摘要:

A boron‐loaded liquid scintillator is described which gives a much greater difference in the pulse shapes for &ggr; rays and for slow neutrons than any of the liquids currently used. A detailed study of the pulse shapes indicates that the &ggr;‐ray sensitivity of a neutron detector filled with this liquid can be reduced by a factor of 500 with only a 5% decrease in the neutron sensitivity by application of pulse‐shape discrimination. A survey of the pulse‐shape characteristics of a number of scintillators currently used, together with the results for the new liquid, is presented, and the performance of the new detector with a simple system of pulse‐shape discrimination is described.

ISSN:0034-6748    

DOI:10.1063/1.1719592

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

An electrical conductance instrument has been constructed for use with molten oxides at temperatures up to 1700°C. The principle of operation involves a measurement of the resistance between two partially immersed wire electrodes. The dependencies of cell constant on liquid depth, immersion depth, frequency, and resistance are described. An unusual relationship between cell constant and melt resistance appears to be associated with the geometry of the electrode arrangement. The calibration scheme involves the use of a series of standard solutions of varying conductance and a log‐log plot of &kgr;std.vs &OHgr;meas.. The instrument has been successfully used at temperatures up to 1700°C.

ISSN:0034-6748    

DOI:10.1063/1.1719593

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The effect of finite resistance in the vacuum‐tank walls on the longitudinal stability of an intense beam of particles in an accelerator is investigated theoretically. We show that even if the particle frequency is an increasing function of particle energy, the wall resistance can render the beam unstable against longitudinal bunching. In the absence of frequency spread in the unperturbed beam, the instability occurs with a growth rate that is proportional to (N/&sgr;)½, whereNis the number of particles in the beam and &sgr; is the conductivity of the surface material. By means of the Vlasov equation a criterion for beam stability is obtained. In the limit of highly conducting walls the criterion involves the frequency spread in the unperturbed beam, the number of particlesN, the beam energy, geometrical properties of the accelerator, but not the conductivity &sgr;. A numerical example presented indicates that certain observations of beam behavior in the MURA 40 MeV electron accelerator may be related to the phenomenon we investigated.

ISSN:0034-6748    

DOI:10.1063/1.1719594

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The transverse electromagnetic interaction of an intense azimuthally uniform beam of particles with itself, including the effect of a resistive vacuum tank, is investigated theoretically. It is shown that a beam of particles all having velocity &ngr; is unstable against the development of transverse waves having a phase velocity close to (1 −v/n)&ngr;, wherevis the number of transverse free betatron oscillations occurring in one revolution andnis a positive integer greater thanv. The growth rate for the instability is proportional toN/&sgr;½, whereNis the number of particles in the beam and &sgr; is the conductivity of the surface material of the vacuum tank. Stabilizing mechanisms are examined by means of the Vlasov equation and it is shown that a spread in the quantity (n−v)&ngr;, evaluated for particles in the unperturbed beam, will prevent the instability. A criterion for the spread required is shown, in the limit of walls of high conductivity, to depend upon the beam intensity and energy as well as upon certain geometrical properties of the accelerator, but not upon the conductivity. Numerical examples covering a range of particle accelerators are presented, and suggest that the theory is in agreement with the coherent beam behavior recently observed in a number of accelerators.

ISSN:0034-6748    

DOI:10.1063/1.1719595

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A sample enclosure compatible with the Norelco goniometer permits x‐ray diffraction measurements on liquids confined under their own vapor pressure or an inert gas. Diffraction is in reflection‐type geometry using a free liquid surface. The prototype, made of plastic, has been operated between 0 and 50°C.

ISSN:0034-6748    

DOI:10.1063/1.1719596

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The avoidance of the ``total‐voltage effect'' in acceleration tubes, by the use of plane electrodes with their normal inclined to the tube axis, is described. This inclined‐field structure serves to sweep nonbeam charged particles out of the acceleration region soon after their formation and to reduce the probability of regenerative multiplication. A summary is presented of experiments which illustrate the major properties of this type of tube.

ISSN:0034-6748    

DOI:10.1063/1.1719597

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

An application of charged coaxial pulse‐forming cables to measurements on rapidly moving electrically conductive projectiles when accelerated in a compressed gas gun is presented. Two quantities associated with high stress impacting of materials, time and instantaneous velocity at impact, are determined. Electrical signals with risetimes of less than 3 nsec are obtained and used as fiducials to determine the precise location of moving surfaces in time and space. Average velocities over three short intervals are measured to within ±0.08%. Impact and event timing to ±10 nsec is accomplished.

ISSN:0034-6748    

DOI:10.1063/1.1719598

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A solid state logarithmic pulse amplifier has been developed primarily for use in single shot large dynamic range experiments. It has a risetime of less than 100 nsec, a logarithmic range of 3 decades, and a usable range of greater than 4 decades. A temperature control circuit is used to maintain critical transistors at a constant temperature to achieve a thermal stability of approximately 2% referred to the input for a 10°C ambient temperature change.

ISSN:0034-6748    

DOI:10.1063/1.1719599

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A digital time‐interval analyzer is described, which records the number of intervals between successive events of a duration less than a certain timeTwith great precision. The range ofTlies between 10 and 1000 &mgr;sec. The application of the analyzer to the measurement of the resolving time of a scintillation counter arrangement is described.

ISSN:0034-6748    

DOI:10.1063/1.1719600

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A sensitive ion cyclotron resonance spectrometer designed to study low energy ion‐molecule interactions in a weakly ionized gas is described. It is capable of determining simultaneously the collision frequency and average concentration of ions having a particular charge‐to‐mass ratio. General design considerations discussed include sensitivity, linewidth, resolution, and line broadening at highE/P. Effects of electron buildup are also discussed. The measurement chamber is intended to operate within a 1500 G, 102 cm long solenoid. Ion sources and electrode arrangements are described. Power absorption is detected by a narrow band, derivative type system for which circuit diagrams are given. The spectrometer has a resolution of about 3% and can detect an average concentration of 1–10 ions/cm3.

ISSN:0034-6748    

DOI:10.1063/1.1719601

出版商:AIP    

年代:1965

数据来源: AIP