Apparatus and Method for Generating Short Pulses for NMR and NQR Processing
Patent, filed 15 Nov 96, patented 8 Sep 98
DEPARTMENT OF THE NAVY WASHINGTON DC
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An apparatus using nuclear magnetic or quadrupole resonance to detect selected nuclei in a specimen e.g., specimens containing a class of explosives or narcotics. The apparatus includes a pulsing unit to generate an RF pulse or a train of pseudo-random RF pulses used in stochastic NQR. Each of the pulses has an RF signal reaching a full amplitude within a quarter-cycle substantially no pulse rise delay and having a recovery delay of less than Qpi cycles substantially no recovery delay. The apparatus also includes a transmitter e.g., a coil to irradiate the specimen with a train of pseudo-random RF pulses and to detect after each pulse a resonance signal generated by the specimen in response to each corresponding pulse of the train of pseudo- random RF pulses. The pulsing unit has a capacitor con- nected to a DC power source by a first switch and connected to the coil by a second switch. When the first switch is closed, the DC power source charges the capacitor. After the first switch is opened, the capacitor generates the pulses through the closing and opening of the second switch. The second switch disconnects the coil from the capacitor to end a pulse transmission when the voltage across the coil y is at zero, thereby allowing immediate reception and detection of resonance signals.
- Nuclear Instrumentation
- Atomic and Molecular Physics and Spectroscopy