摘要:

The geometrical efficiency of the prototype neutral beam injector unit for the JT‐60 was measured experimentally and was compared with numerical estimates. The measurements agreed well with the calculations in the wide range of perveance by taking into account the distortion of the beamlet intensity distribution function from a Gaussian distribution. Overdense operation of the ion source was preferable in that the high geometrical efficiency could be obtained at high perveance values.

ISSN:0034-6748    

DOI:10.1063/1.1137503

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Extensive and informative plasma measurements have been made with the intense and energetic neutral‐particle beams that are used for fueling and heating magnetically confined, controlled‐fusion experimental plasmas. This diagnostic technique does not perturb the plasma because only the unused transmitted fraction of a neutral beam is detected. Orthogonal arrays of highly collimated detectors of the simple secondary‐electron‐emission type are used in magnetic‐mirror experiments to measure neutral‐beam attenuation (directly related to the plasma line density) along chords through the plasma volume at different radial and axial positions. Data from these arrays yield radial and axial plasma‐density profiles, ion angular distributions at the plasma midplane, estimates of the neutral‐beam input power to the plasma, and information on macroscopic plasma motion. Representative results obtained by applying this useful diagnostic technique to the recently completed tandem‐mirror experiment TMX are included here. This diagnostic method can also be advantageously applied to other controlled‐fusion experiments that use neutral‐beam injection.

ISSN:0034-6748    

DOI:10.1063/1.1137504

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The electron temperature in a pulsed high‐&bgr; ( &bgr;≡2&mgr;nkT/B2≊1) plasma is studied as a function of time using a miniature array of 12 planar Langmuir probes. Instead of sweeping the bias voltage on the collectors, each is set at a different voltage corresponding to points along the characteristicI–Vcurve. A fast‐analog multiplexer, together with a computerized data‐acquisition system, allows determination ofTeto within a few percent accuracy, with a time resolution of 1 &mgr;s. The probe is used to study temperature fluctuations and heat transport in a plasma current sheet.

ISSN:0034-6748    

DOI:10.1063/1.1137505

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A new high‐voltage pulse‐forming line, the radial isolated Blumlein (RIB), is described. The new configuration produces an output voltage pulse into a matched load equal to the charge voltage on the line (as in a conventional Blumlein circuit); however, the prepulse level is negligible and both sides of the load remain at electrostatic ground potential. The RIB is rapidly charged to allow 24 oil dielectric spark channels to close within ∼2 ns. With this number of channels, 94% of the theoretical peak voltage is achieved even though the pulse duration is only 15 ns. Using a foilless diode load, the device has been used to generate 4‐MeV, 100‐kA electron beam pulses.

ISSN:0034-6748    

DOI:10.1063/1.1137506

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Details of design and construction of a simple and rugged thermocouple differential thermometer are presented. Gold +0.03 at. % iron wire is used, with niobium leads connected to a SQUID. It is demonstrated that at 1 K the response time is about 15 ms and that the temperature sensitivity of 10−7K with a 10‐Hz filter is Johnson‐noise limited. Additional qualities such as small size, little self‐heating, and high reproducibility make this device ideal for differential thermometry at low temperatures.

ISSN:0034-6748    

DOI:10.1063/1.1137507

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The performance of diffused planar germanium thermometers is found to be reliable at temperaturesT>90 mK. At lower temperatures performance can be limited by overheating caused by measuring and spurious currents. The heating is associated with a thermal impedanceZ∝T−4which is larger than that found in typical bulk germanium thermometers. Surprisingly,Zis found to be essentially independent of the size of the planar resistor.

ISSN:0034-6748    

DOI:10.1063/1.1137508

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A new approach for the determination of the temperature of rotating bodies is described, which makes use of the fact that the sample is rotating with virtually no friction. The basic principle is that a temperature change causes thermal expansion, and hence a change in the moment of inertia which, due to conservation of angular momentum, results in a change of rotational frequency. The method was used to determine the temperature of a magnetically suspended cylinder of pure iron within ±5 K while cooling down from 800 to 300 K. The contact‐free suspension is ideally suited to study the radiative interaction of the sample with its environment. It is shown that on the basis of the Stefan–Boltzmann equation the time constant of radiation exchange and the emissive power of the sample can be evaluated. From the results of these investigations the measuring limit of a spinning rotor vacuum gauge due to temperature fluctuations can be estimated.

ISSN:0034-6748    

DOI:10.1063/1.1137509

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A beam‐gas collision experiment to measure excitation cross sections for translation‐to‐vibration (T‐V) energy‐transfer collision processes that produce short‐wavelength infrared radiation (SWIR) has been assembled and used to obtain the (0,0°,0 → 0,0°,1) excitation cross section for CO2by collision with Ar. A unique modulation technique used in this system involves pulse‐modulating one of the reactants, injecting the pulses into a flowing plasma carrier, supersonically expanding the pulse and carrier, and extracting a beam from the expansion while preserving the modulation of the reactant. Enhanced radiation due to thermalization of excited CO2at sphere pressures greater than single collision conditions, has been measured and a correction factor for this effect obtained. Measurements of the argon velocity and flux in a helium beam, CO2number density in an integrating sphere, and infrared radiation at 4.25 &mgr;m were made to determine the excitation cross section at a collision velocity of 2.3 km s−1. The average of three sets of measurements yields a value of &sgr;*=3.7(±3)×19−19cm2.

ISSN:0034-6748    

DOI:10.1063/1.1137510

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A gated photon counting instrument which is capable of operation at the full 100‐MHz repetition rate of mode‐locked ion lasers is described. This instrument provides a high throughput alternative to more complex and costly instrumentation commonly used in time‐correlated single photon counting. Applications to the measurement of subnanosecond fluorescence lifetimes at a 96.8‐MHz laser repetition rate and to the reduction of matrix quenching effects in fluorometry at a 5‐MHz laser rate are presented.

ISSN:0034-6748    

DOI:10.1063/1.1137511

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An accurate light scattering photometer capable of measuring both the angular distribution of intensity and the intensity fluctuation spectrum of laser light scattered from a wide variety of samples including solutions of polymers and other macromolecules is described. The photometer employs 18 fixed scattering angles ranging from 2.6° to 163° and is sufficiently accurate to measure a molecular radius of gyration as small as 60 A˚ reliably. Stray elastically scattered light normally comprises less than 1% of the light scattered from pure toluene at the smallest scattering angle and is unmeasurable at other angles. The apparatus employs optical fibers to transmit the scattered light to a single photomultiplier tube and functions automatically under microprocessor control, with sample temperature controlled to ±0.1 mK.

ISSN:0034-6748    

DOI:10.1063/1.1137512

出版商:AIP    

年代:1983

数据来源: AIP