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\section{whatever}

\subsection{New Raster with No Dwell (Contributed by R.~Michaels)}

Thanks to the efforts of Chen Yan (Hall C staff) 
and his collaborators, we successfully deployed 
a new fast raster in Hall A which 
is a copy of the Hall C design (Tech Note 97-004).
This raster achieves a uniform rectangular
density distribution of beam on the target 
by moving the beam with a time-varying dipole
magnetic field whose waveform is triangular
with very little dwell time at the peaks.  
This is a major improvement over 
our previous sinusoidal raster.  
The electronics design is an ``H-bridge''
in which switches are opened and closed 
at 25 kHz, to switch between two directions 
of current (100 A peak-to-peak) through the raster.
The current is driven by HV supplies.  At the 
moment one pair of switches is closed, the current
rises according to the exponential law $(1 - e^{-Rt/L})$
where $R$ = resistance, $t$ = time, $L$ = inductance.
The current turns out to be highly linear 
for the choice of components.  To switch the
direction of current, one pair of switches 
are opened and another pair 
closed simultaneously and rapidly.
The electronic and mechanical demands
required state-of-the-art components:
power terminal bus strips between HexaFETs, 
storage capacitors, polypropylene snubber 
capacitors, silver-plated thick copper terminals, 
and carefully designed pathways to 
reduce HV spikes and cross talk.
The system has proven to be highly reliable
in both Halls A and C.

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