Laser equipment

Although practical generation of energy by laser-assisted thermonuclear fusion remains well ia the future, the program has provided some of the most exacting requirements for laser technology and has led to advances ia laser equipment that have been adopted ia other areas. Thus the research and development associated with thermonuclear fusion work has helped to spur advances ia laser technology useful for many other appHcations. 

One of SACHEM s products is tetramethylammonium hydroxide (TMAH), which is sold to semiconductor industries. Suspended particles in TMAH solutions could cause severe mechanical damage to the electronic devices manufactured by their customers. The determination of the particle content in such solutions is therefore critical. It is performed with a laser-equipped particle counter, which provides 70% detection efficiency. The counting must take place in a clean room because tiny airborne particles can land in the solutions and give them a false high reading. A class 1000 environment is required in this case, which means that the count of particles in the air that are greater than or equal to 0.5 jrm in diameter must be less than 1000 per cubic foot. Typically, a customer s specification for TMAH solutions is less than 100 particles per milliliter for particles greater than or equal to 0.5 fim in diameter. 

Paul Plumb of SACHEM Inc. counts particles in the ultrapure solutions of TMAH by a laser-equipped particle counter in the clean room. Notice the hair net and special lab coat. 

Particle size distribution was measured with Coulter LS 230 laser equipment. Solids were determined with a drying scale. 

Some of the earlier experiments were carried out using our home-built colliding pulse modelocked (CPM) ring dye laser. Equipped with two excimer... 

The lignin model compounds and their derivatives used in this study were custom synthesized at Queen s University by Dr. R. Bowers (Colour Your Enzyme). CIDEP and conventional ESR experiments were conducted using either a Varian E-104 spectrometer or a customized Bruker X-band spectrometer, modified similarly as previously described (7). The light source used for in situ irradiation was either a super high pressure 200 W mercury lamp, a Lambda-Physik EMG101-MSC XeCl excimer laser at 308 nm., or a Quanta-Ray GCR-11 Nd YAG solid state laser equipped for all four harmonic generations. 

A 2-liter stainless steel vessel, partially filled with I2 crystals, was connected directly to the secondary He feed supply line of a supersonic chemical laser. A complete description is given in a separate paper.- The laser cavity had viewing windows on top and bottom so that the nozzle array could be viewed in a direction perpendicular to the optical axis. The pump laser was a Spectra-Physics Model 170-03 Ar+ laser equipped with an intracavity etalon. 

With adequate laser equipment, and precise characterization of the interaction geometry, detector response, and measurement of laser power, sufficient precision to test the theory of the two-loop binding corrections should be obtainable. 

The authors thank R. J. Collins and J. A. Corruthers of the Department of Electrical Engineering, University of Minnesota, for their many helpful suggestions and discussions on the application of laser diffraction techniques. They also thank W. T. Peria of the same department for loaning some laser equipment. The various services provided by the Department of Aerospace Engineering and Mechanics of the University of Minnesota are gratefully acknowledged. 

It is outside the scope of this chapter to examine the detail of the pieces of an advanced laser equipment however, before reviewing the main spectroscopic techniques that are fit for use in combustion science, it is appropriate to get acquainted with the fundamental optical elements that are essential in any measurement of laser spectroscopy. Clearly, it is not possible to go through all the elements and some of them are intentionally left out of the discussion. For a more detailed description, the reader can refer to the book by Eckbreth [7]. All the same, in an attempt to give a brief summary of those optical components that are decisive for a successful result, it is compulsory to begin with the apparatus that plays the major role in the experimental methods considered later the laser system. 

Fig. 2. UV cutting laser tools. (A) The UV cutting laser ablates tissue around the perimeter of the desired area. The capture laser is used in conjunction with a Laser Capture Microdissection (LCM) cap to remove the desired tissue section. The LCM cap is bonded, or tacked, to the cut tissue within the perimeter of the cut section, effectively removing the desired cellular area from the tissue section. (B) A free-form annotation tool is also available to select any size or shaped region for ablation/cutting with the UV laser. (C) Circular regions of defined diameter may be ablated/cut with the UV laser-equipped Veritas instrument.

The fluorescence lifetime measurements were performed with a streak camera (Agat SF 3M, VNIIOFI, Russia). A Nd YAG laser with excitation wavelengths of 532 and 266 nm (the second and fourth harmonic of fundamental radiation) was used as a light source. The laser radiation parameters of the fluorimeter were as follows (for 532 nm) pulse energy 160 (ij, duration 20 ps (fwhm), beam diameter 5 mm. The error in determining the fluorescence lifetimes in time intervals of several nanoseconds did not exceed 5 %. In addition to the laser equipment, the Cary 100 spectrophotometer (Varian, Inc., USA) and the Cary Eclipse spectrofluorimeter (Varian, Inc., USA slits width was 5 nm) were used for optical density measurements and fluorescence registration, respectively. 

We have developed a direct and noninvasive method to determine Tg of polymers at the interface with solid substrates [54, 55]. The strategy is to use fluorescence lifetime measurements using evanescent wave excitation. Figure 15a shows PS-NBD, i.e., PS containing the dye 6-[A-(7-nitrobenz-2-oxa-l,3-diazol-4-yl)amino]hexanoic acid (NBD) [55]. The NBD fraction of PS was sufficiently low to avoid self-quenching of the dye. The NBD dye was excited with the second-harmonic generation of a mode-locked titanium sapphire laser equipped with a... 

Figure 2.36 Schematic arrangement of pulsed laser equipment used to produce carbon clusters. Source Reprinted from Curl RF, Smalley RE, Scientific American, 265 54-63, October 1991.

Recordkeeping The laser equipment operator must carry proof of his or her qualification. 

Who . Only qualified and trained employees can be assigned to install, adjust, and operate laser equipment in accordance with 1926.54. 

Prior to being assigned to install, adjust, or operate laser equipment. 

Beyond 1926.950, employers will find further training provisions in Subpart V. These go over first aid, job briefings, enclosed spaces, personal protective equipment, personal fall arrest systems, working on or near exposed energized parts, testing, overhead fines and live-line barehand work, laser equipment, power-line carrier work, and more. 

A CO2 laser cam be used to punch intricate holes amd cut delicate patterns in plastics. The laser can be directed to etch the plastic surface bau-ely or actuadly vaporize and melt it. There is no physical contact between the plaistic amd the laser equipment, amd no dust or drill chips are produced. 

The radical anion of benzene is reported to present an absorption maximum at 290 nm in aqueous solution and two absorption maxima at approx. 285 and 385 nm in a matrix at 77 Since the radical anion of benzene is known to protonate to H-CHD on a microsecond time-scale, the latter radical may be detected with our laser equipment. Figure 3 shows the spectrum of the transient species obtained, along with that of the H-CHD and HO-CHD radicals of benzene" " whose participation in the overall reaction has already been discussed (see above). The observed transient shows important contributions of the H-CHD and HO-CHD radicals however, absorption at wavelengths higher than 340 nm cannot entirely be attributed to these radicals. 

Engineering controls are normally designed and built into the laser equipment to provide for safety. In most instances, these are included on the equipment (i.e., provided by the laser manufacturer). Some of these controls are protective housing, master switch control, optical viewing systan safety, beam stop or attenuation, laser activation warning system, service access panels, protective housing interlock requirements, and a remote interlock connector. 

Ethanol injection,bipolar electrocoagulation therapy, and argon coagulation are all methods used to restore patency of the esophageal lumen by producing tumor necrosis without the need for expensive laser equipment and the stringent safety precautions required for laser therapy. 

Safety-Critical Equipment Equipment that can present safety hazards to users (e.g.. X-ray and laser equipment) as well as equipment used to control exposures to recognized hazards, and whose improper use could subject users to harm (e.g., fiime hoods, biological safety cabinets, respirators, automated him processors). 

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