Speaker
Description
For advanced shielding design of high energy electron accelerators such as ILC, accuracy of nuclear model and data base used in the theoretical simulations should be validated with the experimental data. For this purpose, shielding experiment of secondary neutrons and muons generated from the beam dump was performed using 2.2, 4.3, 6.4 and 8.45 GeV electron beams at JLAB. The beam dump consists of aluminum and circulated water coolant. In the concrete shield upstream of the beam dump, there are three vertical penetration holes reaching the beam line level 10 m down from the ground level. The concrete shield thicknesses at the three holes are 91, 273 and 570 cm, and aluminum activation detectors were placed in the penetration holes during the irradiation. After the irradiation, gamma rays from the produced Na-24 radionuclides were measured and attenuation profiles of the production rates through the shield were experimentally obtained. Monte Carlo simulations with the experimental conditions were also performed, and they were generally agreed within a factor of 2. From the simulation analyses, Na-24 nuclides were produced by mainly neutrons, and the production rates were exponentially attenuated through the shield for 2.2 and 4.3 GeV electron beam. On the other hand, for 6.3 and 8.45 GeV electron beam, it was found that the contribution to the Na-24 productions due to negative muons were dominant at 570 cm, the thickest location.
This experiment project is performed as the collaboration between KEK and JLAB under the support by the USA-DOE.
