COMMISSIONING OF THE CARBON BEAM GANTRY AT THE
HEIDELBERG ION THERAPY (HIT) ACCELERATOR
M. Galonskaa, S. Scheloskea, R. Ceea, K. Höppnera, C. M. Kleffnerb, A. Petersa, T. HabereraabHeidelberger Ionenstrahl-Therapiezentrum, D-69120 Heidelberg, Germany
GSI Helmholtzzentrum für Schwerionenforschung mbH, D-64291 Darmstadt, Germany

Abstract
The Heidelberg Ion Therapy Facility (HIT) is thefirst dedicated proton and carbon cancer therapy
facility in Europe. It uses full 3D intensity
controlled raster scanning dose delivering method.
The ion energy ranges from about 50 up to 430
MeV/u corresponding to ion penetration depths of
20 to 300 mm in water.
The HIT facility comprises the only heavy ion
gantry worldwide designed for the beam transportof e. g. carbon ions up to an energy of 430 MeV/ucorresponding to a magnetic rigidity of 6.6 Tm. The
gantry rotating angle of 360 degrees enables patient
treatment from arbitrary directions.
This paper gives a brief outline on thecommissioning activities so far.

were transported to the isocenter in January 2008,
the commissioning was interrupted in order to focus
on the start of the clinical operation in thehorizontally fixed treatment lines. In February 2010
comissioning restarted after some optimizations inthe cable tray chain. The commissioning aims at theefficient provision of the pencil beam libraries forthe raster scanning dose delivering, i.e. up to 4 ions
(1H, 12C, 4He, 16O), 255 energy steps, 6 beam foci(3.5-20 mm FWHM) and 10 (15 later) intensities(106-1010), summing up to ~ 90.000 combinations.

THE HEAVY ION GANTRYINTRODUCTIONFig. 1 shows the HIT accelerator consisting of aninjector linac accelerating ions to 7 MeV/u. The
injector is followed by a compact synchrotron
which provides protons and carbon ions withvariable energy to the four high energy beamtransport lines.
The first two beam lines guide the ion beam tohorizontally fixed raster scanning systems forpatient treatment (H1 and H2 in Fig. 1). Treatmentin the first room started successfully in November
2009, while in H2 an enhanced version of themedtech equiqment is under commissioning. The
clinical operation will start fall 2010. A third
horizontal target station is built for quality
assurance, development, and research (Q-A inFig. 1).

Fig. 2: Drawing of the heavy ion gantry at the HIT
including mechanics, beam line components andpatient treatment room (MT Mechatronics)• First and only heavy ion gantry worldwide• Raster scanning included• Optimum dose application by patient treatment
from arbitrary directions• About 450 t of rotating parts• Length / diameter: 25 m / 13 m
• Construction
andintegration
byMTMechatronics (former MAN Technology)
finished by the end of 2007
• See also [1]COMMISSIONING (ORGANISATION)
Fig. 1: Overview of the HIT accelerator
Finally, HIT comprises the worldwide first heavy
ion gantry with integrated beam scanningcapability. While the first proton and carbon beams

Schedule
Commissioning of the heavy ion gantry takes placein the time slots between patient treatment (5 days aweek), and installation work on further treatment
equipment in the second horizontal treatment room.

On average there are about three shifts a week (8hours per shift) for gantry commissioning which
will be finished for protons and carbon beams infall of this year.

an overview of the gantry beam line with the beamdiagnostic devices while Tab. 1 outlines thereference value and the small margin (25 % rel.
deviation) of the beam width and the maximum
allowed position deviation ot the pencil beam.

Commissioning teamFig. 3: Organisation chart, green framed: maincommissioning team consisting of 6 members (beamadjustment, data supply, and theory)
The head of accelerator operation is in charge forsupervision of the project, and in especiallysupervision of the preparation of the gantry beamtimes concerning the functionality of allcomponents involved: e. g. mechanics (e. g.
enabling of gantry rotation etc.), beam diagnostics(e. g. installation of viewing target at the gantry exitetc.), control system and so on. This work is partly
supported by the main commissioning team, forinstance by bug reporting to the HIT and external
expert teams.
The main commissioning team (green framed inFig. 3) is in charge for the scheduling and planningof the beam time experiments concerning ion beamadjustment, ion optics, data supply of the magnetic
structure, and theory.
Besides the preparation of the gantry beam line by
the HIT expert teams there are generally on-callexperts during each shift.
Communication
In order to achieve a substantial progress incommissioning shift by shift an elaborate
documentation and scheduling system is inevitable.
This reporting system includes:• A weekly meeting of the commissioning teamfor presentation and discussion of the results
achieved during experiments and planning offollowing beam times• A detailed written record of each session
presenting results, conclusions, and drawbacks• A data collection of measurements on a network
storage• Records posted to the HIT E-Log [2]• Bug reporting to HIT and external experts
concerned by encoutered problems

ION BEAM CHARACTERISTICS
The gantry commissioning started again inFebruary 2010 with a carbon ion beam. Fig. 4 gives

Fig. 4: Gantry beam line with beam diagnostic
devicesenergystep

FWHM
max. positionreference
focus
range
deviation
[mm]
[mm]
[mm]
1
9.8
7.4-12.3±11
10.7
8.0-13.4±11
12.1
9.1-15.1±1
1
13.4
10.1-16.8
±1
255
3.4
2.6-4.3±1255
5.5
4.1-6.9±1255
7.8
5.9-9.8±1255
9.8
7.4-12.3±1Tab. 1: Reference value of the beam width (FWHM,carbon) with margin (25 % rel. deviation), andmaximum position deviation for the minimum andmaximum ion beam energy and focus steps 1 to 4
The beam width in the HEBT changed since thefirst gantry commissioning at the beginning of 2008
due to a change in synchrotron extraction.
Therefore the high energy beam transport to thegantry and the ion beam characteristics (beamwidths) behind the gantry had to be re-adjusted.
Beam size and position, are measured with aviewing target and camera mounted on the(rotating) exit of the gantry (Fig. 5).
The ion beam adjustment follows the pattern:1) the beam size and position variation over thegantry angle is reduced by optimisation of the ion
beam at the gantry entrance point, i. e. beam size
and angle for a single ion beam energy (Fig. 6, seealso [3][4]). Since the vertical beam emittancedepends on the beam energy (due to adiabatic
damping) the matching at the entrance point
depends on the ion beam energy as well;2) the beam size behind the gantry is adjusted by
the last gantry quadrupole doublet, the control
values of which can be set and stored individuallyfor different gantry positions.

Fig. 5: Viewing target and camera in black housing
at the gantry exit

beam energy, i. e. quadrupoles, dipoles, steerer inthe HEBT. The focusing strength of the last gantry
quadrupoles even has to be set individually fordifferent energies, set values of beam width, andgantry angle.
In order to minimize the commission effort only a
few number of input parameters are set manually;i. e. for a few energy steps, and gantry angles, while
missing data (physical and control data for thepower supplies) is created by means of apolynomial fit between these nodes. Fig. 8 shows
an example for the input setting of a correction tothe quadrupole focussing strength as a function of
the gantry angle. The position of themaxima/minima in the fit curves clearly reveals theperiodic structure of the input parametercorresponding to the gantry angle.
dkL_QD
0.03000.0250dkL [1/m]

0.02000.01500.01000.00500.00000102030

Ga ntry a ngle step

Fig. 6.: Beam envelopes along the HEBT andgantry, red marked: envelope at the gantry
entrance point
In order to reduce the commissioning efforts thesequadrupoles are the only lenses which should be set
corresponding to the gantry angle although this istechnically possible for other magnets as well.
This given procedure ensures that the beam size
ranges (up to now almost) in a 25 % limit comparedto the beam sizes needed for patient treatment for
89, 251, and 430 MeV/u, i. e. for the minimum,maximum and one medium carbon energy. Fig. 7
shows the measured beam size (FWHM) over a fullgantry rotation.

Fig. 7: Beam width (FWHM, left: horizontal, right:
vertical) over a full gantry rotation, energy step
255 (430 MeV/u), focus step 3 (9.0 mm), diagnostic
tool: viewing target behind the gantry
For a single energy the control data for theaccelerator components is calculated from physicalinput parameters. The data supply model accounts
for scaling of the control data with the magnetic
and electric rigidity for different energies. Other
energy dependend effects have to be compensatedby manually adjusting components according to theFig. 8: Correction to a quadrupole focussing
strength as function of the gantry angle step (1 step≡ 10°) with fit (line) between the base points (dots)
for a fixed energy and focus step

OUTLOOK
The next steps in the beam commissioning include
the adjustment of the beam size for several medium
energy steps. After this, the magnet settings forintermediate energies and gantry angle dependend
focussing strengths will be calculated from thepolynomial fit curves for the whole variety ofneeded beam properties, i. e. 255 energy steps, 4
beam radii and 36 gantry angles. This is giving a
total number of 36720 combinations for one ion
species, excluding 10 intensitiy steps andintermediate gantry angles.
The results concerning the beam position are still
preliminary. With the settings so far the beam
position varies within a few mm on the viewing
target as well as in the MWPCs on the gantry.
These variation will be reduced by further
modification of the matching at the gantry entrance
point and, as a further option, by gantry angle
depended corrections of the beam position in thenear future, and later on by position control of therasterscanning technique.
It can be concluded that the described procedures
provide an efficient way of setting the ion beam
properties in a reasonable time.

ACKNOWLEDGEMENT
The authors would like to thank the GSI therapy
accelerator team for commissioning of the HIT
accelerator, which was finished for the horizontal
treatment rooms by the end of 2007 [5]. The
accelerator was handed over to HIT on the 30th ofApril 2008. Thanks to the HIT staff for many
helpful discussions, preparation, and maintenanceof the accelerator parts which are necessary for thegantry commissioning.

REFERENCES[1][2][3][4][5]

R. Fuchs et al., Proc. of the 11th EPAC 08, Genoa, Italy
J. Mosthaf et al., Proc. of the 12th ICALEPCS, Kobe,Japan, 2009
C. M. Kleffner, U. Weinrich, Proc. of the 11th EPAC 08,Genoa, Italy
U. Weinrich, documentation to the gantry commissioning,
2008, unpublished
D. Ondreka et al., Proc. of the 11th EPAC 08, Genoa, Italy