  The Spallation Neutron Source (SNS) is a partnership between six
laboratories. To ensure a truly integrated control system, many standards have
been agreed upon, including the use of EPICS as the basic toolkit. However,
unique within the partnership is the requirement for Lawrence Berkeley National
Lab, responsible for constructing the Front End, to operate it locally before
shipping it to the Oak Ridge National Lab (ORNL) site. Thus, its control system
must be finished in 2001, well before the SNS completion date of 2006.
Consequently many decisions regarding interface hardware, operator screen
layout, equipment types, and so forth had to be made before the other five
partners had completed their designs. In some cases the Front-End has defined a
standard by default; in others an upgrade to a new standard is anticipated by
ORNL later. Nearly all Front-End devices have been commissioned with the EPICS
control system. Of the approximately 1500 signals required, about 60% are now
under daily operational use. The control system is based on "standard
architecture"; however, it has a field-bus dominated layout. This paper will
discuss some unique interface requirements that led to adding new device
families into the EPICS repertoire. It will also describe the choices and
trade-offs made for all major areas.
