| 摘要 |
A device including a housing having an inside diameter defining a first chamber and a port formed through the housing in fluid communication with the first chamber. A shuttle flange, having a diameter, is moveably positioned within the first chamber. The shuttle flange moves during a gas-release cycle between i) a closed position blocking the port containing the compressed gas in the first chamber, and ii) an open position exposing an exit area of the port through which the compressed gas is discharged to produce a primary pressure pulse. Desirably, the primary pressure pulse produced has an average rising slope less than 2.9 bar-m/ms. A method for generating a seismic pressure pulse in water includes the steps of, confining a compressed gas within a chamber having a port, creating an exit area through the port by moving a shuttle along the length of the port during a gas-release cycle, pre-releasing a charge of the compressed gas through the exit area to create a pre-released bubble, choking the exit area, and producing a primary pressure pulse by releasing a main charge of compressed gas through the exit area. The primary pressure pulse may be created approximately at the maximum volume of the pre-released bubble. The primary pressure pulse may be created at approximately half of the bubble period of the pre-released gas bubble.
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