摘要:

A method of equilibrium orbit measurement in a synchrotron which utilizes a small computer for on‐line data acquisition and analysis is presented. It includes a discussion of a low cost transducer circuit which is capable of processing the high frequency, phase sensitive pulse train signals obtained from pickup electrodes located along the circumference of an alternating gradient accelerator. The analog signal thus obtained is directly suitable for use by a computer's analog/digital converter. The speed with which orbits may be measured combined with the inherent flexibility of a programmable device enables accelerator physicists and machine operators to more readily probe into the behavior of the Brookhaven AGS.

ISSN:0034-6748    

DOI:10.1063/1.1683913

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The linear control theory for constant‐temperature anemometers can be extended to the nonlinear case which applies for large velocity fluctuations. The nonlinear theory establishes the domain within which the linear theory is valid and reveals some nonlinear effects for large velocity fluctuations. Calculations using a second order approximation have been carried out for velocity fluctuations as large as ±64% of the mean velocity. They show in case of a sinosoidal input function the generation of a second harmonic at the output which limits the usefulness of the anemometer at high frequencies. In case of a large velocity step, a longer time is required to indicate the step correctly than is required for the indication of a small step.

ISSN:0034-6748    

DOI:10.1063/1.1683914

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An electro‐optic shutter has been realized for use as a component of a Nd glass laser system delivering high peak power pulses. Its main characteristics are (a) switching time less than 1 nsec and (b) dynamic contrast ratio (i.e., peak pulse intensity/intensity preceding the leading edge) higher than 40 dB. This system is capable of delivering optical pulses with half‐peak durations of 1 nsec. Two different synchronization schemes have been applied. The first one utilizes a Kerr‐cell Q‐switched laser. The same voltage step triggers, in turn, the laser and the shutter. The second one utilizes a rotating prism Q‐switched laser. A fraction of the laser emission is used to trigger a spark gap which controls the electro‐optic shutter.

ISSN:0034-6748    

DOI:10.1063/1.1683915

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

In measurements of circular polarization of gamma rays in which the radiation is detected by a scintillator coupled to a photomultiplier, the phototube has to be shielded from the reversible fringing magnetic field of the polarization analyzer. Weak residual fields, however, produce a small gain shift between the photomultiplier outputs during the periods of opposite magnetizations of the polarimeter. By applying slightly different voltages to the photomultiplier simultaneously with reversals of the magnetic field, this shift can be eliminated. A simple effective method of utilizing this suggestion is outlined.

ISSN:0034-6748    

DOI:10.1063/1.1683916

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An optical‐EPR sample probe using tunable coaxial coupling, for use at fixed temperatures in the range 1–300 K, has been designed and constructed. It allows both critical coupling of the resonant cavity to the microwave system and good sample illumination, while minimizing thermal agitation.

ISSN:0034-6748    

DOI:10.1063/1.1683917

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A phosphoroscopic instrument with a high time resolution and flexibility capable of operation in several modes (phosphorescence, fluorescence, light scattering, and absorbance change) was constructed for the study of energy transfer in photosynthesis. Its operation time range is from about 20 &mgr;sec to more than 1 sec. Optical, mechanical, and electronic designs of the instrument are shown. Typical recordings obtained with the apparatus operated in several different modes are presented.

ISSN:0034-6748    

DOI:10.1063/1.1683918

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The applicability of pyroelectric thermometry to temperature change or temperature rate measurement at low temperatures was studied, with particular emphasis on calorimetry. The pyroelectric coefficients, dc dielectric constants, and volume resistivities of three ferroelectric ceramic materials, Clevite Ceramic B, PZT‐4, and PZT‐5A, were measured over the temperature range 4.2 to 300K. The pyroelectric coefficients were found to be reproducible, but large electric fields, thermal shock, and aging affected them. Expressions are derived for the temperature responsivity (voltage output per unit temperature change), noise equivalent temperature change (temperature change equivalent to the electrical noise in a pyroelectric thermometer), and figure of merit (a parameter characterizing the physical properties of a pyroelectric material). Typical temperature responsivities of 8.0 and 165 V/K, and values of noise equivalent temperature change of 2.5 and 0.12 &mgr;K, at 5 and 300K, respectively, are calculated. Recommendations are given for the use of a pyroelectric thermometer in a low temperature calorimeter.

ISSN:0034-6748    

DOI:10.1063/1.1683919

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The sum‐delay amplifier and the gate generator are in separate single‐width NIM modules. The amplifier has five input channels which can be switched in or out. The delay can be switch selected to be 0, 1, or 2 &mgr;sec. The gate generator is very flexible. It will accept almost any type of input signal and produce an output pulse which can be adjusted to meet most gating requirements. One frequent use of the instrument is to observe the performance of an electronic system while an experiment is being performed.

ISSN:0034-6748    

DOI:10.1063/1.1683920

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A single focusing, 30.48 cm radius, 60° sector magnet mass spectrometer was constructed with symmetric conjugate foci calculated from fringe field data and corresponding to a beam deflection of 68°. Experimental and calculated optical characteristics agree well. A rotating coil probe and a rate coil are employed as field sensors for a nulling device and for field scanning. The magnetic field can be set to 27 values corresponding to the center of spectral lines and zero lines on both sides of each peak. The automatic scanning consists of: (1) rapid field change between adjacent field values (∼500 G/sec); (2) locking in at the preset field values (∼0.3 sec); (3) remaining in a channel for a preset time during which the ion beam current is integrated and the data digitized. Repeated arbitrary excursions between channels do not cause effective field variations of more than |&Dgr;B/B| = 2×10−5. For 0.2 mm source and 0.64 mm collector slit settings, a typical peak at mass 88 is flat for 2.7 G to 0.01% at a 14 kV accelerating potential. Data consist of channel intensity, scale factors, and internally provided clock time; data signals drive a typewriter and tape punch. A cyclic scan of five isotopes including background requires 35 sec. A segment of data (∼10 cycles) is processed by the computer and the results returned to the operator.

ISSN:0034-6748    

DOI:10.1063/1.1683921

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The stability of a superconducting, current‐carrying ring levitated in a static magnetic field is investigated theoretically. The azimuthally symmetric supporting field has componentsBr, B&thgr;, andBz. A first‐order perturbation calculation is performed to determine the oscillation frequencies of the stable modes and the stability criteria for the potentially unstable modes. In the absence of external feedback and/or image currents in the surrounding walls, the ring is unstable. The stability criteria involve the ring current and mass as well as the configuration of the external field and the surrounding walls. It is found that the ring may be stabilized by proper choice of the wall configuration, and if a given configuration is not such as to satisfy the stability criteria, the magnitude of external feedback necessary may be determined from the results.

ISSN:0034-6748    

DOI:10.1063/1.1683922

出版商:AIP    

年代:1969

数据来源: AIP