The Control and Diagnostics System for the CEBAF Injector Page: 1 of 3
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THE CONTROL AND DIAGNOSTICS SYSTEM
FOR THE CEBAF INJECTOR*
P. Adderley, W. Barry, R. Bork, R. Cucinotta, C. Grubb,
J. Heefner, J. Kewisch, P. Kloeppel, G. Lahti, T. Mason,
E. Navarro, R. Pico, H. Robertson, R. Rossmanith,
J. Sage, and M. Wise.
Continuous Electron Beam Accelerator Facility
Introduction
We present the first experience with the CEBAF injector5
control and diagnostics system. The computer architecture of
the control system has been described elsewhere.2 The injector
system is a model for the CEBAF controls. A computer system
controls the gun, the steering magnets, and the focusing ele-
ments, and in the near future also the injector rf system. The
beam parameters such as current, position, and emittance are
measured by various monitors and are automatically analyzed
by the computer.
The CEBAF injector.
The injector (Fig. i) is the first part of the CEBAF ac-
celerator beam transport to be operational. After the gun
(Fig. 2), it has components that are similar to others that
will be used throughout the accelerator: safety interlocks, rf,
variable power supplies, intercepting devices, and other beam
diagnostics. The injector control system will therefore be de-
veloped as a model for that of the entire machine.
The control room.
The operator can direct all accelerator functions by using
computers in the control room (Fig. 3). The injector controls
consist of a supervisory HP560 computer that drives other com-
puters that actually control the functions; an HP330 controls
the gun, while an HP318 runs diagnostics and transport. The
supervisory computer also drives a pair of large high-resolution
color monitors with keyboards and a common track ball and
set of assignable knobs. Smaller monitors are used for pro-
gram development, and can also be used as remote terminals
for local troubleshooting of hardware problems.
Display: gun control.
The gun control panel allows the operator to set the fila-
ment current, high voltage, and grid voltage either by typing
in the desired values or by knobbing them in.
Display: beam transport and diagnostics.
The injector control panel (Fig. 4) allows the operator
to insert or remove viewers or other intercepting devices, set
magnet currents, and operate the camera for analysis of the
images. The insertion devices are toggled by the switch at the
track ball, while the magnet power supplies can be set either by
use of the assignable knobs or by typing in the desired settings.
The display also shows the status of the local computers and
their associated CAMAC crates. Messages such as warnings
from the local computers are displayed. The operator can save
the settings of all magnets controlled by the display, and can
recall and automatically install a previously saved configura-
tion.
Magnet control. The field strength of a magnet is altered by
assigning a knob to the power supply of the magnet in question
and then dialing in the desired shunt voltage. Alternatively, it
can be set by keying in the new value. The display shows the
requested shunt voltage and that actually measured.
* This work was supported by the U.S. Department of En-
ergy under contract DE-AC05-84ER40150.Plungers. The plungers that insert or remove interceptin
devices into or out of the beam are toggled from the screen
The plungers now in use (Fig. 5) are driven by air cylinders
Mounted on their shafts are viewer foils, Faraday cups, or beam
profile monitors (harps).
Viewer screens. Several different materials have been
tested successfully for use as phosphors on the viewscreens
The one shown in Figure 6 is a disk of beryllium oxide. An-
other is a deposit of chromium-doped aluminum oxide on an
aluminum backing.
Harp. The harp is a beam profile monitor that consists
of a frame supporting a pair of thin (50 gm) tungsten filament;
mounted parallel to each other, 1 cm apart. It is driven rapidly
through the beam by an air cylinder; the profile is -then inferred
by observing the current (Fig. 7).
TV monitor analysis. From the control panel, the opera-
tor can call for a local computer to grab a CCTV frame and
analyze it. Analysis consists of background subtraction, po_
sitioning relative to fiducial marks, and profile measurement.
The display can show either the analyzed image or a graph-
ical presentation of the two-dimensional position and profile
(Fig. 8).
Offline devices.
Some passive devices do not require operator intervention,
and so are not yet incorporated into the control system.
Current monitor. Current can be measured with a precision
of 0.2pA by means of a toroidal parametric current transformer
(Fig. 9) of a type developed and in use at CERN.3
Resonant cavity current and position monitor. Beam
current as low as 1yA and position at that current as precise as
1 mm can be measured by a pair of resonant cavities (Fig. 10).
At higher currents, the position measurement is proportionally
more precise.4
Loop position monitor. Beam position can be measured
with a precision of 1 mm for amplitude-modulated beam cur-
rents with modulation as small as 0.1A. The monitor (Fig. 11)
is a ferrite-loaded loop that resonates at approximately 10
MHz.5
References
1. W. Diamond and R. Pico, Proceedings of this conference.
2. R. Bork et al., Proceedings of this conference.
3. K. Unser, IEEE Trans Nucl Sci NS-28,2344-6 (1981); Klaus
B. Unser, Atomkernenergie-Kerntechnik 47,48-52 (1985)
4. P. Kloeppel, CEBAF technical note TN-0039.
5. W. Barry and M. Wise, Proceedings of this conference.
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Adderley, P.; Barry, W.; Bork, R.; Cucinotta, R.; Grubb, C.; Heefner, J. et al. The Control and Diagnostics System for the CEBAF Injector, article, October 1, 1988; Newport News, Virginia. (https://digital.library.unt.edu/ark:/67531/metadc724373/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.