Youngseok Lee

Development of a saw gas sensor for monitoring so2 gas

Abstract We have developed a new type of SO 2 gas sensor by applying a particular inorganic thin film on SAW (surface acoustic wave) devices. The sensor consists of twin SAW oscillators with a centre frequency of 54 MHz fabricated on LiTaO 3 piezoelectric single crystals. One delay line of the sensor is coated with a CdS thin film that selectively adsorbs and desorbs SO 2 , while the other is uncoated for use as a stable reference. Deposition of CdS thin film has been carried out by the spray pyrolysis method using an ultrasonic nozzle. Mass loading and electric-field changes induced by the SO 2 gas adsorbed onto the CdS film result in corresponding frequency shifts directly proportional to the gas concentration. The relative change in the frequency of the two oscillators is monitored with a digital signal-processing circuit. SO 2 sensor properties investigated include sensitivity, response time and repeatability. The sensor shows promising performance as a microsensing tool and is capable of measuring concentrations in air less than 200 parts per billion of SO 2 .

Measurement of neutron total cross-sections of Dy and Hf in the energy region from 0.002 to 100 keV

Abstract The neutron total cross-sections of Dy and Hf have been measured in the energy region from 0.002 to 100 keV by the neutron time-of-flight method with a 46 MeV electron linear accelerator of the Research Reactor Institute, Kyoto University. A 6Li glass scintillator has been used as a neutron detector and metallic plates of Dy and Hf samples, 0.5–5.0 mm thick, have been used for the neutron transmission measurement. The neutron flight path from the water-cooled Ta target to the 6Li glass scintillator is 22.1±0.01 m. The background level has been determined by the block-off method and/or by using notch-filters of Co (132 eV), Ag (5.2 and 16.3 eV) and Mn (336 eV) and a Cd sheet. The present measurements are in general agreement with the previous ones and the evaluated data in ENDF/B-VI.

Experimental Study of Proton Induced Cross-sections on Natural Cadmium Leading to the Production of 111 Radionuclide

We measured the production cross-sections of 111 In induced by proton on the natCd at several proton energies between 4 MeV and 40 MeV by using a stacked-foil activation technique at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The present results were compared with the earlier reported experimental data and the theoretical calculations by using both the TALYS code and the ALICE-IPPE code. An overall good agreement was found with the recently reported experimental data and the TALYS prediction, as well. Integral yields of 111In were also deduced from the measured cross-sections.

Neutron Capture Cross Section Measurements of Tc-99 and Rh at Energies below 40 keV by Linac Time-of-Flight Method

The neutron capture cross sections of 99Tc and Rh have been measured relative to the 10B(n, α) standard cross section at energies below about 40 keV by the neutron time-of-flight (TOF) method using a 46 MeV electron linear accelerator (linac) at the Research Reactor Institute, Kyoto University (KURRI). A pair of C6D6 scintillation detectors has been used for the relative measurement of the 99Tc(n, γ) cross section, and the result has been normalized to the reference cross section value (19.57b) at 0.0253 eV in ENDF/B-VI. A total energy absorption detector, which was composed of 12 pieces of Bi4Ge3O12 (BGO) scintillators, was employed for the absolute capture cross section measurement of Rh. Both of the measured cross sections have been compared with the existing experimental data and the evaluated data in ENDF/B-VI, JENDL-3.2 and JEF-2.2.

Production Cross Sections of 186Re Radionuclide from the Proton Bombardment on Natural Tungsten

The excitation function of the natW(p,xn)186Re nuclear reaction was measured as a function of the proton energy in the range of 6 - 40 MeV by using a stacked-foil activation technique combined with high-purity germanium gamma-ray spectroscopy at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The present results are in good agreement with the earlier reported experimental data and the theoretical calculation based on the TALYS code. The thick target integral yield was also deduced from the measured excitation function and stopping power of natW over the energy range from threshold up to 40 MeV.

Measurement of Neutron Total Cross Section of Ag and Sm at Pohang Neutron Facility

The neutron total cross section of natural Ag and Sm has been measured in the energy region from 0.1 eV to 100 eV by the neutron time-of-flight method at Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled Ta target with a water moderator, and an 11 m long time-of-flight path. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm has been used as a neutron detector and metallic plates of Ag and Sm samples have been used for the neutron transmission measurement. The background level has been deterrnined by using notch-filters of Co, In, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and that from neutron capture, we have employed a neutron-gamma separation system based on their different pulse shapes. The present measurements are in general agreement with the previous ones and the evaluated data in ENDF/B-VI. The resonance parameters of Ag isotopes (107Ag and 109Ag) have been extracted from the transmission data by using the SAMMY code.

Measurement of keV-neutron capture cross-sections for 164Dy

Abstract The neutron capture cross-sections of 164 Dy were measured in the neutron energy region of 10 to 90xa0keV using the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology. Pulsed keV neutrons were produced from the 7 Li(p,n) 7 Be reaction by bombarding a lithium target with the 1.5-ns bunched proton beam from the Pelletron accelerator. The incident neutron spectrum on a capture sample was measured by means of a TOF method with a 6 Li-glass detector. Capture γ-rays were detected with a large anti-Compton NaI(Tl) spectrometer, employing a TOF method. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross-sections were obtained by using the standard capture cross-sections of 197 Au. The present results were compared with the previous measurements and the evaluated values of ENDF/B-VI.

Measurement of the Proton-induced Reaction Cross-sections of natZr(p,xn)86,87m,87(m+g),88Y up to 40 MeV

We measured the production cross-sections of 86,87m,87(m+g),88Y radioisotopes for proton-induced reactions on natural zirconium by using a stacked-foil activation technique in the energy range of 4-40 MeV at the MC50 cyclotron of the Korean Institute of Radiological and Medical Sciences. The activation method and the stacked-foil technique using the high-resolution HPGe gamma spectrometry were applied to determine the production cross-sections. The beam current was determined by the monitor reactions natCu(p,x)62Zn and 27Al(p,x)22,24Na. This work reports new data for the above reactions. The results were also compared with ALICE-IPPE model calculations compiled in MENDL-2P file. This experiment is in partial agreement with model calculations. The optimum energy range for the production of 86Y is 40 – 30 MeV The highest yield of 86Y amounts to 33.37 MBq/μAh over this energy range and the levels of the 87Y, 87mY and 88Y impurities to 2.3, 26.55 and 0.33 %, respectively at EOB. The natZr(p,x) process may be a suitable route for the production of the medically important radioisotope 86Y.

Measurement of Neutron Capture Cross Section of 162Dy Between 0.003 eV and 10 keV using Total Energy Absorption Detector

The neutron capture cross section of 162Dy has been measured in the energy region from 0.003 eV to 10 keV by using the neutron time-of-flight (TOF) method with a 46 MeV electron linear accelerator (linac) at the Research Reactor Institute, Kyoto University (KURRI). To obtain the absolute capture cross section, an assembly of twelve pieces of Bi4Ge3O12 (BGO) scintillators (each size: 5 cm x 5 cm, 7.5 cm long) was placed at a distance of 12.7±0.02 m from the neutron source and was employed as a total energy absorption detector for the prompt capture gamma-ray measurement. The enriched sample of 162Dy (156Dy : < 0.01 %, , 58Dy : < 0.01 %, 160Dy : 0.08 %, 161Dy : 1.24 %, 162Dy : 96.17 %, 163Dy : 1.79 %, 164Dy : 0.72 %) has a form of metallic plate (15 mm in diameter and 0.225 mm in thickness). A natural boron sample (18 mm x 18 mm, 1.10 g/cm2) was employed to monitor the neutron flux and spectrum of the TOF beam using the standard reference cross section of the 10B(n, α) reaction. The 162Dy or 10B capture sample was set at the center of the through hole in the BGO assembly. The current measurement has been carried out with uncertainties of 2.9 to 59.8 % in the relevant energy region. The experimental data measured by Danelyan et al. are in good agreement with the current measurement from 0.02 eV to 1 eV. The data by Kononov et al. are close to this measurement, although one can observe the tendency that the measurement is a little higher than those by Bokhovko et al. above several tens of keV. The evaluated data in ENDF/B-VI are in general agreement with the current measurement. The measurement has supplied the first data that has not been measured before in the energy range of 1 eV to 0.2 keV.

New type double mode SAW resonator filters on 64/spl deg/ Y-X LiNbO/sub 3/

The double mode filters have the serious shortcoming that out-of-band rejection above the passband is quite poor. Hence a new structure of double mode SAW resonator filters is designed with the COM (Coupling Of Modes) theory with better out-of-band rejection characteristics while keeping all the beauties of the conventional double mode SAW filters. The second goal of the design is to reduce the planar size of the structure so that mass productivity of low frequency devices can be improved. Based on the conventional double mode filter structure, several IDTs and reflector gratings are added to or subtracted from it. As results of the investigation, several new double mode SAW resonator filter structures are developed. For the design, the effect of many design factors are investigated and the optimum values are determined. The new structure shows 10 dB more out-of-band rejection than the conventional type with 25% smaller device size. Good agreement is demonstrated between the analytical results and experimental results for an illustrative 325 MHz four pole resonator filter on 64/spl deg/ Y-X LiNbO/sub 3/.