RIKEN Accel. Prog. Rep. 50 (2017)

Ⅱ-9. Instrumentation

NeuLAND demonstrator performance in EOS experiments
I. Gašparić,∗1,∗2 K. Boretzky,∗3 H. Törnqvist,∗2,∗4 T. Aumann,∗3,∗4 L. Atar,∗2,∗4 A. Horvat,∗4 Y. Leifels,∗3D. Rossi,∗4 H. Simon,∗3 and H. Scheit∗4 for the SπRIT and R3 B-NeuLAND Collaborations

ToF (ns)vs. deposited energy in the ﬁrst plane of NeuLAND.
The spectrum exhibits characteristic lines for the various charged particles, and protons, deuterons, tritons,
3He, and 4 He are identiﬁed.
22010220018016014010120100806040n1γ200050100

150200250300

350400
Edep (MeV)

Fig. 2. Particle identiﬁcation plot in the 1st plane with astrong VETO condition.

x V (cm)

To check the performance of the suppression ofcharged particles, the same spectrum was producedagain (Fig. 2) with a condition on events where nohit was recorded in the full VETO detector (strongVETO condition). A loss of neutrons with that condition was evaluated from Geant simulations, and it wason a percent level.
150

4000

100

3500

5030002500

02000-501500-1001000-150500-150

y (cm)The NeuLAND demonstrator is a fraction of theneutron detector R3 B-NeuLAND1) , which is beingbuilt at FAIR in Germany. Since the beginning of 2015,it has been used within the SAMURAI experimental
setup at RIKEN. It consists of 400 plastic scintillator bars arranged in 8 planes with 50 bars oriented
either horizontally or vertically. The size of each bar
is 250×250×5 cm3 , which makes the total depth ofdetector 40 cm.
The detector is usually placed at 0◦ to the beam line
downstream of the SAMURAI magnet to detect neutrons from peripheral reactions of a radioactive beam
particle on a target, whereas charged particles are bent
away. A VETO detector consisting of eight 1-cm-thickplastic scintillator paddles is mounted in front of NeuLAND to reject background, mostly produced frombeam-like particles in the fragment branch (typically∼5% of events).
In the experiments S015 and S022 (April/May2016),2) where the nuclear EOS was studied in central
collisions of Sn isotopes, the detector was placed at 30◦
to the beam line. The proton/neutron and triton/3 Heyield ratios and ﬂows were measured. NeuLAND wasused to detect light charged particles, such as hydrogenand helium ions, together with neutrons and gammas.
The VETO detector in this study of central collisions
plays an essential role for the distinction of charged
and neutral particles in contrast to other experiments,
where neutrons are expected to be dominant and theVETO serves for background discrimination only.

-100-50050

100150x N (cm)

100250220502002000V

ToF (ns)

0300

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150-50180

103

100-100

50-150160-150140-50050100150
y (cm)

0N

120100

-100

p80

d102

t4HeHeFig. 3. Spatial correlation between hits in NeuLAND andVETO detectors.

360

1040
20
0050

100

150

200

250

300

350
400
Edep (MeV)

1Fig. 1. Particle identiﬁcation plot in the 1st plane.

A considerable amount of light charged particles(∼40% of events) with a large range of energies (fromzero to the beam energy) was detected in the NeuLAND demonstrator. Figure 1 shows the time of ﬂight∗1∗2∗3∗4Ruđer Bošković Institute, ZagrebRIKEN Nishina Center
GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt
Institut für Kernphysik, TU Darmstadt- 176 -In order to analyze charged particles and neutrons
in the same events, a more elaborated VETO analysis is under investigation, including spatial correlation
between hits in NeuLAND (xN , yN ) and VETO (xV ,yV ) (Fig. 3), as well as timing correlations. The set ofVETO hits needs to be linked to hits in NeuLAND todetermine unambiguously which NeuLAND hits originate from charged particles and which from neutrons.
References
1) http://www.fair-center.de/fileadmin/fair/
http://www.fair-center.de/fileadmin/fair/experiments/
experiments/NUSTAR/Pdf/TDRs/NeuLAND-TDR-Web.pdf.
NUSTAR/Pdf/TDRs/NeuLAND-TDR-Web.pdf.
2) R. Shane et al. Nucl. Instr. Meth. A 784, 513 (2015).