نوع مقاله : مقاله پژوهشی

نویسندگان

پژوهشکده پلاسما و گداخت هسته‌ای، پژوهشگاه علوم و فنون هسته‌ای، سازمان انرژی اتمی، صندوق پستی: 51113-14399، تهران- ایران

10.24200/nst.2022.1450

چکیده

در این مقاله، مطالعه شبیه‌سازی گرمایش کیاتیکی الکترون‌ها، طی برهم‌کنش پالس لیزر با اتم‌های هلیم و ناشی از تابش‌های رامان رو به عقب، با استفاده از کد شبیه‌سازیذره‌ای، انجام شده است. برای این منظور، تحولات پالس لیزر خود سازگار از طریق تبدیل فوریه فضای- زمان پتانسیل برداری عرضی، در زمان‌های مختلف انتشار بررسی و نشان داده شده است که از آن‌جا که یونش در انتشار تابش رامان رو به عقب تأثیر دارد، به طور محسوس، در آستانه گرمایش کیاتیکی الکترون‌ها نیز نقش دارد. با توجه به نتایج به‌دست آمده، مشخص شده است که در پالس لیزر با زمان خیزش بلند، (در این‌جا fs 100)، در زمان‌های اولیه، تابش‌های رامان رو به عقب، به‌وسیله نویز اولیه‌ قوی‌تر آغاز می‌شوند. بنابراین، با در نظر گرفتن یونش، شرط لازم برای آستانه آشوب زودتر حاصل شده که به نوبه خود باعث می‌شود تا گرمایش کیاتیکی الکترون‌ها نیز، در مقایسه با حالتی که پالس لیزر در پلاسمای پیش فرض منتشر می‌شود سریع‌تر شروع شود. در نتیجه، در توافق با ماهیت آشوب، الکترون‌ها از طریق سازوکار کیاتیکی در پلاسمای حاصل از یونش میدانی انرژی بیش‌تری به دست می‌آورند.

کلیدواژه‌ها

عنوان مقاله [English]

Investigation of the Raman backward radiation evolutions leading to chaos in the interaction of intense laser pulses with Helium atoms

نویسندگان [English]

  • Z. Dehghani
  • E. Khalilzadeh
  • A. Chakhmachi

Plasma and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 14399-51113, Tehran, Iran

چکیده [English]

This paper investigates the stochastic heating of electrons caused by Raman backscatter radiations during the interaction of a laser pulse with helium atoms by means of a parallel particle-in-cell (PIC) code. At different propagation times, the self-consistent laser pulse changes are investigated via the space-time Fourier transform of the transverse vector potential. It is demonstrated that, since ionization has a striking influence on the emission of Raman backscattered radiation, it also plays an important role in the threshold of electron stochastic heating. As demonstrated by the experiments, the Raman backscattered radiations are initiated by a strong initial noise when a laser pulse has a long rise time, 100 fs. Hence, the fundamental condition for the chaos threshold is satisfied sooner by examining ionization effects. In this manner, stochastic heating of the electrons is initiated more rapidly than if the laser pulse were emitted in the preplasma. Accordingly, in concurrence with the idea of chaos, the electrons acquire more energy via the stochastic mechanism in the field-ionized plasma.

کلیدواژه‌ها [English]

  • Raman backward radiation
  • chaos
  • PIC simulation code
  • intense laser pulse
  • Helium atom
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