[en] We have designed a neutron calorimeter dedicated to the measurement of the nuclear symmetry energy in the planned Korea rare-isotope accelerator. The design was optimized to precisely measure the neutron energy with high efficiency in a wide energy range from about 30 to 300 MeV. The final configuration of the detector is a hybrid of the homogeneous and the sampling calorimeters with a veto counter in the front. The homogeneous part is ideal for measuring low-energy neutrons below ∼ 50 MeV whereas the sampling part is efficient for measuring high-energy neutrons. The detection efficiency is estimated to be about 88% for neutron energies larger than 50 MeV and decreases to ∼78% at 30 MeV.We have estimated the energy resolution as a function of the incident energy based on the time-of-flight method. Assuming an ideal detector performance with null time resolution, the relative energy resolution decreases as the incident neutron energy increases. However, under a more realistic situation with a finite time resolution for the detector, the energy resolution monotonically increases with increasing the neutron energy, following a logarithmic function. Imposing an energy resolution of better than 3% at the highest neutron energy, we find the nominal position of the hybrid calorimeter to be 15 m from the target for a time resolution of 1.0 ns, but the detector needs to be free to move closer to or farther from the target, depending on the physics goal.

[en] In this paper, we report on the development of a scintillation-fiber detection method for dose verification in hadron therapy. In order to achieve the position sensitivity required for precision measurement of doses, a detector composed of 1-mm-thick scintillation fibers and a multi-channel photodiode was constructed and tested with 45-MeV proton beams provided by the MC50 proton cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The results of the beam test showed that the spatial resolution of the data determined by using the standard deviation σ was ∼1.0 mm, which is sufficiently accurate to verify beam-induced doses in hadron therapy. Furthermore, the quantitative accuracy appearing in the data is on the order of ∼1%. We expect the detector composed of scintillation fibers and operating in the charge-integration mode to allow us to perform quality measurement of doses in various hadron therapies.

[en] The prompt gamma neutron activation analysis (PGNAA) system is a useful tool to detect the concentrations of the various composite elements of a sample by measuring the prompt gammas that are activated by neutrons. The composition in terms of the constituent elements is essential information for the identification of the material species of any unknown object. A PGNAA system initiated by a high-power laser has been designed and optimized by using a Monte-Carlo simulation. In order to improve the signal-to-background ratio, we designed an improved neutron-shielding structure and imposed a proper time window in the analysis. In particular, the yield ratio of nitrogen to carbon in a TNT sample was investigated in detail. These simulation results demonstrate that the gamma rays from an explosive sample under a vast level of background can indeed be identified.

[en] The performance of the prototype modules of neutron detectors for the Large Acceptance Multi-Purpose Spectrometer (LAMPS) was investigated, using cosmic muons and neutron beams at 65 and 392 MeV, provided by the Research Center for Nuclear Physics (RCNP). The timing and position resolutions were estimated using cosmic muons as 309 ps and 4.8 cm, respectively. The energy resolution depended on the incident energy of neutrons: 1.3% at 65 MeV and 3.1% at 392 MeV. The neutron-detection efficiency also showed weak energy dependence as it decreased from (9.0 ± 1.6)% at 65 MeV to (6.3 ± 1.0)% at 392 MeV.

[en] The Rare Isotope Accelerator complex for ON-line experiments (RAON) is a new radioactive ion beam accelerator facility under construction in Korea. The large acceptance multi-purpose spectrometer (LAMPS) is one of the experimental devices for nuclear physics at RAON. It focuses on the nuclear symmetry energy at supra-saturation densities. The LAMPS Collaboration has developed and constructed various detector elements, including a time projection chamber (TPC) and a forward neutron detector array. From the positron beam test, the drift velocity of the secondary electrons in the TPC is $5.3\pm <!--\; ??\; -->0.2$ cm/μs with P10 gas mixture, and the position resolution for pads with dimensions of 4 $\times <!--\; ??\; -->$ 15 mm${}^2$ is in the range of $\sim <!--\; ???\; -->$ 0.6–0.8 mm, depending on the beam position. From the neutron beam test, the energy resolution of the prototype neutron detector module is determined to be 3.4%, and the position resolution is estimated to be better than 5.28 cm. At present, the construction of the LAMPS neutron detector system is in progress.