Closed-cycle refrigerator for masers
Reducing maser temperature from 4.5 to 3.0 degrees Kelvin increases gain from 45 to 72 decibles.
Wiebe, E. R.↗
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Two pumps reduce maser weight
Weight and cost of conventional hydrogen maser is reduced significantly by replacing large ion pump with hydrogen sorption pump and miniature ion pump for scavenging hydrogen and residual gases.
Source record↗
The superconducting cavity-stabilized maser oscillator
The possibility of integrating a superconducting cavity with a traveling wave maser is explored to obtain a frequency standard with very high spectral purity.
Higa, W. H.↗
Stimulated Raman scattering and the extreme high-velocity H2O maser features in W49
Stimulated Raman scattering of the intense 22.2-GHz water-vapor maser radiation within W49 is examined as a possible explanation of the extremely broad spectrum of W49 extending to + or - 200 km/sec apparent Doppler velocity. Under the most favorable conditions, Raman scattering from ammonia molecules is calculated to be observable. It is unlikely that the Raman process contributes appreciably in the case of W49, as it fails to predict the observed spatial and spectral distribution of the radiation.
Boyd, R. W.↗
Vacuum leadthrough for hydrogen maser
Nonmagnetic leadthroughs are used in hydrogen maser for electrical interconnection into vacuum chamber. Seal uses uranium glass to form vacuum seal to tungsten rod. Epoxy resin seals glass-coated rod to aluminum body. Connector was subjected to temperature cycling between minus 65 degrees to 150 C, six to seven times over a sixteen hour period.
Norris, D. A.↗
Hydrogen-maser frequency standard
Wall shift in frequency of proposed variable-shift maser that is caused by collisions between hydrogen atoms and container walls, could easily be determined, thereby allowing building of frequency standard with accuracy of 1 part in 10 to 14th power.
Reinhardt, V.↗
Study of Improvement of Hydrogen Maser Frequency Standard
The research work dealt primarily with reducing the atom leakage rate using as storage surfaces the FEP Teflon surfaces conventionally used in contemporary hydrogen maser frequency standards. Some work was also done on a possible alternative to the conventional surfaces, but the results here and elsewhere suggest that the alternative surface is not promising enough to warrant much further work.
Crampton, S. B.↗
FEP plug protects H2 masers
Lifetime of hydrogen-maser bulb is increased by replacing beam stop plate with thick fluorinated ethylene-propylene (FEP) plug inserted in hole opposite beam entrance stem of bulb.
Deluca, J. J.↗
External bulb variable volume maser
A maser functioning as a frequency standard stable to one part in 10 to the 14th power includes a variable volume, constant surface area storage bulb having a fixed volume portion located in a resonant cavity from which the frequency standard is derived. A variable volume portion of the bulb, exterior to the resonant cavity, has a maximum volume on the same order of magnitude as the fixed volume bulb portion. The cavity has a length to radius ratio of at least 3:1 so that the operation is attained without the need for a feedback loop. A baffle plate, between the fixed and variable volume bulb portions, includes apertures for enabling hydrogen atoms to pass between the two bulb portions and is an electromagnetic shield that prevents coupling of the electromagnetic field of the cavity into the variable volume bulb portion.
Reinhardt, V. S.↗
S-band maser phase delay stability tests
The results of the S-band traveling wave maser phase delay stability measurements performed at DSS 62 are presented. These tests were required for the Pioneer-Venus wind experiment.
Urech, J. M.↗
An improved storage bulb mount for DSN hydrogen masers
The presently used JPL hydrogen maser suspended atomic storage bulb and a rigid, single-plane mounted bulb are compared. The new bulb incorporates three major design changes: (1) mounting design; (2) alterations to the collimator; and (3) decrease in mass. These design changes are expected to increase the long-term stability of the frequency standard by reducing its sensitivity to vibration and thermal effects.
Dachel, P. R.↗
Mass loss and OH maser emission from Mira variables
The mass, radius, and luminosity of 26 Mira variables that are known OH sources of radio emission at 1612 MHz have been estimated. The time-independent solution of Salpeter's (1974) stellar-wind equation and a period-density relation are used to solve for basic stellar parameters, with the aid of the terminal expansion velocity of the OH maser cloud. Masses obtained from these calculations are consistent with other estimated values for masses of Mira variables. Good agreement is obtained when comparing the rate of mass loss as determined from Reimers's (1977) semiempirical relation with estimates of the mass-loss rate as deduced from theoretical models involving radiation pressure on grains. These calculations suggest a strong correlation between the mass-loss rate and the pulsation period. Arguments concerning the general properties of silicate grains from radiation-pressure-driven stellar-wind equations are discussed.
Michalitsianos, A. G.↗
H2O masers near OB associations
Four new water masers have been found in the vicinity of three OB associations. One of these, in Cep OB3, is among the most intense sources yet discovered and may be related to the most recent epoch of star formation in the OB association. Two others, one in CMa OB1, the other in M16, have large radial velocities relative to their associated molecular clouds. These results are discussed in the context of star formation and CO line self-reversal within the individual sources.
Blitz, L.↗
A reflected-wave ruby maser with K-band tuning range and large instantaneous bandwidth
A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a closed-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13 + or - 2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communications.
Moore, C. R.↗
NASA NR hydrogen maser
The Johns Hopkins University, Applied Physics Laboratory, under contract to NASA/Goddard Space Flight Center, is engineering a new generation of field operable hydrogen masers (NR) based on prior NASA NP and NX designs. These units incorporate improvements in magnetic shielding, lower noise electronics, better thermal control and have a microprocessor for operation, monitoring and diagnostic functions. They are ruggedly built for transportability and ease of service anywhere in the world.
Rueger, L. J.↗
Effects of hydrogen atom spin exchange collisions on atomic hydrogen maser oscillation frequency
Frequency shifts due to collisions between hydrogen atoms in an atomic hydrogen maser frequency standard are studied. Investigations of frequency shifts proportional to the spin exchange frequency shift cross section and those proportional to the duration of exchange collisions are discussed. The feasibility of operating a hydrogen frequency standard at liquid helium temperatures is examined.
Crampton, S. B.↗
Hydrogen maser implementation in the Deep Space Network at the Jet Propulsion Laboratory
The Frequency Standard Test Laboratory and its activities are described. The test laboratory has the capability to measure the frequency stability of five frequency standards including environmental parameters. Nine frequency standards may be evaluated simultaneously upon completion of the current instrumentation expansion program. Frequency stability measurements and environmental data on five H-masers are presented.
Kuhnle, P. F.↗
A catalog of nonstellar water maser sources
A list of 195 nonstellar galactic sources of water maser emission has been compiled. This list is not a comprehensive catalog of all the available information; it is intended to be used as an index. As such, it contains only coordinates, velocities, and selected references. The extragalatic sources are listed in a separate table.
Dinger, A. S. C.↗