摘要:

A number of experiments are described which test the interactions of particles with rf accelerating voltages in an FFAG acclerator. The experiments confirm predictions of a theory of Symon and Sessler and demonstrate the feasibility of ``stacking'' successively accelerated groups of particles with a density close to that of a single group.

ISSN:0034-6748    

DOI:10.1063/1.1715823

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Monoenergetic neutron fluxes can be measured at neutron energies above 1 Mev by observing recoil protons scattered at forward angles from a hydrogenous radiator. A counter telescope system for observing the recoil protons is described which has a relatively high efficiency for neutron detection. The major part of the paper is devoted to backgrounds and corrections, the calculation of telescope efficiency, and the accuracy of neutron flux measurements. Tables are given which make possible a simple determination of the efficiency of a counter system at neutron energies between 1 and 30 Mev. An appendix presents a semiempirical formulation ofn‐pscattering which is used in obtaining counter efficiencies.

ISSN:0034-6748    

DOI:10.1063/1.1715824

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A method is described whereby the life of an oxide cathode can be substantially increased when subjected to repeated air exposures. This is accomplished by preventing the hydrate formation, and consequently reducing flaking of the cathode coating. Further limitations to cathode life caused by the effects of poisoning are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715789

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new electronic read‐out system has been devised which enables one to obtain a fast answer from a chronotron to be used with accelerator beams of particles. It allows for an analysis of time delay with variable and continuous time intervals. The timing is pulse‐height independent with an accuracy increasing for large pulses. The recovery time is in the range of one microsecond.With delay‐line clipped coincidence pulses from two photomultipliers being fed into a 12‐channel chronotron with a 30‐m&mgr;sec range, a time resolution with half‐width at half maximum of 1.2 m&mgr;sec was readily obtained. Using only 4 channels, with a range of 10 m&mgr;sec, a half‐width at half maximum of 6×10−10sec was observed. A simplified version with only three channels has made a useful fast coincidence circuit.

ISSN:0034-6748    

DOI:10.1063/1.1715790

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A fast scaler is described that employs a fast flip‐flop circuit of unique design. With techniques applied to fast trigger circuits, this flip‐flop circuit has been triggered at a rate higher than 50 megacycles per second and has a double‐pulse resolution of 20 millimicroseconds. A 40‐megacycle scaler, with a scale of eight and employing this fast flip‐flop as a basic element, has been built at this Laboratory.

ISSN:0034-6748    

DOI:10.1063/1.1715791

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An instrument to measure fluorescence lifetimes of the order of millimicroseconds is described. It utilizes a hydrogen flash lamp and high‐speed oscilloscope. The fluorescence decay is displayed on the oscilloscope, and using the method of moments the observed fluorescence is corrected for the response of the lamp and the detection equipment. The instrument was used to study the primary photochemical processes of photosynthesis. Measured lifetimes are given for the various photosynthetic pigments (in vitro), some organic dyes, and chlorophyll fluorescence in algae. With this instrument it has been possible to measure the delayed energy transfer in living systems.

ISSN:0034-6748    

DOI:10.1063/1.1715792

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A simple circuit utilizing a hydrogen flash tube is described. The duration of the pulses of light is equal to or less than one millimicrosecond.

ISSN:0034-6748    

DOI:10.1063/1.1715793

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A neutron detector with a threshold at 20.6 Mev is described which is based on theC12(n,2n)C11reaction in liquid organic scintillators.The efficiency of the detector is almost independent of neutron energy from ∼40 Mev to ∼400 Mev. The detector can be used to measure with an error of 6% high‐energy neutron fluxes in the tolerance range (20–50n/cm2sec).

ISSN:0034-6748    

DOI:10.1063/1.1715794

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A theoretical analysis is made of the error in thermal conductivity, measured by the guarded hot‐plate apparatus, resulting from a temperature difference, or unbalance, between the test area and guard ring. The solution is obtained by the application of two successive Schwarz transformations, the assumptions having been verified by relaxation calculations. An expression is derived for the error heat flow in the test specimens. The agreement between calculated and measured values of the error heat flow for three different hot plates for which experimental data are available is 5% or better. It is therefore now possible to calculate the maximum tolerable unbalance to achieve any desired accuracy in thermal conductivity measured by the guarded hot plate.

ISSN:0034-6748    

DOI:10.1063/1.1715795

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new experimental technique for measuring rotational hysteresis losses over the frequency range 3 to 30 cps is described. A sample disk of ferromagnetic material is mounted on a top. The top is caused to spin about a vertical axis normal to the plane of the disk and of the magnetic field provided by an electromagnet. After removal of the driving force, the top dissipates its stored energy in losses in the sample and in bearing and windage losses. The bearing and windage losses are obtained by also performing the experiment in a magnetic field‐free region. The rate of change of rotational energy of the top is determined by measuring the angular velocity of the top as a function of time.

ISSN:0034-6748    

DOI:10.1063/1.1715796

出版商:AIP    

年代:1957

数据来源: AIP