共查询到18条相似文献,搜索用时 187 毫秒
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氩气等单原子气体的折射率,是检验量子力学从头算理论的重要参数。基于圆柱微波谐振法,精确测量了234~303 K、 0~750 kPa范围内氩气的折射率。测量了圆柱腔内不同压力下4种横磁 (TM) 模式的微波谐振频率,对谐振频率进行非理想因素修正后,结合真空下的微波谐振频率获得氩气的折射率。圆柱腔内微波谐振频率测量不确定度为2×10-8,4种模式获得的氩气折射率的相对标准偏差小于1×10-6。通过氩气的折射率计算获得了氩气的第一介电维里系数,与国际上已发表的结果具有良好的一致性。基于建立的实验系统,后续可开展其他气体的折射率测量。 相似文献
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实验以上海天文台SOHM-4型氢原子钟脉泽信号和新研制的模拟-数字混合型锁相环路为基础,主要分析锁相环路参数对氢原子钟输出信号的短期频率稳定度和单边带相位噪声的影响。针对氢脉泽信号高Q值的特殊性,通过理论分析和实验验证寻求与其相匹配的最佳环路参数。实验结果表明,锁相环路的参数设置直接影响到氢原子钟输出信号的性能;在脉泽信号不变的情况下,改进后的锁相环路和主电子学系统可使氢原子钟的频率稳定度提高至1.7×10-13/1s, 3.3×10-14/10s, 9.1×10-15/100s, 2.9×10-15/1 000s, 1.4×10-15/10000s,即较之原有的技术指标,在各取样时间范围内,频率稳定度的测试结果均提高了半个量级。 相似文献
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采用固相法制备了新型微波介质陶瓷HoVO4。研究了微波性能与微观形貌、致密度和拉曼半高宽之间的关系,并分析了拉曼光谱中化学键的振动模。HoVO4在1 150℃烧结得到最优微波介电性能:εr=11.52,Q×f=27 271 GHz,τf=-22.39×10-6/℃。选取正τf值的TiO 2与负τf值的HoVO4进行复合,得到谐振频率温度系数近零的微波陶瓷,当TiO2掺杂量为6%、烧结温度为1 200℃时获得最佳微波介电性能为:εr=14.14,Q×f=18 978 GHz,τf=2.4324×10-6/℃。 相似文献
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利用氩气的量子力学“从头算”理论和相关实验测量结果,基于圆柱微波谐振法建立了气体折射率热力学温度计实验系统,测量了253~303 K范围内的热力学温度。通过测量圆柱微波谐振腔内4个横磁模式的微波谐振频率,获得了氩气在700 kPa附近的气体折射率,不同微波模式得到的氩气折射率一致性优于1×10-8,进一步结合氩气的维里状态方程得到热力学温度。热力学温度T和ITS-90国际温标T90差异不确定度为11.6 mK,与国际温度咨询委员会的评估值具有良好的一致性。未来随着氩气理论计算和实验系统压力测量不确定度的深入研究,该方法测定热力学温度的不确定度会进一步改善。 相似文献
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Prestage J.D. Tjoelker R.L. Wang R.T. Dick G.J. Maleki L. 《IEEE transactions on instrumentation and measurement》1993,42(2):200-205
The frequency stability of an atomic standard based on 199 Hg+ ions confined in a hybrid RF/DC linear trap is described. The 40.5-GHz clock transition has been measured to be 17 mHz wide, representing a quality factor greater than 2×1012. A 160-mHz line is used to steer the output of a 5-MHz crystal oscillator to obtain a stability of 2×10-15 for 24000-s averaging times. In a separate measurement, a 37-mHz line is used to steer the output of the superconducting cavity maser oscillator to reach 1×10-15 stability at 10000 s 相似文献
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Luiten A.N. Mann A.G. Costa M.E. Blair D.G. 《IEEE transactions on instrumentation and measurement》1995,44(2):132-135
Microwave oscillators of exceptional short-term stability have been realized from cryogenic sapphire resonators with loaded Q factors in excess of 109 at 11.9 GHz and 6 K. This has been achieved by a power stabilized loop oscillator with active Pound frequency stabilization. These oscillators have exhibited a fractional frequency stability of 3-4×10-15 for integration times from 0.3 to 100 s. The relative drift of these two oscillators over one day is a few times 10-13. To reduce the long-term drift, which is principally due to excessive room temperature sensitivity, we have added cryogenic sensors for the power and frequency stabilization servos to one of these oscillators. We have also implemented a servo to reduce the room temperature sensitivity of our phase modulators. Testing of this oscillator against a Shanghai Observatory H-maser has shown an Allan deviation of 4×10-15 from 600 to 2000 s 相似文献
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Dick G.J. Santiago D.G. Wang R.T. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1995,42(5):812-819
We report on the design and test of a whispering gallery sapphire resonator for which the dominant (WGHn11) microwave mode family shows frequency-stable, compensated operation for temperatures above 77 K. The resonator makes possible a new ultra-stable oscillator (USO) capability that promises performance improvements over the best available crystal quartz oscillators in a compact cryogenic package. A mechanical compensation mechanism, enabled by the difference between copper and sapphire expansion coefficients, tunes the resonator to cancel the temperature variation of sapphire's dielectric constant. In experimental tests, the WGH811 mode showed a frequency turnover temperature of 87 K in agreement with finite element calculations. Preliminary tests of oscillator operation show an Allan Deviation of frequency variation of 1.4-6×10-12 for measuring times 1 s ⩽τ⩽100 s with unstabilized resonator housing temperature and a mode Q of 2×106. We project a frequency stability 10-14 for this resonator with stabilized housing temperature and with a mode Q of 107 相似文献
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Tobar M.E. Giles A.J. Edwards S. Searls J.H. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1994,41(3):391-396
Two low-noise high-Q sapphire-loaded cavity (SLC) resonators, with unloaded Q values of 2×105 and very low densities of spurious modes, have been constructed. They were designed to operate at 0°C with a center frequency of 10.000000 GHz. The cavity was cooled with a thermoelectric (TE) Peltier element, and in practice achieved the required center frequency near 1°C. The resonator has a measured frequency-temperature coefficient of -0.7 MHz/K, and a Q factor which is measured to be proportional to T-2.5. An upper limit to the SLC residual phase noise of ℒ (100) Hz=-147 dBc/Hz, ℒ (1 kHz)=-155 dBc/Hz, and ℒ (10) kHz=-160 dBc/Hz has been measured. Also, we have created a free-running loop oscillator based on one of the SLC resonators, and measured a phase noise of ℒ(f)~-10-30log [f] dBc/Hz between f=10 /Hz and 25 kHz, using the other as a discriminator 相似文献
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Fisk P.T.H. Sellars M.J. Lawn M.A. Coles C. Mann A.G. Blair D.G. 《IEEE transactions on instrumentation and measurement》1995,44(2):113-116
A microwave frequency standard based on buffer-gas cooled 171 Yb+ ions confined in a linear Paul trap has been demonstrated in prototype form. The standard exhibits a fractional frequency instability characterized by an Allan deviation σy (τ)=3.7×10-13τ-1/2 for τ<3000 s. Microwave Ramsey fringes with a Q factor of 1.5×1013 have been observed 相似文献
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Heavner T.P. Jefferts S.R. Dunn G.H. 《IEEE transactions on instrumentation and measurement》1999,48(2):189-191
We have used a cryogenic (4 K) Penning ion trap mass spectrometer to measure the mass ratios of 6Li+/12C 2+, 6Li+/D3+, and D2+/He+. We developed techniques to create ions outside of the cryogenic trap environment and to transport them into the trap where a small number (1-10) were confined. The ions' frequencies of oscillation were measured using a high-Q tuned circuit to detect image currents induced in the trap electrodes. The measurements involving 6Li+ result in a value for the atomic mass of 6Li of 6.015 122 795(16) u, with a fractional uncertainty of ±2.7×10-9 representing a factor of 30 improvement over the published, tabulated value. A measurement of the D2+/He+ mass ratio has an uncertainty of ±1.1×10-9 and is within 0.6×10-9 of the tabulated value, thus demonstrating that our techniques are reliable 相似文献
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A phase-locked laser frequency chain was used to measure the absolute frequency of a HeNe/CH4 laser relative to the primary Cs standard, with measurement uncertainty less than ±1 part in 1012. The frequency depends on laser parameters; a spread of 8.3×10-11 was observed. This was attributed to the variation of Lamb dip asymmetry resulting from the gas-lens effect and the accompanying diffraction loss variation near resonance. Means of improving laser frequency reproducibility by reducing cavity diffraction loss variation were studied experimentally. The frequency obtained with a cavity exhibiting the smallest Lamb dip asymmetry was found to be 88 376 181 599.07±0.07 kHz 相似文献
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The AC electrical behaviour of sandwich devices fabricated entirely in vacuum using thermally evaporated thin films of 99+% pure 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4 oxadiazole (Bu–PBD) and gold electrodes, is observed over the frequency range 104 to 107 Hz and the temperature range 297 to 398 K. The capacitance and dissipation factor decrease with increasing frequency and at high frequency (>2×106 Hz) the capacitance and dissipation factor are not temperature dependent. The results obtained show the relative importance of the variable range hopping model and band theory in describing the film conductivity. 相似文献