RIKEN Accel. Prog. Rep. 48 (2015)

Ⅱ-9. Instrumentation

Fast clear technique for NEBULA data acquisition for SAMURAI17experiment
Y. Togano,∗1,∗2 Y. Kubota,∗2,∗3 H. Baba,∗2 and H. Otsu,∗2 for the SAMURAI17 collaboration
A fast clear technique for NEBULA data acquisition(DAQ) was newly introduced for the 132 Sn(p, n) experiment at SAMURAI.1) The technique enabled themeasurement of recoil neutrons and projectile-like neutrons in coincidence. NEBULA DAQ could not workwith the main trigger for the (p, n) reaction measurement because the recoil neutrons were slow.
The incoming 132 Sn beams were detected by beamtagging detectors: SBT1 and SBT2. We deﬁne thesignal from SBT1 as “Beam” in this report. Recoilneutrons from the (p, n) reaction were measured using WINDS2) surrounding a liquid hydrogen target.
The charged outgoing particles were analyzed by using
the SAMURAI system. The outgoing neutrons fromthe breakup of reaction products were measured byusing NEBULA. The main trigger of the experiment
was a coincidence of Beam and WINDS. Because ofthe slow neutrons from the (p, n) reaction detected byusing WINDS, the trigger decision of the experimentwas ∼ 300 ns slower than the that with the standard
SAMURAI setup.3)
The main trigger for the experiment was controlled
by using the GTO module.4,5) The trigger for NEBULA DAQ was a coincidence of Beam and NEBULA signals (Beam × N EBU LA trigger). The analog and time information of NEBULA was obtainedby using CAEN V792 QDC and V775 TDC modules, respectively. The VME module used to interrupt NEBULA DAQ was RPV-130 by REPIC. The
fast clear of V792 and V775 could be performed by
inputting the fast clear signal to the modules during
their data conversion. The dead time of the fast clear
was 600 ns. Figure 1 shows the circuit diagram ofNEBULA DAQ for the fast clear. The interrupt ofNEBULA DAQ was performed by using a 10 µs delayed main trigger signal to allow time for the data
conversion of QDC and TDC. If the DAQ system wasinterrupted when NEBULA data were empty owing tono Beam × N EBU LA trigger or the dead time of fastclear, the NEBULA data were recorded as an empty
event. The fast clear signal was generated by anticoincidence between Beam×N EBU LA (synchronizedwith DAQ start/stop) and the main trigger. If themain trigger was ﬁred to acquire data during the deadtime of fast clear for NEBULA, a fast clear ﬂag wasstored by a coincidence register (coin. reg. 1). The
NEBULA-accepted trigger was Beam×N EBU LA vetoed by the dead time of NEBULA DAQ and the fastclear of V775/V792. A ﬂag for Beam × N EBU LAwas stored by a coincidence register if it was coincident with the main trigger (coin reg. 2). NEBULA
DAQ could be switched to the singles mode, in which
the trigger was generated by NEBULA itself for calibrations, in B2F experimental area.
In the experiment, the typical rate of the main trigger and the Beam × N EBU LA trigger were 2.4 kHz
and 1.6 kHz, respectively. Owing to the dead time ofthe fast clear, ∼ 0.7% of NEBULA data could not becollected. Fig. 2 shows the time versus crystal ID plotof NEBULA. The locus at approximately 60 ns corresponds to fast neutrons from the target region indicating that NEBULA DAQ functions eﬀectively. This fastclear technique can be applied to other experiments byadjusting the delay for the Beam × N EBU LA signal(300 ns in this experiment).

Fig. 2. Time versus crystal ID plot of NEBULA.

References

Fig. 1. Circuit diagram for NEBULA DAQ with fast clear.
∗1
∗2
∗3

Department of Physics, Tokyo Institute of Technology
RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo

1) M. Sasano et al.: RIKEN Accel. Prog. Rep. 48 (2015).
2) K. Yako et al.: RIKEN Accel. Prog. Rep. 45, 137(2012).
3) T. Kobayashi et al.: Nucl. Instrum. Meth. B 317, 294(2013).
4) H. Otsu et al.: RIKEN Accel. Prog. Rep. 46, 146 (2013).
5) H. Baba et al.: RIKEN Accel. Prog. Rep. 47, 235(2014).

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