The evolution of Jefferson Lab's control system Page: 2 of 5
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Starbase graphics library and Link Level Access network
protocol. The system provided control via CAMAC
hardware and GPIB crate controllers.
The TACL system provided effective tools for all
essential control system requirements. The graphical
logic and display editors were easy to use, and
programmers and engineers could quickly develop
control algorithms and graphical user interfaces for many
different accelerator systems. The local LAN and super
LAN network programs shipped data from local
computers controlling hardware in the field to all
supervisory computers hosting operator displays. The
system performed reliably and efficiently on small
systems such as the Cryogenic Test Facility, Injector Test
Stand, and RF Test Stand that were developed in
preparation for the larger operational cryogenics plant
and full accelerator. However, as various systems of the
accelerator completed the construction phase, controls
were installed for far more control points than originally
estimated. As a result, the performance degraded, and
system-wide updates became too slow.
The Logic program was responsible for executing
predefined control algorithms on the local computers.
The Logic Editor provided a rich set of functions for
customizing control logic, but the runtime Logic program
only had the capability to run the algorithm as one large
monolithic block, preventing control or variation of the
speed of execution. Additionally, the execution of the
control logic was implemented in an interpreted fashion,
limiting the overall speed of execution. A later version of
the Logic program implemented a compiled execution
option, speeding up execution by a factor of 4-10 times,
depending on the CPU type. This improvement, however,
did nothing to help with the network data update speed.
The GPIB interface to CAMAC hardware proved reliable
and performed quickly enough, but limited the control
system to one type of hardware interface.
The graphical user interface tool provided an easy to
use editor, and good run-time execution, but unlike newer
systems, had no windowing environment and therefore
could only display one control page per monitor.
With the growing realization of the limitations of the
existing control system, several options were proposed to
ensure the control system would meet the future needs of
accelerator commissioning and physics beam delivery.
One proposal was an upgrade of the TACL system to
overcome the performance and feature deficiencies. The
other two options centered on importing a control system
and making necessary additions to customize the system
for Jefferson Lab. For this proposal, the long used control
system from Fermilab, Accelerator Controls NETwork
(ACNET), was considered along with EPICS, at the time
a fairly new control system, in use at Los Alamos and
Argonne National Laboratories (LANL and ANL).
Due to the short time available, and the feasibility of
using an existing control system, we did not consider
starting another in house programming effort from
scratch. In years past, virtually all laboratories developed
their control systems this way, before software sharing
became a viable and efficient option. Once it was
believed possible to effectively share and co-develop a
control system with other labs, the benefits in terms of
code reusability, wider expertise and shared labor were
too attractive to ignore.
With three different paths to choose from, it was not at
all clear which would provide the best solution and could
be accomplished within the short time frame needed to
support the lab schedule for commissioning and
operations. Each alternative seemed to involve a
considerable amount of effort, and each had different
strong points working in their favor.
3.2 TACL Upgrade
An upgrade of the TACL system would allow usage of
the already developed device control, utilize all existing
hardware and minimize procurement and installation
costs. Additionally, virtually all of the in house expertise
was with Unix systems and TACL, so no additional
training would be required. The toolkit approach was
favored to reduce the required programming effort for
adding new applications. Unfortunately, this option
involved labor intensive changes deep in the TACL
system that would in fact duplicate much of the effort
already invested in EPICS.
Fermilab's control system, ACNET, was a VAX/VMS
based system, with many years of reliably running a large
control system in its favor. This option would have
involved replacing much of the existing control hardware
in addition to replacing all Unix machines with
VAX/VMS systems. Changing to a new operating system
would require retraining developers. Additionally, this
system involved custom coding each system application,
with no tools available to make this task more efficient.
In general, this system was viewed by the lab as a very
robust, but aging system that did not take advantage of
newer technologies. In the initial analysis, ACNET's
existing base of high level applications was seen as a
plus, but even after importing the base system, these
applications would have required significant rework to
function for the CEBAF accelerator.
The EPICS system , a more recent development,
began at LANL, and was adopted by ANL along with
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White, K. S.; Bickley, M. & Watson, W. The evolution of Jefferson Lab's control system, report, October 1, 1999; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc702983/m1/2/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.