II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Present status of beam transport line from SRC to BigRIPS
K. Kusaka,∗1 K. Yoshida,∗1 M. Ohtake,∗1 and Y. Yanagisawa∗1
A beam transport line delivering the primary beam
extracted from the SRC to the BigRIPS target has been
operated since 2007, and it is called the “T-course” beamline. The T-course beam line consists of 3 bending magnets and 17 quadrupoles.1) Two identical 50◦ bendingmagnets DMT2 and DMT3 in the T-course are “2-Tesla”
room-temperature dipoles, with a maximum current of650 A. They are designed as resistive-type magnets withsaddle-shaped correction coils in addition to main coils.
The correction coils are installed in the gap of the magnet, and were originally excited with the main coils inseries. Each main coil has 72 turns and consists of 6
double pancakes, in which a 13.5 × 13.5 mm hollow conductor is wound 6 times in each layer. In contrast, eachcorrection coil is a 12-turn double pancake in which a14 × 10 mm rectangular hollow conductor is wound 6
times in each layer.1)
The layer isolation of the lower correction coil of theDMT3 magnet was damaged in an October 2017 incident,2) and the upper correction coil was found to be
short-circuited in November 2019.3) Furthermore, thelower main coil of the DMT3 was damaged in a test
excitation performed in March 2020.4) When we energized only the main coils with a total current of 800 A
by adding an auxiliary power supply to the original one,
unstable behaviors were observed at the excitation voltages of the second and fourth pancakes of the lower maincoil.4) Although we considered that the upper main coil
was not critically damaged, we decided to replace themain coils with new ones.
We designed the new main coils for the DMT3 magnet
such that they are excited with the original DMT3 power
supply using neither correction coils nor additional auxiliary DC power supply in its circuit. We increased thenumber of turns of each main coil from 72 to 84. Furthermore, the shape of each main coil was designed to ﬁt in
the original DMT3 iron pole and yoke without any modiﬁcations. As shown in Fig. 1, the 12-layer new main coilin the upper-half has a pentagonal-shaped cross-section.
We choose the same 13.5 × 13.5 mm hollow conductor as
in the original DMT3 main coils. Each new coil consistsof three types of double pancake coils in which a hollow
conductor is wound 4, 6, and 8 times in each layer, respectively. Each new pentagonal-shaped coil is formedby combining one 4-turn, one 6-turn, and four 8-turnpancakes with epoxy resin. Because the lengths of cooling water channels are diﬀerent, we introduce valves andﬂow meters in each cooling channel at the cooling water header. The new coils were fabricated and tested by
HANMI TECHWIN in Korea under the supervision ofToshiba and shipped to RIKEN in July 2021. The newcoils were successfully installed in the DMT3 magnet onsite, as shown in Fig. 2. Associated plumbing and wiring∗1RIKEN Nishina Center

Fig. 1. Schematic of the upper-half cross section of DMT3
magnet with new main coil.

Fig. 2. Installation of new coil in DMT3 iron yokes.

Fig. 3. DMT3 magnet with new coils in T-course beam line.

works were ﬁnished in August 2021. After a series of test
excitations, the DMT3 magnet with the new main coils
was excited, and a 238 U beam was successfully transported from the SRC to the BigRIPS target in the beamtime from November to December 2021.
References
1) K. Kusaka et al., IEEE Trans. Appl. Supercond. 18, 318(2008), and references therein.
2) K. Kusaka et al., RIKEN Accel. Prog. Rep. 51, 173 (2018).
3) K. Kusaka et al., RIKEN Accel. Prog. Rep. 53, 104 (2019).
4) K. Kusaka et al., RIKEN Accel. Prog. Rep. 54, 104 (2020).

- 72 -1