The processing electronics system for the pointed mode operation ofIXAE on the Indian satellite IRS-P3

Indian Remote Sensing Satellite-P3 (IRS-P3: 1996-017A) was launched into a near-Earth, polar, Sun-synchronous orbit by India's Polar Satellite Launch Vehicle (PSLV-D3) on March 21, 1996. The Indian X-ray Astronomy Experiment (IXAE) is one of the prime payloads onboard IRS-P3. IXAE has two sets of detectors: three pointed-mode proportional counters (PPCs) and one X-ray Sky Monitor (XSM). IRS-P3 is configured to operate in two modes, namely, Earth-pointing mode and stellar-pointing mode. In Earth-pointing mode the remote sensing payloads are in operation; in addition, XSM maps the sky for bright X-ray sources and X-ray transients. In stellar mode, the PPCs observe several Galactic, bright X-ray, and extragalactic sources. The microprocessor-based processing electronics system was designed and developed for PPC data-handling and telemetering the stored data to the ground station. The system has been working well from the day the IXAE was commissioned. The processing electronics system for the PPCs, its interfaces, and the in-orbit instrument performance are described. Some results of the pointed mode observations are also presented     

Very low output-impedance RF system for a proton synchrotron withlow drive power requirements

In order to solve a power consumption problem of the driver stage in the cathode-follower RF system, a grid-cathode driving scheme is investigated by means of an isolation transformer. A very low output impedance can be realized together with a voltage gain a few tens of times higher than that of a cathode-follower. The model system has been tested under frequency modulation in the 1-3-MHz range at 40-Hz repetition; the output impedance is less than 30 Ω and the driver voltage 62 V to produce a 1.2-kV peak at the cavity gap     

Single-event effects in resolver-to-digital converters

Single-event effects (SEEs) in two resolver-to-digital converters (RDCs) have been studied using heavy ions and pulsed laser light. The important role of the pulsed laser in establishing single-event upset (SEU) and single-event latchup (SEL) levels prior to accelerator testing is described, as is its role in evaluating the test software and hardware and in gaining a better understanding of the origins of the SEEs. Results from pulsed-laser testing are in quantitative agreement with those from heavy-ion testing: the RDC-19220 is sensitive to both SEUs and SELs whereas the AD2S80 is less sensitive to SEUs and immune to SEL     

Boundary element alternating method applied to analyze the stress concentration problems of multiple elliptical holes in an infinite domain

This paper presents an efficient boundary element alternating method for analyzing the interactions among multiple elliptical holes in a two dimensional infinite domain under remote uniform stresses. Instead of the analytical solution used in the conventional alternating method, the stress distribution in an infinite domain with a single elliptical hole subjected to the arbitrary tractions across the boundary is solved by the boundary element method. Then this solution correlates with a successive iterative superposition process capable of satisfying the prescribed boundary for each elliptical holes of the problem. Both the effects of various sizes of holes and ligaments among ellipses on the stress concentration are studied in detail. In addition, the computed results and the available referenced solutions closely corresponds to each other indicate the method’s accuracy and efficiency.     

Experimental study of the effect of non-circular flow geometry on the critical heat flux

An experimental study of the effect of flow geometry (circular, rectangular, triangular, and dumb-bell shaped) on the critical heat flux (CHF) was performed using R-134a as a coolant. The CHF is affected by the following geometric parameters: hydraulic-equivalent diameter, heated length, gap size, channel shape, and curvature. It may also be affected by the thermal conductivity of the wall material and wall thickness. The effect of flow geometry on CHF is influenced by flow parameters. The effect of these parameters on CHF was examined, and recommendations for predicting the CHF in non-circular geometries have been made.