Measurements of secondary neutrons produced from thick targets bombarded by high-energy helium and carbon ions

The angular and energy distributions of neutrons produced by 100 and 180 MeV/nucleon He and 100, 180, and 400 MeV/nucleon C ions stopping in thick C, Al, Cu, and Pb targets were measured using the Heavy-Ion Medical Accelerator in Chiba of the National Institute of Radiological Science (NIRS), Japan. The neutron spectra in the forward direction have broad peaks of {approximately}60 to 70% of the incident particle energy per nucleon due to the break-up process, and they spread up to almost twice the projectile energy per nucleon. The neutron spectra are similar for the same incident energy of 100 MeV/nucleon for both He and C ions. The phenomenological hybrid analysis, based on the moving source model and the Gaussian fitting of the break-up process, could well represent the measured thick target neutron spectra. The experimental results are also compared with the calculations using the heavy-ion code, and the calculated results agree with the measured results within a factor of 2 margin of accuracy. This systematic study on neutron production from thick targets by high-energy heavy ions is the first experimental work performed by NIRS and will be useful for designing the shielding for the high-energy heavy-ion accelerator facility.

[1]  G. Morgan,et al.  Neutron Yields from Stopping- and Near-Stopping-Length Targets for 256-MeV Protons , 1990 .

[2]  E. Tanabe,et al.  Thick-target neutron yield for charged particles , 1995 .

[3]  R. A. Cecil,et al.  Neutron angular and energy distributions from 710-MeV alphas stopping in water, carbon, steel, and lead, and 640-MeV alphas stopping in lead , 1980 .

[4]  Takashi Nakamura,et al.  Estimation of neutron yields from thick targets by high energy 4He ions for the design of shielding for a heavy ion medical accelerator , 1992 .

[5]  Wen-qing Shen,et al.  Total reaction cross section for heavy-ion collisions and its relation to the neutron excess degree of freedom , 1989 .

[6]  K. Tesch,et al.  A Simple Estimation of the Lateral Shielding for Proton Accelerators in the Energy Range 50 to 1000 MeV , 1985 .

[7]  H. Weidenmüller,et al.  Generalized exciton model for the description of preequilibrium angular distributions , 1976 .

[8]  Richard Madey,et al.  Improved predections of neutron detection efficiency for hydrocarbon scintillators from 1 MeV to about 300 MeV , 1979 .

[9]  M. A. Lone,et al.  Total neutron yields from 100 MeV protons on Cu, Fe, and Th , 1987 .

[10]  W. R. Burrus,et al.  NEUTRON AND PROTON SPECTRA FROM TARGETS BOMBARDED BY 450-MeV PROTONS. , 1972 .

[11]  J. Siebers,et al.  Shielding measurements for 230-MeV protons , 1993 .

[12]  C. E. Moss,et al.  Differential Neutron Production Cross Sections and Neutron Yields from Stopping-Length Targets for 113-MeV Protons , 1989 .

[13]  Takada,et al.  Analysis of the (N,xN') reactions by quantum molecular dynamics plus statistical decay model. , 1995, Physical review. C, Nuclear physics.

[14]  Á. Horváth,et al.  Neutron yields from 155 MeV/nucleon carbon and helium stopping in aluminum. , 1999, Nuclear science and engineering : the journal of the American Nuclear Society.