II-9. Instrumentation

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Fourth report on oﬄine tests for RF carpet transportation in RF ion
guide gas cell at the SLOWRI facility
A. Takamine,∗1 S. Iimura,∗1,∗2,∗3 D. Hou,∗3,∗4,∗5 M. Wada,∗3 M. Rosenbusch,∗3 S. Chen,∗3,∗6 W. Xian,∗3,∗6S. Yan,∗3,∗7 P. Schury,∗3 Y. Ito,∗1,∗8 T. M. Kojima,∗1 T. Sonoda,∗1 Y. X. Watanabe,∗3 H. Ueno,∗1 andH. Ishiyama∗1

1stRFC

2ndRFC

1stRFCIon trajectory
Fig. 1. Sketch of 1st RFC and 2nd RFCs around the exit
hole with an ion trajectory in blue.
∗1∗2∗3∗4∗5∗6∗7∗8RIKEN Nishina CenterDepartment of Physics, Osaka University
Wako Nuclear Science Center (WNSC), IPNS, KEK
Institute of Modern Physics, Chinese Academy of Sciences
School of Nuclear Science and Technology, Lanzhou University
Department of Physics, The University of Hong Kong
Institute of Mass Spectrometry and Atmospheric Environment, Jinan University
Advanced Science Research Center, JAEA

1150 kHz125 kHz100 kHz75 kHz
50 kHz
30 kHz
10 kHz0.8Transport efficiency

A new gutter structure RF ion guide gas cell1) was developed at the SLOWRI facility. The gas cell comprises
two RF carpet (RFC) stages. We previously reported
on the transportation eﬃciencies of the 1st stage RFC
for various gas pressures and various RF frequencies.2,3)
In this report, the transport eﬃciency including the 2ndstage RFC is presented.
The 2nd RFC comprises concentric ring electrodes
with a pitch of 0.26 mm (electrode width of 0.1 mm andinter-electrode spacing of 0.16 mm); there is a ϕ0.65 mm
exit hole at the center of the 2nd RFC. Ions are collected
onto the 1st carpet and transported to the inner edgesof the pair of the 1st RFCs. After they are pulled overthe edge to the 2nd RFC by a DC ﬁeld, they are delivered to the exit hole by the “ion surﬁng” transporttechnique that uses the combination of two-phases RF
and four-phases audio-frequency (AF) ﬁelds4) (Fig. 1).
A segmented quadrupole ion beam guide (smQPIG) is
placed behind the exit hole. The ions are transported toa high vacuum region by the smQPIG through diﬀerential pumping stages.
We recently investigated the transport eﬃciency including the 2nd RFC in oﬄine tests. Cesium ions were
produced from a surface ionization ion source at the in-0.6
0.4
0.200510152025

AF voltages applied to 2nd RFC [Vpp]Fig. 2. Oﬄine test results on the transport eﬃciency for Cs+
as a function of AF voltages at various AF frequencies.

ner wall of the gas cell. The entire setup has been described in Ref. 1). We measured the ion currents on
the RFCs and subsequently on the smQPIG. The RFC
transport eﬃciency was deﬁned as the ratio of the twocurrents.
Figure 2 shows the test results in 133 mbar of room
temeperature He gas as a function of the AF voltages
for various AF frequencies. The RF voltages applied
to the 1st and 2nd RFCs were 103 Vpp at 8.15 MHzand 111 Vpp at 10.06 MHz, respectively. The push DC
ﬁeld between the 1st and 2nd RFCs was ∼40 V/cm.
We achieved ∼90% transport eﬃciency with an AF frequency of 125 kHz in this measurement. The plotsshow a sudden drop at 12–15 Vpp for AF frequencies≥125 kHz, because the AF signals became highly distorted by the AF/RF coupling circuitry. An attempt toimprove the circuit characteristics is afoot.
This gas cell was coupled to an MRTOF mass spectrograph for a parasitic experiment during the HiCARI
campaign in 2020. The online experiment results about
this gas cell are reported in other articles by S. Iimura
and D. Hou in this issue.
References

1) A. Takamine et al., RIKEN Accel. Prog. Rep. 52, 139 (2019).
2) S. Iimura et al., RIKEN Accel. Prog. Rep. 53, 107 (2020).
3) A. Takamine et al., RIKEN Accel. Prog. Rep. 53, 108 (2020).
4) G. Bollen, Int. J. Mass Spectrom. 299, 131 (2011).

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