Alfred Kahan
Hanscom Air Force Base
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Featured researches published by Alfred Kahan.
Journal of Applied Physics | 1985
Herbert G. Lipson; Alfred Kahan
As‐received and 60Co‐irradiated cultured quartz is characterized using low‐temperature near‐infrared Fourier spectroscopy, and peaks associated with as‐grown hydroxide (OH) and aluminum hydroxide (Al‐OH) point‐defect centers are measured. Defect‐center distributions are determined from scanning small crystal regions parallel or normal to the crystal‐growth axis. Large variations in point defects are observed arising from variations in substitutional and interstitial impurity concentrations along the crystal‐growth axis. For the initial radiation doses as‐grown OH decreases uniformly across the crystal and forms Al‐OH, but Al‐OH peak strength varies considerably in different crystal sections. This indicates the possibility of radiation‐induced hydrogen diffusion over large distances to compensate nonuniformities in aluminum‐ion distribution. With increasing dose as‐grown OH may stabilize to a constant level in some crystal regions but deplete in other sections. For some crystals, Al‐OH continues to form ev...
IEEE Transactions on Nuclear Science | 1978
Paul Pellegrini; F. K. Euler; Alfred Kahan; Terry M. Flanagan; T. F. Wrobel
Radiation effects on 5 MHz 5th overtone AT cut Premium-Q quartz resonators are evaluated, comparing sweeping processes and resonator fabrication procedures. The resonators were irradiated at operating temperatures in oven controlled oscillator test beds with pulsed 10 MeV electrons from 200 rads up to 1 Mrad as well as with continuous 60Co gamma rays. Steady-state (permanent) and transient radiation-induced frequency changes were measured, the persistence of radiative preconditioning was investigated and the effect on drift rate was evaluated. From saturation characteristics of the steady-state frequency offset as function of total electron dose, the formation rate cross sections of several radiation-induced crystal defects have been evaluated. Formation of at least one defect is sensitive to differences in the sweeping process. In some resonators, frequency recovery after irradiation is dominated by an exponential decay mechanism with a time constant of 3.7 days. Under continuous gamma ray exposure with dose rates between 10 and 90 rad/hour, the frequency response is characterized by a steep initial rise followed by different patterns of saturation and recovery.
IEEE Transactions on Nuclear Science | 1984
Herbert G. Lipson; Alfred Kahan
Quartz electrodiffused (swept) in an air or vacuum atmosphere, or irradiated with 60Co, is characterized using low temperature infrared Fourier spectroscopy, and peaks associated with as-grown hydroxide and aluminum hydroxide point defect centers are measured. The distribution of hydroxide related defect centers along the z-growth or sweeping axis for high quality quartz is determined from scanning small crystal regions normal to the axis.
annual symposium on frequency control | 1982
F. K. Euler; Herbert G. Lipson; Alfred Kahan; Alton F. Armington
Abstract : We report acoustic loss measurements from room temperature to above 500 degrees of C on resonator disks fabricated from high-grade as-grown and swept synthetic quartz, containing both Li(+) and Na(+) alkali impurities. As-grown quartz disks showed an exponential rise of acoustic loss 1/Q with temperature T, starting above 200 degrees of C. Swept samples show the onset of a rise above 400 degrees of C and show high-temperature losses which increase irreversibly with time and are tentatively attributed to the presence of residual alkali. Loss peaks above 300 degrees of C were found in the swept disks. Some of these disappear after exposure to temperatures above 400 degrees of C.
ieee frequency control symposium | 1981
Herbert G. Lipson; Alfred Kahan; Richard N. Brown; F. K. Euler
Summary We report the results of electrical resistance at series resonance as a measure of acoustic loss between 150 and 350 OC for resonators fabricated from high grade synthetic and electrolyzed (swept) quartz. An exponential increase of resonator resistance with temperature is observed for all asgrown quartz. This increase is attributed to either lithium or sodium impurity migration. The swept companions of these materials do not show the exponential rise and no essential difference is found between air and vacuum swept material. Strong A1-OH- related bands are observed by infrared spectroscopy in both air and vacuum swept samples. From short-term vacuum sweeping experiments we find that a reduction in as-grown OH--band strengths occurs almost immediately after the onset of sweeping, but the A1-OH- bands do not form until after a few hours of sweeping time. In air swept samples, with hydrogen supplied by the water vapor in the atmosphere, A1-OH- bands appear almost immediately and as-grown OH--bands remain essentially unchanged.
annual symposium on frequency control | 1982
Alfred Kahan
Abstract : The turnover temperatures, Tto, of quartz plates vibrating in the thickness mode are calculated for doubly rotated orientations in the temperature range of -200 to +200 degrees C. In addition to the standard cuts of interest situated along the loci of zero values of the first order temperature coefficients of frequency, we find another family of doubly rotated quartz orientations, vibrating in c-mode resonance, with Tto values 70 degrees C and above. The significance of these orientations are that for the same Tto they are considerably less sensitive to crystallography orientation than currently utilized singly or doubly rotated cuts. For Tto = 90 degrees C, the static frequency as a function of temperature coefficients of these orientations are between the AT-cut and BT-cuts, and they become less sensitive to temperature with increasing Tto.
Journal of Crystal Growth | 1968
Herbert G. Lipson; Alfred Kahan; Joseph A. Adamski; E. Farrell; M.J. Redman; J. Kawamura
Abstract This paper presents the results of the characterization, by optical spectroscopic, chemical, and X-ray methods, of flame fusion grown magnesium aluminate spinels containing variable amounts of excess alumina and chromium doping. The emphasis of this study is to establish non-destructive physical measurement methods to indicate the quality, internal structural changes, and the stoichiometric composition of the crystals.
Journal of Applied Physics | 1985
Alfred Kahan; F. K. Euler
We calculated the turnover temperatures Tto of crystallographically doubly rotated quartz plates vibrating in the thickness mode. In addition to the known cuts situated along the loci of zero value of the first‐order temperature coefficient of frequency, there is another family of orientations, with Tto≥75 °C, which, compared to other singly or doubly rotated cuts, are relatively insensitive to crystallographic orientations. We designate these orientations as the AK cut. We report experimental static frequency as a function of temperature characteristics f(T) for 14 AK‐cut orientations, with angular combinations 30°≤φ≤46.1° and 21° ≤θ≤28.44°. Tto values are between 80 and 150 °C, in good agreement with computations. The f(T) curves have been fitted with third‐order polynomials. Compared to the fundamental mode of vibrations, the 3rd overtone shows a larger number of modes, and resonance amplitudes are weaker. The frequencies of the harmonic and anharmonic modes are in fairly good agreement with calculatio...
Physical Review | 1964
Herbert G. Lipson; Alfred Kahan
annual symposium on frequency control | 1987
Alfred Kahan; F. K. Euler; Herbert G. Lipson; C.Y. Chen; L.E. Halliburton