Upgrading the Fermilab Linac local control system Page: 1 of 3
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UPGRADING THE FERMILAB LIN AC LOCAL CONTROL SYSTEM
Elliott S. McCrary, Robert W. Goodwin and Michael F. Shea
Fermi National Accelerator Laboratory, Batavia, IL 605101
A new control system for the Fermilab Linac is being de-
signed, built and implemented. First, the nine-year-old linac
control system  is being replaced. Second, a control system for
the new 805 MHz part of the linac  is being built. The two
systems are essentially identical, so that when the installations are
complete, we will still have a single Linac Control System.
Replacing the OM Control System
The old control system, commissioned in 1982 and detailed
in reference , is incompatible with our controls plans for the
upgraded linac. The old system, based on locally designed and
built components using Multibus-1, an 8MHz MC68000 cpu
board and the SDLC network, is difficult to expand, to maintain
and to integrate into the more modem system envisioned for the
The design criteria of the replacement control system are:
1. Retain the desirable features of the old system, including
local access to the equipment and the monitoring and reporting of
of the local information at the repetition rate of the accelerator, 15
Hz. (In particular, if a reading goes out of tolerance, the control
system can disable beam on the next pulse.)
2. Minimize the software effort,
3. Use commercial hardware as much as possible,
4. Limit the amount.of downtime necessary for the
In order to minimize the software effort, the same system
used in the D0 high-energy physics experiment at Fermilab ,
which itself is based on the existing linac control system, is being
used. Essentially nothing needs to be changed to use this system,
although some features have been added. The D0 control system
is quite large, so the relatively small linac control system will not
require very much additional effort, except during commissioning.
The replacement system for the existing linac is shown sche-
matically in Figure 1. Its major features are outlined here. The
EEEE 802.5 Token Ring network connects a series of VMEbus
Figure 1, Upgraded controls for the existing Fermilab Linac.
•f Operated by the Universities Research Association under con-
tract for the Department of Energy.
Figure 2, Typical VME station in the Upgraded Controls for the Linac
crates to each other and, through a bridge, to the rest of the Fer-
milab accelerator complex. The VME crates contain the hard-
ware necessary to connect to each other (token ring) and to
control die existing linac hardware, see Figure 2. Contained in
each crate are the following core set of VME cards: a cpu card,
the MVME133A; a token ring card; a crate utility card; and non-
volatile RAM. Other I/O will also be used. Because the new
system has been designed to handle up to 2000 analog channels,
it is not necessary to have a new system foT each ok! RF station.
A ratio of one computer control station for every three RF stations
has been adopted.
We are considering two ways to interface to the old linac
hardware, as suggested in the grey box of Figure 2. The first way.
Figure 3a, is to use three commercial, six-byte digital I/O cards
configured to match exactly the old system’s eighteen-byte I/O
scheme. This scheme requires that a VME crate be located near
the digitizing hardware. Two of the crates would be slaved to the
first by linking the VME memories. A VME card has been de-
veloped to give limited memory access to several remote VME
crates from a master crate. This card is called a “vertical
interconnect” or VI. It maps 16 Mbyte blocks of VME memory
(24-bit addressing) into each of four digital crates. As many as 24
slave crates are served Grom six VI master cards in a single local
station. For each control station there are two additional VME
crates. Each of the three VME crates contains the digital I/O
cards necessary to interface with the old hardware.
This method has been successfully tested on the extra 201
MHz RF station in the linac. The RF stations which now have a
Multibus-based 12-bit D/A board (used foT dipole magnet set-
1 VME union
Bnia« AX). Ota.
Figure 3, two ways to connect to the old linac hardware
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McCrory, E.S.; Goodwin, R.W. & Shea, M.F. Upgrading the Fermilab Linac local control system, article, February 1, 1991; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc1100591/m1/1/: accessed November 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.