NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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the range ±1 V are digitised to a7 bit resolution and summed in
a 16 bit register. The time interval per point is variable bet-
ween 2 Ps and 50 ms and the averaged signal may be displayed on
an oscilloscope to 7 bit accuracy. In the particular experimental
set-up used the full 16 bit output of each register was read out
through a Data Laboratories 1002/100c interface coupled to a Data
Dynamics teletype.
The M12 electromagnet used in this work had originally been
part of an RS 2 high resolution CWNMR
spectrometer manufactured by
AEI. The maximum period of time over which the signal could be
accumulated
in the signal averager was in some cases limited by
the slight drift in the magnetic field.
5.2 MODIFICATION OF THE SPECTROMETER
PULSE PROGRAMMER
The four pulse units of the spectrometer are located in inter-
changeable plug-in units. Each unit consists of two monostable
flip-flops; one for determining the pulse length and one for deter-
mining the delay time with respect to the previous pulse. However,
because the delay times are set via decade counters, they are
correct only when the pulse delay time is less or equal to that
of the preceeding pulse. Such a condition means that some simple
pulse sequences cannot be performed using the standard spectrometer.
To overcome this problem a Mullard FJK 101 integrated
mono-
stable circuit was set-up to provide a positive DC pulse of contin-
uously variable duration between 0.5 us and 120 ms compatible with
the internal logic of the spectrometer. The complete circuit was
mounted in an aluminium box with a plug connector so as to be inter-
changeable with any of the plug-in pulse units. The monostable