Irving F Stowers | University of California (original) (raw)
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Papers by Irving F Stowers
Examination of wear debris formed during the low-speed fretting of silver reveals spherically and... more Examination of wear debris formed during the low-speed fretting of silver reveals spherically and cylindrically shaped particles. A decrease in the coefficient of friction with time and a low wear coefficient may be attributed to the rolling action of this spherical debris.
We have extended our atomistic molecular dynamics modeling of precision machin ing processes to t... more We have extended our atomistic molecular dynamics modeling of precision machin ing processes to the tens-of-nanometers scale attainable in experimental studies of single-point diamond turning. Our calculated cutting forces agree remarkably well with the experimental measurements, and the simulations suggests a possible mechanism for the formation of segmented chips during high speed machining. We have also extended our modeling capabilities to three spatial dimensions. We find a rather interesting result—dislocation motion is not an efficient mechanism for accommodating strain due to point indentations on the nanometer scale in three dimensions.
Ductile grinding can dramatically reduce the cost of fabricating large optics. However, much rese... more Ductile grinding can dramatically reduce the cost of fabricating large optics. However, much research must be done to determine the transition between ductile and brittle grind ing. We have surveyed sites doing ductile grinding and have ground small glass samples at LLNL. In addition, we began to develop a number of techniques to permit the ductile grinding of glass. With continued effort, we should be able to ductile grind entire areas without incurring brittle fracture.
Over the last decade a wide variety of processes applicable to ultraprecision contouring and poli... more Over the last decade a wide variety of processes applicable to ultraprecision contouring and polishing have evolved. Examples of these processes include float polishing, elastic emission machining, erosive jet, ion milling, plasma assisted chemical etching, and precision ductile grinding. These processes are reviewed with the intent of comparing their removal rates, resultant surface roughness, demonstrated contour accuracy, and applicability to the manufacture of large optical components. The incentive for this study is the evolution of a deterministic manufacturing process able to lower the cost of fabricating large precision optical components by an order of magnitude.
The Combined Bibliography assembles in one document the 1970-1989 reports, conference proceedings... more The Combined Bibliography assembles in one document the 1970-1989 reports, conference proceedings, and publications authored by members of the Engineering Directorate - Materials Fabrication Division and the Precision Engineering Program. It was prepared from data recovered from the LLNL Library's and report database and from DOE's Energy Database using Pro-Cite.
Optical Manufacturing and Testing III, 1999
Journal of Vacuum Science and Technology, 1978
A high pressure 6.9 MPa solvent spraying technique was developed to remove small (greater than 5 ... more A high pressure 6.9 MPa solvent spraying technique was developed to remove small (greater than 5 microns) contaminant particles from large (100 sq m) surface areas. Chemically polished and etched stainless steel components are solvent sprayed to achieve cleanliness levels of less than 10 particle/sq cm greater than 5 microns diameter. The high pressure and high liquid velocity cleaning technique is able to remove 99.9 percent of the 5 microns diameter particles in 5 to 10 seconds. Special Class 100 clean room procedures and equipment were developed to verify the cleanliness of the cleaned components and to ensure their remaining clean during installation and operation. The basic technique should find wide application in any field requiring precision cleaned surfaces.
Energy Technology Review, May 1, 1981
A method is presented to protect the Nova laser system against damaging back-reflected light. A p... more A method is presented to protect the Nova laser system against damaging back-reflected light. A plasma shutter shoots a reflective plasma across the beam path in the 400 ns-interval between the passage of the main beam pulse and the return of the reflected light. Testing shows that this light is more than adequate to stop light of the intensity expected from Nova. Calculations with LASNEX (a code for simulating the interactions of laser light with plasma) indicate that a beam with an intensity of 1 TW/sq mm will burn through only 2% of the plasma thickness. Prices of the plasma shutter are compared with those of the alternative system, the Faraday rotator-polarizer isolator, and it is found that each plasma shutter will cost only 80,000asopposedto80,000 as opposed to 80,000asopposedto500,000 for each isolator.
Proceedings of the 1994 Simulation Multiconference on Grand Challenges in Computer Simulation, 1994
ABSTRACT
Mrs Bulletin, May 1, 1993
Selected elastomer dielectrics are characterized as high voltage insulators for use in pulse powe... more Selected elastomer dielectrics are characterized as high voltage insulators for use in pulse power systems. Silicone, ethylene propylene rubber and polyurethene were tested, but most of the data is for silicone. The particular power system developed uses a formed silicone insulator 76 cm in dia. and 3 mm thick as the major insulator between capacitors, railgap switches, load, and return
Description/Abstract Argus is a twin beam, 20 cm output aperture, Nd: glass laser system that has... more Description/Abstract Argus is a twin beam, 20 cm output aperture, Nd: glass laser system that has delivered 4TW to a laser fusion target. This performance is based on the concepts that multiple spatial filtering can prevent beam fill factors. Damage to optics due to self ...
Small Satellite Technologies and Applications Ii, Aug 1, 1992
MODILs (Manufacturing Operations and Development Integration Laboratory) were established to miti... more MODILs (Manufacturing Operations and Development Integration Laboratory) were established to mitigate risk and cost escalation of producing SDI systems. The Spacecraft Fabrication and Test MODIL has been established to impact spacecraft producibility and create a spacecraft industry quantity production culture. We describe the background of MODILs, objectives and scope, current organization (including cooperating government agencies), and the current thrusts of Materials and Structures. Test and Assembly, Spacecraft Integration Technology, and Precision Technologies. The current plan is to initiate selected productivity demonstration projects with industry to show benefits of the MODIL approach and prepare comprehensive plans for follow-up activities.
Journal of the IEST, 2003
Stanley C. Sommer has been with the National Ignition Facility (NIF) Project since 1993 and curre... more Stanley C. Sommer has been with the National Ignition Facility (NIF) Project since 1993 and currently is the Lawrence Livermore National Laboratory (LLNL) Clean Construction Protocol Manager and is responsible for developing and implementing the methodology for clean beampath installation in the Laser and Target Area Building (LTAB). A licensed Professional Engineer, with mechanical engineering degrees from Stanford University (MS, 1993) and University of California, Davis (BS, 1989), he is a member of the American Society of Mechanical Engineers and the Earthquake Engineering Research Institute.
Examination of wear debris formed during the low-speed fretting of silver reveals spherically and... more Examination of wear debris formed during the low-speed fretting of silver reveals spherically and cylindrically shaped particles. A decrease in the coefficient of friction with time and a low wear coefficient may be attributed to the rolling action of this spherical debris.
We have extended our atomistic molecular dynamics modeling of precision machin ing processes to t... more We have extended our atomistic molecular dynamics modeling of precision machin ing processes to the tens-of-nanometers scale attainable in experimental studies of single-point diamond turning. Our calculated cutting forces agree remarkably well with the experimental measurements, and the simulations suggests a possible mechanism for the formation of segmented chips during high speed machining. We have also extended our modeling capabilities to three spatial dimensions. We find a rather interesting result—dislocation motion is not an efficient mechanism for accommodating strain due to point indentations on the nanometer scale in three dimensions.
Ductile grinding can dramatically reduce the cost of fabricating large optics. However, much rese... more Ductile grinding can dramatically reduce the cost of fabricating large optics. However, much research must be done to determine the transition between ductile and brittle grind ing. We have surveyed sites doing ductile grinding and have ground small glass samples at LLNL. In addition, we began to develop a number of techniques to permit the ductile grinding of glass. With continued effort, we should be able to ductile grind entire areas without incurring brittle fracture.
Over the last decade a wide variety of processes applicable to ultraprecision contouring and poli... more Over the last decade a wide variety of processes applicable to ultraprecision contouring and polishing have evolved. Examples of these processes include float polishing, elastic emission machining, erosive jet, ion milling, plasma assisted chemical etching, and precision ductile grinding. These processes are reviewed with the intent of comparing their removal rates, resultant surface roughness, demonstrated contour accuracy, and applicability to the manufacture of large optical components. The incentive for this study is the evolution of a deterministic manufacturing process able to lower the cost of fabricating large precision optical components by an order of magnitude.
The Combined Bibliography assembles in one document the 1970-1989 reports, conference proceedings... more The Combined Bibliography assembles in one document the 1970-1989 reports, conference proceedings, and publications authored by members of the Engineering Directorate - Materials Fabrication Division and the Precision Engineering Program. It was prepared from data recovered from the LLNL Library's and report database and from DOE's Energy Database using Pro-Cite.
Optical Manufacturing and Testing III, 1999
Journal of Vacuum Science and Technology, 1978
A high pressure 6.9 MPa solvent spraying technique was developed to remove small (greater than 5 ... more A high pressure 6.9 MPa solvent spraying technique was developed to remove small (greater than 5 microns) contaminant particles from large (100 sq m) surface areas. Chemically polished and etched stainless steel components are solvent sprayed to achieve cleanliness levels of less than 10 particle/sq cm greater than 5 microns diameter. The high pressure and high liquid velocity cleaning technique is able to remove 99.9 percent of the 5 microns diameter particles in 5 to 10 seconds. Special Class 100 clean room procedures and equipment were developed to verify the cleanliness of the cleaned components and to ensure their remaining clean during installation and operation. The basic technique should find wide application in any field requiring precision cleaned surfaces.
Energy Technology Review, May 1, 1981
A method is presented to protect the Nova laser system against damaging back-reflected light. A p... more A method is presented to protect the Nova laser system against damaging back-reflected light. A plasma shutter shoots a reflective plasma across the beam path in the 400 ns-interval between the passage of the main beam pulse and the return of the reflected light. Testing shows that this light is more than adequate to stop light of the intensity expected from Nova. Calculations with LASNEX (a code for simulating the interactions of laser light with plasma) indicate that a beam with an intensity of 1 TW/sq mm will burn through only 2% of the plasma thickness. Prices of the plasma shutter are compared with those of the alternative system, the Faraday rotator-polarizer isolator, and it is found that each plasma shutter will cost only 80,000asopposedto80,000 as opposed to 80,000asopposedto500,000 for each isolator.
Proceedings of the 1994 Simulation Multiconference on Grand Challenges in Computer Simulation, 1994
ABSTRACT
Mrs Bulletin, May 1, 1993
Selected elastomer dielectrics are characterized as high voltage insulators for use in pulse powe... more Selected elastomer dielectrics are characterized as high voltage insulators for use in pulse power systems. Silicone, ethylene propylene rubber and polyurethene were tested, but most of the data is for silicone. The particular power system developed uses a formed silicone insulator 76 cm in dia. and 3 mm thick as the major insulator between capacitors, railgap switches, load, and return
Description/Abstract Argus is a twin beam, 20 cm output aperture, Nd: glass laser system that has... more Description/Abstract Argus is a twin beam, 20 cm output aperture, Nd: glass laser system that has delivered 4TW to a laser fusion target. This performance is based on the concepts that multiple spatial filtering can prevent beam fill factors. Damage to optics due to self ...
Small Satellite Technologies and Applications Ii, Aug 1, 1992
MODILs (Manufacturing Operations and Development Integration Laboratory) were established to miti... more MODILs (Manufacturing Operations and Development Integration Laboratory) were established to mitigate risk and cost escalation of producing SDI systems. The Spacecraft Fabrication and Test MODIL has been established to impact spacecraft producibility and create a spacecraft industry quantity production culture. We describe the background of MODILs, objectives and scope, current organization (including cooperating government agencies), and the current thrusts of Materials and Structures. Test and Assembly, Spacecraft Integration Technology, and Precision Technologies. The current plan is to initiate selected productivity demonstration projects with industry to show benefits of the MODIL approach and prepare comprehensive plans for follow-up activities.
Journal of the IEST, 2003
Stanley C. Sommer has been with the National Ignition Facility (NIF) Project since 1993 and curre... more Stanley C. Sommer has been with the National Ignition Facility (NIF) Project since 1993 and currently is the Lawrence Livermore National Laboratory (LLNL) Clean Construction Protocol Manager and is responsible for developing and implementing the methodology for clean beampath installation in the Laser and Target Area Building (LTAB). A licensed Professional Engineer, with mechanical engineering degrees from Stanford University (MS, 1993) and University of California, Davis (BS, 1989), he is a member of the American Society of Mechanical Engineers and the Earthquake Engineering Research Institute.
A nomogram is a graphical calculating device designed to allow the approximate graphical computat... more A nomogram is a graphical calculating device designed to allow the approximate graphical computation of a mathematical function. This nomogram computes the adhesive wear rate base on the Archard formula.
The performance of a clean room, defined as the steady state airborne particulate size distributi... more The performance of a clean room, defined as the steady state airborne
particulate size distribution and average rate of particle settling, may be
predicted to first order by either of two simple models. The models take into consideration 1) the average outdoor particulate concentration, 2) the
concentration of particulate matter generated within the room, 3) the
efficiency of the air filters, and 4) the flow characteristics of the room.
An explicit assumption of the amount of lateral mixing occurring within the
room must be made. By using these models it is possible to determine the
sensitivity of the airborne particulate level and the settling rate to changes
in room parameters such as the air flow rate, filter efficiency, recirculation
rate, and indoor and outdoor particulate generation rate.
A general conclusion from these models, which is applicable to all clean
rooms, is that when Federal Standard 209 - Class 10 or cleaner conditions are desired, it is necessary to utilize high efficiency filters (HEPA) in the
fresh air supply before mixing this air with room return air. It is also necessary to incorporate greater than 90% recirculation to achieve Class 10
conditions.
The Particle Cleanliness Validation System grew from a need to accurately quantify surface partic... more The Particle Cleanliness Validation System grew from a need to accurately quantify surface particle cleanliness
• The PCVS is a combination of
—a particle collection system
—a microscope based data reduction system
• Particles are collected onto membrane filter paper which is swiped over the surface for a proscribed distance
We have extended our atomistic molecular dynamics modeling of precision machin ing processes to t... more We have extended our atomistic molecular dynamics modeling of precision machin ing processes to the tens-of-nanometers scale attainable in experimental studies of single-point diamond turning. Our calculated cutting forces agree remarkably well with the experimental measurements, and the simulations suggests a possible mechanism for the formation of segmented chips during high speed machining. We have also extended our modeling capabilities to three spatial dimensions. We find a rather interesting result—dislocation motion is not an efficient mechanism for accommodating strain due to point indentations on the nanometer scale in three dimensions.
When the stadium-size, National Ignition Facility (NIF) is fully operational at the Lawrence Live... more When the stadium-size, National Ignition Facility (NIF) is fully operational at the Lawrence Livermore National Laboratory (LLNL), its 192 laser beams will deliver 1.8 megajoules (500 terawatts) of energy onto a target to create extremely high temperatures and pressures for inertial confinement fusion research. Due to the high-energy-physics requirements of the NIF optical components, the optics and their surrounding beampath as well as the supporting utility systems must be fabricated, cleaned, assembled, and commissioned for precision cleanliness. This paper will provide an overview of the NIF cleanliness requirements, the clean construction protocol (CCP) specifications for the beampath and clean utilities, and techniques for verifying the CCP specifications.
The advent of very large laser systems with thousands of optical components has necessitated an i... more The advent of very large laser systems with thousands of optical components has necessitated an investigation of methods for cleaning both coated and uncoated optical elements.
To perform adequately in laser systems, optical surfaces must be free from both films and particulate matter. Films have undesirable absorption bands and particles scatter light. Furthermore, in high power laser systems contaminants on the surface or trapped between the layers of coatings are known to lower the damage threshold. All surfaces must therefore, be clean when the optical elements are coated and installed and must remain clean for years after installation.
A general numerical method for the solution of plane elastic-plastic stress and strain fields by ... more A general numerical method for the solution of plane elastic-plastic
stress and strain fields by the superposition of edge dislocation stress
fields is presented. The method has been implemented as a program with
the restrictions of a maximum shear stress trajectory grid and the use
of Swedlow and Yang's finite element method for obtaining an elastic solution.