Bernerd E. Campbell

Laser-EXAFS: Fast Extended X-ray Absorption Fine Structure Spectroscopy with a Single Pulse of Laser-Produced X-rays

The extended x-ray absorption fine structure (EXAFS) spectrum of aluminum has been measured with a nanosecond pulse of soft x-rays generated by a laser-produced plasma. This technique provides a practical alternative to synchrotorn radiation for the acquisition of EXAFS data. It also provides a unique capability for the analysis of molecular structure in highly transient chemical species.

Laser Plasma X-Ray Source Optimization For Lithography

The laser-plasma X-ray source has been evaluated for submicrometer X-ray lithography exposure machines. X-ray lithography systems based on commercially available lasers of reasonable cost appear to be feasible. Such machines would make full wafer exposures of silicon slices with a throughput consistent with current manufacturing requirements.

Amplified−spontaneous−emission suppressor for Q−switched lasers

A passive device for suppressing amplified spontaneous emission in Q−switched lasers has been developed. The technique is applicable to lasers of any aperture.

Laser removal of contaminant films from metal surfaces

In precision cleaning operations, it is essential to remove all traces of organic films and other contaminants, such as particles and fibers, from critical aerospace components. In the past, this was accomplished effectively with powerful solvents such as CFC-113, which can no longer be used because of its adverse effects on the environment. Among many alternative cleaning technologies under investigation, use of lasers to remove contaminants has recently shown promise in several applications, particularly in the area of particle removal from semiconductor surfaces for microcircuit manufacture. We present here, results of some of the first definitive studies of removal of organic films from metal surfaces using pulsed lasers. The substrate metals included aluminum and stainless steel, test coupons of which were contaminated with controlled amounts of organic substances (oils and greases) that might be present from normal use or handling of parts made from these materials. The test coupons were laser cleaned with short pulses having wavelengths selected to span a range of physical removal mechanisms from photo-chemical ablation to pure thermal effects (248, 355, and 1064 nm). Cleaning thresholds were measured using sloped irradiance profiles and post-test SEM observation of the position of the boundary between cleaned and uncleaned zones. These test results were combined with engineering studies of optical fiber beam delivery approaches in the design of a system for precision cleaning of the inside surfaces of metal tubes. Quantitative results of the laser cleaning tests and their implications for optical fiber-based laser cleaning systems are presented.In precision cleaning operations, it is essential to remove all traces of organic films and other contaminants, such as particles and fibers, from critical aerospace components. In the past, this was accomplished effectively with powerful solvents such as CFC-113, which can no longer be used because of its adverse effects on the environment. Among many alternative cleaning technologies under investigation, use of lasers to remove contaminants has recently shown promise in several applications, particularly in the area of particle removal from semiconductor surfaces for microcircuit manufacture. We present here, results of some of the first definitive studies of removal of organic films from metal surfaces using pulsed lasers. The substrate metals included aluminum and stainless steel, test coupons of which were contaminated with controlled amounts of organic substances (oils and greases) that might be present from normal use or handling of parts made from these materials. The test coupons were laser clean...

APPLICATIONS OF X-RAYS FROM LASER PRODUCED PLASMAS

Progress in the development of high power lasers during the past decade has opened the door to many new areas of applications. The best known, of course, is the possibility of achieving controlled thermonuclear fusion by means of laser heated plasma. However, several applications of laser plasma x-rays have more attractive current prospects. There are many points of similarity between the x-ray and fusion problem. Both, for example, require laser heating of plasmas to the kilovolt regime. But there are significant differences. The x-ray work usually involves heating of high Z materials, while the fusionable materials are low Z. Most of the x-ray applications do not require target compressions, and can use simple planar targets. Additionally, neither the plasma temperature nor the laser efficiency requirements are as severe. The main effect of these differences is that the lasers for x-ray production can be much smaller and less expensive than lasers for fusion. We have recently demonstrated that x-rays can be efficiently generated with mode locked laser pulses of several hundred mj1. The characteristics that differentiate a laser plasma x-ray source from conventional sources are: (1) The x-ray spectrum comes from highly stripped species and is predominantly L line radiation or continuum in the kilovolt regime. Heliumlike K lines are also obtainable. (2) The pulse width is very short in the ~0.1 to 10 ns range. (3) The source size is very small, ~10–200 µm diameter.

Current status of laser fusion research at Battelle.

The central research discussed is the analysis and control of laser-produced high-Z plasmas. Research consisting mainly of laser development, model and code development, and target irradiations is described. Some medical applications of the research are also mentioned. (MOW)