摘要:

An ultraviolet microbeam apparatus utilizing the principle of incident illumination has been developed for the irradiation of small parts of living cells or other microscopic objects. A reflecting microscope objective is used simultaneously in a visible light viewing‐aiming system and in a bombardment system to focus a spot of ultraviolet light (as small as one micron in diameter) onto part of an experimental preparation. Provision is made in the apparatus for auxiliary phase contrast viewing and for monitoring of the energy in the microbeam. Details of construction and alignment are given and the distribution of intensities in the microbeam is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715750

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A fast gray wedge analyzer for operation at input pulse rates up to 107per second has been designed and built. Circuits and operation of the instrument are described. Operation of the instrument depends on two trigger circuits which are initiated by the input pulse. Pulses of fixed amplitude (100 and 30 m&mgr;sec long) from the trigger circuits operate two gates, a pulse lengthener, a sweep, and an unblanking circuit. The combination of the two gates allows pulses separated by less than 15 m&mgr;sec to be resolved, and the instrument has a fixed deadtime of approximately 100 m&mgr;sec. Fast circuit recovery and high‐duty cycle are achieved by driving trigger and pulse shaping circuits on both leading and trailing edges of pulses.

ISSN:0034-6748    

DOI:10.1063/1.1715751

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Electromagnets have been built for continuous operation in liquid hydrogen. A steady field of 62 000 oersted, corresponding to a power dissipation of 15 kw has been obtained in freely boiling hydrogen with a coil 5 in. long, 2.5 in. internal diameter, and 7.5 in. external diameter.Some of the mechanical, electrical, heat transfer, economical, and safety problems encountered in this work are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715752

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A system of two coupled cavities is described replacing the single cavity of an NH3maser. Using this system the curve of the oscillation frequency against cavity temperature presents a plateau, thus reducing considerably the ``pulling'' effects of the cavity.

ISSN:0034-6748    

DOI:10.1063/1.1715753

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A pressure gauge covering both the Pirani and liquid manometer ranges, easily adaptable for continuous recording, has been devised and successfully operated. In the pressure range of the Pirani gauge, the working principle is that of the thermal conductivity at low pressures; at higher pressures, on the contrary, a convection stream takes place, which depends on pressure and determines temperature variations in the filament. Experimental results give maximum sensitivity in the range 0.5–5 torr and a reasonable sensitivity for pressures up to one atmosphere.

ISSN:0034-6748    

DOI:10.1063/1.1715754

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An integrator circuit is described, together with programmer and timer, which was constructed for measuring signal‐current from a photomultiplier tube as used in astronomical photometry. At the end of a timed run, the voltage data are impressed upon a strip‐chart pen recorder. The current‐range of such instrument encompasses a span from 10−6to 10−11ampere, full scale, with stability and linearity. Furthermore, the design is such that, using a suitable programing circuit, any number of identical integrator units can be employed to measure a like number of separate phototube currents simultaneously over a given timed run; and afterwards the separate voltages are recorded in sequence upon the one recorder. This feature makes the herein described system very useful for simultaneous multicolor photoelectric photometry.

ISSN:0034-6748    

DOI:10.1063/1.1715755

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A simple high‐vacuum pump which combines large areas of evaporated barium with a source of ionization is described. Though of moderate pumping speed this barium‐ionization pump is capable of maintaining high vacuum in unoutgassed sealed‐off systems even in the presence of organic sealing materials. Simplicity is achieved by use of externally applied heat for barium evaporation which may be performed initially or periodically as required. Data are presented which show the capabilities and limitations of such absorption systems. The similarity of this absorption process to that producing oxidation of metals in air is noted.

ISSN:0034-6748    

DOI:10.1063/1.1715756

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Boron trimethyl counters have operated successfully as neutron sensitive proportional counters. Differential pulse‐height spectra for these counters show good resolution. The electron mobility in boron trimethyl is measured by the method of Nicholson in theX/Pregion from 0.8 to 7.0 v/cm/mm Hg. The data indicate a constant mobility aboveX/P=2.5 volts/cm/mm Hg but the mobility increases rapidly for lower values.

ISSN:0034-6748    

DOI:10.1063/1.1715757

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A ``sing‐around'' velocimeter of high stability and precision has been developed and tested. The instrument, which is of the fixed‐path type, automatically measures and/or records the speed of sound in non‐dispersive liquids. Stabilities of about 50 ppm over a 24‐hr period can be achieved.

ISSN:0034-6748    

DOI:10.1063/1.1715758

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An instrument for monitoring of personnel in combined neutron and gamma radiation fields is shown to record the rem dose due to fast and slow neutrons and gamma rays. The instrument consists of a thermal neutron ionization chamber worn under the arm. The relative neutron to gamma response is trimmed by means of a gadolinium coating on the ionization chamber. The use of the human body as the moderator is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715759

出版商:AIP    

年代:1957

数据来源: AIP