Possible ways to improve the hydrogen maser accuracy are stated. Use of a special bulb, made of quartz, allowing simulation of two different mean diameters is proposed. It is experimentally proved that it allows one to achieve very good operating conditions in the temperature range 300-395 K. Measurement, with this bulb, of the temperature dependence of a FEP 120 teflon coating is reported. A change of FEP 120 properties is observed at a temperature of 360 K. This is confirmed by operating a hydrogen maser with a classical spherical bulb. A null of the mean phase shift per collisions occurs at a temperature of 385 K. Good precision of wall shift measurements made with the special bulb, in the temperature range 300-360 K allowed one to achieve an accuracy of 6-x and to determine the unperturbed hydrogen hyperfine transition frequency f~ with a precision of 7 x The result is f H = 1420405 751.773 f 0.001 Hz.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.