摘要:

A pulse‐height analyzer using conversion of pulse amplitude to time is described. It has an accuracy, resolution, linearity, and stability better than one percent. It can be exposed to pulse rates of several thousand per second and records on tape up to 50 pulses per second. It is equivalent to a 250‐channel discriminator of relative simplicity.

ISSN:0034-6748    

DOI:10.1063/1.1770582

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The possible use of U‐ and O‐tube manometers as extremely accurate and sensitive accelerometers is investigated. It is found that their steady‐state fluid‐level displacement is linearly related to the applied acceleration. Both the Navier‐Stokes equation and Lagrange's equation are used to derive the equation of motion of the fluid level for a multiple cross‐section tube. Nonlinear terms are derived to represent the turbulence introduced by change of cross section. Means of obtaining an overdamped, nearly linear, long time‐constant accelerometer are discussed. A study of the effect of design on response reveals that almost any desired specifications can be achieved by an appropriate modification of structure and/or fluid medium. Experimental tests, conducted on a platform vibrated in a one‐dimensional sinusoid by a rotating cam, confirm predictions based on the theory.

ISSN:0034-6748    

DOI:10.1063/1.1770583

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A microbalance has been developed for the simultaneous measurement of the apparent weight and volume of a single protein crystal immersed in its mother liquor. The crystal density, computed from these values, is not subject to the errors, resulting from an altered environment, which are present in the usual flotation procedures. The technique, moreover, may also be used for following the volume and density changes which occur on changing the composition of the immersing liquid. The sensitivity is easily controlled by the choice of the diameter of the fiber used in the weighing mechanism. This balance may be of use in other systems where the apparent weight and/or volume of an object, immersed in a liquid of known composition, is required.

ISSN:0034-6748    

DOI:10.1063/1.1770584

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A simple method is proposed for describing the detectivity of photoconductive cells.First it is pointed out that at signal modulation frequencies well below the frequency that corresponds to the time constant of the cell, the responsivity of the cell is independent of the frequency. For the same range of signal modulation frequencies, the noise power (mean‐square noise voltage) per unit frequency bandwidth is inversely proportional to the frequency. It is a very general property of radiation detectors obeying Lambert's law that the detectivity varies inversely as the square root of the sensitive area.As a result of the facts just stated, one is led to the conclusion that if one multiplies the measured detectivity by the square root of the cell's sensitive area and by the square root of the band width of the noise, and if one divides by the square root of the frequency of the test signal, one obtains a result that is independent of the test band width and test frequency and is independent also of the sensitive area of the cell. The detectivityDso obtained is defined in Eq. (3) and is called the ``detectivity in the reference conditionC.''The detectivityDis not proposed as a replacement for a detailed description of the test conditions and test results. It is an auxiliary quantity to be computed from the test results. It has the advantage over any other single test result that the knowledge of it alone permits a direct and significant comparison of two cells, even though the cells are of different area and are tested under different conditions.A discussion is included of the various auxiliary ``ground rules'' that must be observed if one wishes to state the detectivity of a cell with complete unambiguity.

ISSN:0034-6748    

DOI:10.1063/1.1770585

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An expansion cloud chamber has been developed which operates at a pressure before the expansion of about 45 millimeters of mercury. Since evaporation is rapid and the temperature very low during the sensitive time of the chamber, the density of the gas is higher after the expansion than before. The composition of the gas before the expansion is approximately 40 percent water vapor and 60 percent permanent gas. When the chamber is operated with oxygen or argon, the stopping power of the gas during the sensitive time is 7.6 percent that of NTP air. When it is operated with helium, the stopping power is 5.7 percent that of NTP air.

ISSN:0034-6748    

DOI:10.1063/1.1770586

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A method for preparing and mounting NaI‐TlI crystals for scintillation spectrometers which gives high optical efficiency, stability and good gamma‐ray energy resolution is described. Variations in energy resolution of photomultipliers and NaI‐TlI crystals is shown. Approximately 200‐ev electron energy loss in a NaI‐TlI crystal is required to release a single photoelectron from a photocathode whose efficiency is 60 microamperes per lumen.

ISSN:0034-6748    

DOI:10.1063/1.1770587

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A cloud chamber with a magnetic selection favoring low‐energy particles is discussed. Technical aspects of shielding, expansion, mechanism, sweeping field, and poisoning troubles are included. Discussion of the present mode of operation for a study of &pgr;−capture in helium is given.

ISSN:0034-6748    

DOI:10.1063/1.1770588

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An apparatus has been developed with which thermal conductivities can be measured in the temperature range from 40°C to 100°C with a probable error of ±0.003 cal sec−1cm−1deg−1or ±3 percent, whichever is the larger. It requires only a small sample (0.1875×0.1875×1.75 inches), does not require the attaching of thermocouples to the sample, and permits introduction and removal of the sample by remote control, if this is necessary. The apparatus is therefore especially useful to measure the thermal conductivity of large single crystals and also to observe the effect upon thermal conductivity of heat treatment, irradiation, or any other treatment that will not deform the sample yet which cannot be carried out readily with thermocouples attached to the sample.

ISSN:0034-6748    

DOI:10.1063/1.1770589

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Twenty‐two boron trifluoride counters were run at counting rates of about 106counts per min in the proportional region until they had all lost their plateaus of voltageversuscounting rate. This occurred in from 108to 109counts. The pulse heights decreased to the point at which maximum sensitivity of the circuitry failed to record more than 103counts per min, although many more small pulses could be detected on an oscilloscope. Raising the voltage did not restore the pulse heights. The counters did not recover after inactive periods of up to four months. Gas samples from several of the counters were analyzed on a mass spectrometer. A theory is proposed which would explain the deterioration on the basis of a negative ion sheath which is formed when the BF3dissociates.

ISSN:0034-6748    

DOI:10.1063/1.1770591

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Small, completely sealed, magnetically operated pumps have been constructed for use in circulation of corrosive gases. Successful and extended use has been obtained with gases such as uranium hexafluoride and hydrogen fluoride at pressures up to 175 psig and 100°C. Pumping characteristics with respect to air at atmospheric suction pressure are given.

ISSN:0034-6748    

DOI:10.1063/1.1770592

出版商:AIP    

年代:1953

数据来源: AIP