Lady called the service center complaining that she could not find the lock
signal. The service rep was very helpful asking her several questions to
insure that the probe was properly cabled etc. Just when the service rep was
seriously scratching his head the lady mentioned that her screen had reversed
colors. The service rep asked if she had helium in her magnet. She replied
that she had filled the magnet that morning, but she had to do it again as most
of the helium had 'escaped'.
This one is a true story. A fild engineer was training a new field engineer.
They were cyro shimming an R2D2 magnet. As the trainee was removing the wand
the helium boil-off, from the other port, suddenly and dramatically increased.
He shoved the wand back down into the magnet and tried to stop the quench by
placing his hand over the open port. Fortunately he was not seriously hurt.
Bob Dudley