Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 47 (2014)

Development of TPC readout system for SπRIT project
T. Isobe,∗1 H. Baba,∗1 N. Nakatsuka,∗2 T. Murakami,∗2 W.G. Lynch,∗3 G. Jhang,∗4 W. Powell,∗5 andE. Pollacco,∗6 for the SπRIT Collaboration

∗1
∗2
∗3
∗4
∗5
∗6

RIKEN Nishina Center
Department of Physics, Kyoto University
National Superconducting Cyclotron Laboratory, Michigan
State University
Department of Physics, Korea University
Department of Physics, University of Liverpool
CEA Saclay IRFU/SPhN

Fig. 1. Cosmic signal detected by SπRIT-TPC with GETelectronics. Each line corresponds to one channel. OneAsAd board contains four ASIC chips (AGET). One
ASIC corresponds to 32 channels. The GET system
employs SCA type flash ADC. Up to 512 time buckets
can be used for analog data buffering. The pedestal is
not suppressed in this figure.

0-100y (mm)For the measurement of multiple charged particle
tracks in a heavy-ion collision experiment at RIBF,
a time projection chamber (TPC) will be installed inthe SAMURAI superconducting dipole magnet. Themain aim of the experiment is to study the density dependence of symmetry energy defined in the nuclear
equation of state. This project is carried out by aninternational collaboration, the “Sπ(PI)RIT collaboration”; SπRIT means Samurai PIon Reconstruction andIon Tracker. As the readout electronics for more than
12k channels of TPC, a novel readout system, GET,1)
is employed. GET stands for General Electronics for
TPC and has been developed mainly by a collaboration between French institutes and American institute.
The details of the GET system for the SπRIT project
have been reported by Isobe et al.2) .
For the first experiment at RIBF, we obtained thepre-production AsAd board, which is one of the important boards of the GET system and which was tested
with SπRIT TPC at MSU. The pre-production AsAdboard is controlled using the Xilinx evaluation boardof ML507. ML507 can control only one board. For
the massive readout of TPC, a dedicated concentration board, the CoBo board, which can control up to4 boards, will be produced. Figure 1 shows the cosmic ray signal height of each channel as a function ofthe time bucket. There are 512 time buckets for onechannel, and a sampling rate of up to 100 MHz is available. In the case of SπRIT TPC, a sampling rate of
50 MHz with 256 time buckets is planned to be used
to cover the 10 µs drift time, which corresponds to adrift length of 50 cm with a 5 cm/µs drift velocity in
P10 gas. Based on the information taken by the GETelectronics, we succeeded to reconstruct the track asshown in Fig. 2. Now the analysis of the cosmic raydata is ongoing. It is planned that electron track data
will eventually be taken with radioactive source.
As the data acquisition system, we plan to employ
NARVAL,2) which is used in the French nuclear physics
laboratory, such as GANIL. The size of data producedby the SπRIT plus GET system is estimated to be
more than 100 MByte per second. NARVAL is selected
as it can handle data of such large size.
Finally, 48 electronic boards will be mounted on theTPC and will be tested with cosmic rays in 2014. Af--200-300-400-500
4003002001000mm -100) -200-300-400x(020040060080010001200)

z (mmFig. 2. Cosmic track reconstructed by SπRIT-TPC. The
black line denotes the 3D track. The red and blue lines
denote the projected track on each plane. A 100-MHz
sampling rate is used.

ter that, the TPC will be mounted on the SAMURAI
magnet for the first heavy ion collision experiment.
References
1) E. Pollacco et al.: Physics Procedia 37, 1799 (2012).
2) T. Isobe et al.: RIKEN Accel. Prog. Rep. 46, 151(2013).
3) X. Grave.: Proc. 14th IEEENPSS Real-Time Conf ,65(2005).

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