摘要:

The construction of a soft flash x‐ray (FX) apparatus with a new type of FX tube for biomedical use is described. The FX apparatus may be used for condenser charging voltages of 50–90 kV and peak currents of 20–40 kA. The electric pulse width of the FX waveforms was almost constant and its value was about 0.3 &mgr;s. The effective focal spot varied according to the condenser charging voltage, the anode–cathode (A–C) distance, etc., ranging from 0.2–3.0 mm in diameter. We selected two combinations of electrodes: (a) for normal focusing and a high dose rate; (b) for fine focusing and a low dose rate. The FX intensity was determined by the condenser charging voltage and the A–C distance, while the FX quality (average spectrum distribution) was determined by the average voltage of the FX tube and insertion of metal filters. The average voltage of the FX tube varied according to the condenser charging voltage and the A–C gap impedance. Various clear FX images were obtained by controlling the FX intensity, quality, and the focal spot size. We used Fuji Computed Radiography (FCR) in conjunction with our FX radiography, and by controlling the FX quality and the focal spot size, we obtained some interesting biomedical radiograms.

ISSN:0034-6748    

DOI:10.1063/1.1138609

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new furnace for neutron diffraction experiments is capable of heating and cooling a sample very rapidly. The rapid heating is done by two circular infrared lamps placed over and under a sample, whose radiation is roughly focused on the sample by a reflector. The rapid cooling is done by high‐pressure gas blows against the sample from two circular nozzles which are also placed over and under the sample. This system enables us to obtain the heating rate of over 1000°C/min and cooling rate of −500°C/min for an alloy of 10 mm diameter and 30 mm length. The performance is sufficient to carry out some kinetics measurements in real‐time neutron diffraction by the use of a position‐sensitive detector. This kind of experiment is demonstrated by the observation of the relaxation process of order–disorder transitions in CuZn and Ni3Mn alloys.

ISSN:0034-6748    

DOI:10.1063/1.1138610

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have compared the low‐frequency capacitance of a glass thermometer made of very pure SiO2doped with ∼1200 ppm OH−with a60CoCosingle‐crystal &ggr;‐ray anisotropy primary thermometer in the range of 15–40 mK in magnetic fields up to 6 T. Within our temperature accuracy of ±5% no shift of the capacitance due to the applied fields was observed.

ISSN:0034-6748    

DOI:10.1063/1.1138611

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A simple scheme of improving the control characteristics of an ON–OFF controller by deliberately coupling external fluctuations is described. The principle of the technique is presented along with some experimental results.

ISSN:0034-6748    

DOI:10.1063/1.1138612

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

High‐density polyethylene has good spectral transmission characteristics in the range from 20–500 cm−1. This, coupled with its ease of fabrication and low cost, make it an excellent choice for far‐infrared absorption cell windows which operate at room temperature. However, because of its relatively large thermal coefficient of expansion and its brittleness (at low temperatures), the usual type of polyethylene absorption cell windows are difficult to make leaktight at low temperatures, especially if there is a moderately high pressure inside the absorption cell. In this article the problems associated with the use of such windows at low temperatures and moderately high pressures are discussed and a successful window design which overcomes these problems is described. These windows have been incorporated in a cell which has been used to measure the collision‐induced absorption of various nonpolar gases at low temperatures. In these experiments the cell was cycled hundreds of times at pressures up to 96.5 bar and at temperatures down to 126 K.

ISSN:0034-6748    

DOI:10.1063/1.1138613

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Piezoresistive carbon sensors were used to determine the stress‐time history in unsintered powders during shock‐wave compaction in a gas gun. Powders of both spherical and irregular shape were examined, including steel, aluminum–silicon alloy, copper, tungsten, and aluminum nitride. A calibration relationship was established between direct sensor response and stress levels determined by impedance matching; it corrects apparent systematic errors in the manufacturer’s calibration for stresses in excess of about 2.0 GPa.

ISSN:0034-6748    

DOI:10.1063/1.1138614

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A wide variety of enclosed structures either require or cannot entirely prevent leakage from their interior space to the outside. Existing methods for measuring such leakage have important disadvantages. We have developed a device and technique that permits leakage areas to be measured from within or without the enclosure without causing unacceptable disturbance. The apparatus uses low‐frequency (1 Hz) acoustic monopoles to generate an internal pressure signal which is then analyzed synchronously to provide a measurement of leakage area. We have successfully applied this technique to measuring air tightness in residential houses, and believe it can be easily adapted for use in field, laboratory, or classroom applications. We are currently evaluating why the values we obtained were, on average, 14% lower than those obtained through conventional methods and we are investigating the apparent inability of the device, as presently designed, to measure large leaks.

ISSN:0034-6748    

DOI:10.1063/1.1138615

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A simple modification is described for converting the digital program code format of an Evans Associates model 4145 programmable time delay module from binary‐coded decimal to binary. The modification results in a delay module which is more easily interfaced to a computer, has a greater programmable delay range with equivalent temporal resolution, and requires less power. Similar modifications are expected to have the same results on the models 4145‐1 and 4146 modules.

ISSN:0034-6748    

DOI:10.1063/1.1138616

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A commercially available piezoelectric device has been shown capable of starting a microwave discharge. This device can be used in place of a Tesla coil, reducing the chance of damaging nearby electronics.

ISSN:0034-6748    

DOI:10.1063/1.1138617

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A headspace analysis attachment for a Varian model 3700 gas chromatograph is described. The attachment differs from most commercial headspace attachments in the size sample bottle that it can accommodate. Graphical data obtained using the attachment is given.

ISSN:0034-6748    

DOI:10.1063/1.1138563

出版商:AIP    

年代:1986

数据来源: AIP