A worldwide survey of precipitating low‐energy protons was made during a magnetically quiet 2½‐day period in November 1965. Several of the particle detectors aboard a low‐altitude, polar‐orbiting satellite measured protons above thresholds of approximately 10, 21, 38, and 56 kev. Data were obtained from two types of instruments: plastic scintillators on photomultipliers with foil‐determined thresholds at 10 and 57 kev; and channel multipliers with foil‐determined thresholds at 21, 38, and 56 kev. Precipitating proton fluxes were observed on traversals of both the northern and southern auroral zones. The maximum flux of precipitating protons observed was 0.3 erg/cm² sec. A preliminary analysis at the positions of the peaks resulted in spectrums that were generally consistent with an exponential number flux shape with characteristic energies that were usually in the range 10–20 kev, and in angular distributions that were consistent with isotropy over the loss cone within about a factor of 2. Evidence of two distinct zones of precipitation on the day side has been obtained. The median peak intensity near local midnight was about a factor of 5 greater than at local times near noon.
Measurements of the photoelectron spectrum at White Sands Missile Range in June 1965 are reported and compared with theory. The agreement is satisfactory and shows that a realistic treatment of photoelectrons, at least at low altitudes, is feasible with current information on atmospheric structure, solar fluxes, and cross sections. The theoretical model is also compared with measurements by Hinteregger in August 1959. Theory and experiment agree satisfactorily in this case also if one assumes a solar cycle variation of extreme ultraviolet solar radiation comparable with that observed for the 10‐cm radio flux.
Data acquisition hardware in accelerator control systems is connected by a field bus to networked computers that supply data to consoles. Industry attempts to standardize on a low level field bus have not succeeded in providing a single wellsupported bus. This paper describes a data acquisition chassis that connects to VMEbus computers using ARCNET, a full featured token-passing local area network, as the field bus. The performance qf this technique as implemented in the control system for the FermiJab Linac is given.
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