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Секция «Актуальные на учные проблемы в мире (глазами молодьх исследователей)»
UDK 629.783-006
THE STANDARDS OF FREQUENCY AND TIME
E. (D.) Borisova Scientific supervisor - V. (M.) Vladimirov Foreign language supervisor - I. (N.) Shostak
Reshetnev Siberian State Aerospace University 31, Krasnoyarsky Rabochy Av., Krasnoyarsk, 660037, Russian Federation
Standard ^ frequency and time is considered, its concept, types and styles, the basic principles of hydrogen standard of frequency and time. Also, the use of frequency and time standards and their development is considered.
Keywords: standard frequency and time, stability (instability) of frequency, the hydrogen generator.
СТАНДАРТЫ ЧАСТОТЫ И ВРЕМЕНИ
Е. Д. Борисова Научный руководитель - В. М. Владимиров Руководитель по иностранному языку - И. Н. Шостак
Сибирский государственный аэрокосмический университет имени академика М. Ф. Решетнева
Российская Федерация, 660037, г. Красноярск, просп. им. газ. «Красноярский рабочий», 31
Рассматривается стандарт частоты и времени, его понятие, виды и типы, основные принципы работы водородного стандарта частоты и времени. Также рассматривается применение стандартов частоты и времени и их развитие.
Ключевые слова: стандарт частоты и времени, стабильность (нестабильность) частоты, водородный генератор.
Standard frequency and time (SFT) is source of electromagnetic signals with highly stable frequency. SFTs are used in metrology, navigation, radio astronomy and in other areas. In particular SFTs are used with GLONASS (Global Navigation Satellite System) systems. SFTs are divided into standards of radio range and optical ones. In its turn, SFTs of radio range are divided into quartz and quantum.
Stability (instability) of frequency is an important parameter of SFTs. Stability of frequency is a characteristic of auto generators. It shows the deviation of frequency of the generator from the initial value and is defined by the relation Af/f. Where Af is the value of the frequency drift, f - the initial (nominal) value of the frequency. This relation is called relative stability (instability) of frequency.
For quartz generators relative instability of frequency is Af/f = 10-6 - 10-8, for quantum generators -Af/f= 10-11 - 10-15.
Quantum generators will be discussed later because they are more accurate than quartz generators.
Quantum SFTs of radio range are devices producing electromagnetic oscillations with a stable time frequency, which use quantum transitions of particles (atoms, molecules, ions) from one energy state to another. Quantum SFTs are divided into two classes: passive and active.
Types of standard: at the hydrogen generator, at the cesium atomic beam tube, at the atoms 87Rb with optical pumping, generator at ammonia, at a mercury generator and etc.
The main characteristics of quantum SFTs are presented in table [1].
The hydrogen generator will be considered as an example.
The hydrogen generator has a source (picture 1). This source produces beam of atoms, which in its turn is subjected to sorting over the states and at the same time is focused with sorting system [2]. Magnetic system is used for sorting because hydrogen atoms possess a magnetic dipole moment. Then the beam gets into resonator, where it loses energy. Storage bottle (volume 1-2L) is placed in the center of the resonator, which is tuned to the atomic transition frequency. It is made of quartz glass and is covered inside with mate-
Актуальные проблемы авиации и космонавтики - 2015. Том 2
rial (paraffin, teflon). These materials consist of molecules which interact weakly with hydrogen atoms [3]. Such a storage bottle provides large lifetime of atoms. The flow of atoms in the bottle is 1012-1013of atoms per second. Partial pressure is 10-5 Pa.
Characteristics of the types quantum SFTs
Characteristics Type of standard
At the hydrogen generator At the cesium atomic beam tube At the atoms 87Rb with optical pumping
Accuracy of frequency 1x10-12 1x10-13 1x10-10
Relative error of reproduction of the actual value of the frequency 5x10-14 5x10-14 1x10-12
Root mean square (RMS) relative deviation of frequency: t = 1 s t = 1 day 5x10-12 5x10-15 1x10-12 5x10-15 1x10-12 5x10-13
Frequency of working atomic transition, MHz 1 420,405 9192,631 6 834,682
Picture 1. Schematic representation of quantum hydrogen generator
The hydrogen generator works at the quantum transition in the hyperfine structure of the hydrogen atom. Hydrogen is in basic condition (S) (picture 2). Namely the transition: (F = 1, mF = 0) ^ (F = 0, mF = 0). The upper energy level is split into three Zeeman's levels (±1, 0).
mjF-= + i1
~~rtlF =0 2 —
1,42 ^ntF = — 1 3
m#,=0. -
0 0,1 0,2 0,3
b, t -
Picture 2. The energy levels of the hydrogen atom In the S-state in a magnetic field
Секция «Актуальные на учные проблемы в мире (глазами молодых исследователей)»
The frequency of this transition is 1 420.405 MHz.
Standards have been used in scientific experiments, industry, metrology and global navigation satellite systems.The latest technology of radio electronics makes them less and improves frequency stability.
References
1. Basarov V. J. (1975) Quantum Frequency standards, Entsiklopediya fiziki i tekhniki. List available at: http://www.femto.com.ua/articles/part_1/1571.html, 26 june [26 june 2014].
2. Oduan K. (2002) Izmerenie vremeni, Osnovy GPS., Tekhnosfera, p. 400. (In Russ.).
3. Pikhtelev A. I. (1978) Standarty chastoty I vremeni na osnove kvantovykh generatorov I diskriminatorov. M. : Sov. Radio. P. 304 (In Russ.).
© Borisova E. (D.), 2015
