Showing papers by "Varian Associates published in 1965"

Hydrogen-Maser Principles and Techniques

Abstract: Hydrogen maser construction and operation design principles emphasizing microwave cavity, low magnetic field, hydrogen storage and maser tuning techniques

Short-Term Stability of Passive Atomic Frequency Standards

Abstract: The instability of passive atomic frequency standards caused by shot noise introduced by the atomic reference is calculated. This instability can be characterized by a figure of merit for the atomic reference, and the asymptotic functions for the rms frequency fluctuation for long and short averaging times expressed in terms of this quantity. Measurements of the rms frequency fluctuation of cesium atomic beam and rubidium vapor frequency standards are compared with theory, and the predicted performances of various existing and proposed atomic standards are tabulated. It is feasible to build atomic beam frequency standards whose stability for averaging times less than one second is limited by noise in the crystal oscillator rather than by shot noise, a criterion generally met by rubidium vapor frequency standards. For long averaging times, shot noise will always be the fundamental limiting factor in atomic frequency standard stability.

Means for avoiding locking in ring lasers

Abstract: Means are disclosed for frequency modulating opposing modes in a ring laser assembly whereby locking is minimized or eliminated. The use of three types of modulators comprising an acoustic generator, a light shutter and an electro-optic crystal are described. In each case, the modulators are driven in accordance with a time-varying signal provided by a signal generator.

A Positron Linear Accelerator Design

Abstract: A 450 Mev electron 350 Mev positron linear accelerator system is described which has been designed as an injector for a storage ring. Several positron containment systems are considered and a stepped solenoidal magnetic field is chosen as optimum with the converter immersed in the high magnetic field. The parameters of this system are derived for maximum positron beam within specified energy spread and emittance. Performance is reported for initial operation at 40 Mev positron energy.

Nuclear Quadrupole Resonance Thermometry

Abstract: The technique of Nuclear Quadrupole Resonance thermometry is described. It is shown that the N.Q.R. thermometer exhibits unique properties of sensitivity, range, and reproducibility that are all desirable qualities for a temperature standard. The response to temperature is a unique characteristic of the working substance, which in this case is KClO3. Experimentally, the center frequency of the absorption line of Cl35 in pure samples of KClO3 at 77 °K is reproducible to approximately 2 Hz. This corresponds to an absolute accuracy of better than ± 0.001 °K. The purity of the samples is achieved by recrystallization of commercial reagents. The range of the thermometer extends from 10 °K to approximately 450 °K. A description of a simple system which locks an oscillator to the N.Q.R. absorption line is given. A new method of determining accurately the frequency of the center of the line using magnetic field broadening is also described. With this technique a sensitivity of ± 0.0002 °K is expected. In line with these results, evaluation of a thermometer based on the temperature dependence of the nuclear magnetic resonance frequency in antiferromagnetic salts is made.

Injector and Waveguide Design Parameters for a High Energy Electron-Positron Linear Accelerator

Abstract: This paper discusses the electron beam optics design of a six klystron, twelve section, 450 Mev electron 350 Mev positron linear accelerator which has been designed as an injector for a storage ring. The beam centerline comprises three zones; namely, the injection system, the high current waveguide sections and the high energy gain sections. The injection system is arranged such that the beam from a pulsed diode source is chopped and prebunched at 2856 Mc to provide well defined tightly focussed short bunches of electrons for injection into the first accelerator section. A nanosecond inflection system, located between the chopper and prebuncher cavities, provides variable short pulse capability as well as 9.5 Mc modulation of the beam to produce a train of short pulses during each gun pulse. The first four waveguide sections are designed for an unloaded beam energy of 107.5 Mev, and 500 ma peak current at 60 Mev with 10 MW peak r-f power at each input coupler. A positron converter is located at the end of these sections and immediately prior to the high energy gain portion of the machine which comprises eight waveguides each of which is 504 cm in length and designed for an unloaded beam energy of 45.4 Mev with 10 MW peak r-f input power. Details of the microwave design parameters and some electron beam characteristics are presented together with preliminary measurements of actual beam performance.

High Current Traveling Wave Electron Linear Accelerators

Abstract: The steady state and stored energy operational regimes of microwave electron linear accelerators are discussed with reference to high current capability. Avoidance of the beam blow-up pulse shortening phenomenon enables long pulse beam currents considerably greater than the maximum conversion efficiency value to be demonstrated. Heavy beam loading effects and choice of frequency are discussed with respect to this steady state operation, and it is shown that conversion efficiencies of greater than 90 per cent can be readily achieved. Stored energy considerations indicate that an increase in peak current of one or two orders of magnitude may be achieved for pulses of short duration with relatively conventional accelerator waveguides. Electron orbit theory including space charge effects for this transient condition is developed. Some experimental data obtained with a 10 Mev linear accelerator using a short pulse inflection system is presented. A concluding discussion deals with design criteria for stored energy operation in high power traveling waye structures and encourages further exploitation by providing higher current high potential sources capable of prebuncher or r-f chopped short pulse injection.

Fat content and liquid-to-solid ratio of chocolate by wide line nuclear magnetic resonance.

Abstract: Wide line nuclear magnetic resonance (NMR) was used for fast and accurate determination of the fat content and liquid-to-solid ratio of chocolate The transition range of solid to liquid was found to be extremely narrow The temp effect on the NMR signal is discussed and correction methods are suggested to that effect A method was developed for the separate determination of butter fat and cocoa fat in addition to the total fat content determination in milk chocolate