Atomistic Simulations of Ultra-Relativistic Particles Channeling and Radiation in Crystalline Structures

该项目旨在利用晶体波荡器(CU)在原子细节水平上对一种新型的高能(从~100keV到GeV范围，相应波长小于0.1埃)单色电磁辐射的光源(LS)进行高级计算探索。后者代表暴露在极端相对论(高达数百GeV)电子束或正电子束中的定向周期性弯曲晶体(PBC)。在高能光弹极限下(几十GeV及以上)，为了保持CUR对高辐射损失率的稳定性，可以采用一种更复杂的晶体结构-准PBC(QPBC)，其弯曲幅度和周期随侵彻距离而变化。该项目内的一项研究方案结合了晶体结构(理想和不完美)、极端相对论粒子动力学的理论、计算模型和设计，并考虑了与晶体原子的相互作用和辐射阻尼力的作用，以及带电射弹的光子发射过程。将开发一种用于多尺度建模的先进算法，该算法能够有效地模拟粒子通过宏观尺寸的真实晶体结构的传播，以及计算发射辐射的光谱角分布。多尺度全原子分子动力学模拟真实(不完美)晶体中粒子的传播和辐射，结合现代数值算法、先进的计算设备和计算技术，将使结果的预测能力达到可与实验相当甚至更高的精度水平。它将把计算建模变成可以替代(或替代)昂贵的实验室实验的仪器工具，从而降低实验和技术成本。在本项目过程中获得的理论和计算结果将与现有的实验数据进行比较，并将促进LSS的进一步技术发展。从长远来看，基于铜的伽马射线LS有可能产生波长数量级小于1埃的相干辐射(自由电子激光类型)，即在现有基于磁波荡器的LS无法达到的波长范围内。这样的LSS将在基础科学中有许多应用，包括核和固体物理以及生命科学。

The project aims at the advanced computational exploration, carried out at the atomistic level of details, of a novel Light Source (LS) of high energy (from ~100 keV up to GeV range, the corresponding wavelength less than 0.1 Angstrom) monochromatic electromagnetic radiation by means of a Crystalline Undulator (CU). The latter stands for an oriented periodically bent crystal (PBC) exposed to the beam of ultrarelativistic (up to hundreds of GeV) electrons or positrons. In the limit of highly energetic light projectiles (tens of GeV and higher), to maintain the stability of CUR against high rate of radiative losses, a more complex crystalline structure, - quasi PBC (qPBC), can be used in which bending amplitude and period are varied with the penetration distance. A research programme within the project combines theory, computational modeling and design of the crystalline structures (both ideal and imperfect), of the ultra-relativistic particles dynamics with account for the interaction with crystal atoms and for the action of the radiation damping force, and of the photon emission processes by charged projectiles. An advanced algorithm for multiscale modeling will be developed which enables efficient simulation of particles propagation through realistic crystalline structures of macroscopic sizes as well as calculation of the spectral-angular distribution of the emitted radiation. The multiscale all-atom MD simulations of the particle propagation and radiation in realistic (imperfect) crystals combined with modern numerical algorithms, advanced computational facilities and computing technologies will bring the predictive power of the results obtained up to the accuracy level comparable or even higher than achievable experimentally. It will turn computational modeling into the instrumental tool that could substitute (or become an alternative to) expensive laboratory experiments, and thus reduce the experimental and technological costs. Theoretical and computational results obtained in the course of this project will be compared with available experimental data and will stimulate further technological developments of the LSs. In a longer term, a CU-based gamma-ray LS has a potential to generate coherent radiation (the FEL type) with wavelengths orders of magnitudes less than 1 Angstrom, i.e. within the wavelength range that cannot be reached in existing LSs based on magnetic undulators. Such LSs will have many applications in the basic sciences including nuclear and solid-state physics and the life sciences.