An Operators Tool for Advanced Synchrotron Injection Diagnostics
W. Bayer∗ , G. Froehlich, W. Kaufmann, U. Scheeler, P. Schuett, Ch. Wetzel
GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt, Germany
Abstract
The operation of an accelerator facility like that at GSI
Helmholtz Center for Heavy Ion Research near Darmstadt,
Germany is very complex. The beam setup for a dedicatedexperiment requires the measurement of several beam parameters, e. g. stripping efficiency, energy, revolution frequency and so on. Different beam diagnostics along theaccelerator and beam transport lines provide for this purpose appropriate signals. As beam time is rare due to great
demand the operators are asked to setup beam in less andless time. One approach to enable that is to simplify thehandling of beam diagnostic tools and to preprocess thosesignals so that the operator gets a measurement result in aminimum of time. We report on the development of our
Schottky analysis in the SIS18 as an example for that. The
history is summarised and the control room front end ispresented.

are equipped with beam diagnostics and operating tools forUNILAC, SIS 18 and ESR. The remaining two consoles
are used for dedicated beam diagnostics at the synchrotron,
which is mainly used by experts during machine experiments, and the operation of the ion sources and the safetysystem.

INTRODUCTION
The accelerator complex at GSI consists of the UNIversal LInear ACcelerator UNILAC, the heavy ion synchrotron SIS 18 and the Experimental Storage Ring ESR(see Fig. 1). All machines deliver ion beams from protons
up to uranium. The main linac, an Alvarez DTL, is on one
side supplied with beam from the High Charge state Injector HLI and its ECR ion source on the other side from theHigh Current Injector HSI and its two ion sources (MUCIS/ MEVVA and Penning type). The ions are accelerated from 2.2 keV/u at the entrance of each injector up to11.4 MeV/u after the DTL. Via a transfer channel (TK) thebeam is delivered to SIS 18. The synchrotron supplies theESR and the experimental area with ion beams of variousenergies.

Figure 2: Top: Sketch of the main control room. Bottom:
Part of the SIS 18 console with several monitors for operating software, oscilloscopes and a spectrum analyser.

OPERATION OF SIS 18

Figure 1: Overview of GSI and accelerators.
All accelerators are operated from the main control room(see Fig. 2) which consits of five consoles. Three of them
∗ w.bayer@gsi.deFigure 3 gives an overview of the SIS [2]. It has a circumference of 216 m and consists of 12 congeneric sections of three quadrupoles (for doublett and triplett focusing) and two dipoles. The latter have a maximum bending
power of 18 Tm and a bending radius of 10 m. The beam
injected from the UNILAC in section 12 is accelerated withtwo ferrite cavities, that operate in a frequency range of 0.8
to 5.6 MHz, and extracted in section 6. The maximum energy of protons amounts 4 GeV/u (β = 0.98) and that of
238 73+U1 GeV/u (β = 0.88).
The beam delivered from the UNILAC consists of abunch train of 300 µs length, from which a part of 160 µs
length is cut by a chopper for injection to SIS 18 (seeFig. 4). About 165 micro pulses are injected per turn (multiturn injection) with respect to the HSI rf frequency of36 MHz. Cooling the beam with the electron cooler several
bunch trains can be injected in a multi-multiturn injection

trum Analyzer 9 kHz - 3 GHz (SA), which is triggered at acertain timing event of SIS 18. It can be remote controledwith GPIB commands via IEC-Bus [1]. The signal of theSchottky probe is directly connected to the SA over a signal
selector as shown in Fig. 6.

Figure 5: Pick-up probes as mounted in SIS 18, left: phaseprobe, right: Schottky probe.
Figure 3: Schematic overview of SIS 18.
Mostly during beam setup intensities of the order of 106
particles have to be measured. Therefore the signal of aphase probe is mixed with the rf master signal of one of theaccelerating cavities which increases the sensitivity of thismeasurement, because all frequencies that do not belong to
the beam are suppressed.

scheme.

Figure 4: Timing of the UNILAC ion beam.
For the operation of SIS 18 two tasks have to be fulfiled, beam setup and monitoring of beam parameters. In
both cases beam intensity and energy as well as momentum
spread take centre stage. The sensitivity of the usually usedbeam current transformers is too low in order to optimise
beam intensity during beam setup. A signal from a phaseprobe can be used to get a better signal-to-noise ratio as described in the next section.
The injection energy can be determined by a time-of-flightmeasurement with phase probes along the transfer channel
to SIS 18. Using those probes, also the energy spread of
the UNILAC beam of ∆E ≈ ±100 keV/u can be adaptedwith two re-bunchers to the SIS 18 acceptance of ∆E ≈±23 keV/u, but the methode takes a lot of work, is unsuitedfor monitoring and has no quantitative result. In both cases
it is favourably to use Schottky analysis as it results in mostprecise values, can be performed quickly and is suited foronline monitoring.
Using a spectrum analyser and a dedicated data aquisition
all those measurements and monitoring tasks can be performed using only one device.

BEAM DIAGNOSTICS
Beside other beam diagnostics two phase probes and one
Schottky probe as shown in Fig. 5 are mounted in SIS 18. In
order to use them for the above mentioned operation tasks
a dedicated data aquisition is needed. The front-end device in the main control room is an Advantest R3132 Spec-Figure 6: Schematic overview of the data aquisition.

THE SIS-BEAM-DIAGNOSTICS TOOL
Due to the complexity of the above described data aquisition and the SA itself the operation of this system for nonexperts is a real challenge. In order to integrate it into usual
accelerator operation a development of a dedicated frontend software to control the data aquisition and the SA wasnecessary. The requirements to this software are simplification of operation of the complete system and suitabilityfor monitoring.

Boundary Conditions for the Development
The control system of the accelerator at GSI is based onVMS. In the near future it will be substituted by a systembased on Linux, but up to few years ago operation software
had to be exclusively developed on VMS with the programming language Fortran 95 and X11/ Motif for the GUI design. For the latter an in-house generated widget-set is used
as well as a widget construction tool which helps the software programmer to build the GUI code.
There are two main constraints new operation software
has to fulfill. First, the GUI must be operable intuitively,i. e. also people who have low experience with a certainGUI should be able to work with it. Second, the look ofa new GUI should be similar to existent ones so that theacceptance is as high as possible.

about 4.5 years, the shift-work of the DAQ developer andthe circumstance that no offical request and thus only a low
priority for the software development existed.

GUI of SIS-Beam-Diagnostics Tool
Figure 7 shows the top level GUI, where subprograms toperform device settings and measurements are called. InFig. 8 an example for the structure of a measurement GUI
is given. This is equal in all measurement programs but ofcourse the possibilities to setup the devices are adapted tothe different measurements.

History & Challenges
During the commissioning of SIS 18 1989/ 1990 mosttasks were performed by experts, thus e. g. Schottky scans
were performed using a phase probe as an electrostatic
pick-up. A system for intensity measurements with highsignal-to-noise ratio existed. One year later the Schottky
pick-up probe as shown in Fig. 5 was mounted and an adequate DAQ allowed experts to perform the analysis. Since
then Schottky analysis was mainly used during experiments
for machine development.
Since 2001 several upgrade measures at UNILAC andSIS 18 started to increase the beam intensity and to fulfill
requirements of the proposed and approved Facility for Antiproton and heavy Ion Research (FAIR) at GSI [3]. As theimprovement of beam quality during normal operation can
only be received increasing the quality of machine setup
several new beam diagnostics tools were developed in parallel and it was decided to provide Schottky analysis fornon-experts.
Thus, in 2005 the development of the so called SISBeamDiagnostics software, that should combine measurement tasks with phase and Schottky probe. Mid of 2006
the 1st version of this software was provided to the main
control room. Until 2009 it was tested and modification
requests were collected so that during the 1st half-year of
2009 the software could be revised. Since mid of 2009 themost convenient version is more and more used during normal operation by non-experts.
During the development different challenges had to beovercome. Some essential topics of the 1st specification
like to read, write and set the revolution frequency could
not be realised as the main control software of SIS 18 is amore or less standalone software and the communication
to other software is limited to essential needs. The limited
possibilities of VMS, X11/ Motiv and the widget-set madesome compromises for the GUI necessary.
The most limiting problems however concern to the remotecontrol of the Advantest SA. As not all GPIB commands
work properly it was decided to call setup profiles for different measurements locally stored at the SA. Periodical
requests of status, settings and measurement results disturb
local operation of the SA, e. g. by experts who use the software only for setup, because contrary to the manual the SA
cannot be set into local operation mode via GPIB. As theSA and the terminal on which the software runs are locatedin the same console periodical requests were avoided.
There were two main reasons for the development time ofFigure 7: GUI of the top level program. Buttons on theleft: subprograms for device settings of phase probe (1),
Schottky probe (2), others (3). Buttons on the right: subprograms for measurement of beam intensity (1), revolution frequency (2), ∆p/ p (3).

Figure 8: Example for the structure of a measurement GUI.
Top: display for beam parameters (1) and selectors for virtual accelerators (2). Mid left: setup parameters of DAQ
devices (3). Mid right: setup parameters of SA (4). Bottom: Status display (5).

RESULTS
In this section several measurement results as they wereachieved during machine setup and monitoring machineparameters are presented.
Figure 9 shows an example for intensity monitoring using the phase probe signal mixed with an rf signal and it
gives an impression of the high measurement sensitivity.

Figure 11: Top left: unused carbon stripper foil, top right:
used carbon stripper foil, bottom: observation of stripper
foil ageing.
Figure 9: Example for intensity monitoring of ∼ 1.4 · 109
particles 238 U73+ on a logarithmic scale.
Schottky analysis and the measurement of ∆p/ p during machine setup is important as can be seen in Fig. 10.
The green line represents the Schottky analysis without rebunching the beam in the transfer channel and the yellow
line the same but with rebunching. In this example there
is a factor of approximately 3 in ∆p /p between both measurements. Additionally this measurement is used to determine whether the re-bunchers only bunch the beam or ifthey accelerate the beam somehow.

ready show impressively, that it is necessary to implement
those measurements in normal operation.

CONCLUSION
The development of the SIS-BeamDiagnostics tool wasvery successful, as now beam intensity measurement andSchottky analysis for variing beam parameters like energy
and ion species can now be performed also by non-experts
during beam setup and normal operation. The amount ofpeople who use this tool regularly is steadily growing sincea proper runing software is available. Thus, the quality ofbeam delivery could be increased and even experimentalist
observed that.
But it was a good piece of work and the development
took longer than estimated. There was a large commitment
on side of the operation group so that all requirements for
operation could be fulfilled. Many experiences have been
made to process similar developments more smoothly inthe future.

ACKNOWLEDGEMENT
Figure 10: Optimisation of buncher settings.
In the transfer channel to SIS 18 the beam has to be
stripped by thin carbon foils (200 up to 600 µg/cm2 ) again
to reach highest beam energies at extraction level [4]. As
presented in top of Fig. 11 after a certain time of use thefoil gets ripply and due to sputtering it gets slightly thinner.
This ageing process can be observed by Schottky analysis as shown in the lower part of Fig. 11 because for theused foil (green line) ∆p/ p is larger due to the ripple andthe revolution frequency is slightly higher due to less foil
thickness. Therefore monitoring the Schottky signals indicates when stripper foils should be substituted.
Certainly there are furhter application tasks, e. g. the observation of the cooling process, but the cases above al-Thanks to W. Barth, P. Forck, M. Kaiser, B. Kindler,
P. Kowina and the main control room crew for support ofpictures.

REFERENCES[1] ADVANTEST Corporation, R3132 Series Spectrum Analyzer
Operation Manual, 1999, http://webhard.ajurental.
com/support/Manual/R3132.pdf.
[2] K. Blasche, B. Franczak, The Heavy Ion Synchrotron SIS,
EPAC’92, Munich, Germany, 1992, p. 9.
[3] P. Spiller, et al., Approaches to High Intensities for FAIR,
EPAC’06, Edinburgh, Scottland, 2006, p. 24.
[4] W. Barth, et al., Commissioning of the New GSI-Charge
State Separator System for High Current Heavy Ion Beams,
LINAC’08, Victoria, BC, Canada, 2008, p. 175.