摘要:

A frequency domain approach is applied to the University of Western Australia’s resonant bar detector to determine its potential sensitivity and calculate the limiting noise sources. To understand its behavior the sensitivity is calculated as a function of various noise components. To minimize seismic noise upconversion, the system is operated in the cold damping regime at the turning point in the antenna frequency versus pump frequency characteristic. For this configuration it is shown that the spectral strain sensitivity of a high‐Qantenna with a parametric transducer can exceed 10−21&sqrt;Hz with approximately a 20 Hz bandwidth, using existing microwave technology. This corresponds to a strain sensitivity of less than 10−19for a 1 ms gravitational pulse. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146503

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The best sensitivity of a laser interferometric gravitational wave detector can only be achieved after considerable reduction is made in fluctuations of the geometry of the laser beam. Beam geometry fluctuations can be divided into four main types; lateral beam movement, tilt of the beam, variations in the beam width, and fluctuations in the beam curvature. Here we describe new techniques of measurement. The results for two types of laser beam geometry fluctuation—lateral movement and width fluctuation—for an argon‐ion laser and for a diode pumped monolithic ring Nd:YAG laser are presented. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145622

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We review and present an analysis of the major issues in the design of test mass control systems for laser interferometer gravitational wave detectors. Based on this analysis, we present a design for a computer controlled modular analog servo control system which is well suited to the control of a large number of degrees of freedom in long baseline instruments. The system has been tested on an interferometer using multistage cantilever spring isolators. The system enables simple monitoring, testing, and display of many channels simultaneously, while retaining the advantages of analog proportional‐integral‐derivative control electronics. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145623

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Perth Astronomy Research Group has developed an automated supernova search program, using the 61 cm Perth–Lowell reflecting telescope at Perth Observatory in Western Australia, equipped with a CCD camera. The system is currently capable of observing about 15 objects per hour, using 3 min exposures, and has a detection threshold of 18th–19th magnitude. The entire system has been constructed using low‐cost IBM‐compatible computers. Two original discoveries (SN 1993K, SN 1994R) have so far been made during automated search runs. This paper describes the hardware and software used for the supernova search program, and shows some preliminary results from the search system. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145624

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report frequency locking of a Nd:YAG tunable laser to a 2000 finesse 87‐cm‐long Fabry–Pe´rot cavity in air using the Pound–Drever technique. The novelty is that the necessary phase modulation of the beam is obtained using the laser directly instead of an external phase modulator (Pockels cell). The spurious relative amplitude modulation using this method was ∼3×10−5with a modulation index &bgr;∼1 and the spectral density of the frequency difference between the laser and the cavity is below 1 mHz/&sqrt;Hz in the region 1–500 Hz. ©1995 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1145555

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Intense, frequency‐stabilized single‐mode laser sources are essential in precision distance measurements. We report a new scheme for stabilizing the oscillation of a three‐mode laser so that a maximum output intensity can be realized. When one of the modes oscillates at its maximum intensity, the other two oscillate at each side of the central mode in the gain curve. The two intermode beats generated from the adjacent mode outputs are utilized to stabilize the laser frequency. Both the sum and the difference of the two beat frequencies vary because the frequency of each intermode beat varies with respect to cavity expansion via the phenomenon of ‘‘frequency pulling.’’ These secondary beat signals are utilized as control signals for stabilizing the laser output frequency. To evaluate the effectiveness of the proposed concept, we compared two possible stabilization techniques involving the addition and subtraction of beat frequencies from the perspective of design simplicity, reliability, and ease of operation. Our investigation has shown that stabilization using the difference of two intermode beat frequencies, is superior. Excellent frequency stability (instability=10−10) of the laser was achieved during experiments. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145556

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The system of single bunch injection (SBI) for the storage ring NIJI‐IV was completed. The system was used for the injection of the short pulse beams from an electron gun into only one of the 16 rf buckets in the ring. On a compact storage ring, the multipulse beams in one pulse train can be stored into only one of many bunches by one injection. The optimum number of the grid pulse in one pulse train was determined to improve the storage efficiency and the storage current by one injection. The keeping time of the bump orbit was calculated by using the transfer matrices. The optimum pulse number obtained by the calculation is 2. In the SBI system, the number of grid pulses in one pulse train can be selected by the gate circuit. A snap off diode and a clip line are used to generate 2 ns grid pulses. The measured grid pulse was shorter than the longitudinal space 5.5 ns of the rf bucket with voltage of −80 V. The EIMAC Y‐646B cathode‐grid assembly is used as the electron source. It is expected that the injection system provides a higher peak current and easier free electron laser use operation in comparison with the rf‐knockout system. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145557

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The design goals and the performance data for the exactly focusing spherical grating monochromator at BESSY which is installed on a crossed field undulator for circularly polarized undulator radiation is described. By employing a variable deviation angle at the grating it is possible to exactly focus the entrance slit on the exit slit at all wavelengths. In addition, the optical aberrations are very small, leading to a high resolution over the energy range of the monochromator. The performance has been verified by analysis of the He (1s−1 np) and the Kr (3d−15/2,3/2 np) resonance series. A resolution ofE/&Dgr;E≊17 500 at 65 eV in second order has been achieved. Since commissioning, this monochromator has been used for a variety of experiments requiring both plane‐ and circularly polarized undulator radiation. ©1995 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1145558

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A static Fourier‐transform spectrometer has been designed based on Wollaston prisms. It produces an interferogram in the spatial domain which is recorded using a 2D camera. A combination of two Wollaston prisms localizes the interference fringes coincident with the plane of the detector, thereby facilitating an extremely compact design. A personal computer is used to calculate the wavelength spectrum of the input light from the Fourier transform of the interferogram. In addition to its use as a compact and efficient spectrometer, the instrument’s use as a laser wavemeter has also been demonstrated. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145559

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The signal‐to‐noise ratio in a time‐resolved Fourier transform (FT) infrared emission experiment is improved by pulse‐to‐pulse normalization. The signal from the FT spectrometer is normalized by the total infrared fluorescence produced on each laser pulse. A factor of 20 enhancement in signal‐to‐noise ratio is demonstrated with normalization when the fluctuation of the laser pulse energy is the dominant noise source. Applications are discussed pertaining to cases where other noise sources such as detector and amplifier noise cannot be neglected and when information from the time evolution of the spectrum is required. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145560

出版商:AIP    

年代:1995

数据来源: AIP