Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 49 (2016)

Temperaturemeasurements
measurements ofof thethe highhigh power
power beamTemperature
beamdump
dumpofofthe
theBigRIPSBigRIPS
separator
separator
K. Yoshida,䠆1 Y. Yanagisawa,䠆1 Z. Korkulu,*1 H. Takeda,䠆1 K. Kusaka,䠆1 M. Ohtake,䠆1 N. Fukuda,䠆1 H. Suzuki,䠆1D. S. Ahn,䠆1 Y. Shimizu,䠆1 T. Sumikama,䠆1 N. Inabe,䠆1 and T. Kubo䠆1The high-power beam dump1,2) that stops intense primarybeams from the super-conducting cyclotron SRC is one of
the crucial devices of the BigRIPS fragment separator. Thebeam dump consists of the side dump and the exit dump.
The two exit beam dumps, for an intense 238U beam and forthe other beams, were designed to handle various ion beams
with intensities up to 1 pPA.2) Two exit dumps had the samestructure except for the distance from the dump surface andthe cooling channel; 1 mm for 238U and 3 mm for the other.
The latter exit beam dump and the side dump wereconstructed in 2007. Since then, it has been successfully
operated with various beams including a 238U beam
although the available beam intensity was low. The designof the beam dumps was based on the sophisticated thermalmodel simulation1,2) and its validity has not been verified
because the available beam intensity was not so high.
Recently the intense 48Ca beam became available. As thefirst step of the evaluation of the cooling capacity of thebeam dump, the temperature measurements of the exit beam
dump were performed with the intense 48Ca beam.
The inner-side exit beam dump1,2) that was made by theCu-Cr-Zr alloy and the M8 screw threads were formed as
the cooling channels was irradiated by the 48Ca beam withan energy of 345 MeV/n and intensity of 460 pnA. Cooled
water with a temperature of 13 Υ, pressure of 1.0 MPa,and flow speed of 10 m/s were supplied to the dump as thecoolant. Temperatures are measured by using athermocouple (T. C.) mounted on the dump at 3 mm behindthe dump surface. By changing the position of the dump,
horizontal distribution of the temperature was measured
against the beam spot. Various beam heat densities wereobtained by tuning the first superconducting quadrupole
triplet STQ1 located upstream of the dump. The spot sizesof the beam at the dump were estimated from the primarybeam profile (size and angle) measured separately at thesecond focus F2 located at the downstream of the dump.
The first order matrix of the ion optics of the BigRIPS
separator was used for the estimation.
In Fig.1, the observed temperatures are shown for threedifferent beam spot sizes, resulting in the different heatdensities. The results of finite element calculations usingthe ANSYS code3) are also shown in the figure. In thecalculations, thermal conductivity was assumed to be aconstant at 375 W/mK. The heat transfer coefficient of thecooling channel was also assumed to be 90 - 130 kW/m2K
for wall temperatures of 15 - 180Υ, which corresponded tothree times larger values of that of smooth tube with same
diameter (ȭ8). 4) The heat transfer coefficient of the smoothtube was calculated with the JAERI formula.5) As seen inthe lower panels of Fig. 1, a good agreement was obtained
between the results of the thermal model simulation and theobserved temperatures. It suggests that the estimation of thecooling capacity of the beam dump is reasonable sincesimilar model calculations were made in the estimation.

Fig.1 Beam dump temperatures for various beam sizes. Dots are measured values and lines and 2D figures are the results of the ANSYS calculations.
䠆1

References

RIKEN Nishina Center

1) N. Fukuda et al., RIKEN Accel. Prog. Rep. 41, 119 (2008).
2) K. Yoshida et al., Nucl. Instr. Methods B 317, 373 (2013).
3) ANSYS Inc. Product Release 15.0, USA.
4) K. Masaki et al., Fusion Eng. Des. 61-62, 171 (2002).
5) J. Boscary et al., Fusion Eng. Des. 43, 147 (1998).
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