VACUUM CONTROL SYSTEMSUPGRADE AND ANALYSIS FEATURES AT DESYWolfgang Gerhardt, DESY, Hamburg, Germany
Abstract
The vacuum control systems of the particle
accelerators at DESY are being progressively upgradedusing the DESY PETRA style system described at
PCaPAC96. It is based on a network of PC and Novell
File Server Systems. To date, the DESY particle
accelerators HERA-e, DORIS and LINAC 3 have beensuccessfully transferred to the upgraded system. The new
vacuum systems support analysis of status and dynamicprocesses. Investigation of individual pressure
measurements and pressure profiles of a whole machineare possible. Short and long range archives of the recent
and distant past are included. The long range archive is aseparate system which performs data logging for manyother device controls as well. Special emphasis is put onto
the data visualisation. Time accelerated views of pressure
profiles help to watch the development of vacuum quality
or locate a developing leak. Experience gained on theDESY Vacuum Control Systems Upgrade and theVacuum Analysis Features will be described.

1• A LAN clock is realized by an IPX broadcast sent bythe Cycle PC once per second• Applications on the Device Server PC are triggered by
the LAN clock to perform the read-out of the device
status, to process the data and to send them into theLAN• The client applications on the console PCs listen to
LAN and display the current device status• The server applications on the Device Server listen fordevice operating commands coming from the consolePCs.
These principles of the PETRA Vacuum Control
System VCS were adapted for the upgrade of the VCS tothe other accelerators at DESY.

INTRODUCTION

The preacceleration of protons and electrons for theHadron Electron Ring Accelerator HERA is done by themachine PETRA[4]. The PETRA Control System isbased entirely PC hard- and software since the spring of1996. The specific solution of the PETRA VacuumControl system VCS is shown in figure 1.
Characteristics of this PC based Control System are• All PCs are connected by an ethernet LAN1 with afileserver running Novell Netware 4.11
• Console PCs running client applications are thegraphical user interfaces• Device Server PCs running server applications are theinterface to the inhouse field bus SEDAC2 [1][2]which is the long distance connection to hardware
device controllers• MS Visual Basic 3.0 is used for development of Clientand Server applications under MS Windows 3.11
• The communication of Client and Server applications
is realized by inhouse-developed custom controls(VBX3) which also support the Novell IPX protocol[3]• Standard Novell file access to the file server• Data and program code are hosted on the file server
1

Local Area Network
Serial Data Acquisition and Control system
3
VBX is the extension of Custom Control Files
2

Figure 1: PETRA Vacuum Control System

2

THE VACUUM CONTROL SYSTEMSUPGRADE OF HERA-e, DORIS ANDLINAC3

A direct transfer of the PC software of the PETRA
VCS to the other machines was not possible due to thedifferences in the device controllers (hardwaregenerations) and additional devices not present in thePETRA VCS.
A redesign of the Device Server applications wasneeded to take into account the new operation modes
available with microprocessor based vacuum controllers.

The new and additional information about thevacuum devices had to be integrated into the client
applications on the console PC.
Additionally there was the desire to maintain asmuch as possible the proven graphical interface as it is atPETRA for the vacuum operators.

2.1 DORIS
Applications for the separate operation of themicroprocessor based controllers were developed. Consoland Device server applications for Titanium-Sublimation
pumps not used at PETRA were written.
The DORIS VCS was redesigned in this way in1997.

2.2 HERA-e
The HERA-e VCS has a much greater number ofgetter pumps as PETRA (about 800, PETRA: 200). So
major changes of the Console and Device Server
applications were neccessary because of the limited
packetlength of the IPX communication interface.
The operation programs for the microprocessor
based device controller and for the Titanium Sublimation
Pumps could be transfered from the DORIS VCS.

3 ANALYSIS OF PRESSURE STATUS
3.1 Pressure Display
In the operation mode of the accelerators the getterpumps supply the main pressure information of thevacuum chamber.
A single pressure value is visualized by a verticalgreen bar on the screen at the console. The scale runs
from about 1E-12 to 1E-05 mbar.
A pressure profile of all the single pressure values
taken around the accelerator ring is collected within lessthan one second. The display is visually prepared in thecomb representation[5]. So even for the HERA-e
accelerator there is a clear overview of the nearly 800
pressure values.
The position and length of the pressure bars on thescreen correspond to the position and pressure values inthe machine.

3.3 Marker

Applications were developed for the following
devices not used at PETRA and DORIS• Turbo Pump Stations• High Voltage operation

For the visualization of changes of pressure in time
the Marker function is used.
A reference machine profile can be fixed at one
instant by setting the Markers: At the top of each pressure
bar a small red horizontal bar is painted. These Marker
signs are permanent until the Marker is set or cleared.
If the pressure values of the profile change in time
the amount of the change with respect to the reference
profile is directly visible in the different positions of theMarker and the endpoints of the pressure bars.

2.1 LINAC3

3.4 Range Check

At LINAC3, differences in the power supplies of
the getter pumps led to changes in the software of theDevice Server applications.
In some vacuum sections of the LINAC3 accelerator
there is a lack of pressure information by getter pumps; inthese machine sections Pirani and Penning pressure meterare installed. Major changes in the Console and Device
server applications were done to show the pressure valuesof these different devices in one display.

To focus the attention to a pressure value which has
exceeded a previously defined limit there is the Range
Check function: The color of the corresponding pressurebar is changed to red as long as the limit value isexceeded.

These modifications in the software for the VCS ofPETRA does not effect the reliability of the new VCS ofHERA-e, DORIS and LINAC3.
In contrary the better performance in terms of ahigher time resolution of status information (HERA-e: 1second, 40 seconds before) and the analysis features bringmore clarity into vacuum system operations.

Per mouse click a history of every single pressure
measurement in the accelerator of the last five minutes isprovided.
At an update rate of once per second a time profile ofthe selected pressure measurement can be watched on thescreen.
The data for these histories are held in the memoryof the Device Server PCs: About 250KB for HERA-e. At
the request of a console PC the Device Server sends thedata for the selected pump via IPX telegram over theLAN: 600 bytes per second.

4ANALYSIS OF PRESSURE DYNAMICS

4.1 Five Minute Archive: History4.2 One Hour Archive: Playback
The pressure profiles of the whole machine for every
second of the last hour are held in the memory of theconsole PC. Thus the data for 3600 profile pictures areavailable for a playback: Showing picture-for- picture atten per second supplies a time accelerated vacuum movie
that starts in the present and goes to the past.
• A one hour vacuum history of a whole machinepressure profile shrinks to a six minute playbackshow.
• A developing leak propagating as a pressure wave
through the vacuum tube can be studied again andagain. The option to go step-by-step, picture-forpicture through the show enables one to locate a leak.
• The process of the developing vacuum quality in thelast hour becomes dramatic in this time- acceleratedview.

4.3.1 One Month Archive: World Wide Web
There is a separate long range archive system. It isindependent from the Vacuum Control System andperforms the data logging for all the different DeviceControl Systems running on PCs.
There are following archived vacuum parameters:• Average pressure of the whole machine• All the single pressure measurements• Status information of the gate valves
At present the hard disc capacity for the HERA-e
vacuum data is sufficient for• 31 days with a time resolution of 20 minutes• 7 days with a time resolution of 2 minutes
At this time the archived data are presented in theWorld Wide Web in terms of numbers.

4.3.2 One Month Archive: Playback Archive
The Playback Archive is the Playback with aninterface to the Long Range Archive.
So the pressure data can be presented in theaccustomed comb representation.
For any selected time range out of the 31 days thePlayback Archive allows viewing a vacuum movie. Thetime steps are variable. An eight hour vacuum shift could
shrink to an eight minute playback show.

5CONCLUSION

The PC concept of the PETRA Vacuum Control
Systemwas transferred very successfully to theaccelerators HERA-e, DORIS and LINAC3.
The systems are reliable, have a high performance interms of the time resolution of presenting the vacuum
device status and the described analysis features help tobring clarity into vacuum system operations.

6REFERENCES[1] H. Frese and G. Hochweller, ”The Serial Data
Acquisition System at PETRA”, IEEE Nucl. Sci.
26, 1979, pp. 3384.
[2] R. Stadtmüller, ”SedPc - Interfacing SEDAC andPCs”, Proceedings PCaPAC’96, DESY, 1997
[3] M. Peters, ”Extensions for Visual Basic”,
Proceedings PCaPAC’96, DESY, 1997
[4] R. Schmitz, ”A Control System for the DESY
Accelerator Chains”, these proceedings[5] W. Gerhardt, ”Vacuum Control at PETRA”,
Proceedings PCaPAC’96, DESY, 1997