Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

Thermo-mechanical calculations of the high power beam dump of theBigRIPS separator
Z. Korkulu,∗1 K. Yoshida,∗1 Y. Yanagisawa,∗1 and T. Kubo∗1,∗2,∗3
The beam dump is a critical component for the inﬂight fragment separator that uses high-power primarybeams at the RI Beam Factory (RIBF). The exit beam
dump and side dump of the BigRIPS fragment separator were designed and constructed in 2007. The maximum beam power is planned to be 82 kW for 238 U
at 345 MeV/nucleon, and most of the beam power isdissipated to a target and a beam dump. The beam
dump system has been successfully operated so far, although the available beam power is still less than thegoal power value. The temperature of the beam dump
was measured and the observed temperature was compared with the value calculated by the ﬁnite element
analysis (FEA).1) An important aspect in high-power
beam dump design is to limit the maximal temperature
due to beam energy loss in the material. Controlling
this absorbed power is a key challenge. The technicalchallenges include overheating and excessive thermomechanical stress load variations caused by the highbeam intensity. Since the available beam intensity islower than the goal value, the ﬁnite element thermal
analysis code, ANSYS,2) was used to study these technical issues for 1 particle µA which corresponds to abeam power of 82 kW in the case of 238 U. Steady state
structural FEA was performed to estimate the static
stress around the exit beam dump.
To perform the thermo-mechanical simulation a 3D
solid model of the exit beam dump was considered andmeshed with high-order tetrahedral elements, whichis shown in Fig. 1. The exit dump is a V-shaped
CuCrZr plate equipped with screw tubes (M8 1.25pitch screw formed every 14 mm) as cooling channels.3)
Cooled water with a temperature of 13◦ C, a pressureof 1.0 MPa, and a ﬂow speed of 10 m/s was supplied
to the dump as the coolant. The heat transfer coeﬃcient of the screw tube was calculated (using JAERIformula4) ) and used in the simulation. The mechanical temperature-dependent properties of the CuCrZrfor the FEA are taken from similar work.5) The literature results show that the CuCrZr alloy exhibits
good strength and plasticity simultaneously between
room temperature and 350◦ C. The value of the ultimate tensile strength is 308±15 MPa at 350◦ C. This
ensures that the CuCrZr alloy has enough strength tobe applied under the high temperature condition.
Figure 1 shows the solid model of the exit beam
dump and the result of the equivalent stress on the∗1∗2∗3

RIKEN Nishina Center
National Superconducting Cyclotron Laboratory, Michigan
State University
Facility for Rare Isotope Beams, Michigan State University- 172 -Fig. 1. Calculated equvialent (von-Misses) stress on theexit beam dump.

exit beam dump by the static structural analysis. Thebeam size at the stopping location was estimated fromthe ﬁrst-order optics calculation of the BigRIPS separator with respect to the primary beam trajectory. In
the calculation, the input power was given as the heatgeneration, which is approximately 49 W/mm3 . The
maximum temperature of the beam center is approximately 355◦ C and the maximum von-Misses stress is291 MPa under the above mentioned conditions.
The simulation results showed that the maximum
temperature exceeds the critical limit (350◦ C) to avoid
creep and softening under irradiation for the CuCrZralloy while the maximum stress is found at the limitof the ultimate tensile strength. The thermal creep effect needs to be considered at a temperature more than350◦ C. When the thermal and thermo-mechanical data
can be measured, the beam dump should be tested
with a high intensity beam in order to understand andcharacterize the thermo-mechanical challenges and validate simulation results.
References
1) K. Yoshida et al., RIKEN Accel. Prog. Rep. 49, 159(2016).
2) ANSYS, Inc. Product Release 16.0, USA.
3) K. Yoshida et al., Nucl. Instrum. Methods B 317, 373(2013).
4) J. Boscary et al., Fusion Eng. Des. 43, 147 (1998).
5) D. Zhu et al., J. Nucl. Mater. 455, 185 (2014).