Advanced Crystal Growth Technology

Although the fundamental mechanism of crystal growth has received and continues to receive deserved attention as a research activity, similar research efforts addressing the need for advanced materials and processing technology required to grow future high quality crystals has been sorely lacking. The purpose of this research effort is to develop advanced rapid growth processing technologies and materials suitable for providing the quality of products needed for advanced laser and photonics applications. In particular we are interested in developing a methodology for growing high quality KDP crystals based on an understanding of the fundamental mechanisms affecting growth. One problem in particular is the issue of control of impurities during the growth process. Many unwanted impurities are derived from the growth system containers and can adversely affect the optical quality and aspect ratio (shape) of the crystals. Previous studies have shown that even trace concentrations ({approx}10{sup -9} M) of impurities affect growth and even 'insignificant' species can have a large impact. It is also known that impurities affect the two growth faces of KDP very differently. Traces of trivalent metal impurities such as Fe{sup 3+}, Cr{sup 3+}, and Al{sup 3+} in solution are known to inhibit growth of the prismatic {l_brace}100{r_brace} faces of KDP while having little effect on the growth of the pyramidal {l_brace}101{r_brace} faces. This differentiation opens the possibility of intentionally adding select ions to control the aspect ratio of the crystal to obtain a more advantageous shape. This document summarizes our research efforts to improve KDP crystal growth. The first step was to control unwanted impurity addition from the growth vessel by developing an FEP liner to act as a barrier to the glass container. The other focus to develop an understanding of select impurities on growth rates in order to be able to use them to control the habit or shape of the crystal for yield improvement

Products of motor burnout. Final report

The Montreal Protocol of 1987 effectively banned a long list of chlorofluorocarbons (CFCs) traditionally used in air conditioning and refrigeration applications. The refrigeration and air conditioning industries have responded by developing and testing new, alternative refrigerants that are less damaging to the atmosphere upon release. Despite a reputation for quality and reliability, air conditioning systems do occasionally fail. One of the more common failure modes in a hermetic system is a motor burnout. Motor burnouts can occur by various mechanisms. One of the most common scenarios is a locked motor rotor, which may result from a damaged bearing. The resulting electrical motor burnout is caused by overheating of the locked rotor and subsequent failure of the insulation. This is primarily a thermal breakdown process

A System for Measuring Defect Induced Beam Modulation on Inertial Confinement Fusion-class Laser Optics

A multi-wavelength laser based system has been constructed to measure defect induced beam modulation (diffraction) from ICF class laser optics. The Nd:YLF-based modulation measurement system (MMS) uses simple beam collimation and imaging to capture diffraction patterns from optical defects onto an 8-bit digital camera at 1053, 527 and 351 nm. The imaging system has a field of view of 4.5 x 2.8 mm{sup 2} and is capable of imaging any plane from 0 to 30 cm downstream from the defect. The system is calibrated using a 477 micron chromium dot on glass for which the downstream diffraction patterns were calculated numerically. Under nominal conditions the system can measure maximum peak modulations of approximately 7:1. An image division algorithm is used to calculate the peak modulation from the diffracted and empty field images after the baseline residual light background is subtracted from both. The peak modulation can then be plotted versus downstream position. The system includes a stage capable of holding optics up to 50 pounds with x and y translation of 40 cm and has been used to measure beam modulation due to solgel coating defects, surface digs on KDP crystals, lenslets in bulk fused silica and laser damage sites mitigated with CO{sub 2} lasers

ARTI/MCRL Project Report products of motor burnout (Second quarter report)

The OSP (Operating Safety Procedure) required for performance of electrical arc testing of CFC replacement fluids was renewed. Electrical breakdown tests at one (1) atmosphere pressure have been performed for R-22, R-134a, and R-125/R-143a (50:50 blend; AZ-50), and breakdown products identified. No differences in HCFC breakdown products are seen in the presence or absence of lubricant oils. The design of the high pressure-high temperature test stand has been finalized, and construction initiated during this quarter. Three motor stators and rotors were received from Tecumseh Products Company for use in motor burnout tests. A test plan for the motor breakdown tests is in preparation

Products of motor burnout. Second quarterly technical report, October 1, 1994--December 31, 1994

The OSP (Operating Safety Procedure) required for performance of electrical arc testing of CFC replacement fluids was renewed. Electrical breakdown tests at one atmosphere pressure have been performed for R-22, R-134a, and R-125/R-143a (50:50 blend; R-507), and breakdown products identified. No differences in HCFC breakdown products are seen in the presence or absence of lubricant oils. The design of the high pressure-high temperature test stand has been finalized, and construction initiated during this quarter. Three motor stators and rotors were received from Tecumseh Products Company for use in motor burnout tests. A test plan for the motor breakdown tests is in preparation

Investigation of the Breakdown Products Produced from Electrical Discharge in Selected CFC Replacement Fluids

LLNL personnel have designed and constructed a special purpose electrical test stand to evaluate CFCs and CFC replacement fluids under simulated AC, DC, and pulsed breakdown conditions. The test stand includes an electrical diagnostic system which allows the measurement of breakdown voltage, discharge current, arc power, and energy associated with each pulse. The appropriate data that is collected in order to correlate the quantity of by-products produced with the pertinent control variables, such as voltage, current, pulse width, pulse repetition frequency, and energy. Along with the electrical test stand, LLNL has extensive chemical analysis facilities that enable us to perform gas chromatographic and gas chromatographic-mass spectrometric analysis of various fluids to identify and quantify the breakdown products formed under various scenarios of electrical energy deposition

Compounds produced by motor burnouts of refrigeration systems

The phase-out of chlorofluorocarbons has necessitated the introduction of alternate refrigerants. R22 (CF{sub 2}ClH), R134a (CF{sub 3}CH{sub 2}F), and R507 (50/50 CHF{sub 2}CF{sub 3}/CF{sub 3}CH{sub 3}) are newer fluids which are used in cooling systems. Recently, concern over the possible formation of toxic compounds during electrical arcing through these fluids has prompted us to identify their electrical breakdown products by electron ionization GC/MS. For example, it is known that perfluoroisobutylene (PFIB), which have an threshold limit value of 10 ppb (set by the American Conference of Government Industrial Hygienists), is produced from the thermal and electrical breakdown of some refrigerants. We have used specially designed test cells, equipped with electrodes, to simulate the electrical breakdown of R22, R134a, and R507 in refrigeration systems

Development of continuous glass melting for production of Nd-doped phosphate glasses for the NIF and LMJ laser system

The NIF and LMJ laser systems require about 3380 and 4752 Nd-doped laser glass slabs, respectively. Continuous laser glass melting and forming will be used for the first time to manufacture these slabs. Two vendors have been chosen to produce the glass: Hoya Corporation and Schott Glass Technologies. The laser glass melting systems that each of these two vendors have designed, built and tested are arguably the most advanced in the world. Production of the laser glass will begin on a pilot scale in the fall of 1999