Twin mirrors for laser interferometric gravitational-wave detectors

Gravitational-wave detectors such as Virgo and the laser interferometric gravitational-wave observatory (LIGO) use a long-baseline Michelson interferometer with Fabry-Perot cavities in the arms to search for gravitational waves. The symmetry between the two Fabry-Perot cavities is crucial to reduce the interferometer's sensitivity to the laser amplitude and frequency noise. To this purpose, the transmittance of the mirrors in both cavities should be as close as possible. This paper describes the realization and the characterization of the first twin large low-loss mirrors with transmissions differing by less than 0.01%.     

Stability of giant Fabry-Perot cavities of interferometric gravitational-wave detectors

We consider the coupling of the thermoelastic mirror deformations to the resonance of giant cavities involved in interferometric detectors of gravitational waves. As this problem is coupled and nonlinear, instabilities could occur a priori. We analytically solve the coupled problem of thermoelastic deformations and their effect on the laser field, perturbatively, and we show that within the realm of our (physically reasonable) assumptions there are no instabilities that can simulate a false event in the observational frequency range of 1 Hz to 1 kHz.     

Readout and control of a power-recycled interferometric gravitational-wave antenna

Interferometric gravitational-wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by the addition of multiple coupled optical resonators. The use of optical cavities is essential for reaching the required sensitivity but sets challenges for the control system, which must maintain the cavities near resonance. The goal for the strain sensitivity of the Laser Interferometer Gravitational-Wave Observatory (LIGO) is 10(-21) rms, integrated over a 100-Hz bandwidth centered at 150 Hz. We present the major design features of the LIGO length and frequency sensing and control system, which will hold the differential length to within 5 x 10(-14) m of the operating point. We also highlight the restrictions imposed by couplings of noise into the gravitational-wave readout signal and the required immunity against them.     

Sensing and control in dual-recycling laser interferometer gravitational-wave detectors

We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced. We present the implications of the results from these experiments for Advanced LIGO and other future interferometric gravitational-wave detectors.     

Shot noise in gravitational-wave detectors with Fabry-Perot arms

Shot-noise-limited sensitivity is calculated for gravitational-wave interferometers with Fabry-Perot arms, similar to those being installed at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Italian-French Laser Interferometer Collaboration (VIRGO) facility. This calculation includes the effect of nonstationary shot noise that is due to phase modulation of the light. The resulting formula is experimentally verified by a test interferometer with suspended mirrors in the 40-m arms.     

Force measurements of a superconducting-film actuator for a cryogenic interferometric gravitational-wave detector

We measured forces applied by an actuator with a YBa₂Cu₃O₇ (YBCO) film at near 77 K for the Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. An actuator consisting of both a YBCO film of 1.6 μm thickness and 0.81 cm² area and a solenoid coil exerted a force of up to 0.2 mN on a test mass. The presented actuator system can be used to displace the mirror of LCGT for fringe lock of the interferometer.     

Development of a frequency-detuned interferometer as a prototype experiment for next-generation gravitational-wave detectors

We report on our prototype experiment that uses a 4-m detuned resonant sideband extraction interferometer with suspended mirrors, which has almost the same configuration as the next-generation, gravitational-wave detectors. We have developed a new control scheme and have succeeded in the operation of such an interferometer with suspended mirrors for the first time ever as far as we know. We believe that this is the first such instrument that can see the radiation pressure signal enhancement, which can improve the sensitivity of next-generation gravitational-wave detectors.     

White-light interferometric fiber-optic pressure sensor

A novel configuration for a fiber-optic white-light interferometric sensor is presented which allows for absolute measurements of hydrostatic pressure with an improved operation range. The performance of two fibers (York bow-tie 800 and especially designed elliptical-core side-hole fiber) used as sensing elements was experimentally studied. The sensor itself was composed of two equal lengths of the fiber spliced at 90°. This structure assures temperature compensation and enables application of a Wollaston prism as a receiving interferometer. A step delay line made of crystalline quartz was used to increase the operation range of the sensor     

Radiation hardness of cryogenic silicon detectors

We shall review test results which show that silicon detectors can withstand at 130 K temperature a fluence of 2×10¹⁵ cm^–2 of 1 MeV neutrons, which is about 10 times higher than the fluence tolerated by the best detectors operated close to room temperature. The tests were carried out on simple pad devices and on microstrip detectors of different types. The devices were irradiated at room temperature using reactor neutrons, and in situ at low temperatures using high-energy protons and lead ions. No substantial difference was observed between samples irradiated at low temperature and those irradiated at room temperature, after beneficial annealing. The design of low-mass modules for low-temperature trackers is discussed briefly, together with the cooling circuits for small and large systems.     

Numerical calculations of diffraction losses in advanced interferometric gravitational wave detectors

Knowledge of the diffraction losses in higher-order modes of large optical cavities is essential for predicting three-mode parametric photon-phonon scattering, which can lead to mechanical instabilities in long-baseline gravitational wave detectors. We explore different numerical methods in order to determine the diffraction losses of the higher-order optical modes. Diffraction losses not only affect the power buildup inside the cavity but also influence the shape and frequency of the mode, which ultimately affect the parametric instability gain. Results depend on both the optical mode shape (order) and the mirror diameter. We also present a physical interpretation of these results.     

Radiation damage in silicon strip detectors

Silicon strip detectors with 5 μm spatial resolution have been used during 1982–1985 in the ACCMOR spectrometer at CERN. After a local beam flux of about 10¹⁴ minimum ionizing particles per cm² we observe a significant increase in dark current and systematic distortions in the measured coordinates which are explained in terms of a decrease in the effective donor concentration.     

Radiation damage test of silicon multistrip detectors

Radiation damage test of silicon multistrip detectors were performed using an 800 GeV proton beam. The local proton fluence was up to 10¹⁴/cm². The observed prominent changes were the proportional increase of the leakage current with the integrated beam intensity and the change of the effective impurity density. The effective impurity density decreases with fluence up to ≈4×10¹³/cm² but for greater fluences, it increases. This may indicate the type conversion of the bulk silicon. We have also observed the change of the carrier collection properties, which may be caused by the synergistic effect of the charge-up of surface SiO₂ and the decrease of the effective impurity density in bulk silicon.     

用于光纤干涉传感器的高稳定PGC解调技术

相位生成载波(PGC)解调技术具有高灵敏度、线性度好和动态范围广的优点,因此广泛应用于分布式光纤传感器中.本文提出了一种单路微分相除和微分自相乘的PGC(PGC-SDD-DSM)解调算法,该解调算法对载波相位调制深度和光强度干扰均不敏感.仿真实验显示,与PGC单路微分相除(PGC-SDD)解调算法、传统的PGC微分交叉...     

差压气密性检测仪设计与实现

设计了基于差压法原理的以ARM处理器为控制核心的通用型气密性检测仪.该仪器系统通过气控阀控制气路对工件的充放气过程,并利用高精度差压传感器获得由气体泄露产生的差压值,人机交互界面采用触摸屏模块.结果表明,该检测仪方便快捷、测试精度高、稳定性好.     

Radiation stability of carbon nanostructures

A theoretical study of the radiation stability of carbon nanostructures irradiated by an electron beam has been made. Calculations have been performed with the use of an analytical expression for the cross-section for scattering of relativistic electrons by carbon atoms, as well as of the data on the threshold energy of atomic displacement from the carbon lattice obtained by the molecular dynamics method. Stability limits of carbon nanostructures and basic parameters of the process have been found. The calculated values of the characteristic time of the process are in good agreement with the available experimental data.     

Radiation pressure and the acoustoelectric effect

The radiation pressure on an absorber of electromagnetic waves is independent of the absorption mechanism since it stems from the absorption of the real momentum of the radiation. A periodic acoustic wave in a solid has essentially zero real momentum. Its pressure on an absorber is shown to be a function of the mechanism for absorbing energy. The acoustoelectric effect represents a particular way of absorbing energy such that the absorber works on the wave velocity of the acoustic wave. The result is a pressure which has the same form as that for electromagnetic radiation but is independent of the real momentum of the acoustic wave. Other modes of absorbing energy are described which yield pressures significantly different from the acoustoelectric pressure.     

Development of large area silicon detectors: Special properties and radiation stability

Large area totally depleted silicon detectors with a sensitive surface of up to 35 cm² have been developed for applications in high energy physics with emphasis on electromagnetic and hadronic shower calorimeters. Special fabrication processes and related diode properties, including long-term stability, will be discussed. Special attention is given to edge effects which are investigated with a scanning proton microbeam. The radiation sensitivity of such detectors was extensively studied through capacitance-voltage as well as capacitance-frequency measurements.     

Improvement of the seismic noise attenuation performance of the Monolithic Geometric Anti-Spring filters for gravitational wave interferometric detectors

The Monolithic Geometric Anti-Spring (GAS) filter is one of the most efficient vertical seismic isolation devices for Gravitational Wave (GW) interferometers. However, the attenuation of this filter was previously limited to around 60 dB due to the high frequency saturation associated with the filter's distributed mass—a problem typical of passive mechanical filters. We show that it is possible to circumvent this limit using a compensation wand based on the Center Of Percussion (COP) effect. When this device is mounted in parallel with the blade springs of a GAS filter, attenuation improves to 80 dB in the region above 10 Hz. Using this device it is therefore possible to design simpler attenuation chains consisting of fewer stages.