KEKB’s superconducting cavity has been adopted for the storage ring of TPS, Taiwan Photon Source

National Synchrotron Radiation Research Center (NSRRC) in Taiwan began construction of the Taiwan Photon Source (TPS), a new third- generation synchrotron radiation facility of 3 GeV, attaching to the existing Taiwan Light Source (TLS). NSRRC has decided to adopt KEKB’s superconducting accelerating cavity to the RF acceleration of the electron storage ring, and exchanged an agreement on the production of three cavities with Mitsubishi Heavy Industries, Ltd. in May this year. Their completion and the delivery are scheduled in 2012. The TPS is a third- generation synchrotron radiation facility to be constructed adjacent to the existing TLS as shown in Fig. 1, and aiming the electron beam accumulation up to 500 mA at 3 GeV. A number of insertion devices will be installed, and supplying several hundreds kW of high RF power to the beam as a continuous wave (CW) is required. Also the RF cavity must have a capability to damp harmful higher harmonics excited by such a high- current beam.

<Figure 1> Taiwan National Synchrotron Radiation Research Center bird's- eye view (by courtesy of NSRRC).

In recent years, superconducting cavities have been applied to a number of synchrotron light sources in the world, due to the ability to provide high accelerating voltage in CW. These are called higher-hormonic damped cavity, and three types, KEKB (Nb, 500-509 MHz), CESR-B(Cornell, Nb, 500 MHz), and SOLEIL(developed by CERN, Nb-Cu, 352 MHz) have been working. NSRRC has already introduced the CESR-B-type superconducting cavity in order to improve the performance of existing TLS, trying to acquire a superconducting cavity technology by themselves as well as stacking higher beam current. On the other hand, China Institute of HighEnergy Physics has developed the 500 MHz cavity for BEPC-II based on the KEKB type 509 MHz, and demonstrated the acceleration performance of KEKB cavity as expected.

Table 1 shows the operation parameters of the RF acceleration required by the TPS. As a result of a detailed study, the TPS team has selected the KEKB superconducting cavity as the most suitable device to match these operation parameters. The reason was not only that the KEKB cavity has been operated in KEKB stably for 10 years with up to 1.4 A beam current and 350 kW input power, but it has a capability to optimize the coupling coefficient of the input coupler according to the beam load.

Based on an MoU, signed between the NSRRC and KEK, NSRRC will participate in the technology development of large current superconducting cavity, and KEK will perform technical assistance to the development of 500 MHz cavity for NSRRC. It will be a good chance of technology exchange between the two, aiming at developments of accelerator technology to each other toward the future.

<Table 1> TPS storage ring parameters

<Figure 2> The superconducting damped cavity operating at KEKB.

〜 Author : Accelerator Division , K.O〜

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