RIKEN Accel. Prog. Rep. 50 (2017)

Ⅱ-9. Instrumentation

Particle selection using RF signal for Rare RI Ring experiments
∗3
∗1
∗1
∗1
∗1
∗2
∗1Y.
D.
A.
T.
T.
Y. Yamaguchi,
Yamaguchi,∗1
M. Wakasugi,
Wakasugi∗1
Y. Abe,Abe,∗1
D.Nagae,
Nagae,∗1∗1H.
H.Baba,Baba∗1A. Ozawa,
Ozawa,∗2
T. Uesaka,
Uesaka,∗1
T. Yamaguchi,
Yamaguchi∗3
Y.
M.
andRareRing
collaboration
forforthethe
Rare
RIRI
Ring
collaboration

We commissioned the Rare RI Ring by using secondary beams around 78 Ge nuclei in November.1) The
secondary beams were produced via the in-ﬂight ﬁssion of a 345 MeV/nucleon 238 U primary beam witha 9 Be target. To inject rare RI to the ring reliably, aself-trigger injection method was adopted in the ring.
In this method, the RI of interest itself generates atrigger signal for the injection kicker at F3. It is necessary to perform a particle identiﬁcation (PID) before
generating the trigger signals and to transmit the trigger signal to the fast kicker system2) as soon as possible. The PID is based on the TOF-Bρ-ΔE method,in which the time-of-ﬂight (TOF), magnetic rigidity(Bρ), and energy loss (ΔE) are measured. In orderto perform PID, the TOF between F2 and F3 usinga plastic scintillation counter and the ΔE at F3 using an ionization chamber were measured, as shownin Fig. 1. An acceptable momentum window of thering is ±0.3%, which corresponds to the isotone region
shown in the ﬁgure.

in Fig. 2. The adjustment of the particles to be restricted was carried out by changing the external delayin the circuit.
In the experiment, we demonstrated the technique.
Figure 3 shows the diﬀerence in particles that generate
trigger signals obtained when changing the externaldelay. When we changed the delay time every 2 ns,particles reaching at certain time do not participate
in the trigger. By using this technique, for example,
in the case of 75 Cu, we succeeded in improving thepurity by more than one order of magnitude. From thisresult, it became possible to eﬃciently inject nuclei inthe neutron-rich region. Moreover, this technique canbe applied not only to the experiments of the Rare
RI Ring but also to experiments in RI Beam Factory(RIBF). It is possible, for example, to acquire only
event data of nuclides of interest.
LDiscriminator

F3 PlasticR
RF forAccelerators

Trigger(Kicker / DAQ)

Discriminator

Veto
External Delay

DiscriminatorFig. 2. Conceptual diagram of circuit for particle selection
in generating trigger signal using RF signal for accelerators and timing signal at F3.

Fig. 1. PID plot of secondary particles with TOF and ΔE.

As can be seen from Fig. 1, the yield of nuclei on
the neutron-rich side is very low. Because the purity of
the neutron-rich nuclei is also low, the ratio included in
the trigger signal, which was generated by the F3 plastic scintillation counter becomes lower. Because themaximum injection repetition frequency of the kicker
system is 100 Hz, the measurement for such nuclei becomes time consuming. Therefore, we developed a newtechnique for restriction by TOF in order to eﬃciently
measure such nuclei. We combined a radio frequency(RF) timing signal for accelerators with the trigger signal. This is because the timing of the RF signal andthe arrival time of the RI beam have a certain time relationship so that only the RI arriving at a certain time
can be used as a trigger signal by combining the RFsignals. A conceptual diagram of the circuit is shown
∗1
∗2
∗3

RIKEN Nishina Center
Institute of Physics, University of Tsukuba
Department of Physics, Saitama University

Fig. 3. Results of particle restriction using RF timing signal. The external delay time was diﬀerent in each setting.

References
1) D. Nagae et al. : In this report.
2) Y. Yamaguchi et al., Phys. Scr. T166 014056 (2015).

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