Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 52 (2019)

Input power coupler for SRILAC
K. Ozeki,∗1 O. Kamigaito,∗1 N. Sakamoto,∗1 K. Suda,∗1 and K. Yamada∗1
As an upgrade project of the RIKEN Linear Accelerator (RILAC), the construction of a superconducting
heavy ion linear accelerator (Superconducting RILAC,denoted as SRILAC hereinafter) is now in progress.1,2)
In this report, the progress in the implementation of input power couplers to feed RF power to the resonator isreported.
For the construction of a prototype accelerator system
based on the superconducting quarter-wavelength resonator (QWR),3–9) which was carried out prior to thisproject, the couplers were designed to have double disktype ceramic vacuum windows to ensure the vacuum of
QWR as well as to avoid the long antenna design.10,11)
On the other hand, the couplers for the SRILAC were
designed to have single disk-type ceramic vacuum window, in order to simplify the structure and reduce theproduction cost. The geometry around the vacuum window was designed to have a characteristic impedance of50 Ω using CST Microwave Studio.12)
The couplers were produced by Mitsubishi Heavy Industries Machinery Systems Ltd. A total of ten couplers
were delivered in sequence. A photograph of the couplers
is shown in Fig. 1.
The couplers must be kept completely clean and degassed in advance in order to prevent contamination of
the QWR. All the operations described below were performed in an ISO class-1 clean room.
At the beginning, the following rinsing operations
were performed: deconstruction of the coupler, rinsing of each part using ultrapure water, drying, and re-construction.
After the rinsing operations, a pair of couplers wasmounted on an RF test stand chamber (see Fig. 2), andthe RF test stand chamber and the two couplers werebaked at 120◦ C.
Then, the ceramic vacuum window was processed withRF power (RF process). Figure 2 shows the setup of theRF process. While feeding RF power to the system, theinterlocks were set for an emergence of arc light due toa discharge in the coupler, and a loss of vacuum. The
RF process was performed ﬁve times (the two couplers
were processed once), and every time the RF power was
successfully fed up to about 5 kW without any diﬃculty.
After the RF processes were ﬁnished, the couplers
were attached to the QWRs in the ISO class-1 cleanroom. The fabrication of the cryomodules is now inprogress.

Fig. 2. Photograph (left) and schematic (right) of the RF
process. The RF power was fed from the right-side coupler and transmitted to left-side coupler. The left-sidecoupler was terminated with a dummy load. The input,reflected, and transmitted RF powers were measured.

References

Fig. 1. Two sets of input power couplers. Constructed (left)and deconstructed (center and right) parts.
∗1

RIKEN Nishina Center

1) N. Sakamoto et al., in this report.
2) K. Yamada et al., in this report.
3) K. Ozeki et al., Proc. 12th Ann. Meet. PASJ, 1116 (2015).
4) N. Sakamoto et al., Proc. SRF2015, 976 (2015)..
5) K. Ozeki et al., Proc. LINAC16, 598 (2016).
6) K. Yamada et al., Proc. LINAC16, 939 (2016).
7) K. Yamada et al., Proc. 14th Ann. Meet. PASJ, 17 (2017).
8) K. Ozeki et al., RIKEN Accel. Prog. Rep. 51, 131 (2018).
9) N. Sakamoto et al., in this report.
10) K. Ozeki et al., Proc. SRF2015, 1335 (2015).
11) K. Ozeki et al., RIKEN Accel. Prog. Rep. 49, 139 (2016).
12) https://www.cst.com/products/cstmws .

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