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ISSN: 2 6 7 3 - 5 3 5 0d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 C 0 3AN EXPERIMENTAL SETUP FOR PIXE ANALYSISIN A MEDICAL CYCLOTRON AT TENMAK-NUKEN
G. Turemen∗ , S. Bulut, U. Kaya, D. Porsuk, N. O. Serin, E. Yeltepe
TENMAK-NUKEN, Ankara, Türkiye
IRRADIATION SETUP

Abstract
A 30 MeV cyclotron is operated at TENMAK-NUKEN for
producing medical radioisotopes with three beamlines anda fourth beamline is dedicated for research purposes. The
minimum energy of extracted proton beam from cyclotron
is 15 MeV. There is no facility in Türkiye for applying ion
beam analysis techniques (IBA) currently. These techniques
generally require 1-5 MeV proton beam energy. An energy
degrader system was designed and installed on the R&D
beamline for this purpose. The degrader system is capableof decreasing the energy down to 1 MeV with pA to µA current levels. A high vacuum irradiation chamber is designed
and installed at the end of the beamline. The chamber has
ports to install several types of detectors for different IBA
techniques. This work includes the description of the setup
and preliminary PIXE measurements.

INTRODUCTION
Cyclotrons are compact particle accelerator systems usedfor scientific research, medical and industrial applications.
Turkish Energy, Nuclear and Minerals Research Agency (former Turkish Atomic Energy Authority) acquired a 30 MeV
energy proton cyclotron with associated systems dedicatedto the production of medical radioisotopes and scientific research purposes in 2011. The accelerator facility (TENMAKPAF) has three beamlines for production of medical isotopes
and another beamline for scientific research purposes. The
research vault comprises a five-port electromagnet which
can deflect the proton beam up to an angle of ∓40° withrespect to the beam axis. The minimum beam energy andcurrent provided by the cyclotron is 15 MeV and 0.1 µA
respectively. This constraint on energy and current excludes
certain applications. One of these applications is ion beam
analysis (IBA) which finds use in a wide range of disciplines
such as chemistry, biology, solid state physics, materials science, archaeology, anthropology etc. Non-destructive IBA
techniques in general and certain irradiation requests frominternal/external researchers require relatively low particle
energies and low beam currents, i.e. 1-5 MeV energy withpA-nA current levels. A way to decrease the energy andthe current is to let the beam pass through a thin foil during
which the particles interact with the foil medium causing adecrease in energy and current. In this work, development
and tests of the irradiation system and preliminary studies
with PIXE method are described.
∗ gorkem.turemen@tenmak.gov.tr

Low-energy and low-current irradiations for the required
absorbed doses demand additional effort and equipment inmedical cyclotrons due to the design priorities for this typeof accelerators. Therefore an energy degrader system is developed to decrease the energy of the cyclotron extracted
beam. The cyclotron’s original beam current measurement
system is capable of measuring the current down to 0.1 µA
which is convenient for radioisotope production purposes
but not suitable for material irradiations and non-destructive
analysis. Thus, a beam current measurement system is designed to measure the beam current down to tens of pA levels.
Also, an irradiation chamber, an energy degrader system andvarious collimators were manufactured to irradiate assorted
types of samples while controlling the beam energy, sizeand position (see [1] for details). The irradiation system
requires additional conditions for shielding, positioning of
the particle/radiation detectors and data acquisition systems
to perform non-destructive analysis (Fig. 1). The secondary
gamma and neutron radiation generated from the energy degraders is the primary concern due to increased backgroundradiation in X-ray and gamma analysis. A water-cooled degrader system is installed in the cyclotron room, just after the
extraction of the beam, to decrease the radiation backgroundin the R&D room.

FCSample holderHPGeSi(Li)SDD

Figure 1: Irradiation system and detector placement.

Energy Degrader System
A water-cooled degrader (Fig. 2) system degrades thebeam energy down to 3 MeV from 15.6 MeV using threestacked pyrolytic graphite foils with a total thickness of
1.3 mm. The foil stack is sandwiched between copper blocks
and aluminum flanges for adequate cooling and collimation.
The cooling system of the degrader assembly utilizes deionized water from the cyclotron cooling loop with a flow of

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from aluminum to avoid persisting induced radioactivity. A
safety interlock in the PLC software is put into effect to avoid
overheating of the degrader with a PT100 sensor.

Figure 2: Water-cooled energy degrader.

Irradiation Chamber
An in-vacuum irradiation chamber is installed at the endof the R&D beamline. The chamber has openings for various
devices to measure the beam profile, current, energy anddetectors to detect secondary particles and prompt radiation.
A port has a pneumatic cylinder which moves a 40 mm laser
marked alumina beam screen in front of the beam at 45° tothe beam direction. A port with a glass window allows theobservation of the beam profile on the screen and on thesamples. The other ports are reserved for radiation detectors
for other ion beam applications. The chamber has a fourarm motorized carousel sample holder to irradiate different
samples in a single run. A Faraday cup (FC) is installedat the far end of the chamber to measure and monitor thebeam current. The beam from the 5-port magnet enters
the chamber through a conical collimator and a replaceable
circular aluminum collimator along the beam axis. The
former has four isolated electrical connections to monitor
the beam position and size. The vacuum is maintained ataround 1x10−6 mbars with a two-stage pump system.

Radiation Detection SystemA Si(Li) detector (RT-500-5-E/T-M/B, Mirion Technologies) is used for measuring the beam energy and energy
spread. This detector has 5 mm thickness, a resolution of30 keV at 5.5 MeV energy and is capable of measuring
beam energies up to 30 MeV. The energy calibration of thisdetector is done in vacuum with a planar source of mixedalpha emitters (Americium-241, Plutonium-239, Uranium234/238). A pneumatic cylinder moves the Si(Li) detectorin front of the beam perpendicular to the beam axis. A vacuum operable silicon drift detector (SDD-EDS, Rayspec)
for PIXE analysis is installed at an angle of 45 degrees withthe beam axis. This detector has a thickness of 8 µm anda resolution of 133 eV at 5.9 keV. These specifications areconvenient for distinguishing X-rays of different elements
up to 20 keV energy with sufficient counting efficiency.

BEAM SHAPING AND MEASUREMENTS
IBA techniques require low energy and low current ion
beams compared to a beam from a medical cyclotron. The
extracted beam from the cyclotron has a minimum energyof 15 MeV and minimum measurable current of 0.1 µA. Adegrader system is used to lower the beam energy down tothe energies required for IBA techniques. The beam diffusedby the carbon foil is refocused with the quadrupole doubletsand shaped with collimators. The beam energy is degradedto 3.7 MeV with an energy spread of 0.97 MeV FWHM (measured with Si(Li) detector) for an incoming beam energy of
15.9 MeV. Monte Carlo [2] simulations and actual measurement results of the energy and the spread of the beam after
the degrader system is shown in Fig.3. The measured peakshape is close to the simulation results except for a lower
FWHM. The reason for higher FWHM in the simulations
may be not taking into account the two quadrupole doubletsin the code.

Figure 3: Si(Li) measurement and FLUKA simulation.
The following measurements were made for two different
settings in the experiments: In the first case, beam shaping
collimator aperture at the entrance of the irradiation chamber is 1 mm. The recofused beam is measured as 235 pA
in the irradiation chamber Faraday cup for a beam currentof 10 µA at the cyclotron stripper. In the second case, for acollimator aperture of 10 mm, the beam current is measured
as 7 nA in the irradiation chamber Faraday cup for a beam
current of 4 µA at the cyclotron stripper. This corresponds
to a 0.002% and 0.175% current reduction for 1 mm and
10 mm final collimator aperture, respectively. The current
stability at pA levels is shown in Fig.4. It is possible to lower
the current down to 5 pA level with the ∓2.5 pA uncertainty
by optimizing the ion source parameters and applying data
manipulation methods such as noise filtering. The stability of the current is important for charge integration which
directly affects the uncertainty analysis, especially for nonconducting samples in IBA techniques.
The beam size is measured as 11.4 mm on the alumina
screen with a 10 mm collimator. Homogeneity of the beamis measured as 90% for 8 mm beam size using image processing techniques (Fig.5). This homogeneity ensures irradiating
the samples as evenly as possible thus allowing bulk PIXE
analysis of inhomogeneous samples with higher accuracy.
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Beam current (pA)

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Table 1: Comparison of XRF and PIXE Analyses of theStandard Mix Foil

757065

Element
XRF(%) Unc.(∓) PIXE(%) Unc.(∓)
Copper
56.17
N.A
56.16
0.22
Nickel
41.66
N.A
41.95
0.17
Manganese
1.29
N.A
1.23
0.008
Iron
0.68
N.A
0.57
0.005

60
55
50
45
40
35
30
25
20
15
10
5
00100

200

300

400

500

600

700

800

900
Time (s)Figure 4: Current stability.

Figure 5: Beam homogeneity measurement.

with an energy of 3.2 MeV and an average current of 7 nA
for 155 seconds. The H value calculated with the irradiatedgold standard foil is 0.000489. This H value is used forthe analysis of 99.99% copper and mix standard foil (composition: 55% Cu, 45% Ni, thickness: 100 µm) irradiatedunder the same experimental conditions. The elemental
composition is measured as 100% for copper foil and theanalysis results of the mix standard foil are given in Table 1.
PIXE spectrum of the mix standard foil is shown in Fig. 6.
The analysis results indicate negligible dependence of the Hvalue on X-ray energy in the spectral region of interest. The
elemental concentrations of the mix sample is compatible
with measurements done with a portable XRF spectrometer (no uncertainties are reported with this detector). The
software reports the counting statistics uncertainty and peakfitting uncertainty for the PIXE analysis. The reported uncertainty values in Table 1 is the combined uncertainty of thesetwo components. The major component of the combined
uncertainty is due to the peak fitting process. Reducing thebackground in the setup and setting the peak fitting parameters more precisely are expected to decrease the uncertainty
and the limit of detection considerably.

PRELIMINARY PIXE ANALYSES
6

Cu-Kβ1

Mn-Kα1Mn-Kβ1Fe-Kα1

Νi-Kβ1

10000010000

mix foil PIXE

Cu-Kα1Ni-Kα11x10

Fe-Kβ1

Several preliminary experiments are done with the nondestructive analysis system constructed in TENMAK PAF
R&D irradiation vault. GUPIXWIN [3] software is usedin the analyses. This software offers several PIXE analysis
modes. One of these methods, analysis with H value, uses
a certified reference material to calculate a value whichis expected to remain almost constant for a well-definedgeometry, surface roughness and sample composition for
the X-ray energies of interest (1-20 keV). The instrumental
value, H incorporates detector solid angle and calibration
factor of charge integration [4]. It also includes corrections
for geometry, detector crystal thickness and any imprecise
data used in the software [5]. The H value method is selectedin the experiments as the initial choice of analysis technique
due to ease of use, less dependence on energy resolution andtime consuming precise geometric parameter measurementsof the setup required for standardless analysis. The referenceconcentration values of the element(s) in the standard foil isused to calculate the H value of the analysis setup.
The angle between the sample surface normal and thedetector normal is approximately 10°. The X-ray spectra
are acquired with a digital analyser (CAEN). 99.99% goldwith a thickness of 50 µm is irradiated to determine the Hvalue and its variation with X-ray energy by a proton beamCounts [#]Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

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10001001012345678910111213141516Energy [keV]

Figure 6: PIXE spectrum of the mix standard foil.
As for real life samples, the setup is used to determine
the elemental content of 1 TL (Turkish Lira) metal coins.
Coins minted on different dates are placed in the experimental chamber with a mix standard foil. This foil is used todetermine the H value. Table 2 shows a comparison of PIXE
and portable XRF analysis results. We believe that the main
reason for the differences is the changes in the sample position due to the holder mechanism in the PIXE test system

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Table 2: Comparison of XRF and PIXE Analysis Results of1 TL Metal Coins
Element

1 TL(2009) 1 TL(2015) 1 TL(2022)
PIXE XRF PIXE XRF PIXE XRF%%%

Copper73.2 71.78 71.22 70.56 76.70 72.63
Nickel14.37 15.63 14.78 16.34 15.02 15.96
Zinc
9.12 9.53 8.74 9.13 8.57 8.50
Manganese 0.14 0.13 0.33 0.262 0.15 0.12
Iron
0.17 0.17 0.46 0.44 0.07 0.05

[3] M.I. Govil, “Proton Induced X-ray Emission–A tool for nondestructive trace element analysis”, Current Science, vol. 80,
no. 12, pp. 1542–1549, 2001.
[4] J. A. Maxwell, W. J. Teesdale and J. L. Campbell, “The GuelphPIXE software package II”, Nucl. Instrum. Methods Phys. Res.,
Sect. B, vol. 95, no. 3, pp. 407-–421, 1995.
doi:10.1016/0168-583x(94)00540-0[5] A. Shariff, K. Blow, M. Elfman, P. Kristiansson, K. Malmqvist,
and J. Pallon, “Calibration of a new chamber using gupix
software package for pixe analysis”, Nucl. Instrum. Methods
Phys. Res., Sect. B, vol. 189, no. 1, pp. 131-137, 2002.
doi:10.1016/S0168-583X(01)01018-7

and the background X-rays produced by scattered protons
inside the chamber. Therefore, several improvements areplanned in this direction such as using a collimator aroundthe detector, an absorber on the detector endcap and voltage suppressors around the sample for stray electrons andcoating the chamber walls.

CONCLUSION AND OUTLOOK
A non-destructive analysis setup at TENMAK-PAF medical cyclotron facility is designed and assembled in the R&Dvault. This setup is consists of a number of additional beam
shaping equipment and measurement systems required by
IBA methods. PIXE method is applied for the first timein Türkiye and the preliminary results are satisfactory. Detectors for IBA techniques such as PIGE (HPGe) and RBS(PIPS) detectors are installed and measurements are ongoing.
Further modifications are needed to improve the accuracyof the measurements through the use of electron suppressors, adjusting the measurement geometry (i.e. moving thesample closer to the detector), shielding and/or collimating
the detectors. Future plans also include moving the setup to
the 40° port (rightmost port of the 5-port magnet) and utilizing a water-cooled slit to achieve a better energy resolution.
These changes will have a positive impact on the reliabilityof the measurements in the application of complementary
ion beam analysis methods.

ACKNOWLEDGMENTS
This study is funded by TENMAK with a project No.
A2.H1.P9. We would like to thank Dr. Yakup Kalaycı fordoing the XRF measurements.

REFERENCES[1] A. N. Yuksel, G. Turemen, S. Bulut, N. O. Serin, O. Yavas,“Design of beam instrumentation for in-vacuum materials irradiation and testing in a 30 MeV medical cyclotron”, Nucl.
Instrum. Methods Phys. Res., Sect. A, vol. 977, pp. 164290,2020. doi:10.1016/j.nima.2020.164290[2] A. Ferrari, “FLUKA Code-2011.2x.6: A multi-particle transport code”, CERN-2005-10, INFN/TC05/11, SLAC-R-773,
2005.

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