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MULTI-TILE ZINC-OXIDE-BASED RADIATION-HARD FASTSCINTILLATION COUNTER FOR RELATIVISTIC HEAVY-ION BEAM
DIAGNOSTICS: PROTOTYPE DESIGN AND TEST∗†
M. Saifulin1,‡ , P. Boutachkov, C. Trautmann1 , B. Walasek-Höhne
GSI Helmholtz Center for Heavy Ion Research, Darmstadt, Germany
P. Rodnyi, I. Venevtsev, Peter the Great Polytechnic University, St. Petersburg, Russia
E. Gorokhova, JSC S.I. Vavilov State Optical Institute, St. Petersburg, Russia
1
also at Technical University Darmstadt, Darmstadt, Germany
Abstract
This contribution summarizes the design and performance
test of a prototype radiation-hard fast scintillation detector
based on the indium-doped zinc oxide ceramic scintillator,
ZnO(In). The prototype detector has been developed for use
as a beam diagnostics tool for high-energy beam lines of the
SIS18 synchrotron at the GSI Helmholtz Center for Heavy
Ion Research GmbH. The new detector consists of multiple
ZnO(In) scintillating ceramics tiles stacked on the front andback sides of a borosilicate light guide. The performance ofthe detector was tested in comparison to a standard plastic
scintillation detector with 300 MeV/u energy 40 Ar, 197 Au,
208 Pb, and 238 U ion beams.
The investigated prototype exhibits 100% counting efficiency and radiation hardness of a few orders of magnitude higher than the standard plastic scintillation counter.
Therefore, it provides an improved beam diagnostics tool for
relativistic heavy-ion beam measurements.

This is a preprint — the final version is published with IOP

INTRODUCTION
The heavy-ion accelerator facility at the GSI Helmholtz
Center for Heavy Ion Research (Darmstadt, Germany) andother similar ion-beam facilities worldwide provide energetic heavy-ion beams for a wide range of research purposes,
including fundamental nuclear and particle physics, atomic
and plasma physics, material sciences, radiation biology,
and cancer therapy research.
Various diagnostics systems are used to measure heavyion beam parameters to ensure the safety and reliability of
the accelerator facility operation, as well as to optimize thebeam delivery to the experimental locations. For example,
this includes beam position, profile, intensity, energy, andemittance measurements.
The information provided by the beam diagnostics tools isused by the operating team for the online feedback controlsof the accelerator and beam transfer lines. This helps tomaintain the desired quality and stability of the beam. The
beam diagnostics systems are also used by experimental
users directly for the characterization and calibration of the∗ The results presented in this contribution are based on the work performed

before the 24th of February 2022.
funded this work within the ERA.Net RUS Plus Project
RUS_ST2017-051.
‡ m.saifulin@gsi.de (corresponding author)† DLR

experimental setups, which require precise knowledge of theincoming beam parameters.
In particular, at the high-energy beam transfer lines(HEST) of the GSI facility, the intensity of heavy-ion beams
slowly extracted from the SIS18 synchrotron is measured
using three different detector types (particle detector combination, PDC): scintillation counter (SC), ionization chamber(IC) and secondary electron monitor (SEM). Each detector
type is used to cover a specific range of beam intensity [1].
Plastic scintillation counters based on BC-400 (Saint Gobain), or EJ-212 (Eljen Technology) scintillators are currently
used as a part of the HEST ion beam intensity diagnostics,
covering counting rates in the range up to 1 × 106 ions/s. The
heavy-ion beams induce a large amount of radiation damage
when passing through the plastic scintillator. This leads tofrequent detector services where plastic scintillators are exchanged, which is highly undesirable from an operational
point of view.
In this work, we investigated an alternative to the plastic
scintillation counter, that could provide less frequent detector maintenance through the use of a more radiation-hardscintillator. We developed a new detector prototype basedon indium-doped zinc oxide (ZnO(In)) ceramic scintillator.
We report on the new prototype design and performance,
which was evaluated experimentally through in-beam tests
and simulations using the OpenGATE [2].

ZINC OXIDE CERAMIC SCINTILLATOR
Zinc oxide (ZnO) is a well-known inorganic compound
used in various applications [3–5]. In particular, it has beenused for the detection of X-rays and 𝛼-particles [6–9].
ZnO exhibits two luminescence bands when excited bylight or ionizing radiation: (1) emission in the ultraviolet(UV) spectral range (∼390 nm) with a short scintillation
decay time (<1 ns), and (2) emission in a broad-band with amaximum around 550 nm wavelength (green luminescence)with a longer decay time (>1 µs). The green luminescenceis unsuitable for fast-counting applications. Therefore, it isavoided either by annealing in a reducing environment or
doping with a group 3A element impurities, such as Al, Ga,
or In [3, 10, 11].
In-doped and Ga-doped ZnO ceramics prepared by uniaxial hot pressing in vacuum have been investigated aspromising scintillators for fast heavy ion counting appliTUP035

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cations [12–15]. They exhibit orders of magnitude higher
radiation hardness than plastic scintillators, and thus can provide longer exploitation time before scintillator replacement
is required. Furthermore, narrow signals with the pulse
width below 1 ns can be obtained, when ZnO(In) scintillation is registered with a fast photomultiplier tube. This
resolves pile-up limitations for the micro-spill structure measurements [13].
The fast scintillation component in ZnO is located close
to its self-absorption edge. Thus, the detection of fast scintillation photons through a few millimeters thick ZnO is notefficient. This peculiarity and difference compared to standard plastic scintillators have been considered in the new
ZnO-based prototype detector design.

PROTOTYPE DETECTOR DETAILS
Prototype Detector’s Parts
The detector consists of three main components: the active volume, the light guide, and the photosensor, as shownin Fig. 1.

The photosensor, responsible for converting scintillation
light into an electrical output signal, consists of a photomultiplier tube (PMT, Hamamatsu R6427).
The active volume and the light guide are fixed on a 3Dprinted holding structure and wrapped with Teflon to improve light collection and black tape to avoid penetration ofany external light.
In the design of the new ZnO-based scintillation counter,
only the active volume component is replaced, while the plastic light guide and photomultiplier tube remain unchanged
compared to the standard plastic scintillation counter for GSI
beam diagnostics. This design approach ensures the provenperformance and compatibility with existing plastic scintillation counter components, while introducing the enhanced
scintillation properties of ZnO(In) in the active volume.

Materials of the Active Volume
The 0.046 at.% In3+ doped ZnO ceramic scintillators
have been produced at the Joint Stock Company “Researchand Production Corporation S.I. Vavilova” (St. Petersburg,
Russia) using the uni-axial hot pressing in vacuum. The
obtained ZnO(In) ceramics were polished and cut into
15 × 15 × 0.5 mm3 square tiles.
The borosilicate radiation-hard glass (material catalog
name BK7G18) was purchased from SCHOTT (Germany)and cut into the 50 × 50 × 2 mm3 rectangular shape. The material surfaces had a root-mean-square roughness of 2–4 µm.
The ZnO(In) ceramic tiles and BK7G18 plate are fixed
together using a Kapton tape as shown in Fig. 2.

Figure 1: Schematic view of the multi-tile ZnO-based scintillation counter prototype.
The active volume is the central part of the detector that
directly interacts with the incident ion beam. It consists ofsquare-shaped scintillator tiles made of ZnO(In), stacked on
both the front and back sides of a borosilicate glass plate.
When the ion beam passes through the active volume, it
deposits part of its energy in the scintillator and borosilicate
glass layers, leading to the emission of scintillation light.
The scintillation mainly comes from ZnO(In) layers, as
they efficiently convert the deposited energy into light photons. Due to self-absorption, the scintillation photons mainly
go out from the material through the surfaces where ionsenter and exit the scintillating tile. The borosilicate glass,which is transparent to scintillation photons from ZnO(In),acts as a light guide, assisting in collecting scintillation lightfrom the ZnO(In) surfaces. This arrangement enables theextraction of scintillation photons from the active volume.
An additional light guide made of UV-transparent plastic
is used to match the shapes of the borosilicate glass andphotosensor. Optical silicon (Momentive, RTV-615) improves light coupling between the plastic light guide andboth borosilicate glass output and photosensor input.

Figure 2: Photograph of the prototype detector’s active area.
The white crossed circle shows the incident beam direction
and the beam spot size in scale with the active area.

EXPERIMENTAL PERFORMANCE TEST
To evaluate the performance of the prototype detector,
a series of tests were conducted at GSI using ion beams
extracted from the SIS18 accelerator. The experimental
parameters are summarized in Table 1.
The 40 Ar, 197 Au, 208 Pb, and 238 U ions had an initial energyof 300 MeV/u. Before reaching the entrance of the proto-

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Table 1: Experimental Beam Parameters and Photomultiplier Gains Used for the Tests of the Prototype Detector
Ion

Energy, MeV/u Energy loss, MeV PMT gain

40 Ar

300 𝑎
297.14 𝑏

231.85 𝑐
516.89 𝑑240.39 𝑒

2.20 × 106(1300 V)

197 Au300 𝑎288.62 𝑏4654.27 𝑐
10900 𝑑5499.17 𝑒

1.15 × 105(850 V)

208 Pb300 𝑎288.41 𝑏

5006.94 𝑐
11800 𝑑5932.97 𝑒

1.15 × 105(850 V)

300 𝑎
287.32 𝑏

6272.86 𝑐
14900 𝑑7586.86 𝑒

1.15 × 105(850 V)

238 U

𝑎 SIS18 extraction energy, 𝑏 Energy at the prototype detector entrance,

This is a preprint — the final version is published with IOP

𝑐 front ZnO(In), 𝑑 borosilicate glass, 𝑒 back ZnO(In)type detector, the ion beams underwent energy loss. This
loss occurs as the beam exits the vacuum chamber through a
100 µm thick stainless-steel window and travels a 40 cm distance through air. To accurately determine the incident beamenergies and quantify the energy losses within the detector’s
active volume layers, the ATIMA code was employed [16].
For the energy loss calculations, we used 5.5 g/cm3 ZnO(In)and 2.58 g/cm3 BK7G18 material density.
The ion beam was collimated to a circular spot with a diameter of 5 mm before interacting with the prototype detector. The prototype detector was mounted on a stage capableof horizontal and vertical movement, enabling exposure ofdifferent regions of the active volume to the ion beam.
A standard plastic scintillation counter was placed behindthe prototype and used as the reference detector.
Output signals from both the prototype and reference
detectors were digitized and read out with a high-speed
oscilloscope (Tektronix MSO58) with a bandwidth of 2 GHz.
The reference detector provided a trigger for the oscilloscope
read-out. The counting efficiency of the prototype detector
relative to the reference detector was estimated by counting
the number of prototype detector signals higher than 50 mV.
The PMT gain of the prototype detector was adjusted sothat the maximum amplitude of the signal is of the order of
1 V.

RESULTS AND DISCUSSION
Contribution of Borosilicate Glass Signal
By scanning the incident ion beam near the edge of the
prototype’s active volume, we collected signals corresponding to ions passing through: (1) only borosilicate glass plate,(2) borosilicate glass with one layer of ZnO(In), and (3)borosilicate glass with two layers of ZnO(In).
As shown in Fig. 3, the scintillation light yield of theborosilicate glass (BSG) is lower compared to the ZnO(In)

Figure 3: Signals of the prototype detector exposed to
300 MeV/u Au ion beam at the edge of the active volume.
scintillator. In the case of Au ion irradiation, the signal
amplitude from the borosilicate glass layer is around 30 mV,
while the signal amplitude from borosilicate glass with one
layer of ZnO(In) is almost 3 times larger. The signal fromthe borosilicate glass with two layers of ZnO(In) scintillator
is roughly 5 times larger than the signal from the borosilicate
glass.
Despite the lower energy loss in ZnO(In) compared toborosilicate glass (see Table 1), ZnO(In) scintillation light
represents the main part of the output signal amplitude, indicating that it is a brighter scintillator than the BK7G18.
For all three investigated regions, the registered output
signals have a rise time of 2.5 ns. This rise time is related
to the response of the PMT and has nothing to do with thescintillation material and beam position in the active area.
The use of borosilicate glass provides a solution to overcome the challenge related to the self-absorption of ZnO(In).
It provides efficient extraction of scintillation light out fromthe active volume and, at the same time, it has a negligible
contribution to the prototype’s output signal.

Prototype Detector Signals Across Active Volume
Figure 4 shows the prototype output signals registeredwhen different ion beams hit the active volume at different
locations. We collected 10000 output signals corresponding
to individual ions passing through the center of each ZnO(In)scintillating tile located at various horizontal and vertical
positions (various columns and rows), as is shown in Fig. 2.
Depending on the beam position, there is no difference inthe signals registered along the horizontal axis (fixed row,
various columns). In contrary to that, there is a significant
change in the output signal amplitude along the verticalaxis (fixed column, different rows). The signal amplitudedependency along the vertical axis has a similar trend for all
the investigated ion species.
It should be noted that the plastic light guide and PMT areplaced along the vertical axis. The higher amplitude signals
are registered when the beam hits the active volume closer
to the PMT (row 3 in Fig. 4).
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Figure 4: Output signals obtained for various ion beams
hitting the prototype detector at different horizontal andvertical positions. Signals of different ion species are shiftedon the x-axis for better visibility and comparison. Each
subplot corresponds to the center of the scintillating tile inthe corresponding column and row, as shown in Fig. 2.

Light Propagation Simulation
The propagation of the scintillation light from ZnO(In)through BK7G18 glass was simulated using the OpenGATE [2]. As a result of the simulation, it was found that
the ZnO(In) scintillation photons transmission through the
BK7G18 glass varies from 2 to 9% depending on the vertical axis coordinate. Figure 5 shows a comparison of theexperimentally measured signal amplitude and the simulation result, confirming that the prototype signal amplitude
variation is consistent with the ZnO(In) scintillation lighttransmission through the BK7G18 glass.
Further borosilicate glass plate optimizations (geometry
and surface quality) together with OpenGATE simulations
are required to find the optimal shape and surface quality ofthe borosilicate glass to suppress the changes in the output
signal amplitude along the vertical axis of the active volume.

Prototype Detector Counting Efficiency
The counting efficiency has been estimated as a ratio of
the number of ions counted by the prototype divided by the
number of ions counted by the reference detector. Despite
the signal amplitude variation in the vertical axis, the prototype detector exhibits 100% counting efficiency relative tothe plastic scintillator for all the investigated ion species.

SUMMARY
We developed a new radiation-hard fast scintillation detector prototype based on ZnO(In) transparent scintillation
ceramics to be used for relativistic heavy-ion beam intensity
diagnostics.

Figure 5: The signal amplitude changes for the 300 MeV/u
Au beam incident at various positions on the active volume.
Figures (a) and (b) correspond to beam scans along thehorizontal and vertical axis, respectively.
The developed prototype showed 100% counting efficiency relative to the standard plastic scintillation counter
when tested with Ar, Au, Pb, and U heavy-ion beams at
300 MeV/u energy. By considering the few orders of magnitude higher radiation hardness of ZnO(In) than plastic
scintillator, the new prototype provides an improved beamdiagnostics tool.
We observed a spatial dependency of the prototype output
signal amplitudes registered when the ion beam hits different positions on the active volume. We showed that thisdependency is related to the ZnO(In) scintillation light transmission through the borosilicate glass. The experimentallyobserved signal amplitude change is in agreement with thelight transmission through the borosilicate glass simulatedby OpenGATE.
The borosilicate glass, used as a part of the active volume,
exhibited scintillation light yield much lower than ZnO(In).
Thus, it makes a negligible contribution to the prototype
detector output signal and serves mainly as the light guide.
In the current prototype version, we used a rectangularshaped borosilicate light guide. Further investigations ofmore complex shapes of the light guide are needed to eliminate the spatial dependency of the output signal.

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