摘要:

A simple electron spin resonance (ESR) spectrometer for the detection of organic free radicals is described. The salient features are: (1) homodyne balanced mixer detection, (2) improvement of the magnetic field homogeneity by means of two pairs of current shims, and (3) new tuning procedure independent of the resonance spectrum itself, making use of the klystron‐stabilization error signal. At 3200 gauss the magnetic field homogeneity is better than 2:105over a sample volume of 0.25 cm3. The sensitivity is such that 2×1013spins of the free radical DPPH can be detected.

ISSN:0034-6748    

DOI:10.1063/1.1717140

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A simple diaphragm type transducer for small differences in gas pressures is described together with a suitable electronic arrangement for using it as a control element. The sensitivity of the arrangement is limited by ambient temperature effects on the diaphragm. A zero stability of about 0.1 &mgr; Hg has been achieved and this could probably be improved on by sufficiently good thermostating. An important feature of the diaphragm is that it may be subjected to large unbalanced pressures without damage, although such pressures will produce zero shifts equivalent to a few microns of mercury.

ISSN:0034-6748    

DOI:10.1063/1.1717141

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Criteria are discussed for using thermocouples in carbon atmospheres above 2000°C. Experimental data are given for W/Re, W/W‐25 Re, Re/W‐25 Re, graphite/Re, and graphite/Ir thermocouples in carbon atmospheres from room temperature to 2200°C. Reaction temperatures of carbon with thoria, urania, and yttria were measured to be below 1730°, 1620°, and 1590°C, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1717142

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

An all quartz electroscope system is described whose sensitivity may be varied over a wide range by changing one potential. Like other previously described systems, it accumulates a definite quantity of electric charge, for given potentials, and then automatically recharges itself. When this recharging occurs an electrical pulse may be taken off for recording purposes. It is possible to change the sensitivity by a factor of 500.

ISSN:0034-6748    

DOI:10.1063/1.1717143

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A device is described which generates sinusoidal waves of radiant power for use in visual experiments. The instrument covers a continuous range of frequencies from 2 to 75 cps, modulation amplitudes from 0.001 to 1.0, and luminance levels from 0.01 to 1500 mL. Frequency, amplitude, and luminance controls are mutually independent. Both ``equal‐energy'' white light and narrow‐band chromatic stimuli are provided.

ISSN:0034-6748    

DOI:10.1063/1.1717144

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A vacuum tube pulser which was developed for the operation of gas discharge tubes used in plasma research is described. It is capable of supplying a load with rectangular current pulses of as much as 12 to 15 amp for durations from 30 to 500 &mgr;sec with a voltage drop across the load up to 3500 v. The maximum duty cycle at high currents is 0.005.

ISSN:0034-6748    

DOI:10.1063/1.1717145

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

In the study of metal‐high explosive detonation wave interaction, by the pin technique, it is desirable to obtain time measurements to an accuracy of less than 1 m&mgr;sec over a total time interval of 5 &mgr;sec. Commercial instruments capable of a high degree of time resolution were not available and a special instrument was developed for this purpose. A cathode‐ray oscilloscope, displaying deflection type event pulses, is converted into a precise time‐measuring instrument by a calibrated zig‐zag sweep. The record is obtained by single‐shot photography of the cathode‐ray tube sweep which is triggered by the event to be measured. The calibrated zig‐zag sweep is crystal controlled at 2 Mc and has superimposed deflection type time marks, 2 m&mgr;sec wide, at 50‐m&mgr;sec interval, synchronized with the zig‐zag frequency. The apparatus can drive six oscilloscopes simultaneously or in sequence from delayed triggers.

ISSN:0034-6748    

DOI:10.1063/1.1717146

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

When velocity logging oil wells, a sonde is raised from the bottom of the well borehole at a slow, but variable and unpredictable rate. This sonde transmits pulsed acoustic energy at a variable pulse repetition rate into the earth surrounding the borehole and, in addition, detects the refracted acoustic pulses after they have traveled a few feet through the earth surrounding the borehole. In order to ascertain certain characteristics of the earth, it is desirable to record photographically those pulses occurring, not at specified time intervals, but at specified depth intervals. This is accomplished by converting the sonde depth to electrical gate pulses occurring at the desired depth intervals. These gate pulses are used to open a gate which permits only the first acoustic pulse following a gate pulse to pass through the gate and be photographed on a triggered oscilloscope. The equipment is fully automatic in that the camera film is automatically advanced between recorded pulses and precautions are automatically taken to prevent double exposures. Similar instrumentation should be applicable to related problems involving the photographing of system responses as a function of some measurable parameter which varies slowly but unpredictably with time.

ISSN:0034-6748    

DOI:10.1063/1.1717147

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A wall‐stabilized water‐cooled copper ring type arc source is described which operates stably in apparently any gas for periods of an hour or more at currents up to 100 amp. Arc temperatures obtained spectroscopically by absolute line intensity and line profile methods are given for the arc in nitrogen at 92 amp.

ISSN:0034-6748    

DOI:10.1063/1.1717148

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A linear transmission gate for use in scintillation counter coincidence experiments is described. The gate is suitable for negative pulses of microsecond duration and is linear over a range of 0.01 to 5 v. The circuit is relatively simple, uses no vacuum tubes, and is reliable over long periods of use. The use of low‐level gates can increase the usable counting rate of a multichannel coincidence system by an order of magnitude.

ISSN:0034-6748    

DOI:10.1063/1.1717149

出版商:AIP    

年代:1961

数据来源: AIP