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Oct 2001

Volume 72, Issue 10, pp. 3749-4008

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back to top GENERAL INSTRUMENTS

Technique for measuring the ballistic-limit velocity for small mass fragments impacting thin metal plates

Willis Mock and William H. Holt

Rev. Sci. Instrum. 72, 3975 (2001); http://dx.doi.org/10.1063/1.1394180 (4 pages) | Cited 1 time

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A new gas gun technique has been developed in which a small mass fragment is impacted in a precise orientation by a thin metal disk and then recovered. The metal disk is placed inside a hollow sabot that also contains a miniature soft-recovery chamber. After impact, the sabot with the fragment inside is recovered in rags. The fragment will be found either in front of the impactor disk or behind it in the soft-recovery chamber, depending upon whether the disk was perforated. This technique can be used to determine accurate ballistic-limit velocity measurements for fragments with masses less than 0.6 gm. Thirty-six experiments have been performed using this technique for masses in the 0.2–0.6 gm range. Results are presented for several experiments.
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45.40.Gj Ballistics (projectiles; rockets)
06.30.Gv Velocity, acceleration, and rotation
89.20.Dd Military technology and weapons systems; arms control

Time response of protection in event of vacuum failure based on Nude ionization gauge controller

Hui Gao, Qiuping Wang, Weibin Wang, Qinglin Wu, Wentong Chen, Liusi Sheng, and Yunwu Zhang

Rev. Sci. Instrum. 72, 3979 (2001); http://dx.doi.org/10.1063/1.1389493 (4 pages)

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This article describes the design and application of fast-response vacuum protection sensor module, based on the Nude ionization gauge and a homemade controller named GH07X. A simulative test indicated that the controller’s response time was less than 200 μs when 1 atm air rushed into the vacuum system through a pulsed valve with 0.8 mm orifice nozzle and the emitting current of the Nude gauge was 4 mA. The experiment result showed that the response time mainly depended on the gas density as well as the electron emitting current of the Nude gauge filament. Compared with the vacuum protection sensors based on sputter ion pump and cold-cathode gauge, GH07X is faster and reliable besides, GH07X can be used as an ultrahigh-vacuum slow valve interlock controller with response time of 100 ms, which is faster than other gauge controllers. The widely used field–bus interface CAN and common serial interface RS232/RS485 are embedded in GH07X controller system. © 2001 American Institute of Physics.
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07.30.Dz Vacuum gauges
07.05.Dz Control systems

Pulsed x-ray generator for commercial gas lasers

S. Bollanti, F. Bonfigli, P. Di Lazzaro, F. Flora, G. Giordano, T. Letardi, D. Murra, G. Schina, and C. E. Zheng

Rev. Sci. Instrum. 72, 3983 (2001); http://dx.doi.org/10.1063/1.1405789 (5 pages)

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We have designed and tested a 1-m-long x-ray diode based on innovative plasma cathodes, which exploit commercial spark plugs as electron emitters. Based on the results of a numerical study, we optimized both diode geometry (e.g., the angle between anode and cathode surfaces, the thickness of the Al window) and electrical circuitry (e.g., the capacitance in series to each spark plug, the peak voltage of the anode) of our x-ray generator. The overall result is a simple and efficient circuitry, giving a total diode current in excess of 2.1 kA with a breakdown voltage of 70 kV, which generates a 50 ns rise-time x-ray pulse with a spatially averaged dosage of up to 6×10−4 Gy when using a Pb-wrapped anode. The double-diode x-ray generator was operated for 1.5×106 shots at a repetition rate of up to 30 Hz, and the lifetime test was interrupted without any fault. During the lifetime test, it was not necessary to adjust any working parameter. At the end of the lifetime test, the x-ray emission uniformity was better than 80% along the longitudinal axis. This x-ray generator has a lifetime, reliability, and cost fitting the requirements of industrial users. Among the broad range of potential applications, this x-ray generator is particularly suitable to ionize discharge pumped gas lasers, like TEA CO2 and excimer lasers, including those operated by x-ray triggered discharges. © 2001 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.59.Mv High-voltage diodes
42.55.Lt Gas lasers including excimer and metal-vapor lasers

In-plane thermal diffusivity evaluation by infrared thermography

F. Cernuschi, A. Russo, L. Lorenzoni, and A. Figari

Rev. Sci. Instrum. 72, 3988 (2001); http://dx.doi.org/10.1063/1.1400151 (8 pages) | Cited 9 times

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A thermographic technique for measuring the in-plane thermal diffusivity of slabs is presented; it consists of heating the front surface of a platelike sample by a circular Gaussian source. The in-plane thermal diffusivity is obtained by monitoring the time evolution of the spatial distribution of the rear surface temperature by an infrared camera. Specifically, from the temperature distribution taken at different times along a line crossing the heating image of the circular spot center on the rear surface, it is possible to obtain the time evolution of the radius of the Gaussian. In order to get the thermal diffusivity value from the widening of this radius, a method for the reduction of the experimental data is presented; the resulting in-plane thermal diffusivity value is then compared with the value found in the literature and with values furnished by the laser flash and the thermal wave interferometry experiments carried out on the samples extracted by the plate. Satisfactory agreement between all the values was noted. © 2001 American Institute of Physics.
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66.30.Xj Thermal diffusivity
44.10.+i Heat conduction
07.20.-n Thermal instruments and apparatus
68.60.Dv Thermal stability; thermal effects

Development of a thermoelectric power generation system using reciprocating flow combustion in a porous FeSi2 element

Futoshi Katsuki, Toshiro Tomida, Hiroko Nakatani, Masahiro Katoh, and Akihiro Takata

Rev. Sci. Instrum. 72, 3996 (2001); http://dx.doi.org/10.1063/1.1405797 (4 pages) | Cited 4 times

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A thermoelectric power generation system using reciprocating flow combustion in a porous thermoelectric conversion element has been developed and examined in its performance. Mn- (n-type) and Co- (p-type) doped FeSi2 powders were molded into the cylindrical element via a spark plasma sintering process, in which Mn- and Co-doped parts were separated by a thin insulator sheet exclusive of a terminus. The porous element consisted of two semicylindrical p/n couples, arranged electrically in series but thermally in parallel. A thermopower of 1.0–1.2 mV/K at 295–624 K and an apparent internal resistivity of 1.6×10−1 Ω cm at 556–624 K have been obtained for the element. A power generation system was then made using a pair of the elements, which were arranged lengthwise in a cylindrical combustion chamber. A reciprocatory flow of dilute fuel gas was introduced into the element, and it was ignited between the element. A steep temperature gradient of about 200 K/cm was formed lengthwise in both elements. The energy density has reached as much as 7 kW/m3 (excluding combustion chamber and mounting clamp) by the reciprocating flow combustion with a dilute fuel gas which may not even be normally flammable. © 2001 American Institute of Physics.
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84.60.Rb Thermoelectric, electrogasdynamic and other direct energy conversion
72.20.Pa Thermoelectric and thermomagnetic effects
82.33.Vx Reactions in flames, combustion, and explosions
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Rm Porous materials; granular materials
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