摘要:

The fast semiconductor diodes and transistors now available make it possible to design counting circuits which are as fast as standard fast vacuum tube circuits. A simple coincidence circuit using these devices is described. The measured threshold and resolving time characteristics are given. The circuit is free from the difficulty present in some vacuum tube circuits wherein a coincidence count can be made with a pulse below the threshold at one input if a pulse considerably above the threshold is present at another input. The changes in counting arrangements which the simplicity of these circuits permits are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1716639

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A new electron diffraction device is described which is especially suited for the investigation of diffusion problems, phase transitions, and reactions of solids with gases or other solids. It is equipped with a continuously recording camera where a 4×10 in. photoplate passes underneath a narrow slit exposed to the diffraction cone. The resulting photograph shows parallel diffraction lines instead of the usual Debye‐Scherrer rings and gives a gapless picture of the occurring structural changes which are easy to evaluate. If the sample is heated according to a known temperature‐time function, the temperature‐structure dependence may be recorded, and by moving the sample synchronously with the plate through the electron beam, one may record the geometrical distribution of different structures in an inhomogeneous sample. The latter method is especially suited for a rapid investigation of unknown binary or multicomponent phase diagrams. The device includes the following special features: deposition of the sample containing up to 3 different components by evaporation inside the specimen chamber, an attachment for monitoring the sample reflectance during runs, a rotating shutter producing wedge‐shaped sample layers, and a heatable specimen holder for use in transmission as well as in reflection. Finally, a few examples are given showing some applications of the described electron diffraction unit.

ISSN:0034-6748    

DOI:10.1063/1.1716640

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Ring detection has been carried out in a thin‐lens beta‐ray spectrometer by locating anthracene crystals at the ring focus of the electron trajectories. The geometry of the electron focusing has been investigated for gathering powers of 1.6, 1.1, and 0.7% at mean emission angle tangents of 0.400, 0.385, and 0.352 and the resolutions obtained have been tabulated. At a gathering power of 1.6% a line width of better than 1.37% in momentum has been achieved. A comparison of this instrument with other helical spectrometers is made.

ISSN:0034-6748    

DOI:10.1063/1.1716641

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A mass sensitive detector for relativistic particles is proposed whose mass sensitivity increases with increasing particle energy. The counter detects synchrotron radiation emitted by relativistic particles as they travel through a high‐intensity magnetic field. The power emitted in synchrotron radiation varies inversely as the rest mass to the fourth power, and the frequency of the spectral region in which the main power is emitted varies inversely as the rest mass cubed. In 50‐cm path of a presently practicable magnetic field, 105gauss, an electron of 1 Bev emits on the average 10 photons with a total energy of 68 kev, each of about 7 kev. This radiation when converted to visible radiation in NaI crystals is detectable by photomultipliers. In application to cosmic rays, with a steady‐state magnetic field, the counter enables specific recognition of electrons of ≥1 Bev.

ISSN:0034-6748    

DOI:10.1063/1.1716642

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In accelerator magnetic analyzing systems consisting of a beam analyzing system and a reaction product analyzing system, the total resolution of the system may be made, to first order, independent of target thickness or independent of the width of the beam on the target, by proper choice of target orientation angle. By proper choice of geometry, the two may be accomplished simultaneously for a given nuclear reaction, and suitable compromises give reasonably good results for a large variety of applications. In most cases, taking advantage of these effects allows an order of magnitude increase in intensity without affecting the resolution.

ISSN:0034-6748    

DOI:10.1063/1.1716643

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The operating characteristics of the Rosenblum type spark counters in air are examined. A qualitative interpretation of the experimental data is given.The advantages of the device (no background, absence of walls, detection of heavily ionizing particles only) and its disadvantages (limited reproducibility for some incidence directions, small sensitive volume), which limit its practical utilization, are reported.

ISSN:0034-6748    

DOI:10.1063/1.1716644

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In the scintillation spectrometer described, the main detecting crystal of NaI(Tl) is enveloped by a hollow cylinder of NaI(Tl) in anticoincidence with the main crystal. This system completely suppresses the peaks associated with the escape of the two quanta from the annihilation following pair production, and it reduces the Compton background by a factor of 7 for 4.43‐Mev gamma rays and by a factor of 5 for those of 6.1 Mev.

ISSN:0034-6748    

DOI:10.1063/1.1716645

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Using balanced filters with an automatic recording x‐ray diffractometer, almost the same effect of monochromatization as with a crystal monochromator was achieved. The detection efficiency of the balanced filters method was about 30, taking the value as 100 when no filter was used. The effective resolving time of the system involving the electronic circuits was about 5 &mgr;sec using a NaI scintillation counter as a detector. The Cu‐target x‐ray tube was operated on full‐wave rectified 60 cps 40 kvp. The comparison with the other monochromatization methods is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1716646

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The design, operation, and performance of a constant heating adiabatic vacuum calorimeter, suitable for measurement of the heat capacities of corrosive, hygroscopic, easily oxidized, and slightly volatile materials in the temperature range from 50° to 460°C, are described. A sealed glass cell is used to protect the sample.

ISSN:0034-6748    

DOI:10.1063/1.1716647

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A semiautomatic system has been developed for use with a Lindemann‐Ryerson electrometer. The system measures ionization current in the National Bureau of Standards 4&pgr; &ggr;‐ionization chamber by the Townsend balance‐of‐charge method. Two minature semiconductor photocells, with associated electronic circuitry, are used for detecting deflections of the electrometer and for controlling the amount of compensating charge placed on the electrometer. In addition, the starting and stopping of an electronic clock is controlled by a third photocell. The system has an ultimate precision of about 0.02%.

ISSN:0034-6748    

DOI:10.1063/1.1716648

出版商:AIP    

年代:1959

数据来源: AIP