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Title: Atomic velocity distributions out of hydrogen-maser dissociators. Technical report

Abstract

Velocity distributions are determined for atoms effusing out of radio frequency discharge hydrogen dissociators, of the type used in hydrogen masers. This work was motivated by long-term reliability issues related to the possible use of masers as freqency standards for satellites. A primary issue is the maser's hydrogen budget, because many of the common failure modes of a maser involve either the hydrogen source or sink. Because the focusing properties of the state-selecting magnets are velocity dependent, the overall hydrogen budget will depend not only on the dissociation efficiency but also on the velocity distribution of the hydrogen atoms leaving the dissociation. Many times, that distribution has been tacitly assumed to be Maxwellian at wall temperature, but pressure in the dissociator increases. Operating the dissociator to yield a matched to that distribution may significantly improve the efficiency hydrogen use by the maser.

Authors:
;
Publication Date:
Research Org.:
Aerospace Corp., El Segundo, CA (USA). Chemistry and Physics Lab.
OSTI Identifier:
6876635
Alternate Identifier(s):
OSTI ID: 6876635
Report Number(s):
AD-A-219500/6/XAB; TR--0090(5945-05)-1
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 74 ATOMIC AND MOLECULAR PHYSICS; ATOMIC CLOCKS; DESIGN; HYDROGEN; DISSOCIATION; MASERS; EFFICIENCY; ATOMS; DISTRIBUTION; FAILURES; PROGRESS REPORT; RADIOWAVE RADIATION; SATELLITES; STANDARDS; USES; VELOCITY; AMPLIFIERS; DOCUMENT TYPES; ELECTROMAGNETIC RADIATION; ELECTRONIC EQUIPMENT; ELEMENTS; EQUIPMENT; MICROWAVE AMPLIFIERS; MICROWAVE EQUIPMENT; NONMETALS; RADIATIONS 426002* -- Engineering-- Lasers & Masers-- (1990-); 640302 -- Atomic, Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory

Citation Formats

Jaduszliwer, B., and Chan, Y.C.. Atomic velocity distributions out of hydrogen-maser dissociators. Technical report. United States: N. p., 1990. Web.
Jaduszliwer, B., & Chan, Y.C.. Atomic velocity distributions out of hydrogen-maser dissociators. Technical report. United States.
Jaduszliwer, B., and Chan, Y.C.. Thu . "Atomic velocity distributions out of hydrogen-maser dissociators. Technical report". United States. doi:.
@article{osti_6876635,
title = {Atomic velocity distributions out of hydrogen-maser dissociators. Technical report},
author = {Jaduszliwer, B. and Chan, Y.C.},
abstractNote = {Velocity distributions are determined for atoms effusing out of radio frequency discharge hydrogen dissociators, of the type used in hydrogen masers. This work was motivated by long-term reliability issues related to the possible use of masers as freqency standards for satellites. A primary issue is the maser's hydrogen budget, because many of the common failure modes of a maser involve either the hydrogen source or sink. Because the focusing properties of the state-selecting magnets are velocity dependent, the overall hydrogen budget will depend not only on the dissociation efficiency but also on the velocity distribution of the hydrogen atoms leaving the dissociation. Many times, that distribution has been tacitly assumed to be Maxwellian at wall temperature, but pressure in the dissociator increases. Operating the dissociator to yield a matched to that distribution may significantly improve the efficiency hydrogen use by the maser.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 1990},
month = {Thu Feb 15 00:00:00 EST 1990}
}

Technical Report:
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  • The authors have measured atomic hydrogen velocity distributions in an effusive beam coming out of an rf discharge dissociator by using a magnetic deflection technique. Dissociator pressures varied between 0.028 and 0.340 torr. At low dissociator pressures, the measured atomic velocity distributions were narrower than the expected beam-Maxwellians; at higher pressures, they were indistinguishable from beam-Maxwellians at the dissociator wall temperature, indicating full thermalization of the atoms prior to exiting the dissociator. Monte Carlo simulations of the thermalization process within the dissociator reproduce these results and point out the important role of vibrational excitation of the background hydrogen molecules asmore » an energy loss mechanism. These results are significant when designing magnetic state selectors for spin- or hyperfine-polarized atomic hydrogen beams.« less
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