Department of Mechanical Engineering, Boston University, 110 Cummington Street, Boston, Massachusetts 02215, USA.
J Acoust Soc Am. 2010 Apr;127(4):2231-9. doi: 10.1121/1.3353095.
The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 muC will be reported on. Cavitation was initially detected for a beam charge of 0.082 muC by the presence of an acoustic emission approximately 250 mus after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 muC and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber ( approximately 300 mus), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.
橡树岭国家实验室散裂中子源采用高能脉冲质子束轰击汞靶，产生短时间的中子爆发。质子束的吸收会导致汞的快速加热，从而形成声激波和空化泡的成核。随后这些空化泡的坍塌会促进钢靶壁的侵蚀。本文将报道在汞靶中安装了两个被动式空化探测器（兆赫兹聚焦和非聚焦压电换能器），用于监测电荷量范围为 0.041 到 4.1 微库仑的质子束产生的空化情况。当质子束电荷量为 0.082 微库仑时，通过检测到大约 250 微秒后到达的入射质子束的声发射，首次检测到空化。根据坍塌时间，该发射与估计最大气泡半径为 0.19 毫米的惯性空化坍塌一致。预测汞中引发空化的初始压力为 0.6 MPa。对于电荷量为 0.41 微库仑及更高的质子束，气泡的寿命超过了腔室的混响时间（约 300 微秒），并且检测到明显的空化活动窗口，这种现象可能是由于腔室中的混响和空化泡的相互作用造成的。
