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Purpose Disruption of the tumor-brain barrier in meningioma is a crucial factor in peritumoral brain edema (PTBE). We previously reported the possible effect of osteoporosis on the integrity of the arachnoid trabeculae because both the bone and the arachnoid trabeculae are composed of type 1 collagen. We hypothesized that osteoporotic conditions may be associated with PTBE occurrence after radiation treatment in patients with meningioma. Methods A receiver operating characteristic curve analysis was used to identify the optimal cut-off values of mean skull Hounsfield unit for predicting osteopenia and osteoporosis in patients from our registry. Multivariate Cox regression analysis was used to determine whether possible osteoporosis independently predicted PTBE development in patients with meningioma after radiation. Results A total of 106 intracranial meningiomas were included for the study. All patients received linear accelerator-based radiation therapy in our hospital over an approximate 6-year period. Multivariate Cox regression analysis identified that hypothetical osteoporosis was an independent predictive factor for the development of PTBE in patients with meningioma after linear accelerator-based radiation treatment (hazard ratio 5.20; 95% confidence interval 1.11–24.46; p = 0.037). Conclusions Our study suggests that possible osteoporotic conditions may affect PTBE development after linear accelerator-based radiation treatment for intracranial meningioma. However, due to the study’s small number of patients, these findings need to be validated in future studies with larger cohorts, before firm recommendations can be made. Graphic abstract

The silver-activated zinc sulfide, ZnS(Ag), sensor to detect alpha-particles is normally fabricated by means of heat-melting or epoxy mixing spread. However, the fabrication process is very complicated so that it creates high costs and requires special high-tech equipment to manufacture the detector. For this reason, we have developed a new fabrication method which has the advantages of process simplicity and also high efficiency. The alpha particle response of the detector manufactured by the new spreading method was evaluated at varied thicknesses of ZnS(Ag) and the detection efficiency was better than for other methods like liquid brush method with an Am-241 alpha radiation source. Compared to conventional ZnS(Ag) detectors, the new detector shows a good detection efficiency, and its simple and low cost design makes it an economical and commercial alternative to more expensive alpha survey instruments.

Neutron detector based on radiation-hard semiconductor materials like SiC, diamond and AlN has recently emerged as an attractive device for an in-core reactor neutron flux monitoring, a spent fuel characterization, and a home land security application. For the purpose of field measurement activity, a radiation detector having a low-power consumption, a mechanical stability and a radiation hardness is required. Our research was focused on the development of a radiation-resistive neutron semiconductor detector based on a wide band-gap SiC semiconductor. And also it will be operated at a zero-biased voltage using a strong internal electric field. The charge collection efficiency (CCE) was over 80% when the biased voltage was zero. When the biased voltage was applied above 20 V, the charge collection efficiency reached 100%.

A new solid state detector based on 6H-SiC is one of the promising devices in the nuclear industry for high-level radiation applications in a harsh high-temperature environment. SiC is a semi-conductor with a 3.03-eV band gap energy, and known as a radiation-resistance material. SiC detectors were fabricated by using a 6H-SiC wafer. The properties of the 6H-SiC wafer were over a 106 ohm-cm resistivity, a 380 μm thickness, and a (0001)-oriented type. The 6H-SiC detector was prepared by the processes of a dicing, etching, removal of an oxidation layer and a mounting on an alumina substrate. SiC detector was 10×10 mm2 with a 19.6mm2 active area. The circular metal contacts consisted of a Si-face/Ni/Au and a C-face/Ni/Au structure. Thin LiF and B film was coated onto the SiC detector surface for a neutron converter. The electrical current-voltage performances of the detectors were measured by using the Keithley 4200-SCS parameter analyzer with self voltage sources. Neutron responses were measured by using a 2...

Compound semiconductors of high Z value material have been studied intensively for X-ray and γ -ray spectroscopy at room temperature. CdZnTe has wide band gap energy as 1.6 eV and can provide high quantum efficiency with reasonably good energy resolution at room temperature. This study is aimed at determining radionuclide analysis ability by measuring energy resolution of CZT detector which will be applied at nuclear material identification purpose. For experiment we used a CZT detector (5 × 5 × 5 mm3) which is manufactured by eV Products. We have performed our measurement at varied temperatures similar to the outdoor environment for the investigation about temperature dependence of energy resolution and peak centroid fluctuation of CZT detector by using gas cooling and Peltier cooling methods. In order to test radionuclide identification we used various radionuclide samples; plutonium, europium and other standard sources. Pulse height spectra were obtained by standard electronics which consists of a prea...

CZT is one of the most promising materials for X-ray and γ-ray radiation detectors operated at room temperature. We have studied the fabrication process of the CZT planar-type detector, which includes the physical and chemical surface treatment, the fabrication of metal contact, and the surface passivation. CZT planar-type detectors with various metal-semiconductor contacts were made. The dark current and the γ-rays from 241Am were measured with each detector, and they were compared. From the above studies, the effective fabrication method of CZT detector could be deduced. Our work could be helpful to fabricate the high resolution CZT detector, which could be used in various application areas such as nuclear medicine, radiation safety, X-ray and γ-ray astronomy and homeland security

CZT detector is one of the most promising radiation detectors for hard X-ray and γ-ray measurement. The energy spectrum of CZT detector has to be simulated to optimize the detector design. A CZT detector was fabricated with dimensions of 5 × 5 × 2 mm3. A Peltier cooler with a size of 40 × 40 mm2 was installed below the fabricated CZT detector to reduce the operation temperature of the detector. Energy spectra of were measured with 59.5 keV γ-ray from 241Am. A Monte Carlo code was developed to simulate the CZT energy spectrum, which was measured with a planar-type CZT detector, and the result was compared with the measured one. The simulation was extended to the CZT detector with strip electrodes.

A High Pressure Xenon ionization chamber is a promising radiation detector for environmental radiation measurement due to its radiation hardness, its physical rigidity, and its capability of operation at a high temperature up to about 170 °C. A cylindrical high pressure xenon ionization chamber, which was configured with a shielding mesh to improve its energy resolution, was designed on the basis of an electron transfer simulation code (EGSnrc) to extract an optimal density of Xe gas and a thickness of the chamber wall. An electron drift simulation code, Garfield, which was coupled with a Maxwell electric filed calculator, was also employed for the electron drift simulations due to the geometry of the shielding mesh. Shielding inefficiency was also calculated. A spherical ionization chamber was also designed and fabricated to monitor environmental radiation. A noble gas system was constructed to create a noble gas with a high purity and to inject the noble gas up to 60 atm. The combination of an oxygen ab...

The fully depleted SiC Schottky barrier detector was fabricated from a semi-insulating (SI) bulk crystal with a thickness of 388 μm and an orientation of the on axis (0 0 0 1). The bulk SI 6H-SiC detector structure consists of a Ni/Au contact at the Si-face and a Ti/Au contact at the C-face. The fabricated detector dimensions are 10×10 mm with a diameter of 6 mm for the contact dimension. The band gap of the 6H-SiC was determined by using an optical photon absorption spectroscopy in the ranges between 200 and 600 nm. The band gap of 6H-SiC is determined as 3.03 eV. The current density response according to the biased voltage was measured. The Schottky barrier height was determined as 0.86 eV on the basis of the thermo-ionic emission theory. The bulk SI 6H-SiC detector with a multi-layer structure, Au/Ni/6H-SiC/Ti/Au showed a good response for the α radiation in air and at room temperature.

It is known that the current collected from an ionization chamber exposed to a constant radiation intensity changes in magnitude when the polarity of the collecting potential is reversed. It is called the polarity effect of the ionization chamber. There are many possible causes that induce the polarity effect and one of them can be a field distortion due to a potential difference between the guard electrode and the collector. We studied how much the polarity effect depends on the design of the electrodes in the thimble-type ionization chamber. Two thimble-type ionization chambers, which had different electrode structures, were designed and fabricated at KAERI. We calculated the field distortions due to the potential difference between the guard electrode and the collector for the two ionization chambers. MAXWELL and Garfield were employed to calculate the electron drift lines inside the chamber. The polarity effects of the two ionization chambers were measured, and they were consistent with the field calculation. We could conclude that the polarity effect is mostly induced from the field distortion due to the potential difference between the guard electrode and the collector in our experiment and it depends significantly on the design of the electrodes.

GaAs is a wide band gap semiconductor (1.42 eV) with potential use as a room temperature radiation detector. We have studied the radiation response of a prototype semiconductor detector by using a undoped semi-insulating (SI) GaAs wafer. The properties of the GaAs wafer are a resistivity of 10 ohm-cm, an orientation of (100) and a diameter of 50.8mm. The dimensions of the GaAs SI detectors were about 5x5 mm with a 350 um thickness. Prior to a metallization process, the surfaces of the GaAs wafer were cleaned by a solvent and rinsed with de-ionized (DI) water, and the removal of an oxidation layer by a diluted acid solution was performed. Metal/semiconductor contacts on the surface were fabricated by using a thermal evaporator in a high vacuum condition. The prototype GaAs detector had circular metal contacts of Ni/Au at each side and the diameter of a circular contact was 3 mm. The current-voltage characteristics of GaAs semiconductor detector were measured by using HP parameter analyzer with voltage sources. We measured the leakage currents at different temperature conditions. Also, the radiation response was evaluated by Am-241 source at variable operating temperature.

We have studied the radiation response of a prototype SiC radiation detector by using a 6H-SiC wafer. Metal contacts on the surface of the SiC samples were fabricated by using a thermal evaporator in a vacuum condition. Among the SiC samples, several samples were heated by a Rapid Temperature Annealing(RTA) device for 10 minutes at 300°C. The metal contacts on the annealed and non-annealed samples were scanned by using AFM(Atomic Force Microscope) before and after an annealing process. The current-voltage characteristics of the SiC detectors were measured by parameter analyzer and the radiation response was evaluated by 238Pu with 5.5 MeV α-ray at room temperature and a atmospheric pressure. After annealing process, the surface roughness and the current-voltage characteristics decreased. The Schottky barrier heights of non-annealed and annealed SiC samples were determined as 0.638 eV and 0.688 eV, respectively. Also radiation response spectra of the annealed and non-annealed detectors were similar.

Leakage current is one of the main noise sources of in radiation detectors, especially in a semiconductor radiation detector used for energy spectroscopy. A Silicon Surface Barrier (SSB) radiation detector was constructed to study the correlation between its surface roughness and leakage current. The surface roughness was analyzed with an Atomic Force Microscopy (AFM). All the constructed SSB radiation detectors in this study were processed in same way, but the etching solutions used to roughen the silicon surface were different. The correlation coefficient between the surface roughness and the leakage current was 0.848. This value indicates that the surface roughness and the leakage current have a relatively strong relationship, and a proper etching condition can minimize the leakage current in a semiconductor radiation detector based on silicon. The energy spectrum for an alpha particle from 238 Pu was also measured with the constructed SSB radiation detector.

Since plastic detectors are easy to fabricate and have good scintillation properties, they have been used as various forms for cosmic-ray detection. Major factors to determine a detector's efficiency are scintillator size, scintillation transfer material, and the photo acceptor equipment. The size of a plastic scintillator and the photo acceptor equipment (photo multiplier tube, photodiode, etc.) can be decided easily in the design process but the scintillation transfer material has to be selected circumspectly. Light guides using Polymethylmethacrylate (PMMA) have a very high transmittance, but are large in size and very expensive, while a wavelength shifter fiber can transfer the scintillation at a decreased transfer efficiency. Therefore, a detector using a wavelength shifter fiber requires a proper optimization for maximum efficiency. In this study, three detectors of 1000×500×10 mm3 size were fabricated. The wavelength shifter fibers were mounted by optical cement into grooves and the detection efficiency for charged particles was evaluated. The main goal was to measure the detection efficiency for cosmic-ray charged particles detector using a wavelength shifter fiber in order to evaluate the possibility of replacing the expensive PMMA light guides. And, this study was compared with efficiency of “ATHLET” charged particle detector. We are going to prove that we can fabricate a cosmic-ray charged particle detector with a performance identical to an advanced nation's one.

We designed and fabricated a thimble type ionization chamber with the guard-ring electrode. During the measurement, the potential between the guard electrode and the collecting electrode can be drifted, which will change the active volume of the ionization chamber. From MAXWELL and Garfield calculation, the variation of the active volume of the ionization chamber was obtained with changing the potential difference between the collector and guard electrode. We made ionization chambers with two designs of the guard ring. The polarity effect of two ion chamber was measured, and the result of it shows the consistency with the simulation.

Since GEM was introduced, it has been developed in many application areas. We have developed the neutron detector with GEM coated with the converting foil. The neutron efficiency of a foil was calculated with MCNP and TRIM. The neutron efficiency of multi GEM foils was also calculated. The boron compound was coated on the drift plate, and the neutron was measured with a gas chamber installed with GEM. The process of boron-coating on GEM foil, and the stabilization of it has been under way in KAERI.