Natural Guide Star (NGS) and Laser Guide Star (LGS) Adaptive Optics (AO) have been offered for routine science
operations to the W. M. Keck Observatory community since 2000 and late 2004, respectively. The AO operations team
is now supporting ~100 nights of AO observing with four different instruments, including over fifty nights of LGS AO
per semester. In this paper we describe improvements to AO operations to handle the large number of nights and to
accommodate the recent upgrade to the wavefront sensor and wavefront controller. We report on the observing
efficiency, image quality, scientific productivity, impact analysis from satellite safety procedures and discuss the support
load required to operate AO at Keck. We conclude the paper by presenting our plans for dual LGS AO operations with
Keck I - Keck II LGS, starting in 2009.
This paper describes the recent upgrade performed on the W. M. Keck Observatory Adaptive Optics (AO) systems, in
which the wavefront sensors and wavefront controllers were replaced with components based on new technology. The
performance of the upgraded system has yielded an increase in limiting guide star magnitude, an increased Strehl ratio
for both Laser Guide Star (LGS) and Natural Guide Star (NGS) modes, and has significantly improved reliability and
maintainability compared to the original system. Moreover, the controller is scalable, allowing for future upgrades and
improvements as needed. We present an overview of the project; describe the basic architecture of the new wavefront
sensor and controller; discuss some of the unique features of the system, including the closed loop mirror positioning
system, custom wavefront sensor optics, and full-frame-rate telemetry server; and conclude with results from
engineering and science tests of the new controller on the Keck II AO system.
The purpose of this paper is to report on new adaptive optics (AO) developments at the W. M. Keck Observatory since the 2004 SPIE meeting.1 These developments include commissioning of the Keck II laser guide star (LGS) facility, development of new wavefront controllers and sensors, design of the Keck I LGS facility and studies in support of a next generation Keck AO system.
The sensitivity of an image position grid to local heat applied to the TIR surface of a prism in a Wynne Dyson design was examined. The mechanisms resulting in the shape and magnitude of the shape change are explored qualitatively and with FEA analysis. The FEA package was used to generate temperature and deformation results, which were then ported to a ray trace program and the impact on the image grid was determined. A device was made to check the validity of the models. The heat load was applied by inserting thermocouple instrumented Watlow cartridge heaters in an aluminum block, placing the aluminum block 127 microns from the TIR surface, and heating an 8mm square surface area of the block to 1.3C, 2.5C and 5.0C. These heat loads resulted in peak image errors of 68nm/C with vector error maps in an annular pattern roughly centered on the geometrical center of the heat load. The models developed were useful for qualitative predictions of the performance, but need tuning to increase the accuracy. Although linear superposition cannot be used to calculate the effect of combined local heat sources, due to the non-linear behavior of the thermal effects, the results can be used to estimate the maximum stray local heat that can be tolerated on this optical surface.
The continuos advancement of optical lithography into the regime of sub-100nm patterning capability requires the utilization of shorter exposure wavelengths such as 157nm. This in turn requires modifications in lens performance and stepper body performance. Advances in index homogeneity have made it possible to develop 157nm lens systems suitable for investigating sub-100nm lithography. Recent advances in the transmission of modified fused silica as a reticle material have made it more desirable to pursue 157nm lithography tools. MicroSteppers are a necessary vehicle to obtain photoresist and process information pertaining to the efficacy of this technology for production at the 100nm and 70nm device nodes.
There are four major imaging issues when using a flat panel display (FPD) stepper: stitching, overlay, CD control, and the variation in CDs across stitching boundaries (CD stitching or CD continuity). Simulations have been performed in an effort to analyze the performance of FPD steppers, and a comparison is made between the performance criteria of FPD steppers and IC steppers.