摘要:

The torsion pendulum is not only a mainstay instrument in the world of precision measurement and gravitational physics, but is important in electrical science, biophysics, petrology, metallurgy, and various other fields of endeavor. Whether used in the ‘‘static’’ (deflection) mode, the ‘‘dynamic’’ (oscillating) mode, or in some more complex configuration, instrumentation of this kind enables one to isolate and measure weak effects that would otherwise be difficult if not impossible to observe against the background gravitational field of the earth. In this review, we present a brief history of fiber‐suspended apparatus and assess the fundamental limits of performance of the dumbbell pendulum. We then inventory the different versions of such systems presently used by gravitational physicists and discuss the various interrogation techniques used to monitor the movement of the suspended test mass. Next, we tabulate some of the applications for torsion instruments outside of gravitational physics, and close with a few comments on the direction of research in this area.

ISSN:0034-6748    

DOI:10.1063/1.1144248

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We present a method of lowering below 2.5 Hz the vertical normal mode frequencies of the Pisa Super Attenuator by using permanent magnets which provide an antispring force. This method allows a more efficient suppression of the seismic noise decreasing the lower limit of the frequency region devoted to gravitational wave detection.  

ISSN:0034-6748    

DOI:10.1063/1.1144249

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Use of a double thyratron pulse modulator in a large‐bore copper vapor laser is demonstrated. Design of the laser consisting of a discharge tube of 70‐mm diameter and 1500‐mm length is discussed. The laser gave 55‐W output power at 4.8‐kHz repetition rate using neon as the buffer gas with 9.1‐kW modulator switching of electrical power. The efficiency of the laser was about 0.6%.

ISSN:0034-6748    

DOI:10.1063/1.1144250

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We propose and demonstrate the use of a photostimulable phosphor material, BaFBr:Eu2+, for recording two‐dimensional intensity distributions within output beams of vacuum ultraviolet lasers. The sensitivity characteristics were measured not only for nanosecond pulsed radiation from KrF, ArF, and Ar2excimer lasers but also for quasi‐continuous‐wave synchrotron radiation. We designed and constructed a laser beam profiler to record, read, and erase images in vacuum. The intensity distribution in the output beams from an Ar2excimer laser was measured with it, and then the threshold gas pressure for obtaining the well collimated beams was found to be 22 kg/cm2. The intensity is not uniform in the beams but stronger in the peripheral part than in the central one.

ISSN:0034-6748    

DOI:10.1063/1.1144251

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The focal point of a laser beam inside a liquid‐helium cryostat has been spatially stabilized. Both passive and active stabilization techniques are employed. The position of the focal point is maintained to submicrometer dimensions in the plane transverse to the beam path. The instabilities along the beam propagation direction are reduced to the order of 10 &mgr;m.

ISSN:0034-6748    

DOI:10.1063/1.1144456

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

This paper describes a laser three‐focus velocimeter for measurement of particle size and velocity to make the system compact and portable. An array of independently driven laser diodes is used to obtain the stable output of the laser beams without the thermal interference between the laser diodes and to exclude ambiguity of velocity direction. The method measuring velocity and size of a transparent and spherical particle is shown. The optical characteristics are analyzed. Using a flow of glass beads, it is confirmed that this velocimeter is a useful tool for measuring particle size and velocity simultaneously.

ISSN:0034-6748    

DOI:10.1063/1.1144252

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A versatile single‐photon timing instrument based on the reversed timing configuration has been constructed. Unlike similar instruments, the apparatus described here is capable of recording a broad range of excited‐state decay times owing to a switched fiber optic delay. This allows the user to readily collect time‐resolved luminescence data over a variable time window in the reversed‐timing configuration. With proper adjustment of the appropriate components, one can acquire a luminescence decay over a variable time range from less than 1 ns to nearly 1 &mgr;s. The full width at half‐maximum of the instrument response function is 42 ps. The utility of a switched fiber optic delay is discussed and the device’s construction is described.

ISSN:0034-6748    

DOI:10.1063/1.1144253

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have developed a circuit for maintaining a fixed phase relationship between two optical choppers. The basis of this circuit employs a phase‐locked loop using both proportional and integral terms in the feedback control voltage. Using additional circuitry, the electronics can compensate for drifts in the phase as well as frequency of both choppers in the frequency range from 200 Hz to 3 kHz. These phased optical choppers have been used to block background light simultaneous with a chopped cw laser in experiments that measure long lived fluorescence.  

ISSN:0034-6748    

DOI:10.1063/1.1144254

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have developed an electrostatically driven tuning fork chopper which is compatible with an ultrahigh vacuum (UHV) environment. Constructed with a commercially available tuning fork using stainless steel and alumina parts, the chopper is capable of operating while exposed to high temperature samples and corrosive gases. Operation in an UHV environment while modulating both optical and molecular beams is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1144255

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The performance of an optical reflective position sensor is evaluated as the position feedback element in the microposition control of a linear electromagnetic motor. The open loop position sensor characteristics are first measured to determine the analog controller design parameters. The performance of the controller, evaluated using an integrated Michelson interferometer, measures the control loop bidirectional accuracy, hysteresis, long‐term stability, and position linearity. Compensation of the small nonlinearity measured required linearization of the input command signal and a practical application is demonstrated with a constant velocity scan of one of the interferometer mirrors. A final result is the submicron square wave modulation of the interferometer output with its scan mirror under closed‐loop control using feedback from the reflective position sensor.

ISSN:0034-6748    

DOI:10.1063/1.1144256

出版商:AIP    

年代:1993

数据来源: AIP