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Laser machine shops care a lot about the M 2 parameter of their lasers because the beams will focus to an area that is M 4 times larger than that of a Gaussian beam with the same wavelength and D4σ waist width; in other words, the fluence scales as 1/M 4. The rule of thumb is that M 2 increases as the laser power
ISMB: Indian Standard Medium Weight Beam, ISJB: Indian Standard Junior Beams, ISLB: Indian Standard Light Weight Beams, and ISWB: Indian Standard Wide Flange Beams. Beams are designated as per respective abbreviated reference followed by the depth of section, such as for example ISMB 450 , where 450 is the depth of section in millimetres (mm).
The rule of thumb is that M 2 increases as the laser power increases. It is difficult to obtain excellent beam quality and high average power (100 W to kWs) due to thermal lensing in the laser gain medium. The M 2 parameter is determined experimentally as follows: [2]
DIN 1025 is a DIN standard which defines the dimensions, masses and sectional properties of hot rolled I-beams.. The standard is divided in 5 parts: DIN 1025-1: Hot rolled I-sections - Part 1: Narrow flange I-sections, I-serie - Dimensions, masses, sectional properties
The American National Standard Z136.1-2007 for Safe Use of Lasers (p. 6) defines the beam diameter as the distance between diametrically opposed points in that cross-section of a beam where the power per unit area is 1/e (0.368) times that of the peak power per unit area.
The beam quality of a laser beam is characterized by how well its propagation matches an ideal Gaussian beam at the same wavelength. The beam quality factor M squared (M 2 ) is found by measuring the size of the beam at its waist, and its divergence far from the waist, and taking the product of the two, known as the beam parameter product .
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[5] [3] As a rule of thumb, the depth should be 1 ⁄ 24 of the span. [5] The width of the ribs is typically 130 mm (5 in) to 150 mm (6 in), and ribs usually have steel rod reinforcements. [5] The distance between ribs is typically 915 mm (3 ft). [3] The height of the ribs and beams should be 1 ⁄ 25 of the span between columns. [3]