Andrew Buffington

Real-Time Correction of Atmospherically Degraded Telescope Images Through Image Sharpening

We present a new technique for the correction of atmospheric distortion in telescope images. Most of this distortion arises from a random phase variation of the incoming light across the telescope aperture. This variation limits the resolving power of even large telescopes to about one arc second. If the sharpness of the images is defined in a suitable way, this sharpness is maximized only when the phase distortion of the incoming light is zero. We present computer simulations of a simple feedback system in which active optical elements, set to maximize the sharpness, correct most of the atmospheric distortion. Photon statistics set the limiting magnitude of the object for which a practical feedback system can work. Details in a sixth magnitude object smaller than 0.1 sec of arc should be resolvable. The system can be conveniently employed within existing telescopes.

A Measurement of the Cosmic-Ray Antiproton Flux and a Search for Antihelium

A balloon-borne instrument has measured the cosmic-ray antiproton flux between 130 and 320 MeV and searched for antihelium between 130 and 370 MeV per nuclear. These particles were selected from the background of normal-matter cosmic rays by combining a selective trigger with a detailed spark chamber visualization of each recorded event. Antiprotons are identified by their characteristic annihilation radiation. Residue from background processes meeting the selection criteria is small. The observed 14 antiprotons yield a measured differential flux of 1.7±0.5X 10^(-4) antiprotons m^(-2) sr(-1) s^(-1)i Mev^(-1) at the top of the atmosphere. The corresponding antiproton/pro-ton ratio is 2.2±0.6X10^(-4), only slightly smaller than the ratio observed by other experiments at higher energies. Thus the antiprotons have a spectral shape similar to the protons, at least down to about 100 MeV. The expected flux of these particles can be calculated under the assumption that they were created by collisions of high-energy cosmic rays with the interstellar gas. Calculations using the standard leaky box model for propagation in the Galaxy predict a flux two orders of magnitude smaller than that observed. A small low-energy flux is predicted due to a kinematic suppression of the production of low-energy antiprotons. The discrepancy between calculations and experiment may be evidence that cosmic-ray protons have passed through substantially more than 5 g cm^(-2) of material during their lifetime. In addition, the combined results from this experiment and previous ones may be evidence for stochastic, energy-changing processes in interstellar space which act upon the secondary antiprotons after their creation. The search for cosmic-ray antihelium sets a 95% confidence level upper limit on the He /He ratio of 2.2 X 10^(-5).

Correction of atmospheric distortion with an image-sharpening telescope*

We have built and tested a 30 × 5 cm aperture telescope which used six movable mirrors to compensate for atmospherically induced phase distortion. A feedback system adjusts the mirrors in real time to maximize the intensity of light passing through a narrow slit in the image plane. We have achieved essentially diffraction-limited performance when imaging both laser and white-light objects through 250 m of turbulent atmosphere. The behavior of our telescope was accurately predicted by computer simulations. The system has yet to achieve its full potential, but has already operated successfully for objects as dim as 5th magnitude.

Measurement of Primary Cosmic-Ray Electrons and Positrons from 4 to 50 GeV

We have used a bremsstrahlung-identification technique to measure separate e

Abundances and spectra for cosmic-ray nuclei from lithium to iron for 2 to 150 GeV per nucleon

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First observatory results with an image-sharpening telescope*

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A measurement of cosmic-ray beryllium isotopes from 200 to 1500 MeV per nucleon

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Sharpening Stellar Images

spectra in the primary cosmic rays from 4 to 50 GeV. Above our average geomagnetic cutoff of 4.0 GV/c, we find fluxes of 4.4plus- or-minus0.3 e

Superconducting magnetic spectrometer for cosmic ray nuclei.

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Active image restoration with a flexible mirror

and 0.37plus-or-minus0.09 e