New Waveform Surveillance and Diagnostics for the LEP Injection
Kickers
E. Carlier, V. Mertens and H. Verhagen
European Organization for Nuclear Research (CERN) - SL Division,CH - 1211 Geneva 23, Switzerland
Abstract
The introduction of the Bunch Train Scheme in LEP requires a more precise and automatic supervision of the stability of
the LEP injection kickers in timing and amplitude. Comprehensive and user-friendly diagnostic tools are required for indepth investigation of equipment behaviour. A new system is currently being prepared using to a large extent commercial
data acquisition hardware and hardware-independent software products.

1. EQUIPMENT
The LEP injection kickers [1] are fast pulsed magnets used to inject electron and positron bunches, arriving from preaccelerators into the desired beam orbit in LEP. Three kicker magnets equally spaced along LEP, produce a fast orbit
deformation of the stored bunches as shown in figure 1. At the moment when the kicker magnet deflects an alreadycirculating bunch close to the field-free side of the septum, a newly injected bunch arrives at its field side and is bent by theseptum magnet nearly parallel to the trajectory of the stored bunches. The duration of the fast orbit deformation must be
sufficiently short to deflect only the stored bunch to which the new particles are to be added and must be exactly timed toavoid injection losses and residual beam oscillation.
KICKER 1
QD

QF

KICKER 2
QD

QF

KICKER 3
QD

QF

QD

CIRCULATING BEAM

KICKER SEPTUM

10 mm

ARRIVING NEW BEAM

Fig 1.

20 m

Layout of the fast orbit deflection for LEP injection, (QF, QD: focusing and defocusing quadrupole magnets).

The efficiency of the LEP injection kickers depends on two major parameters: the stability and reproducibility of thekick amplitude (better than 1 %) and the stability and precision of the kicker timing with respect to the injected andcirculating beam (better than 25 ns). A typical kicker pulse, together with a signal of the injected beam current, is shown infigure 2.

Fig 2.

Typical kicker pulse (1) (300 A/div.) and injected beam current (2) (1 µs/div.).

2. SCOPE OF THE PROJECT

So far no permanent surveillance of the LEP injection kicker signals exists. The kick/beam timing synchronisation andthe stability of the kick amplitude can only be controlled manually and only for following pulses, since no storage ofprevious pulses is foreseen. Faulty behaviour of the equipment can therefore only be confirmed if the symptoms persist.
Monitoring of the evolution of the parameters in time to keep optimum performance is manpower-intensive.
Considerable improvements were nevertheless mandatory with the advent of the so-called ‘bunch train scheme’ [2] at
LEP in 1995. In this scheme a much greater number of bunches circulate in the machine and a more precise injection
scheme is needed. It has now become more important than before to precisely supervise and maintain the performance of theinjection kickers and to trace back reasons of faults rapidly and with certainty.
It has therefore been decided to provide better surveillance and diagnostic facilities in the framework of an improvement
project. These facilities comprise tools to select, acquire, log, retrieve and visualise signals from the beam pickup and thekicker system, to analyse them and to compare them with reference pulses. These tools should be either callable on request
for diagnostic and adjustment, or run continuously in the background for equipment surveillance, with the possibility of
informing the equipment specialists of any malfunctions. Finally, they could be used to readjust the timing and pulse
heights automatically, if so desired.

3. GENERAL LAYOUT
In order to use commercial data acquisition hardware, to avoid as much as possible hardware dependence and to keep ahigh level of modularity, the application is being developed in the framework of LabVIEW [3].
The software part of the application is organized in a client/server scheme and divided into three layers: the dataacquisition, the data analysis and the data presentation. The two first layers constituting the server part are running on afront-end computer located close to the acquisition hardware in order to reduce the data exchange over the network and profit
from the event-driven capabilities of LabVIEW. The third layer, the client part of the application, is the graphical userinterface which runs on HP workstations.
Hardware dependent
Hardware independent

Signals

AcquisitionandControl

Logging DB

AnalysisPresentation
GUISlow control
AlarmsTS Tool Kit

Fig 3. Software structure.
The acquisition layer includes the measurement devices and their integration. The hardware independence is achieved byusing the LabVIEW virtual instruments driver library. The analysis layer comprises the tools used for signal surveillanceand diagnostics. It also includes utilities through which the system interacts with other systems such as the general CERN
alarm system, the equipment slow control, or databases. The presentation layer offers an uniform graphical user interface
and look-and-feel for the application and can be run simultaneously from many computers without disturbing theacquisition and analysis processes.
The low level layers are seen by the top layer as virtual instruments. The communication between both levels is
performed through the LabVIEW virtual instruments network based on BSD IPC using Internet stream socket [4].

4. ACQUISITION and DISPLAY
The kicker magnet, beam current and trigger signals are remotely selectable through multiplexer units and acquired
through signal digitizers.
The single shot sampling rate is 500 MS/s for four channels with a resolution of 8 bits. The higher acquisition
repetition rate is equal to 1.2s for a signal duration smaller than 2 ms.
The acquisition hardware will be connected to the existing accelerator control system (represented by a TCP/IP based
Ethernet network) [5] either through a GPIB bus connected to a PC, plug-in DAQ boards integrated within a PC, or a VXI
crate with a VXIpc card at the slot 0 position. In any case, DOS/MS Windows and LabVIEW will be used in the front end
computer level.
The main advantage of the VXI solution is the existence of the VXI "plug&play" standard initiative which simplifies
the setting up of VXI based systems. The same may hold true in the PC plug-in DAQ board solution when using theWindows 95 operating system. The GPIB solution offers the largest selection of instrumentation devices. All three ways ofintegrating the acquisition instruments are supported by LabVIEW.

HP/HP-UX

Xterm

Logging DB

HP/HP-UX
to Slow Control

Ethernet - TCP/IP

VXI

PC/WindowsPC/WindowsDAQ

IEEE488

Fig 4.

LabVIEW

Overview of the high and low level acquisition system.

The waveforms are displayed graphically, on demand, on HP 9000/7xx series workstations, X terminals and PCs withX emulators, using the X Windows system.
A remote on-line Oracle database is used to store the default acquisition settings, the acquired and the reference
waveforms. The connection to the kicker slow control is achieved through a fully configurable, event and data driven
software package running on a HP workstation [6].

5. ANALYSISThe selected waveforms (kickers + beam signals) are acquired upon reception of trigger prepulses when the system ispulsing and beam is available. The latest acquisitions are logged and kept in a local database organised as a FIFO. Upon
request, the waveforms can be transferred and stored, together with the present timing and voltage settings, onto a remote
Oracle database as reference waveforms.
Each newly acquired waveform is automatically compared with the corresponding reference. In order to detect differencesin amplitude or in time, smart trigger facilities (envelope, level or window trigger) are used. If the new waveform is outside
predetermined limits an internal trigger is generated and the last-measured waveforms are automatically stored with thereason for the fault in a remote Oracle database for later analysis.
Tools to select, extract, replay and display the acquisitions either from the local database or from the remote Oracle
database are foreseen.
Upon detection of an internal trigger, a call to an external C function with predetermined parameters is made. This callconnects the analysis layer to the existing equipment slow control software from where further actions can be initiated.
Beside this interlock facility, different levels of alarms (warning, fault,..), depending on the severity of the deviation areprovided. These alarms are sent to the general CERN alarm system through a call to the equipment slow control software[7].
For each new acquisition the difference in amplitude between the measured and reference signals is automaticallychecked at a predetermined number of points. The difference between the signals for the corresponding points is calculated
and sent to the equipment slow control software for pulse to pulse regulation.

6. CONCLUSION
The project is actually in its design phase. Different technical solutions and configurations have been evaluated and it
appears that the use of commercial hardware and software products for this kind of application tends to maximize
flexibility, minimize obsolescence and reduce development time, effort and maintenance.
The use of well established, proven and long-lasting hardware and software leads to a minimum of specificdevelopment, even if the needs or the environment evolve, and this can reduce the cost over the lifetime of the system.
Due to manpower limitations, the realisation of this project will be outsourced to industry.

ACKNOWLEDGEMENTS
The authors would like to thank all persons who have increased their trust in the successful integration of commercial
hardware and software products into the existing accelerator control system and those who have contributed withcomments, suggestions, and information to the evolution of this project.

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