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A study of frustrated system in 2 dimensional triangular lattice antiferromagnet using the Ising model Noor Rika Safitri; Aini Rahmatun Ummi Fadlilah; Denny Darmawan; Yosi Aprian Sari
Jurnal Sains Dasar Vol 2, No 2 (2013): October 2013
Publisher : Faculty of Mathematics and Natural Science, Universitas Negeri Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21831/jsd.v2i2.3294

Abstract

Abstract This research was aimed to simulate the ground state and magnetization of antiferromagnet under the influence of temperature and competing interaction. The effect of competing interaction to phase transition was also investigated. The competition occurred between the nearest neighbour interaction and the next nearest neighbour interaction in the triangular lattice. The simulation was done using the 2 dimensions Ising model with Monte Carlo method combined with Metropolis algorithm. The results showed that the ground state energy increased significantly at the critical temperature (Neel’s temperature). When the competing interaction increased, the ground state energy of the lowest temperature decreased. Based on the magnetization, due to the increase of the competing interactions, the phase transitionfrom antiferromagnet to paramagnet occurred at a higher Neel’s temperature.   Key words: antiferromagnet, Ising model, competing interaction, Neel’s temperature
PEMODELAN BNCT SHIELDING BERBAHAN PARAFIN DAN ALUMINIUM UNTUK FASILITAS MENGGUNAKAN SIMULATOR MCNP A CONCEPTUAL SHIELDING DESIGN USING PARAFFIN AND ALUMINIUM FOR BNCT FACILITY BY MCNP SIMULATOR Afifah Hana Tsurayya; Yosi Aprian Sari; Gede Sutresna Wijaya
Jurnal Ilmu Fisika dan Terapannya (JIFTA) Vol 6, No 5 (2017): Jurnal Fisika
Publisher : Prodi Fisika, Departemen Pendidikan Fisika

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Abstract

AbstrakTelah dilakukan penelitian yang bertujuan untuk mengetahui laju dosis radiasi setelah melewati shielding berbahan parafin dan aluminium serta mengetahui material shielding yang tepat untuk keselamatan pekerja radiasi. Penelitian ini menggunakan simulator MCNP untuk memodelkan sumber neutron BNCT dan shieldingDesain shielding harus dapat menahan radiasi hingga batas laju dosis maksimal sebesar 10,42 µSv/jam dengan asumsi nilai tersebut merupakan batasan yang paling konservatif, yakni dengan lama waktu pekerja 1920 jam dalam satu tahun. Desain awal menghasilkan laju dosis yang masih di atas batas maksimal, maka dari itu dilakukan optimasi dengan menambahkan timbal pada bagian terluar shielding. Hasil yang diperoleh setelah optimasi adalah laju dosis menurun setelah diberi lapisan timbal dengan ketebalan tertentu. Beberapa lokasi yang masih di atas standar diatasi dengan aspek proteksi radiasi yang lain, yaitu jarak dan waktu. Parafin diberi aluminium sebagai casing yang bertujuan untuk memperkuat struktur shielding, dan timbal ditambahkan untuk menyerap radiasi gamma. Kata kunci: BNCT, Shielding, Parafin, Aluminium, MCNPAbstract   The research was aimed to measure the radiation dose rate over the shielding which was made of paraffin and aluminium and to know the right shielding material for safety of radiation workers. The examination used MCNP (Monte Carlo N-Particle) simulator to model the BNCT neutron source and the shielding. The shielding should reduce the radiation to less than the dose limit of 10.42 µSv/hour, which is assumed to be the most conservative limit, i.e. whileduration of workers was 1920 hours. The first design resulted the radiation dose rate which was still above the limit. Therefore, optimization was done by adding the lead on the outer of the shielding. After optimization by adding the leads with certain layer, the radiation dose rate were decreasing. Some locations over the limit could be overcome by the other radiation protection aspect, i.e. distance and time. The paraffin blocks were covered by aluminium to keep the shielding structure, then the lead was used to absorb the gamma rays. Keywords: BNCT, Shieling, Paraffin, Aluminium, MCNP