The first experiment of a THz gyrotron with a pulse magnet

A THz gyrotron with a pulse magnet has been designed, constructed and operated in FIR FU. It is developed as one of high frequency gyrotrons included in Gyrotron FU Series. The gyrotron has already achieved the first experimental result for high frequency operations whose radiation frequency exceeds 1 THz. In this paper, the design detail and the operation test results for sub-terahertz to terahertz range are described. The second harmonic operation is confirmed experimentally at the expected frequency of 1.005 THz due to TE_6,_11 cavity mode at the magnetic field intensity of 19.0 T

STRUKTUR KRISTAL DAN SIFAT KEMAGNETAN NANOPARTIKEL CoZnFe2O4/PEG-4000)

Nanopartikel CoZnFe2O4 dengan struktur mixed spinel yang dienkapsulasi dengan PEG-4000 telah berhasil disintesis menggunakan metode kopresipitasi. Hasil analisis X-Ray diffraction (XRD) menunjukkan nanopartikel CoZnFe2O4 mempunyai karakteristik struktur spinel ferit dengan ukuran kristalit sebesar 14,4 ± 0,2 nm. Setelah dienkaspulasi dengan PEG-4000 ukuran kristalit sedikit menurun menjadi 9,7 ± 0,2 nm. Hasil analisis Fourier Transform Infrared (FTIR) untuk CoZnFe2O4 menunjukkan puncak serapan pada bilangan gelombang sekitar 401-563 cm-1 yang merupakan ikatan vibrasi M-O. Setelah dienkapsulasi dengan dengan PEG-4000 muncul vibrasi baru khas PEG yaitu C-O (1064 cm-1). Pada saat dienkapsulasi, ikatan M-O masih tetap muncul yang menandakan keberadaan nanopartikel CoZnFe2O4. Hasil Transmission Electron Microscopy (TEM) menunjukkan bahwa nanopartikel tampak mengalami aglomerasi. Setelah dienkapsulasi dengan PEG-4000 aglomerasi menjadi berkurang dan nanopartikel menjadi lebih terdispersi. Hasil analisis Vibrating Sample Magnetometer (VSM) menunjukkan nilai koersivitas CoZnFe2O4 adalah 251,9 Oe. Nilai koersivitas menurun menjadi 49,9 Oe setelah dienkapsulasi dengan PEG-4000. Hal ini disebabkan karena perubahan ukuran kristalit. Magnetisasi saturasi nanopartikel CoZnFe2O4 sebelum dienkapsulasi adalah 29,0 emu/g dan menurun setelah dienkapsulasi dengan PEG-4000 menjadi 19,7 emu/g. Hal ini disebabkan karena PEG bersifat paramagnetik dan nonmagnetik

Sintesis Polianilin yang Diperkaya γ-Fe2o3 dari Pasir Besi Lokal Sulawesi Tenggara untuk Aplikasi

This research is aimed to develop the radar absorbing material based on polyaniline enriched by γ-Fe2O3 synthetized from the sandstone. γ-Fe2O3 is, then, derived from calcination process of Fe3O4 powder at the temperature of 400-600oC. Fe3O4 powder itself is extracted from the local sandstone of South East Sulawesi area by using the co-precitipation method with both HCl and NH4OH act as the solvent and precitipation agent, respectively. The polyaniline is synthetized from its monomer, aniline, where both HCl and NH4OH are also used as a dopant and an oxydator agent, respectively. Effect of reaction pH on the crystal size of Fe3O4 is also investigated. The XRD spectrum shows that a rather high purity of Fe3O4 in nano size is being achieved at the pH value of 8 and 9. However, at a rather low pH value (6.5 and 7.5), the additional weak peaks in XRD spectrum shows the existence other metal compounds impurity. The crystal sizes is approximately ~8.01 and 11.07 nm for pH value of 8 and 9. The VSM measurement result shows that the saturated magnetization value of Fe3O4 is 24.45 emu/g. The Fe3O4 is calcined at temperature of 500oC for 3 hours to get γ-Fe2O3. Finally, the polyaniline-γ-Fe2O3 composites were synthetized using an insitu polymerization method where the weight contents of γ-Fe2O3 are 5, 10, 15, and 20 percent. Those materials will be useful as a prospective application in radar absorbing materials technology at frequency ranges of 9-17 GHz

Subterahertz gyrotron developments for collective Thomson scattering in LHD

Collective Thomson scattering (CTS) is expected to provide the spatially resolved velocity distribution functions of not only thermal and tail ions but also alpha particles resulting from fusion reactions. CTS using gyrotrons with frequency higher than the conventional ones used for plasma heating would have advantages to alleviate refraction, cutoff effects, and background electron cyclotron emission noise. Therefore, a high-power pulse gyrotron operating at approximately 400 GHz is being developed for CTS in Large Helical Device (LHD). A single-mode oscillation with a frequency greater than 400 GHz, applying the second-harmonic resonance, was successfully demonstrated in the first stage. At the same time, concrete feasibility study based on ray tracing, scattering spectra, and electron cyclotron emission calculations has been conducted

Mode Selection for a Terahertz Gyrotron Based On a Pulse Magnet System

The TE6,11 mode at 1007.68 GHz has been selected as a candidate for the second harmonic operation of a terahertz gyrotron. The predicted efficiency is 8.6 percent for the output power 0.38 kW. Time-dependent, multi-mode calculations have been carried out to investigate stability of a single-mode operation at second harmonic. It has been found that the second harmonic operation in the TE6,11 mode is possible with the beam current 0.111 A and the magnetic field 19.282T