摘要:

A liquid scintillation counter suitable for measuring H3and C14activities is described. A photomultiplier tube with a high sensitivity and signal‐to‐noise ratio is used, and is cooled to −10°C to further reduce the tube noise background. The phototube is mounted in a chassis containing its preamplifier, and the pulses are then led to a high‐stability amplifier scaler. The radioactive materials are dissolved in aliquots of a xylene solution containingp‐terphenyl (1.9 g/liter) and diphenylhexatriene (0.020 g/liter). Substances which quench the scintillations or color the scintillator solution cannot be counted by this method. A minimum of 4.3×10−10curie of H3, or 1.8×10−11curie of C14may be measured by the counter.

ISSN:0034-6748    

DOI:10.1063/1.1771156

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A machine is described which solves the equations of motion for a charged particle in a two‐dimensional magnetic field. Its accuracy is not limited by the steepness or the asymmetry of the field. Guided by remote control, the mechanism moves continuously over a contour map just as a particle would move through the field itself. The operator matches position, or local field value, with a parameter of the steering control, or curvature of the trajectory. He is able to interpolate continuously between lines of constant field value, thus speeding the process of solution and increasing the accuracy. In five minutes a 40‐inch orbit can be drawn over which the field values vary through 23 000 gauss. Five minutes are required for introducing initial conditions, including momentum. For regions in which the field is more than half maximum, the orbits of the mechanical particle and the electromagnetic particle coincide in their radii of curvature to within 0.5 percent. Accuracy is less for low field values. The performance characteristics have been determined from a working instrument which is fully described. An alternative computer design to the one already in use is also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1771157

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

An interferometer for measuring gas density as a function of time during a transient flow is described. This is an absolute instrument capable of measuring density changes over an approximate range from 10−2to 10−5g/cm3. Since the instrument requires only small optical components, it is relatively simple and inexpensive to construct.

ISSN:0034-6748    

DOI:10.1063/1.1771158

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The construction of a specimen holder and furnace for use as an auxilary piece of equipment with a North American Phillips Company high angle goniometer is described. The apparatus can be used for obtaining x‐ray diffraction patterns at temperatures up to 1600°C, and at pressures in the range of 2×10−6to 3×10−5mm of mercury.

ISSN:0034-6748    

DOI:10.1063/1.1771159

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A fast neutron detector has been prepared by suspending ZnS phosphor powder in ``Bio‐Plastic''. The detector can be easily prepared using only simple laboratory equipment. In the presence of the gamma rays from a Ra‐Be source, the neutrons from the source can be counted using this detector with about one percent efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1771160

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A cylindrical chamber, 8.5 in. in length and 8.5 in. in diameter, containing two sets of parallel multiple‐wire grids has been built and operated as a proportional counter for fast neutron detection. The collecting wires are 0.001 in. in diameter. Filled with pure CH4at about atmospheric pressure and operated at 3400 v, it serves to detect neutrons up to 10 Mev, with an average efficiency of 0.17 percent. The energy distribution of neutrons from 0.3 to 3 Mev can be estimated. The multiple‐wire counter is completely insensitive to gamma radiation under these operating conditions. This instrument has been used to make a survey of fast neutrons around the U. C. L. A. cyclotron. At higher pressures the instrument can presumably be used to measure neutron spectra of higher energy.

ISSN:0034-6748    

DOI:10.1063/1.1771161

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The electron beam of the National Bureau of Standards betatron has been removed by the use of a pulsed magnetic extractor. The electrons were spiraled outward into the extractor that had created a sharp step magnetic field canceling the betatron guiding field for 19° of azimuth. This step magnetic field was produced by a current pulse flowing in an array of parallel wires. The removed beam was well focused. Initial testing up to 24 Mev showed that about 60 percent of the accelerated electrons were extracted in the beam.

ISSN:0034-6748    

DOI:10.1063/1.1771162

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A new type of goniometer has been designed and constructed for neutron diffraction analyses, and particularly for single‐crystal studies. The neutron detecting system employs a scintillation crystal and photomultiplier, or a miniature high‐pressure BF3counter; and the detector and diffracting crystal are located within a cylindrical shielded region, in such a manner that the moving parts are entirely free of heavy shielding elements. When a miniaturized BF3counter is used, no shielding except B4C in plastic immediately surrounding the counter is required. Rotations are accomplished by servo‐controlled motors, with selsyn indicators coupled to an external servo system. This servo control is designed to permit future introduction of automatic crystal and detector setting. The system is small and inexpensive, and has the particular advantage of readily permitting three‐dimensional diffraction measurements.

ISSN:0034-6748    

DOI:10.1063/1.1771163

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A photoelectronic apparatus has been developed which makes possible the continuous simultaneous measurement of the depth of penetration, the speed, and the deceleration of a nondeforming small‐caliber projectile dring armor penetration. The basic operating principle of the apparatus is to have the flight path of the projectile pass perpendicularly through a thin parallel light beam of uniform intensity which activates a vacuum‐type phototube. The output of the phototube is proportional to position or the depth of penetration under appropriate geometry. A voltage signal derived from the phototube circuit is preamplified and differentiated to give voltage signals proportional to speed and deceleration. Permanent records of the signals are made by photography of cathode‐ray tube traces and analyzed. The apparatus is capable of measuring real transient accelerations or decelerations as great as 108ft/sec2(3×109cm/sec2) with average error of 2 percent. Possible applications of the system to mechanical problems as an accelerometer, speed, and displacement measuring device are indicated.

ISSN:0034-6748    

DOI:10.1063/1.1771164

出版商:AIP    

年代:1954

数据来源: AIP