Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

Observation of charge-stripping of 20 keV/q ions upon injection intogas cell cooler-buncher at KISS
P. Schury,∗1 T. Hashimoto,∗1,∗3 Y. Ito,∗4 H. Miyatake,∗1 J. -Y. Moon,∗1,∗3 T. Niwase,∗1,∗5 Y. Hirayama,∗1
M. Rosenbusch,∗1 M. Wada,∗1 X. Y. Watanabe,∗1 and H. Wollnik∗1,∗2

∗1
∗2
∗3
∗4
∗5500

500

Offline reference
Online source

400

Counts / 6.4 ns

400300Counts / 6.4 ns

At the KISS facility, rare isotopes are produced
in-ﬂight by multi-nucleon transfer (MNT) reactions.
They are then stopped and neutralized in high pressure argon gas and transported by gas ﬂow to an exit
nozzle. Atoms of rare isotopes are then re-ionized inan element-selective manner by use of a 2-step laser excitation; the method can only produce singly-charged
ions. The gas cell system ﬂoats on a 20 kV bias, thereby
producing 20 keV/q ions. A magnetic separator withRm ≈ 900 ensures only a single isobar chain is transported downstream to the experimental apparatuses.
One of the primary experimental devices at KISS
is multi-reﬂection time-of-ﬂight mass spectrograph(MRTOF). The MRTOF, however, requires very lowenergy ions. To make the 20 keV/q KISS beam useable
by the MRTOF, a gas cell cooler-bucher (GCCB)1) has
been constructed. This device is similar in construction to a small rf carpet gas cell,2) but is windowless
and pressurized to only 1 mbar. The beam from KISS
stops in the GCCB, and is then extracted to vacuum
and transferred to the MRTOF. The MRTOF makes
rapidly interleaved time-of-ﬂight measurements of analyte (the beam from GCCB) and reference ions.
In the initial test of the GCCB, a 20 keV/q beamof 198 Pt+ was delivered from KISS. Figure 1 showsa time-of-ﬂight spectra measured during that study.
It was presumed that the peak at A/q = 99 was
198
Pt++ and a high-resolution follow-up measurement
conﬁrmed as much.
There are two ion traps between the GCCB andMRTOF. While the ﬁrst of these has a very broadband response, the second trap (referred to as “ﬂattrap”) is somewhat mass selective. The amplitude ofthe ﬂat trap was systematically varied to determine theprobability of conversion to a doubly-charged state. A
time-of-ﬂight spectrum was measured at each amplitude, and the number of singly- and doubly-charged A= 198 ions was recorded. The result, shown in Fig. 2,indicates that ≈80% of incoming Pt ions were converted to the doubly-charged state.
From the occurrence of such charge-stripping reactions we presume the GCCB will also be highly eﬀective at breaking molecular contaminants which are acommon problem for gas cell based studies. We hope
to report on such an eﬀect in the near future.
KEK Wako Nuclear Science Center
New Mexico State University, USA
Institute for Basic Science, Korea
Japan Atomic Energy Agency
Kyushu University

3002001002008090 100 110 120 130 140 150 160 170 180 190 200 210 220

m [u]

100

082

84

86

8890

9294

96

98

100102m [u]Fig. 1. Time-of-ﬂight spectra from oﬄine test of KISS gas
cell cooler-buncher (GCCB) using a 20 keV/q beam of198
Pt+ . The black spectrum shows the reference ions,85, 87
Rb+ and 133 Cs+ . The red spectrum shows the ionsdelivered from the GCCB, dominantly A/q = 99.

Fig. 2. Eﬀect of varying the RF amplitude of the ﬁnal
preparation trap before the MRTOF, indicating that
≈80% of the incoming beam is converted to a doublycharged state.

References

1) Y. Ito et al., JPS Conf. Proc. 6, 030112 (2015).
2) Y. Ito et al., RIKEN Accel. Prog. Rep. 49, 183 (2016).

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