بررسي موج صوتي الكتروني در برهم كنش هاي پلاسما - ليزر

Investigation of electron acoustic wave in laser-plasma interactions

برهم كنش هاي امواج الكترو مغناطيسي با پلاسماي چگال (-3n ≈1020m) و فوق چگال(-3n ≈1026m) از جنبه هاي مختلف در سالهاي اخير مورد توجه قرار گرفته است. ميرايي اين امواج در پلاسما منجر به انتقال انرژي مي گردد. امواج راديويي با طول موج مناسب در ناحيه تشديد لايه هيبريد دوگانه الكترونهاي پلاسما را برانگيخته و امواجي توليد مي كنند كه در گرم كردن پلاسماهاي چگال در توكامك هاي كروي مؤثرند. امواج ليزري نيز با طول موجهايي از مرتبه چندصد نانومتر در پلاسماي فوق چگال مورد استفاده قرار مي گيرند. پديده هايي نظير پراكندگي از امواج صوتي الكتروني با فركانسي كمتر از فركانس 1 پلاسما w

Interaction between electromagnetic waves and dense or overdense plasmas have recently been noticed in many aspects. Damping of these waves could transfer energy. Radio waves with appropriate lengthwave stimulate electrons in upper hybrid resonance and produce waves which are effective for heating of dense plasma in spherical tokamaks. Laser waves with lengthwave order nano-meter have been used in overdense plasmas. Phenomenon like scattering of electron acoustic waves (EAW) with frequencies below the plasma frequency( < p) which reflect incident waves produce instabilities in plasma that play important role for success of fusion. Vlasov-Maxwell code was used to investigate the time evolution of the electron distribution function in a dense plasma(Mega Amper Spherical Tokamak) an overdense plasma (plasma at Inertial Confinement Fusion).we could calculate kλD quantity by determining Debye length and using different wavelengths.. In this research in addition to electron acoustic wave, the influence of polar magnetic field was investigated in Mega Amper Spherical Tokamak (MAST). In spite of the fact that external magnetic field at tokamaks with small aspect ratio, like MAST , don’t have so much impression for heating of the plasma, the result of the simulation indicates that polar magnetic field plays an important role for determining the total magnetic field and it can’t be ignored.