Shaddix Christopher R, Williams Timothy C
Combustion Research Facility, Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550, USA.
Rev Sci Instrum. 2009 Mar;80(3):033702. doi: 10.1063/1.3089224.
Intensified charge-coupled devices (ICCDs) are used extensively in many scientific and engineering environments to image weak or temporally short optical events. To optimize the quantum efficiency of light collection, many of these devices are chosen to have characteristic intensifier gate times that are relatively slow, on the order of tens of nanoseconds. For many measurements associated with nanosecond laser sources, such as scattering-based diagnostics and most laser-induced fluorescence applications, the signals rise and decay sufficiently fast during and after the laser pulse that the intensifier gate may be set to close after the cessation of the signal and still effectively reject interferences associated with longer time scales. However, the relatively long time scale and complex temporal response of laser-induced incandescence (LII) of nanometer-sized particles (such as soot) offer a difficult challenge to the use of slow-gating ICCDs for quantitative measurements. In this paper, ultraviolet Rayleigh scattering imaging is used to quantify the irising effect of a slow-gating scientific ICCD camera, and an analysis is conducted of LII image data collected with this camera as a function of intensifier gate width. The results demonstrate that relatively prompt LII detection, generally desirable to minimize the influences of particle size and local gas pressure and temperature on measurements of the soot volume fraction, is strongly influenced by the irising effect of slow-gating ICCDs.
增强型电荷耦合器件（ICCD）在许多科学和工程环境中被广泛用于对微弱或持续时间短的光学事件进行成像。为了优化光收集的量子效率，许多这类器件被设计成具有相对较慢的特征增强器门控时间，大约为几十纳秒。对于许多与纳秒激光源相关的测量，如基于散射的诊断和大多数激光诱导荧光应用，信号在激光脉冲期间和之后上升和衰减得足够快，以至于增强器门控可以设置为在信号停止后关闭，并且仍然能够有效地抑制与较长时间尺度相关的干扰。然而，纳米级颗粒（如烟尘）的激光诱导白炽（LII）具有相对较长的时间尺度和复杂的时间响应，这给使用慢门控ICCD进行定量测量带来了严峻挑战。在本文中，利用紫外瑞利散射成像来量化慢门控科学ICCD相机的光圈效应，并对用该相机收集的LII图像数据作为增强器门控宽度的函数进行了分析。结果表明，相对快速的LII检测通常对于最小化颗粒尺寸、局部气体压力和温度对烟尘体积分数测量的影响是可取的，但它受到慢门控ICCD光圈效应的强烈影响。
