Developmental Research in Nanosecond Spark Source for Visualizing High-Speed Phenomena

一种简单的纳秒火花源(纳米火花)已经由几个小的陶瓷电容器、一个闸流管和一个同轴电缆组成。在运行过程中，火花头中的500-1400pF电容器通过由闸流管开关的高压脉冲发生器自动预电离，在大约60 ns内脉冲充电。当气体开始分解时，这种电荷可供放电。预电离有利于气体击穿的启动和减小脉冲间的时间抖动。这种纳米火花在6-14千伏和大气压的空气中工作时，产生12-30 ns(半高宽)的光脉冲，时间抖动小于60 ns。火花隙的启动非常可靠，辐射通道非常稳定。该火花已在各种纹影和阴影系统中充分曝光了常规的ASA-100胶片，并获得了一些冲击波的可视化效果。然而，在彩色纹影系统中，需要AS1600的高感光度彩色胶片。一些…通过对间隙加压，可以改进和增强所描述的火花源的更多功能：在略微改进的源版本中，几乎可以在几乎任意压力的任何气体中引燃火花。光强和脉宽随着气体压力的增大而增大。如果脉冲宽度只有很小的影响，用一个充满Xe的腔室可以使辐射量增加十倍。光谱研究表明，Xe气体对红外区的光强有所增加。通过这种方法，我们用ASA 400胶片获得了彩色纹影照片。由于其新颖的预电离技术和实用的设计，所描述的光源满足了用于光学短时测量，特别是在高速现象的可视化中的要求。光输出足以进行高质量的单次拍摄，使这些光源即使不优于市面上的同类设备，也至少与之相当。较少

A simple nanosecond spark source (Nanospark) has been constructed from several small ceramic capacitors, one thyratron and one coaxial cable. During operation, a 500-1400 pF capacitor in the spark head is pulse-charged in about 60 ns with automatic preionization from a high-voltage pulse generator switched by a thyratron. This charge is available for discharge when the gas breakdown starts. The preionization is useful to start the gas breakdown easily and to decrease the pulse-to-pulse time jitter. This Nanospark produces 12-30 ns (FWHM) light pulses with a time jitter of less than 60 ns when perated at 6-14 kV and in air of atmospheric pressure. The initiation of the spark gap is highly reliable and the radiation channel is very stable. The spark has adequately exposed customary ASA 100 film in various schlieren and shadowgraph systems and some shock wave visualizations have been obtained. In colour schlieren systems, however, high-sensitivity colour films of ASA 1600 were needed.Some … More features of the described spark source can be improved and enhanced by pressurizing the gap : in a slightly modified version of the source, the spark can be initiated in practically any gas of almost arbitrary pressure. The light intensity and the pulse width increase with the gas pressure. If the pulse width is of but minor consequence, the quantity of radiation can be increased tenfold with a Xe-filled chamber. The spectral study showed that the light intensity with Xe-gas increases somewhat toward the infrared region. In this way we obtained colour schlieren photographs with ASA 400 films.The described light sources, due to their novel preionization technique and their practical design, fulfill the requirements for being employed in optical short duration measurements, particularly in visualization of high speed phenomena. The light output is sufficient for high quality single-shot photography making these sources at least equivalent if not superior to comparable commercially available equipment. Less