Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 47 (2014)

Performance of a resonant Schottky pick-up for the Rare-RI Ringproject
F. Suzaki,∗1,∗2 J. Zenihiro,∗1 A. Ozawa,∗3 T. Suzuki,∗2 T. Uesaka,∗1 M. Wakasugi,∗1 K. Yamada,∗1
T. Yamaguchi,∗2 Y. Abe,∗1,∗3 Y. Yamaguchi,∗1 and Rare-RI Ring collaboration
Construction of a new storage ring called “Rare-RIRing” was started in 20121,2) at RIBF. This project
aims at precise isochronous mass measurements for
extremely neutron-rich exotic nuclei in the r-process
nucleosynthesis. To precisely tune the ion-optical condition to be isochronous, the resonant Schottky noise
pick-up technique will be employed. We performed anoﬀ-line test of the resonant Schottky pick-up.
Figure 1 shows the resonant Schottky pick-up thatwill be installed in the Rare-RI Ring. It consists of apillbox-type resonant cavity electrically isolated fromthe beam pipe by a ceramic tube. A schematic viewof the pick-up is shown in Fig. 2(a): a chamber shownin blue is the beam pipe and the shaded cylinder surrounding the beam pipe is the cavity equipped withtwo ports (yellow). The ports are movable plunger
pistons that can adjust the resonance frequency (fres )of the eigenmode. Fig. 2(b) shows the cross-sectionalview of the cavity, and the detailed structure of thegap can be seen at the center. The cavity itself is ﬁlledwith air and has the shape of a pillbox with an outer
diameter of 750 mm and length of 200 mm. The innerdiameter is 320 mm. The lower ﬂanges ( see Fig. 1 )are prepared for feedthroughs to take out signals froma loop coil that magnetically couples to the cavity ﬁeldinduced by the beam.
Using a network analyzer, we measured the basic
quantities characterizing the resonant cavity: the resonance frequency, the shunt impedance Rsh , and theunloaded Q factor Q0 . To measure Rsh , the perturbation method was adopted. From the measurements, fres = 171.54(±0.44) MHz, Rsh = 169 kΩ, andQ0 = 1884 were obtained.
For tuning the isochronous ﬁeld settings, the proposed pick-up is required to have an excellent singleion sensitivity. By using the results of the oﬀ-line
test, the output signal power corresponding to a single ion with charge q at resonance3) is estimated to be
P = q 2 × 2.8 × 10−21 W , and the power of thermal
noise Pnoise is 7.1 × 10−19 W. For q ≥ 16, the signal
power exceeds the noise ﬂoor, and the signal from thebeam can be detected by the present Schottky pickup. Therefore, the performance is suﬃcient for precise
tuning of isochronus ﬁeld settings of the Rare-RI Ring.
The resonant Schottky pick-up will be soon installed
into the Rare-RI Ring. Detailed results of the oﬀ-line
test and online beam performance test will be reported
∗1
∗2
∗3

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

in forthcoming publications.

Fig. 1. The resonant Schottky pick-up that will be installedin the Rare-RI Ring. The resonant cavity surrounds
the beam pipe with a ceramic gap. The lower flanges
for feedthroughs are the output coupler loop, and theupper feedthroughs are the movable plunger pistons,
using which the resonance frequency of the eigenmodecan be adjusted.

Fig. 2. Schematic view of a resonant cavity for the Rare-RIRing. (a) The pillbox-type cavity shown translucently
surrounds the beam pipe separated by a ceramic tube.
(b) A cross-sectional view of the cavity showing thedetailed structure of the gap.

References
1) Y. Yamaguchi et al.; Nucl. Instrum. Methods Phys. Res.
B 317 (2013) 629.
2) A. Ozawa et al.; Prog. Theor. Exp. Phys. 2012 (2012)
03C009.
3) F. Nolden et al.; Nucl. Instrum. Methods Phys. Res. A659 (2011) 69.

- 201 -