Microsecond duration pressure pulse generator for in situ dynamically loaded SEM fracture studies

We describe a technique to impulse load small cylindrical specimens for in situ, real-time SEM studies of dynamically loaded fracture. Loading is done magnetically with a solenoidal coil of 10 mm length and 1 mm radius. The entire loading assembly fits on the SEM stage; there is no need for shock-isolated bellows apparatus. The only vacuum feedthrough required is an MHV coaxial bulkhead connection. A ballistic pendulum measurement gave a peak compressive pressure of ～20 MPa, with a pressure pulse width of 1.33 μs. Pressures > 80 MPa can easily be generated. Using this device we have obtained real-time SEM movies of dynamically loaded fracture of rosin.