Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

Operation of GET system as main readout device for SπRIT
experiment at 2016 spring campaign
T. Isobe,∗1 M. Kurata-Nishimura,∗1 H. Baba,∗1 M. Kaneko,∗2 T. Murakami,∗2 W.G. Lynch,∗3 J. Barney,∗3J. Estee,∗3 S. Tangwancharoen,∗3 G. Jhang,∗4 and J.W. Lee∗4 for the SπRIT Collaboration
The SπRIT time projection chamber (TPC) is oneof the main devices for the SπRIT project at RIKENRIBF.1) The SπRIT project aims to study the densitydependent term of the symmetry energy using heavy
RI collision. General electronics for TPC (GET)2) is a
novel readout system employed for the SπRIT-TPC3)
to capture the signals produced by charged particles
passing through TPC. By using the GET system, it
is possible to realize a high resolution, wide dynamicrange, and stable operation of data acquisition. TheGET system for SπRIT-TPC is composed of 48 AsAdboards, 12 CoBo boards and 2 MuTANT boards. 12CoBo boards and 2 MuTANT boards are mounted in 2μ-TCA shelves so that the trigger signal and samplingclock are synchronized among diﬀerent CoBo boards.
During the spring season of 2016, the ﬁrst physics
experiment campaign was performed as well as thecommissioning of the SπRIT system in a SAMURAImagnet. All the readout electronics on TPC worked
under a magnetic ﬁeld of 0.5 T without any problem,and full operation of the GET system was successfully
performed for a two-week physics run. The analog partof the system was conﬁgured to have a dynamic rangeof 120 fC, shaping time of 117 ns, and sampling rateof 25 MHz. The trigger rate was ∼60 Hz, and the total beam rate was ∼10 kHz. The SπRIT-DAQ system
sustained a data rate of 300 MByte/s. The data were
copied to RIKEN HPC storage through a 10-Gbps network for the 1st/oﬄine data analysis. The trigger rateof 60 Hz was expected to be improved after the integration of a partial readout mode, where the channel wasdigitized and can be selected event by event to reducethe conversion time. Since this functionality was not
fully tested as of spring 2016, only the fully digitized
readout mode was used.
Figure 1 and Fig. 2 show the event display of heavy
RI collision taken with SπRIT-TPC and the typicalshape of electric signals detected with GET electronics,
respectively.
As shown in Fig. 1, a large number of charged particle tracks pass through TPC. There are several pads
which seem to be dead. However, the positions of thedead pads vary from event to event. The pads above
the beam trajectory become dead.
The drift electrons produced by the beam is sup∗1
∗2
∗3
∗4

RIKEN Nishina Center
Department of Physics, Kyoto University
National Superconducting Cyclotron Laboratory, Michigan
State University
Department of Physics, Korea University- 167 -posed to be blocked by the gating grid wire plane ofTPC. An excessively large amount of δ-ray electrons
produced by the beam which can penetrate the gating
grid and is expected to aﬀect the readout system.

Fig. 1. Event display of heavy RI collision taken withSπRIT-TPC (top view). One dot corresponds to oneof the channels. The color of each pad shows the maximum value of the signal. The Sn target is located at
the left hand side of this display.

After a large eﬀort to analyze TPC data, the ratio ofcharged pion production will be determined for setting
the constraint on nuclear EoS.

Fig. 2. Typical shape of electric signals produced bycharged particles passing through TPC. Each color corresponds to each pad. Signals on 10 pads out of 12k
pads are shown.

References
1) S. Rebecca et al., Nucl. Inst. Met. A 784, 513 (2015).
2) E. Pollacco et al., Physics Procedia 37, 1799 (2012).
3) T. Isobe et al., RIKEN Accel. Prog. Rep. 48, 204 (2015).