Shockwave propagation from focused-laser-induced plasmas was characterized for implementing calibration-free seedless velocimetry. An emission-free probe beam deflection (EF-PBD) technique and short-gated shadowgraph/schlieren imaging were used for the investigation. Nanosecond laser pulses at 532 nm were focused to induce plasmas generating shockwaves from the focal point at atmospheric condition. A continuous-wave (CW) laser beam was set up to pass nearby for detecting the shock arrival at the beam location; the shock diverts the CW-laser beam, which is sensed by the photodiode. The EF-PBD was devised to minimize the influence of the plasma emission that affects the probe beam intensity measured by the photodiode. The probe beam was moved from the focal point to consecutive locations very close to the plasma (every 0.2 mm from 0 to 1.8 mm) for accurately measuring the shock speed in the region adjacent to the plasma. A point-explosion model was employed for predicting the shockwave propagation phenomenon. It was found that the ambient flow velocity around the plasma affects the shockwave arrival time on the probe beam, which suggests the feasibility of a seedless velocimetry technique. When the distance between the probe beam and the plasma is known, the velocimetry does not require calibration. The proposed velocimetry technique was tested successfully in a range of 30–180 m/s ambient flow.

聚焦激光诱导等离子体在冲击波中传播的特征在于可实现无标定无核测速。无辐射探针束偏转（EF-PBD）技术和短门阴影图/谢利尔成像用于研究。聚焦在532 nm的纳秒激光脉冲，以诱导等离子体在大气条件下从焦点产生冲击波。设置连续波（CW）激光束通过附近，以检测震动到达光束位置的位置；震动使CW激光束转向，该光束被光电二极管感应到。EF-PBD旨在最大程度地减少等离子体发射的影响，该影响会影响光电二极管测得的探测光束强度。探测光束从焦点移到非常靠近等离子体的连续位置（从0到1每0.2毫米）。8毫米）以精确测量等离子体附近区域的冲击速度。采用点爆炸模型预测冲击波的传播现象。已经发现，等离子体周围的环境流速会影响冲击波在探测光束上的到达时间，这表明了无籽测速技术的可行性。当探测光束和等离子体之间的距离已知时，测速仪不需要校准。所提出的测速技术已在30–180 m / s的环境流量范围内成功进行了测试。这表明了无核测速技术的可行性。当探测光束和等离子体之间的距离已知时，测速仪不需要校准。所提出的测速技术已在30–180 m / s的环境流量范围内成功进行了测试。这表明了无核测速技术的可行性。当探测光束和等离子体之间的距离已知时，测速仪不需要校准。所提出的测速技术已在30–180 m / s的环境流量范围内成功进行了测试。