounting on an X-Y platform.
Focusing and light collection system
A more advanced focusing mechanism must be used when LTSD needs to be changed. Laser pulses were focused on the studies using a single lens with a 150 mm focal length. The lens system for the SP-LIBS experiments and the lens fiber cable arrangement for the DP-LIBS experiments each employed a distinct configuration. In LIBS, a lens system with two biconvex lenses was initially used to gather plasma light. The device effectively gathers light and has been used to examine diabetes medication pills. A single biconvex lens with a focal length of 100 mm shines light into the round end of a bundle of 19 distinct fibers in a lens-to-fiber arrangement.
Spectrograph
Spectral resolution and wide spectral range are crucial features of an effective LIBS detection spectrometer. The LIBS signal is frequently scattered using Czerny Turner spectrometers. Although they offer an outstanding spectral resolution, the spectral range is only a few nanometers for many applications. Paschen-Runge and Eschelle spectrometers are spectrometers that carry out simultaneous detection across a broad spectral range. For LIBS measurements, the Echelle spectrometer is more frequently utilized due to its superior resolution and wide spectral range when multi-element analysis may be done while avoiding spectral noise.
Detector
Photomultiplier tubes (PMTS), photodiodes (PDs), photodiode arrays (PDAs), or charge-coupled devices (CCDs) can be used to detect light after it has been dispersed. Great-speed detectors called PMTs or PDs have the major benefit of having high sensitivity in the visible band. Matrix detectors may concurrently detect a broad spectral range while collecting light over an extended length of time. LIBS installations make extensive use of linear and two-dimensional arrays of many sensors in a single device, such as charge pair devices and photodiode arrays. The detector’s resolution increases as the number of sensors in the matrix increases.
Sample Preparation
LIBS has the benefit of requiring little to no sample preparation. Analysis remains ecologically friendly since sample pre-treatment in LIBS is straightforward and frequently does not call for any additional risky chemicals or solvents.