INSTRUMENTATION by Ralph H. Müller
Semiconductors enter new fields
Will Rogers, "all we L IKEknowtheislate what we read in the papers" and much of it is discouraging. One gains the impression that scientific progress in our country is now assured because we have found competent coordinators to coordinate the efforts of the coordinators. We expect to see some fascinating new developments in navigational electronics because some new aids of this nature will be required to land all these good people safely at the National Airport in Washington. One of our news weeklies has even considered the possibility of an invasion from Mars and has duly proposed a superboard of the world's statesmen (complete with photographs) who would cope with the impending disaster. Of course everyone knows what a Martian looks like. He has spindly legs., an enormous chest, an impressive head which is bald as a consequence of excruciating thinking. Beyond doubt he is bent on destruction, and to that end he carries a pencil-size Q-ray annihilator. It is barely possible that he might have no homicidal intent at all, and since he might be in paroxysms of laughter at what he saw, could easily be overpowered. With all such sinister doubts removed we could heave a sigh of relief and get back to our own terrestial brawls. Our Martian might even wear a Chesterfield coat and a Homburg. Even the chest expansions might be missing, having by physiological adaptation or some interplanetary Yogi, learned to eschew oxgen and consume helium or methane instead. If he showed any interest in the local fauna, the chances are he would avoid the Supreme Council of Statesmen and \vould want to talk to our poets, musicians, artists, and a few impractical working scientists. He might be lucky enough to find a philosopher, with
whom he could agree that after knowledge comes wisdom. Over the years we have become inured to the expression so frequently heard in the higher echelons of management "—a good bench man, but—." As a small and trivial contribution to the current overhauling of American science and technology we wish to foster a movement having the slogan—"Bigger and Better Benches." The cooperation of laboratory furniture manufacturers would be useful in this venture. In our former days as a university professor we made some primitive improvements in this direction. Our office was large in proportion to the private research space and it was not long before more instruments and equipment found their way into the office. By suitably anchoring the desk to the floor it was possible to propel one's swivel chair to one of several laboratory tables to make measurements. Suitable launching pads on the tables assured a smooth return trip to the desk, where data could be plotted and evaluated. An unexpected and valuable feature of this system turned up on at least one occasion in which "take-off" ripped a phone cord and the disrupted communication resulted in our missing several committee meetings and conferences. An alert and stern administration soon corrected the fault. The Mark VII version of this chair could well be servo-controlled for specific destinations. A digital revolution counter on the wheels could furnish incontestable evidence in support of extravagant claims of accomplishment in monthly progress reports. Semiconductor Developments
From a few diligent bench men come some recent interesting electronic de-
velopments. The current issue of Electronics contains several useful and provocative articles. A brief, one-page summary by associate editor R. K. Jurgen lists several Hall effect devices [Electronics 32, No. 3, 63 (1959)]. WThen a strip of metal is placed with its plane perpendicular to a magnetic field and an electric current flows longitudinally through the strip, a potential difference is developed between its two opposite edges. This Hall effect becomes more pronounced with semiconductor materials. The author shows that with commercially available materials, this effect can be used as a gyrator and isolator, a product modulator and demodulator, a negative resistance amplifier, a circulator, switch, magneticfield-variation meter, electrical compass, digital-to-analog encoder, magnetic field meter or transducer, and an ammeter or wattmeter. Ferroelectric materials such as barium-strontium titanate permit the electric tuning of oscillators. Thus a ferroelectric capacitator can be changed in capacitance by the application of a d.c. bias voltage. Numerous applications are described by T. W. Butler, Jr. (Ibid., p. 52). To be sure, electric tuning can be accomplished with vacuum tubes. If, for example, a pentode is included in the tank circuit of an oscillator, its reactance will be a function of the grid-cathode potential. The real advance resides in the fact that these solid-state devices can exercise many functions which formerly required much bulky circuitry. Although many analysts and all infrared specialists are acquainted with the optical properties of infrared-transmitting substances, the increasing role of infrared in surveillance, air-borne interception, and missiles has given rise to many unusual developments of such materials. H. F. Hoesterey (Ibid., p. 56) has tabulated the properties of all known materials of this sort which are suitable as windows, domes, and lenses. There are useful comments on the limitations and applications of each mateVOL. 3 1 , NO. 3, MARCH 1959 ·
63 A
INSTRUMENTATION
Now with
ONE instrument
• Measure C14 and H 3 activity to 10
12
Curies
• Measure electrical properties: detect 10-1Y amps; 2 0 microvolts; • and make a variety of other precise measurements Besides being the most accurate, convenient and inexpensive instrument for determining C 14 and H 3 , the CARY Model 31 maybe used to perform a variety of other tasks in the laboratory. FOR E X A M P L E , T h e 3 1 may be used a s :
A sensitive detector for beta and gamma radiation. May often serve as a substitute for geiger or proportional counters. 1 A spectrometer for measuring alpha energy in the presence of substantial beta and gamma emissions. ' A monitor for gamma background, surface alpha contamination, or air contamination. ' A DC amplifier for semi-conductor studies, pH measurement (detects changes to .0005 pH ), insulation leakage measurements, determination of grid currents on vacuum tubes and many other measurements of electrical properties. So, if you are considering instrumentation to perform these tasks, investigate the CARY Model 31. Its versatility, reliability, speed and compactness will save time, money and bench space.
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ANALYTICAL CHEMISTRY
rial. It was startling to us to learn that germanium has a useful transmission range greater than 15 microns and can be fashioned into windows 6 inches in diameter and 4 inches thick! Equally interesting is the statement that arsenic trisulfide is practical to 12 microns and there is no practical limit to the size of the element which can be fabricated. The impact of transistor circuitry has been felt in every branch of instrumentation. It might be said that its initial triumphs were in the realm of miniaturization, but this is no longer the sole function of these solid-state devices. In nuclear science and technology, these devices find increasing application, and for two reasons. First, the simplified circuitry finds numerous uses in counting and monitoring arrangements which formerly required 8foot-high chassis. Second, there are properties of these devices which are profoundly influenced by the various forms of radiation. In connection with the latter, one notes that a recent development by Westinghouse provides a tiny neutron detector which is largely insensitive to y-rays. The detector consists of a tiny slice of silicon or germanium with a sensitive junction near the top surface of the slab. On the top of this diode, a layer of uranium-235 is deposited. If slow neutrons strike it, the fission of TJ233 occurs. The fission fragments induce large pulses in the junction, which are easily detected and counted. It becomes increasingly pleasant to view the rapid progress of science, even if it is increasingly dominated by the organizers and the hucksters. The progress is so prodigious that the handling of an abstract journal requires physical prowess, and for assimilation, the resources of an IBM-704. Despite the phrenetic pace, we like to think of the thoughtful deliberation of the Swedish Academy of Sciences when it honored the fine contributions of Cerenkov, Frank, and Tamm even while the literary contributions of Pasternak gave rise to the expected wrath of Moscow. Just as all physicists appreciate the first honor, in the latter, they understood the other phenomena—a simple matter of signal to noise ratio. We suspect that the spirit of the times has little room for self-inspection and the quiet contemplation of nature. We are no longer in search of the moon—we have passed it and a manmade bacterium has become part of our solar system. If the mountain has labored and brought forth a mouse, one may ask to what degree have we lost our souls and beggared our intellects?
