Showing papers by "Varian Associates published in 1967"

PERT and the beta distribution

Abstract: After reviewing the beta distribution and its properties, a simple technique is described for obtaining exact solutions to the cubic equation which results from the PERT constraint on standard deviation. These solutions are then used, together with the expression for the mode of the beta distribution, to determine graphically the specific values of the parameters of a beta distribution which may be associated with any particular set of PERT estimates. Expressions are derived for approximate values of these parameters in terms of the PERT estimates explicitly, and a comparison is made of the exact and approximate values. The PERT approximation concerning expected time is examined and confirmed to be an excellent simple approximation for the exact value of the associated beta distribution. It is concluded that the beta distributions associated with PERT are not necessarily as restricted, and the differences between the PERT values of expected time and standard deviation and the exact values for the associated beta distribution are not as great, as has previously been indicated in the literature.

Gyromagnetic apparatus employing computer means for correcting its operating parameters

Abstract: A gyromagnetic resonance spectrometer is disclosed which employs a computer for correcting its operating parameters. The gyromagnetic resonance spectrometer includes means for exciting and detecting gyromagnetic resonance of a sample of matter to be investigated in a polarizing magnetic field. The output spectral data from the spectrometer are fed to a computer. The computer includes a memory and a logic unit programmed to process the data stored in the memory according to a pre-determined program. The computer includes programs for causing certain resonance determinative operating parameters of the spectrometer to be varied in certain ways to cause the output spectral data of the spectrometer to vary accordingly. The spectral data are stored in the memory of the computer and the computer processes the stored data to derive certain corrective outputs which are fed from the computer to the spectrometer for correcting the operating resonance determinative parameters of the spectrometer to yield corrected resonance spectral data. The computer may be programmed to correct any one or more of the following operating parameters of the spectrometer: field strength and homogeneity of the polarizing magnetic field, phase and/or frequency of radio frequency resonance exciting field, intensity of the radio frequency resonance exciting field, rate at which the gyromagnetic ratio is swept in the spectrometer to obtain output spectral data, time constants of filter circuits employed in the receiver of the spectrometer, frequencies and intensities of radio frequency energy applied to the sample in performing certain double resonance analysis, sample spinning rate for averaging gradients of the polarizing field, and intensity of the polarizing magnetic field. The computer may use any one of a number of different methods for deriving the corrective outputs for correcting the operating parameters of the spectrometer.

Surface barrier diode having a hypersensitive {72 {30 {0 region forming a hypersensitive voltage variable capacitor

Abstract: A method of making a surface barrier diode, also known as a Schottky diode, having a hypersensitive voltage variable capacitance, is disclosed. The surface barrier diode structure comprises a silicon wafer of n conductivity having an n-type epitaxial layer which is oxidized on its outer surface to form a silicon oxide layer overlaying the epitaxial n-region of the wafer. The silicon oxide coating is relatively thin, as of less than 5000 A, and is formed relatively quickly, i.e., in less than 20 minutes at a temperature within the range of 1150* to 1250* C in order to produce a hypersensitive n impurity accumulation layer immediately adjacent to and underlying the oxide coating. A hole is then opened through the silicon oxide layer and a metal electrode, as of chromium, is deposited directly upon the hypersensitive n region to form the rectifying junction of the diode. The surface barrier diode (Schottky diode) exhibits a hypersensitive voltage variable capacitance effect where ''''hypersensitive voltage variable capacitance'''' means that the capacitance is approximately inversely proportional to the first power of the applied voltage as contrasted with normal voltage variable capacitance effects in PN junction devices wherein the capacitance is approximately inversely proportional to the 1/2 or 1/3 power of the applied voltage.

Bimodal cavity resonator and microwave spectrometers using same

Abstract: A CENTRAL PORTION OF THE CAVITY IS CAPABLE OF SUPPORTING TWO RESONANT MODES WHILE ADJOINING EACH SECTIONS EACH SUPPORT ONLY ONE OF THE MODES. WAVEGUIDES CONNECTED TO EACH OF THE END SECTIONS COUPLE MICROWAVE ENERGY TO THE CAVITY TO EXCITE THE TWO MODES THEREIN. A SAMPLE OF MATTER IS INSERTED INTO THE CENTRAL PORTION SO AS TO BE IRRADIATED BY BOTH MODES. A TUNING SCREW IN EACH OF THE END SECTIONS PERMITS INDEPENDENTLY TUNING THE CAVITY TO THE RESONDANT FREQUENCY OF ONE OF THE RESONANT MODES. ADJUSTING SCREWS IN THE CENTRAL PORTION OF THE CAVITY STRUCTURE PERMIT ADJUSTMENT OF THE CROSS COUPLING BETWEEN THE TWO MODES. THE MICROWAVE SPECTROMETER DESIGNS TAKE ADVANTAGE OF THE ABILITY OF THE CAVITY TO BE INDEPENDENTLY TUNED TO THE RESONANT FREQUENCIES OF EITHER MODE. THE SEVERAL DESIGNS PROVIDE FOR AMPLITUDE MODULATION OF THE FREQUENCY OF THE PUMPING MODE OR SCANNING OF THE FREQUENCY OF THE PUMPING MODE OR MODULATION OF AN APPLIED UNIDIRECTIONAL MAGNETIC FIELD EITHER WITH OR WITHOUT MODULLATION OF THE FREQUENCY OF THE PUMPING MODE.

Ionization detector for gas chromatography

Abstract: AN IONIZATION DETECTOR IN WHICH THE COLLECTING ELECTRODE IS PLACED BETWEEN CHARGED BARRIER ELECTRODES. THE BARRIER ELECTRODES SET UP A POTENTIAL BARRIER AROUND THE COLLECTOR ELECTRODE. CHARGED PARTICLES HAVING ENERGIES HIGH ENOUGH TO SURMOUNT THE POTENTIAL BARRIER FALL INTO THE POTENTIAL WELL BETWEEN THE BARRIER ELECTRODES AND ARE EFFICIENTLY COLLECTED BY THE COLLECTOR ELECTRODE. THE BIAS VOLTAGE ON THE BARRIER ELECTRODES CAN BE ADJUSTED SO THAT ONLY CHARGED PARTICLES OF A DESIRED ENERGY WILL BE COLLECTED. THE DETECTOR CAN BE MADE TO RESPOND SELECTIVELY TO ONLY A DESIRED CLASS OF COMPOUNDS IN THE CHROMATOGRAPHIC COLUMN EFFLUENT BY SUITABLE ADJUSTMENT OF THE BIAS VOLTAGE ON THE BARRIER ELECTRODES.

Magnetically confined electrical discharge getter ion vacuum pump having a cathode projection extending into the anode cell

Abstract: 1,191,223. Ion pumps. VARIAN ASSOCIATES. 20 Aug., 1968 [23 Aug., 1967], No. 39741/68. Heading H1D. In a getter ion pump comprising an anode structure 4 having at least one discharge passageway traversed by a magnetic field B and insulated by a structure 13 from a cathode structure 5, a projection 6 of getter material extending from the cathode 5 into the passageway terminates substantially less than halfway along said passageway, thus forming a magnetron discharge zone 16 and a Penning discharge zone 18. Material sputtered from the projections 6 forms annular deposits 19 on the cathodes 5, thus improving the pumping of noble gases. The insulator 13, e.g. of alumina ceramic, is protected by an annular sputter shield 15 mounted on the anode support rod 9. The cathode plates 5 may be of Ti and the projections 6 of Zr, Mo or Ta to give increased sputtering. The projections 6 may be conical (Fig. 2, not shown), and a single projection extending into one end of the passageway may be used. A plurality of projections may be formed by folding a serrated metal sheet which is associated with a multi-cellular anode (Figs. 4 or 5, not shown). The projections 6 may be integral with the cathode plate 5 or may be insulated therefrom (Fig. 6, not shown) to enable the projections to be held at a lower potential than the cathode, thus providing a triode arrangement with reduced re-sputtering of the deposits 19.

The relative merits of atomic frequency standards

Abstract: The relative merits of atomic frequency standards based upon resonances in hydrogen, rubidium, or cesium depend upon the particular application and the specific requirement for each of several performance factors combined with physical characteristics. While the properties of an ideal atomic frequency standard may be established, practical instruments depart from the ideal as the result of compromises in the apparatus design and construction. The resonance line sharpness is an important factor which is dependent upon the apparatus; however, others my have a greater influence upon the essential characteristics. These include instrumental offsets due to atomic collisions with neighboring atoms or walls and magnetic fields. The intensity of the resonance signal is also essential in the determination of merit. These factors are discussed in relationship to hydrogen maser rubidium gas cell and cesium beam atomic frequency standards and the merits of each are compared. The possible merits of frequency standards based upon thallium beams are also discussed; however, a lack of extensive operating experience limits the knowledge in this case.