摘要:

The general problems involved in constructing boron‐loaded liquid scintillation neutron detectors are considered. The characteristics of particular counters which have been successfully used in neutron transmission measurements by the time‐of‐flight method are then described. The design of these counters was guided by the results of a Monte Carlo study of neutron capture in a boron‐poisoned medium. This calculation gives the probability of neutron capture as a function of neutron energy, counter thickness, and time. The calculated results are compared with experimentally determined efficiencies. The advantages and problems encountered in using the boron‐loaded liquid scintillator with the Argonne fast neutron chopper are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715918

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An automatic adiabatic calorimeter shield control has been built and operated successfully for approximately 700 hours. It has been used with an existent low temperature (10 to 300°K) intermittently heated calorimeter in runs of up to 100 hours duration. Each control unit consists essentially of a difference thermocouple, high sensitivity taut suspension galvanometer, a set of four photomultiplier tubes, a relay servo mechanism, a reversible ac motor and gear train and two ON‐OFF control relays. The observed behavior of the control and the internal consistency of the data obtained during its use indicate that the precision with which it controls the shield temperature is comparable with that obtainable from a trained human operator.

ISSN:0034-6748    

DOI:10.1063/1.1715919

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Troublesome changes of the bridge balance in a twin‐T nuclear resonance bridge have been eliminated by the application of a voltage‐sensitive condenser. A small amplitude, high‐frequency modulation voltage applied to the condenser senses any deviation from balance, and a servo loop provides a dc correction voltage which maintains the bridge balance. No apparent deterioration of the spectrum results from modulation of the bridge.

ISSN:0034-6748    

DOI:10.1063/1.1715920

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A description is given of the dielectric recording technique wherein information is stored as a surface charge on a rotating dielectric coated drum. The specific application of the technique to a multiple channel recorder is shown. A general comparison between the properties of analog dielectric and magnetic drum recording is presented. The comparison shows dielectric recording to have important advantages for some applications.

ISSN:0034-6748    

DOI:10.1063/1.1715921

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Theory of design and construction of a field stabilizer for high‐resolution nuclear magnetic resonance spectrometers is described. Achievable time stability is 1:108. A voltage induced by field variations in suitably located coils is amplified by a galvanometer amplifier, integrated, and fed back to a system of coils biasing the field. The feedback ratio is 70 db from dc up to 0.2 cps. The stabilizer allows measurement of nuclear magnetic resonance signals with resolution of 108under field conditions, independent of field fluctuations produced by temperature variations and stray fields.

ISSN:0034-6748    

DOI:10.1063/1.1715922

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A neutron velocity spectrometer with a 100‐Mev betatron as a source of neutron pulses has been in use at the Knolls Atomic Power Laboratory since 1953, for cross section measurements up to about 50 000 ev. An internal, thick uranium target is bombarded by 80‐Mev electrons when the betatron orbit is rapidly contracted, giving approximately 0.1‐microsecond bursts of neutrons at a 60‐pps repetition rate with a peak intensity of about 7×1015neutrons per second. Measurements of total, capture, and fission cross sections are made with high‐resolution detecting equipment located at points up to 20 meters from the target. The timing, registering, and data‐processing techniques are designed to achieve maximum benefit from the short burst duration.

ISSN:0034-6748    

DOI:10.1063/1.1715923

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Data are presented on the effect of voltage‐divider circuits on the operating characteristics of multiplier phototubes. Linear, superlinear, and saturated behavior of output currentvslight flux are related to divider current. Characteristics are shown for varying sensitivity by controlling interdynode voltage. Divider circuits are described, which protect the multiplier phototube from excessive current flow.

ISSN:0034-6748    

DOI:10.1063/1.1715924

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The principal hazards of operating a liquid hydrogen bubble chamber are failure of equipment (due to overpressure) and uncontrolled escape of hydrogen gas, which may cause an explosion. If safety considerations are incorporated in planning from the job beginning, components can be designed to reduce or eliminate the probability of accidents arising from the known hazards.The degree of safety, the hydrogen safety‐vent system, and the hazards, and operation of the liquid hydrogen bubble chambers at UCRL are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715925

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A description is given of the mechanical gauge and electrical circuit employed for measuring millisecond pressure pulses in a liquid hydrogen bubble chamber, in a pulsed magnetic field region.The pressure pulse produces a deflection of a diaphragm that acts as one electrode of a capacitor. The change in capacitance is measured in an electrical circuit by comparison with a reference capacitor.A common source feeds two cables, one of which is terminated by the pressure‐measuring capacitor (``transducer''), the other by the adjustable comparison unit. Pulses from the common source are reflected from the two terminations, and their difference is amplified and displayed. The circuit employed is such that the distributed capacitance of the cables does not affect the sensitivity of the system. Hence, the interconnecting cables are not limited in length up to several thousand feet.The frequency‐response limit is about 10 kc for units currently used, because of the diaphragm characteristics. Steady‐pressure calibration can be employed in order to determine the pressure and output relation.

ISSN:0034-6748    

DOI:10.1063/1.1715926

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A device is described for producing a uniform distribution of a solution of radioactive material over a large area source. Droplets of controlled size are expressed from a syringe at a constant rate and systematically and uniformly placed over an area up to 50 centimeters square.

ISSN:0034-6748    

DOI:10.1063/1.1715927

出版商:AIP    

年代:1957

数据来源: AIP