共查询到20条相似文献,搜索用时 31 毫秒
1.
Antonucci F Cavalleri A Dolesi R Hueller M Nicolodi D Tu HB Vitale S Weber WJ 《Physical review letters》2012,108(18):181101
We present an experimental analysis of force noise caused by stray electrostatic fields acting on a charged test mass inside a conducting enclosure, a key problem for precise gravitational experiments. Measurement of the average field that couples to the test mass charge, and its fluctuations, is performed with two independent torsion pendulum techniques, including direct measurement of the forces caused by a change in electrostatic charge. We analyze the problem with an improved electrostatic model that, coupled with the experimental data, also indicates how to correctly measure and null the stray field that interacts with the test mass charge. Our measurements allow a conservative upper limit on acceleration noise, of 2 (fm/s2)/Hz(1/2) for frequencies above 0.1 mHz, for the interaction between stray fields and charge in the LISA gravitational wave mission. 相似文献
2.
Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission Laser Interferometer Space Antenna (LISA) is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal test bed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of 30 microV/sqrt Hz above approximately 0.1 mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals. 相似文献
3.
F. Guzmán Cervantes F. Steier G. Wanner G. Heinzel K. Danzmann 《Applied physics. B, Lasers and optics》2008,90(3-4):395-400
When the position of a test mass in one dimension is measured with picometer accuracy, angular alignment jitter inevitably
couples noise into the measurement. We present recent sensitivity measurements of the LISA technology package interferometer
with articulated mirrors as test masses, actuated by piezo-electric transducers. The required longitudinal displacement resolution
of 9 pm above 3 mHz has been demonstrated with an angular noise that corresponds to the expected for on-orbit operation. The excess
noise contribution of this test mass jitter onto the sensitive displacement readout was completely subtracted by fitting the
angular interferometric data streams to the longitudinal displacement measurement. Thus, this cross-coupling constitutes no
limitation to the required performance of the LISA technology package interferometry.
PACS 04.80.Nn; 07.60.Ly; 42.62.Eh 相似文献
4.
Determination of the thermal noise limit in test of weak equivalence principle with a rotating torsion pendulum 下载免费PDF全文
Thermal noise is one of the most fundamental limits to the sensitivity in weak equivalence principle test with a rotating torsion pendulum. Velocity damping and internal damping are two of many contributions at the thermal noise, and which one mainly limits the torsion pendulum in low frequency is difficult to be verified by experiment. Based on the conventional method of fast Fourier transform, we propose a developed method to determine the thermal noise limit and then obtain the precise power spectrum density of the pendulum motion signal. The experiment result verifies that the thermal noise is mainly contributed by the internal damping in the fiber in the low frequency torsion pendulum experiment with a high vacuum. Quantitative data analysis shows that the basic noise level in the experiment is about one to two times of the theoretical value of internal damping thermal noise. 相似文献
5.
S. Barke M. Tr?bs B. Sheard G. Heinzel K. Danzmann 《Applied physics. B, Lasers and optics》2010,98(1):33-39
The Laser Interferometer Space Antenna (LISA) is a joint ESA/NASA mission proposed to observe gravitational waves. One important
noise source in the LISA phase measurement will be on-board reference oscillators. An inter-spacecraft clock tone transfer
chain will be necessary to remove this non-negligible phase noise in post processing. One of the primary components of this
chain are electro-optic modulators (EOMs). At modulation frequencies of 2 GHz, we characterise the excess phase noise of a
fibre-coupled integrated EOM in the LISA measurement band (0.1 mHz to 1 Hz). The upper phase noise limit was found to be almost
an order of magnitude better than required by the LISA mission. In addition, the EOM’s phase dependence on temperature and
optical power was determined. The measured coefficients are within a few milliradians per kelvin and per watt respectively
and thereby negligible with the expected on-board temperature and laser power stability. 相似文献
6.
Measurement of Newton's constant using a torsion balance with angular acceleration feedback 总被引:2,自引:0,他引:2
We measured Newton's gravitational constant G using a new torsion balance method. Our technique greatly reduces several sources of uncertainty compared to previous measurements: (1) It is insensitive to anelastic torsion fiber properties; (2) a flat plate pendulum minimizes the sensitivity due to the pendulum density distribution; (3) continuous attractor rotation reduces background noise. We obtain G = (6.674215+/-0.000092) x 10(-11) m3 kg(-1) s(-2); the Earth's mass is, therefore, M = (5.972245+/-0.000082) x 10(24) kg and the Sun's mass is M = (1.988435+/-0.000027) x 10(30) kg. 相似文献
7.
N. V. Izotov V. N. Puzyrev A. T. Sahakyan A. N. Starodub O. F. Yakushev 《Bulletin of the Lebedev Physics Institute》2018,45(7):195-198
The results of experimental measurements of the hydrodynamic efficiency of laser plasma for aluminum and copper targets are presented. The studies were performed on the “Kanal-2” laser setup system using the ballistic pendulum method. The pressure in the interaction chamber was 10?4 Torr, the pendulum length was 145 mm, the mass of the pendulum with a target was 7.2 g. At the half-height pulse duration of 2.5 ns, the power density on the target surface was ~1013 W/cm2. In the case of aluminum target, the hydrodynamic efficiency coefficient increased from 1.5% to 4.5% with increasing laser pulse energy from 5 J to 10 J, whereas it remained at the level of 5% for the copper target. 相似文献
8.
Raw space-based gravitational-wave data like laser interferometer space antenna's (LISA) phase measurements are dominated by laser frequency noise. The standard technique to make this data usable for gravitational-wave detection is time-delay interferometry (TDI), which cancels laser noise terms by forming suitable combinations of delayed measurements. To do so, TDI relies on inter-spacecraft distances and on how laser noise enters the interferometric data. The basic concepts of an alternative approach which does not rely on independent knowledge of temporal correlations in the dominant noise recently introduced. Instead, this automated principal component interferometry (aPCI) approach only assumes that one can produce some linear combinations of the temporally nearby regularly spaced phase measurements, which cancel the laser noise. Then the data is let to reveal those combinations, thus providing a set of laser-noise-free data channels. The authors' previous approach relies on the simplifying additional assumption that the filters which lead to the laser-noise-free data streams are time-independent. In LISA, however, these filters will vary as the constellation armlengths evolve. Here, a generalization of the basic aPCI concept compatible with data dominated by a still unmodeled but slowly varying dominant noise covariance is discussed. Despite its independence on any model, aPCI successfully mitigates laser frequency noise below the other noises' level, and its sensitivity to gravitational waves is the same as the state-of-the-art second-generation TDI, up to a 2% error. 相似文献
9.
The aim of this paper is to evaluate field values based on electrostatic charge technique of a PM10 mass monitor used for continuous measuring of ambient particulate air pollution. The PM10 mass monitor included electrostatic PM10 mass monitor (EPMM) and wireless monitor systems. In this study, the performance of the EPMM was simultaneously evaluated with a commercially available tapered element oscillating microbalance (TEOM) for measurements at ambient condition. The data of the sensor was connected to the internet through a GSM connection to a public cellular network. The monitoring data of ambient PM was collected and compared for both EPMM and TEOM by measuring at Chiang Mai City Hall during May 1st – 31st, 2015. The two different instruments showed good results that were highly correlated. The comparison between the EPMM and TEOM data values resulted in R2 of 0.8352 and 0.9697, and a slope of 0.8401 and 0.9087 for 1-h and 24-h, respectively. In addition, it was found that the relative humidity played an important role in PM10 mass concentration and its electrical properties of the EPMM. Particularly the EPMM proved its advantages in measuring and detecting PM10 particulate air pollution for mass concentrations in the range from 0 to 500 μg/m3. 相似文献
10.
《Journal of Electrostatics》2014,72(2):120-128
A new technique is proposed to measure the particle mean size using an electrostatic sensor in frequency domain. This paper starts with a finite-element modeling simulator to model the induced electric charge of a ring electrode and to find the electrode sensitivity. The mathematical modeling was used to extract particle size information from the simulated signal in frequency domain. The method is applied in an experimental test where a low-noise signal conditioning was designed with a ring electrode as the electrostatic sensor. The method can be used to establish a cost effective size measurement system using electrostatic sensor. 相似文献
11.
D.S. Li 《Journal of sound and vibration》2010,329(2):123-139
In this paper, the feasibility of using synthesized structural acoustic sensors (SSAS) for active noise control inside irregularly shaped enclosures is investigated. A SSAS consists of a cluster of inter-connected discrete PVDF elements, located on the surface of a vibrating structure enclosing a sound field. An optimal design ensures the sensor output to be directly related to the acoustical potential energy inside the enclosure. Hence, synthesized structural acoustic sensors can provide error signals for an active noise control system, and the use of microphones inside the enclosure can be avoided. A cylindrical shell with a floor partition, which can be used to model an aircraft cabin, is used as a test case. PZT actuators are used as control actuators. Both SISO (single input and single output) and MIMO (multi-input and multi-output) control systems are optimally designed using Genetic Algorithms and implemented with a Filtered-X Feedforward LMS (least-mean-square) controller. Their control performances are evaluated with different types of disturbances. To show the effectiveness of the optimal design approach, some non-optimal control systems are also tested and compared with the optimal one. It is shown that with optimally designed SSAS, an active structural acoustic control system can effectively reduce noise inside the enclosures without using any acoustic transducers. 相似文献
12.
为了统一描述自然界的四种基本相互作用,科学家提出了很多理论模型,其中很多理论认为牛顿反平方定律在近距离下会发生偏离,或存在其他的非牛顿引力作用,而理论的正确与否需要高精度的实验检验.国际上很多研究组在不同间距下采用不同的技术对反平方定律进行了高精度的实验检验,本文重点介绍华中科技大学引力中心采用密度调制法分别在亚毫米与微米范围进行的实验研究进展.在亚毫米范围采用精密扭秤技术,在对牛顿引力进行双补偿、抑制电磁干扰后,结合零实验与非零实验结果,在作用程为70—300μm区间对Yukawa形式的破缺给出国际上精度最高的限制.在微米范围采用悬臂梁作为弱力传感器,通过测量金球和密度调制吸引质量间水平力的变化来检验非牛顿引力是否存在,实验结果不需进行Casimir力和静电力背景扣除,是此间距下不依赖于Casimir力和静电力理论计算模型的两个结果之一. 相似文献
13.
A moving zone of quiet for narrowband noise in a one-dimensional duct using virtual sensing 总被引:1,自引:0,他引:1
Petersen CD Zander AC Cazzolato BS Hansen CH 《The Journal of the Acoustical Society of America》2007,121(3):1459-1470
A frequent problem in active noise control is that the zone of quiet created at the error sensor tends to be very small. This means that the error sensor generally needs to be located close to an observer's ear, which might not always be a convenient or feasible solution. Virtual sensing is a method that can move the zone of quiet away from the error sensor to a desired location that is spatially fixed. This method has been investigated previously, and has shown potential to improve the performance of an active noise control system. However, it is very likely that the desired location of the zone of quiet is not spatially fixed. An active noise control system incorporating a virtual sensing method thus has to be able to create a moving zone of quiet that tracks the observer's ears. This paper presents a method for creating a moving zone of quiet based on the LMS virtual microphone technique. To illustrate the proposed method, it is implemented in an acoustic duct and narrowband control results are presented. These results show that a moving zone of quiet was effectively created inside the duct for narrowband noise. 相似文献
14.
15.
Aline Souza de Paula Francisco Heitor Iunes Pereira-Pinto 《Journal of sound and vibration》2006,294(3):585-595
Pendulum is a mechanical device that instigates either technological or scientific studies, being associated with the measure of time, stabilization devices as well as ballistic applications. Nonlinear characteristic of the pendulum attracts a lot of attention being used to describe different phenomena related to oscillations, bifurcation and chaos. The main purpose of this contribution is the analysis of chaos in an experimental nonlinear pendulum. The pendulum consists of a disc with a lumped mass that is connected to a rotary motion sensor. This assembly is driven by a string-spring device that is attached to an electric motor and also provides torsional stiffness to the system. A magnetic device provides an adjustable dissipation of energy. This experimental apparatus is modeled and numerical simulations are carried out. Free and forced vibrations are analyzed showing that numerical results are in close agreement with those obtained from experimental data. This analysis shows that the experimental pendulum has a rich response, presenting periodic response, chaos and transient chaos. 相似文献
16.
17.
Michael?Hohensee Shau-Yu?Lan Rachel?Houtz Cheong?Chan Brian?Estey Geena?Kim Pei-Chen?Kuan Holger?Müller
We study the use of atom interferometers as detectors for gravitational waves in the mHz–Hz frequency band, which is complementary
to planned optical interferometers, such as laser interferometer gravitational wave observatories (LIGOs) and the Laser Interferometer
Space Antenna (LISA). We describe an optimized atomic gravitational wave interferometric sensor (AGIS), whose sensitivity
is proportional to the baseline length to power of 5/2, as opposed to the linear scaling of a more conservative design. Technical
challenges are briefly discussed, as is a table-top demonstrator AGIS that is presently under construction at Berkeley. We
study a range of potential sources of gravitational waves visible to AGIS, including galactic and extra-galactic binaries.
Based on the predicted shot noise limited performance, AGIS should be capable of detecting type Ia supernovae precursors within
500 pc, up to 200 years beforehand. An optimized detector may be capable of detecting waves from RX J0806.3+1527. 相似文献
18.
We present an analysis of the centrifugal coupling of a simple pendulum to a dissipative support. We show that such a coupling
leads to an amplitude dependent quality factor. For amplitudes which could be present in laser interferometer gravitational
wave detector suspensions, this mechanism could limit the quality factor of the test mass suspension significantly to 1010 and should be considered in the design of advanced LIGO type detectors. 相似文献
19.
20.
Aasvang GM Øverland B Ursin R Moum T 《The Journal of the Acoustical Society of America》2011,129(6):3716-3726
The aim of this study was to explore and compare the effect of noise from railway and road traffic on sleep in subjects habitually exposed to nocturnal noise. Forty young and middle aged healthy subjects were studied with polysomnography (PSG) during two consecutive nights in their own bedroom. Noise measurements and recordings were conducted concurrently outside of the bedroom fac?ade as well as inside the bedroom of each participant. Different noise exposure parameters were calculated (L(p,A,eq,night), L(p,A,Fmax,night), and L(AF5,night)) and analyzed in relation to whole-night sleep parameters. The group exposed to railway noise had significantly less Rapid eye movement, (REM) sleep than the group exposed to road traffic noise. A significant association was found between the maximum level (L(p,A,Fmax,night)) of railway noise and time spent in REM sleep. REM sleep was significantly shorter in the group exposed to at least a single railway noise event above 50 dB inside the bedroom. These results, obtained in an ecological valid setting, support previous laboratory findings that railway noise has a stronger impact than road traffic noise on physiological parameters during sleep, and that the maximum noise level is an important predictor of noise effects on sleep assessed by PSG, at least for railway noise. 相似文献