A mirror has been fabricated with the shape of an off-axis section of a paraboloid by grinding and polishing a sphere into a prestressed blank. The applied stresses were then removed allowing the mirror to spring into the desired paraboloidal shape. The 36-cm diam off-axis section deviated 9.9-microm rms from the polished sphere. The final surface deviated 0.03-microm rms from the desired off-axis section.
A gas-phase time-of-flight (TOF) photoelectron spectrometer has been developed for use with synchrotron radiation. The excellent time structure of the synchrotron radiation at the Stanford Positron Electron Accelerator Ring (SPEAR) has been used as the time base for the TOF measurements. The TOF analyzer employs two multichannel plates (MCPs) in tandem as a fast electron multiplier with a matched 50-Omega anode to form an electron detector with a timing resolution of =70 ps. The spectrometer is presently capable of analyzing electrons over a wide energy range (1-50 eV) at medium energy resolution (=5%) and high angular resolution (+/-3 degrees ).
Several techniques' are discussed for velocity and energy spectrometry of relativistic heavy ions with good resolution. A foil telescope * This work was performed under the auspices of the United States Energy Research and Development Administration.
The Primary Mirror of the Keck Observatory Telescope is made up of an array of 36 hexagonal mirror segments underactive control. The measurement of the relative orientations of the mirror segments is fundamental to their control. The mechanical and electronic design of the sensors used to measure these relative positions is described along with the performance of the sensors under a variety of tests. In use, the sensors will measure relative positions with a resolution of a few nanometers. This resolution and the low noise, drift and thermal sensitivity of the sensors are adequate to stabilize the primary mirror figure to the precision required for optical and infrared astronomy.
A time-zero detector has been developed for use in reaction product mass identification which has as its novel feature a 180 0 isochronous transport of secon~ary electrons in a magnetic field. The secondary electrons produced when. particle's pass through a thin carbon foil are accelerated to approximately two keV by a parallel-wire harp of 99% transmission. The accelerated electrons are then transported 180 0 in a uniform magnetic field of 80 gauss containing a collimator placed at the 90 0 position. A background suppression grid is placed just in front of the electron detector which is comprised of two microchannel plates in series acting as an electron multiplier. The device allows placement of the thin foil perpendicular to the fragment flight path and permits shielding of the electron detector from the beam and reaction products while using only modest accelerating voltages. The time-of-flight resolutions measured between this timing detector and a 120 ~m silicon detector when using 104 MeV 160 ions and 8.78 MeV alpha particles were 90 and 150 psec, respectively (full widths at half maxima).
The next generation of large telescopes currently in the planning stage will be exposed to higher in 1o33inq 1ue to the cost cutting reduction of dome size in relation to aperture. Thin actively figured mirrors and tighter oointinq requirements increase their susceptibility to the general wind Loafing including higher frequency components. The figure control and oointinq servo loons will require wider baniwigth anu1 'higher gain to maintain good optical performance. To design these servo loops requires knoyle g=_ of the yinl ooyer spectra to assess Loop stability and correction performance. 7ind data vas collected from several iifferent observing sites. The measurements yere made with a Pitot tube anemometer mounted on a tower at the leading edge of a site and four differential pressure sensors mounted across the mirror plane.Anemometer measurements were made at two different elevations to provide site wind vs. elevation extrapolation lata. lundrel second measurements, with the data sampled at 53 flz, were pale. Fourier Transforms of the data cover a frequency range of 1.32 to 25 `iz.
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