26

Research Report of Laboratory of Nuclear Science, Tohoku University Vol. 41 (2008)(LNS Experiment : #2576, #2609)

A New Data Acquisition System for 4π EM Calorimeter
FOREST
H. Fujimura1 , R. Hashimoto1 , T. Ishikawa1 , J. Kasagi1 , A. Kawano2 ,S. Kuwasaki1 , K. Maeda3 , Y. Okada1 , Y. Sakamoto2 , M. Sato1 , H. Shimizu1 ,K. Suzuki1 , Y. Tajima4 , and H. Yamazaki112

Laboratory of Nuclear Science, Tohoku University, Sendai 982-0826

Department of Information Science, Tohoku Gakuin University, Sendai 980-851134Department of Physics, Tohoku University, Sendai 980-8578

Networking and Computing Service Center, Yamagata University, Yamagata 990-8560

We have developed a data acquisition (DAQ) system for a 4π electro-magnetic (EM) calorimetercomplex, FOREST [1, 2]. The FOREST consists of three EM calorimeters and front-end electronics ofdifferent parts comply with different standards. The number of detectors to be read out is extremely
increased as compared with that of SCISSORS II. Since FOREST has been constructed step by step over
3 years, we added and reconﬁgured the front-end electronics at every stage. Therefore, our requirementson the DAQ software are scalability and ﬂexibility as well as capability of high speed up to 2 kHz triggerrate. The new DAQ system has been introduced to the FOREST experiment since early June 2008. The
DAQ efﬁciencies have been achieved to be 88% and 76% for 1 kHz and 2 kHz trigger rate, respectively.

§ 1. Framework of DAQ System
The DAQ software framework consists of collector, event builder, and recorder processes based on
the C++ language [3]. Figure 1 shows the dataﬂow of the DAQ system. Event data transfer and command communication between different subsystem processes are handled via the Transmission Control
Protocol/Internet Protocol (TCP/IP). Each TCP/IP communication uses a different port number.
The collector is a readout process which gathers the data from the front-end electronics and converts
the data coming from different modules to a single output stream. The output stream is built with a basic
information including a run number, an event sequential number and a collector ID number, and is sent
to the event builder process. In general, more than one collector is used at the same time. The event
builder process receives the data of event fragments from collectors, and uniﬁes a complete event. The
incoming data fragment is strictly combined according to an event sequential number and is attachedwith a basic information. The output stream is sent to the recorder process to be stored in a data ﬁle ona hard disk. The recorder process attaches a basic run information to the event data, which contains atime stamp, the number of events stored and comments to the data ﬁle.
This framework is easy to add and replace the collector processes and to allow the developmentof the reconﬁgurable hardware. Usually we use more than one collector in order to handle different27

Collector
Collector

Event BuilderRecorderCollector

Fig.1. The dataﬂow of the DAQ system. The data are gathered by collector processes from thefront-end electronics. An event builder process receives the data of event fragments fromthe collectors and builds a single output stream which is stored in a data ﬁle by therecorder process.

electronics standards. Since the main part of the DAQ dead time is caused by readout processes of thefront-end electronics, parallel readout of adequate number of collector systems achieves high trigger rateand high DAQ efﬁciency.

§ 2. Subsystem Conﬁguration of the FOREST Experiment
All the subsystem processes work on different computers in order to reduce the load level. The data
communication between the collectors and the event builder uses a private gigabit Ethernet network
dedicated to the DAQ system. An event trigger signal is distributed to each collector and is read in apolling mode through a REPIC Interrupt & I/O Register RPV-130 in a VME system. Figure 2 shows theDAQ conﬁguration. We have employed 5 collectors described as follows:• TKO-SMP collector
The front-end module is a REPIC TDC RPT-140 in a TRISTAN/KEK Online (TKO) system. The
timing signals from SCISSORS III [1, 4] are measured in this collector system. The digitized data
are collected and stored with Super Memory Partner (SMP) modules in a VME system throughSuper Controller Head (SCH) modules in the TKO systems. All the digitized data in the SMP
buffer are ﬁnally accumulated in a Sanritz PC/AT compatible VME module SVA041 single board
computer through the VMEbus.
Since SMP has two data buffers, it is possible to send the data from the TKO system to SMP during
the data transfer from SMP to SVA041. After a module conversion time of 80 μsec, SMP receives asignal to ask SCH to execute a sparse-data-scan. A SMP busy signal is released and a trigger signal
is sent to the TKO-SMP collector through a RPV-130 after the sparse-data-scan. The collector asks
SMP to switch the recording buffer to the other one and releases the event veto signal. Then SMP
is ready to receive the next data from the TKO system. This buffer switching is occurred eventby event. The dead time of this collector process is about 110 μsec. This is caused by conversion,sparse-data-scan, and data transfer from the TKO system to SMP.
• FERA-UIO collector
The energy deposited in the Backward Gamma (BG) detector [5] is digitized by a LeCroy 4300B
Fast Encoding and Readout ADC (FERA) in a CAMAC system. The data are collected from a28

VME

CAMAC

TKOVME

RPV-130

V792
V792
V792
V792
V792
V792

SVA041

RPV-130

V792
V792
V792
V792
V792

SVA041

TKOVME-ADC

V1190AVME-XDCVMEFERAFERA Drv.
FERA
FERA
FERA

RPT-140UIO
ECL-TTL

RPV-130

RPT-140
RPT-140
RPT-140SCH

SVA041

RPT-140
RPT-140

FERA-UIO

T004
T004

SCH
SMP
SMP

RPV-130

SVA041TKO-SMPVME)KICDKV'JVGTPGV

RPV-130

V1190A
V1190A
V1190ASBS 620

VME-TDC
Event Builder

RecorderCC7700

RPC-160

RPC-160
RPC-160

VME

CAMAC

Fig.2. The DAQ subsystem conﬁguration of the FOREST experiment. The number of collectors is 5. The computers in which the collector and event builder processes work areconnected to a private gigabit Ethernet network.

LeCroy 4301 FERA driver in the CAMAC system through a FERA bus and temporally stored in auniversal I/O (UIO) module [6] in a VME system. The UIO has two data buffers and each bufferis switched to the other every 20 events. After receiving a buffer change request signal, the UIOFERA collector asks UIO to switch a recording buffer to the other one, and releases an event vetosignal. The data sorted in one buffer of UIO are transferred every 20 events to the FERA-UIO
collector which works on a SVA041 in the VME system, while the every-event data fragments fromFERA are stored in the other one. The collector slices the data stream from UIO into 20 event
fragments and sends an output stream in the order of event sequential number.
The ADC data are read without pedestal suppressions; the dead time of every event is about
120 μsec. This is mainly caused by the bus communication speed between UIO and FERA.
• VME-TDC collector
The timing signals from the BG detector are measured with CAEN V1190A 128 Ch Multihit TDC
modules in a VME system. The digitized data are transferred to a personal computer (PC) in29

Table 1. The number of channels connected to the front-end electronics of each collector. The list
is classiﬁed by the FOREST detector assembly. The last line shows the average deadtime of each collector. The TDC modules used are REPIC RPT-140 and CAEN V1190A.
The ADC modules used are LeCroy FERA and CAEN V792. The REPIC RPC-160 is ascaler module.

STB-Tagger II
SCISSORS III
Backward Gamma
Rafﬂesia II
Plastic scintillators
Others
Total
Dead time (μsec)

TKO-SMP
RPT-140116
192————308
110

FERA-UIO
FERA——252——3255120

VME-TDC
V1190A RPC-160—
116—
10252
—
48———
412304
138<50—VME-XDC
V1190A V792——————
1462
90
90
1—
105
152
<40VME-ADC
V792
—
192
————
192
<40

sequential mode via a SBS Technologies (Bit3) PCI-VME interface 620. Since the data buffer ofV1190A is a First-In First-Out (FIFO) structure, it is possible to read out the data stored in theFIFO buffer while the other data taking process, conversion and setting the data to the FIFO buffer,is being treated. The dead time is less than 50 μsec and negligibly small.
The VME-TDC collector also handles REPIC RPC-160 scaler modules in a CAMAC system via a
TOYO Corporation CAMAC controller CC7700. The scaler data are collected every spill off.
• VME-XDC collector
The VME-XDC collector consists of a CAEN V1190A module and CAEN V792 32 Ch QDC modules.
The deposited energy and the timing signals from plastic scintillator detectors in front of the EM
calorimeters [2] are digitized by these VME modules. The data are gathered in sequential mode bya SVA041 in a VME system. Since the data buffer of V1190A and V792 are FIFO, the dead time isless than 40 μsec and negligibly small.
• VME-ADC collector
The energy from each crystal of SCISSORS III is digitized by a CAEN V792. The data are collectedby a SVA041 single board computer in a VME system. Since the data buffer of V792 has a FIFO
structure. the dead time is less than 40 μsec and negligibly small.
The number of channels connected to the front-end electronics of each collector are summarized in theTable 1. The average dead time of each collector is also listed.

§ 3. Beam Test
A performance study using a γ-beam was carried out in June and July 2008. The trigger condition
for the DAQ system was more than one cluster hit measured by FOREST and at least one hit measured
in STB-Tagger II [7, 8]. The typical data size was 2 kB/event with a liquid hydrogen target with athickness of 40 mm. All the ADC data were read out without pedestal suppressions. The DAQ dead time
was about 120 μsec. This is mainly caused by the FERA-UIO and TKO-SMP collector processes, and30
the dead times of the other collectors were negligiblly small. The DAQ efﬁciencies were about 88 % and
76 % for 1 kHz and 2 kHz trigger rate, respectively.

Acknowledgment
The authors express many thanks to Prof. Toshiyuki Takahashi, Dr. Tadashi Kinoshita, and Dr. Fusashi
Miyahara who have contributed to the development of the DAQ system for SCISSORS II based on theTKO standard. Many a technique in this system is also used in the TKO-SMP collector. The authors
deeply appreciate to Prof. Masaharu Nomachi and Dr. Yorihito Sugaya who give us much informationon the UIO module and the communication with it to the FERA driver. The authors are grateful toProf. Hiroyuki Okamura to give the suggestions on selecting a suitable VME module.

References[1]

T. Ishikawa et al.: Research Report of LNS, Tohoku University 39 (2006) 35.

[2]

T. Ishikawa et al.: in this Research Report of LNS, 41 (2008) 7 .

[3]

ISO/IEC 14882:2003[4]

T. Ishikawa et al.: Research Report of LNS, Tohoku University 40 (2007) 23.

[5]

T. Ishikawa et al.: Research Report of LNS, Tohoku University 40 (2007) 19.

[6]

Y. Sugaya and M. Nomachi: Nucl. Instrum. and Meth. A437 (1999) 68.

[7]

T. Nakabayashi et al.: Research Report of LNS, Tohoku University 37 (2004) 17.

[8]

T. Ishikawa et al., in this Research Report of LNS, 41 (2008) 1.