Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

KATANA - a charge-sensitive triggering system
for the SπRIT experiment†
P. Lasko,∗1,∗2,∗5 M. Adamczyk,∗2 J. Brzychczyk,∗2 P. Hirnyk,∗1 J. L ukasik,∗1 P. Pawlowski,∗1,∗5 K. Pelczar,∗2A. Snoch,∗3 A. Sochocka,∗2 Z. Sosin,∗2 J. Barney,∗4,∗5 G. Cerizza,∗4,∗5 J. Estee,∗4,∗5 T. Isobe,∗5 G. Jhang,∗5,∗6∗5,∗7
∗4,∗5
∗5,∗7
∗54M.
M.
W.G.
Murakami,∗5,∗7Santamaria,∗4,∗5M. Kaneko,Kaneko,∗5,∗7M. Kurata-Nishimura,
Kurata-Nishimura,∗5W.G.Lynch,Lynch,∗4T. Murakami,
C. Santamaria,
M.B. Tsang,∗4∗5,∗8and Y. Zhang
KATANA - the Krakow Array for Triggering withAmplitude discrimiNAtion - has been built and used
as a trigger and veto detector for the SπRIT TPC atRIKEN. Its construction allows operating in magnetic
ﬁeld and providing fast response for ionizing particles,
giving an approximate forward multiplicity and charge
information.
The experiments with the SπRIT TPC at RIKEN
were focused on investigation of the central and semicentral heavy-ion (HI) collisions at energies of about
300 MeV per nucleon. The target was located about 3mm upstream of the entrance ﬁeld cage window inside
the SπRIT TPC, so that the HI beam passed throughthe chamber. To obtain suﬃciently large gas ampliﬁcation for pions and light charged particles, a highelectric ﬁeld is required inside the chamber. In suchconditions the ionization produced by the HI beamwould produce an excessive space charge leading toﬁeld distortion and could bring a risk of damage: thecharge produced by gas ionization could exceed thesafe limit for the pad planes of the TPC. For this reason, a gating grid wire plane is mounted below thepad plane1,2) . The grid was normally ’closed’ to keep
the detector oﬀ until a desired collision occurs. Whensuch an event happens, the opening of the gating gridcan occur quickly (in ∼350 ns). Such operation shouldbe performed whenever an incoming projectile reacts
violently with the target nuclei.
The KATANA detector, located downstream of theTPC exit window, was designed to produce a logic signal to open the gating grid when a desired event occurs. During the experiment it played a double role:
to produce a minimum bias or majority trigger, andto provide a veto signal whenever a beam particle ora fragment heavier than Z  20 passed through thechamber. To fulﬁll the requirements, the wall has been
constructed of two parts: a Veto and a Trigger array.
The KATANA-Veto part consisting of 3 thin (1 mm†
∗1
∗2
∗3
∗4
∗4
∗5
∗5
∗6
∗6
∗7
∗7
∗8
∗8Condensed from the article arXiv:1610.06682
IFJ PAN, Kraków
Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Krakw, Poland
Faculty of Physics and Astronomy, Wroclaw University,Kraków
NSCL and Department of Physics and Astronomy, Michigan
NSCLUniversityand Department of Physics and Astronomy, Michigan
StateStateUniversity
RIKEN
Nishina Center
RIKEN Nishina
Center Korea University
Departmentof Physics,
Korea University
Department of Physics, Kyoto
University
Department of Physics, Kyoto
Tsinghua
University
Department of Physics, Tsinghua University- 173 -thick) plastic-scintillator paddles with the middle one
centered on the beam, has been designed to producea veto signal for heavy fragments. The KATANATrigger array, consisting of 12 thicker (10 mm thick)paddles, arranged on both sides of the beam, has been
designed to produce a forward multiplicity trigger.
A technical design of the KATANA detector is presented in Fig. 1. Fifteen scintillators, each 10 cm wideand 40 cm high, are mounted on a rectanglular, aluminum frame. Each scintillator is wrapped in a sheetof a light-reﬂective, metalized Kapton foil. Three vetoplastic bars, marked with dashed lines, are placed in
the middle of the frame. Twelve trigger plastics areplaced unevenly on both sides of the beam (7 on theleft and 5 on the right side) to account for bending of
the beam particles in the magnetic ﬁeld. The Multi
Pixel Photon Counter (MPPC) devices from Hamamatsu which are not sensitive to magnetic ﬁelds havebeen used as the light sensors.
During the experimental runs the device perfectly
fulﬁlled its role.

Fig. 1. A technical drawing of the KATANA detector withthe external dimensions in mm.

This work was supported by the Polish National
Science Center (NCN), under contract Nos. UMO2013/09/B/ST2/04064 and UMO-2013/10/M/ST2/00624 as a part of the SπRIT Project supported bythe U.S. Department of Energy under Grant Nos. DESC0004835, DE-SC0014530, DE-NA0002923, US National Science Foundation Grant No. PHY-1565546
and the Japanese MEXT KAKENHI (Grant-in-Aidfor Scientiﬁc Research on Innovative Areas) grant No.
24105004.
References
1) R. Shane et al., Nucl. Inst. Meth. A 784, 513 (2015).
2) S. Tangwancharoen et al., arXiv:1612.06708.