Abstract The NUCLEON space experiment has been proposed to perform direct measurements of CR energy spectrum and composition up to E ∼ 10 15 eV. The NUCLEON detector consists of layers of different detectors: scintillator detectors with WLS fibers and silicon pad and microstrip ones. The results of beam and space qualification tests of the scintillator detectors are presented

A Kalinin

A Nozdrin

A Sadovski

D Podorozhny

I Chupin

L Tkatchev

V Boreiko

V Grebenyuk

V Shigaev

Z Krumstein

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28th International Cosmic Ray Conference 2217
Performance of the Scintillator System Prototype of the
NUCLEON Space Experiment
L. Tkatchev,2 V. Boreiko,2 V. Grebenyuk,2 I. Chupin,3 A. Kalinin,2 Z.
Krumstein,2 D. Podorozhny,1 A. Nozdrin,2 A. Sadovski,2 V. Shigaev.2
(1) Moscow State Univ., D.V. Skobeltsyn Inst. of Nucl. Phys., Moscow, Russia
(2) Joint Institute for Nuclear Research, Dubna, Russia
(3) Mechanical Construction Bureau ”Raduga”, Dubna, Russia
Abstract
The NUCLEON space experiment has been proposed to perform direct
measurements of CR energy spectrum and composition up to E ∼ 1015 eV. The
NUCLEON detector consists of layers of different detectors: scintillator detectors
with WLS fibers and silicon pad and microstrip ones. The results of beam and
space qualification tests of the scintillator detectors are presented.
1. Introduction
One of the old and still unresolved astrophysical problems is the knee in the
CR energy spectrum at 3 · 1015 eV which was discovered by G.B.Khristiansen in
1958 [1]. Two hypotheses are considered: (i) there is no knee but a new property
in strong interactions at such energies or (ii) there is a knee in the primary CR
spectrum. There are indications that the composition of CR changes, but the
interpretation of the EAS measurements including the latest KASKADE data [2]
is heavily dependent on Monte-Carlo simulation based on the accelerator data.
The new balloon experiments [3] and long-term and large-aperture space
experiments like NUCLEON and ACCESS [4] are going on or in preparation.
The main purpose of NUCLEON is measurements of the CR energy spectrum
and composition at the 1011 − 1015 eV energy range including the fluxes of heavy
CR nuclei beyond the iron peak.
2. Apparatus
The well-known experimental fact is that the average transverse momen-
tum of the secondary particles is practically independent of the initial energy
while the multiplicity increases logarithmically. This property will be used in
NUCLEON to measure the primary particle energy by determining the angular
distribution of secondary charged and neutral particles.
Two types of detectors are proposed for the NUCLEON experiment: mi-
pp. 2217–2220 c©2003 by Universal Academy Press, Inc.
2218
crostrip or pad silicon detectors and scintillator detectors with WLS fibers. In
one of the options considered the first part of NUCLEON consists of two layers
of silicon detectors of thickness 300 µm followed by a few layers of thin plastic
scintillators of thickness ∼1.0 mm and then by a few layers of scintillator strip
detectors of thickness ∼ 5 mm alternated by carbon layers as targets. The mea-
surement of the primary trajectory, charge and vertex is the main task of these
detectors. The designed primary charge resolution is at the level of 0.5%.
 
Fig. 1. Left - transverse section of scintillator strips with WLS fibers: H=5 mm,
L=7.5 mm, fiber diameter d=1 mm. Right - typical spectrum of cosmic muons .
The second part of NUCLEON consists of a γ-converter , two layers of
silicon microstrip detectors with 50 µm pitch and two layers of scintillator strips
of thickness 5 mm. The pair of silicon layers of orthogonal microstrips provides
measurements of angular profiles for each transverse direction independently to
improve the energy resolution. Scintillator layers serve for generating multilevel
trigger signals. According to Monte-Carlo simulation the energy resolution of
∼70% is expected for individual events. The Russian “KOSMOS” type satellite
will be used for the NUCLEON apparatus with exposure time in orbit ≥1 year.
3. Test of scintillator detectors
Scintillator detectors with WLS fibers are commonly used in experiments
of high energy physics[5]. In comparison with the proper characteristics of scin-
tillators the main virtue of such detectors is much longer attenuation distance for
light in fibers (≈ 10m) due to the effect of full internal reflection inside fibers with
multicladding. It gives a possibility to use such detectors in the space astropartical
experiments.
Several types of scintillator strips of polystyrene were studied (Fig.1). The
1 mm fiber was glued in groves of 1.5− 2.0 mm in depth by optical glue BC-600.
2219
0
50
100
150
200
250
300
350
25 50 75 100
x=n*1.5 mm
Cu
rre
nt 
of 
str
ip,
 ar
b.u
nit
s
(a)
0
1
2
3
4
5
6
7
-40 -20 0 20 40
(b)
%
N st
rip
s
Fig. 2. Left - signals of test with β-source 90Sr moving across a strip plane. Right -
dispersion of the average relative amplitudes of 192 strips.
Unpolished strip surface was covered by teflon band to provide diffuse reflection
of light. Application of chemical polystyrene foam instead of teflon band to the
strip surface leads to 20% increase in light output. The typical cosmic muon
spectrum is shown in Fig.1. Average signal at the PMT cathode is at the level of
10 ph.e. in the case of mirror reflection at the opposite end of fiber. A few planes
of scintillator strips were produced. They were tested with one- or multychannel
PMTs. Photodiodes, β-source 90Sr , cosmic muons and accelerator muon beam
were used to initiate a light signal inside strips. An example of the test with a
radioactive source moving across strips is presented in Fig.2.
As mentioned above, thin scintillator detectors could be used in the NU-
CLEON setup to measure the charge of incoming particles. Such a possibility was
tested with the detector prototype which consists of a scintillator plane of thick-
ness 1 mm and a WLS fiber grid with 10 mm pitch fixed on the scintillator surface
by glue. The plane with fibers was covered by tyvek paper to provide diffuse re-
flection of light. All or a part of fibers were connected to PMT HAMAMATSU
5900. Results of the test are presented in Fig.3a that indicates a possibility to
measure heavy nucleus charge. This conclusion has to be confirmed in nuclear
beam tests.
2220
4. Mechanical tests of scintillator strip detectors
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60 70 80 90
Position(mm)A
m
pl
it
ud
e(
ar
b.
un
it
s)
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
0 20 40 60 80 100 120
Position(mm)
R
at
e(
ar
b.
un
it
s)
Fig. 3. a) Thin scintillator test with
β-source 90Sr . b) The relative
light output of strips measured be-
fore and after mechanical tests.
Several prototypes of the plates in
space configurations were tested to optimize
their parameters and check the mechanical
stability at the launch. The outgoing fibers
are the most delicate part. Besides, because
of space limitation the fibers should be bent
at 90◦ and the curvature radius should be at
least 10 cm to avoid cracking of the cladding
and destruction of the reflection conditions.
To meet these requirements the space be-
tween strips and PMT with bent fibers was
filled in by polyurethane with the density of
0.17g/cm3. The light output of strips was
measured before and after mechanical tests
and shown in Fig.3b. The problem of ageing
is under consideration.
5. Conclusion
The launch of the NUCLEON detec-
tor into orbit in 2006 gives the possibility of
taking more precise CR data at 1011 − 1015
eV and new data for nuclei with Z > 30 at energies around 109 eV/nucleus. Pro-
totypes of scintillator strip detectors were produced and tested with encouraging
results for their use in space experiments.
6. References
1. Kulikov G.V. and Khristiansen G.B. 1959, Soviet Physics JETR Vol.35(8),
Number 3, p.441.
2. KASKADE experiment results: Bertana M. et.al., 2001Proc. 27th ICRC Ham-
burg, p.742: Haung A. et.al., 2001 Proc. 27th ICRC Hamburg, p. 63; Haung
A. et al., 1999, Proc. 26th ICRC. Salt Lake City, HE 2.2.02; Hoerand J.R. et
al., 1999, Proc. 26th ICRC. Salt Lake City, HE 2.2.41.
3. ATIC Collaboration. 1999. Proc. 26th ICRC. Salt Lake City, Utah. v.5, p.9.
Cahbanner F.H. et al.1999. Proc. 26th ICRC. Salt Lake City, Utah. v.5, p.25.
Beatty J J. et al.1999. Proc. 26th ICRC. Salt Lake City, Utah. v.5, p.6.
4. NUCLEON space experiment project: Podorozhnyi D. et al., 2001, Proc. 27th
ICRC Hamburg, p. 2188.
ACCESS space experiment project: http://www.gsfc.nasa.gov/ACCESS
5. The MINOS experiment TDR, NuMI-L-337, Sept. 1998; Adams A. et al., 1995,
NIM. A366, 263; CDF II TDR, FNAL Pub-96/390-E; The STAR collaboration,
LBL, Pub-5347.


Performance of the Scintillator System Prototype of the NUCLEON Space Experiment

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Performance of the Scintillator System Prototype of the NUCLEON Space Experiment

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