II-1 – Glow Discharge Sputter Deposition

A sample probe for pulsed nuclear magnetic resonance that replaces the normal resonant circuit by a lumped parameter delay line is described. Theoretical analysis shows that the delay line probe has a signal‐to‐noise ratio and conversion efficiency of power into rotating magnetic field equivalent to a resonant circuit of Q =(2π) (delay time) (Larmor frequency). However, the delay line probe has a much wider bandwidth, much shorter transient decay time, and faster recovery from the rf excitation pulse. Experimental results are included that demonstrate submicrosecond recovery times for the observation of the signal.

A fast recovery pulsed nuclear magnetic resonance sample probe using a delay line

A probe (80) for irradiating a sample with RF energy during transmitting periods and detecting an NQR or NMR signal from a substance contained within the sample during receiving periods. The probe (80) comprises a variable impedance unit (20) for changing the Q-factor of the probe and a probe coil. The probe (80) is responsive to powerful RF pulses applied thereto to excite RF magnetic field in the probe coil during the transmitting periods. The impedance (20) is controllable to provide a Q-factor for the probe (80) at: an optimal level during a prescribed transmitting period of an RF pulse for irradiating the sample with said RF energy; a minimal level during a prescribed recovery period immediately following said transmitting period to rapidly dampen transient signals from the probe; and a maximal level during a prescribed receiving period for detecting an NQR or NMR signal from the target substance if present, immediately following the recovery period.

Q-factor switching method and apparatus for detecting nuclear quadrupole and nuclear magnetic resonance signals

A coupling scheme and a probe damper for use with a pulsed nuclear magnetic resonance single coil probe are described. The designs for both circuits incorporate the unique properties of PIN diodes. The performances of the circuits at the signal processing level are evaluated at 4.3, 15.78, and 49.0 MHz.

Coupling scheme and probe damper for pulsed nuclear magnetic resonance single coil probe

NMR probe with short recovery time

A circuit design is presented for a probe damper suitable for single coil NMR probes which improves the time for ringdown following an rf pulse by a factor of 2.5. The damping is provided for a precisely controlled time and removed positively to enable the use of high‐Q single‐coil NMR probes for samples with very short T2's. The damper can be adapted for use with negative or positive transmitter gating pulses.

Gregory W. Schmidt

Papers

A Single‐Coil Probe Damper for Pulsed Nuclear Magnetic Resonance