By Sabina AliJun 14 2019An innovative technique has been developed by an international group of scientists, including researchers from Skolkovo Institute of Science and Technology (Skoltech), for producing powerful X- and gamma-ray radiation predicated on Nonlinear Compton Scattering.
The results of the study have been reported in the renowned journal, Physical Review Letters, and this breakthrough invention will soon receive an international patent.
The Compton Effect can be compared to playing tennis but in a strange manner. A photon and an electron play the roles of the ball and racket, respectively. When a photon gets reflected from the fast electron racket, it attains extra energy. Although, the speed limit prohibits a photon from flying even faster, it can easily alter its color, that is, wavelength. By leveraging this simple game, the wavelength of the photon coming from the visible range can be transformed into X-rays and gamma-rays.
Throughout the world, hard photon sources predicated on Inverse (linear) Compton Scattering are extensively utilized and they usually comprise of the laser system and the electron accelerator. Such sources offer a major benefit—they enable creating a narrow bandwidth radiation with the wavelength that can be easily tuned by changing the electrons’ energy.
Increasing the intensity of the laser system is the simplest way for increasing the number of the created gamma-ray and X-ray photons. To put this in simple terms, if the laser radiation is packed more compactly in space (assuming that the diffraction is small), the scattering events between electrons and laser photons will be more.
This happens to be a popular phenomenon, along with the fact that significant spectral broadening will occur if the laser radiation power in Compton Scattering is increased. This is because of the light pressure, which tends to slow down the electrons. That is, the tennis racket while reflecting a huge number of tiny tennis balls simultaneously is slowed down; therefore, less energy will be received by the reflected balls. Here, the issue is that intense laser radiation is not continuous, and instead emerges as pulses in time. Initially, the intensity of the robust laser pulses gradually grows and then progressively dies out. As a result, the light pressure is uneven and the slow-down of the electrons is also different at different moments of time resulting in varied energy of reflected photons.
The research team, which also includes Skoltech Professor Sergey Rykovanov, developed a novel technique for producing powerful mono-energetic gamma- and X-ray radiation predicated on Nonlinear Compton Scattering.
Such spectral line broadening is parasitic since we want to obtain a narrow bandwidth photon source with a well-defined wavelength. Together with Vasily Kharin from Research Institute in Moscow and Daniel Seipt from University of Michigan in USA we invented a very simple method to remove the parasitic Compton line broadening for intense laser pulses and significantly increase the number of generated X and gamma-ray photons. To do this one has to carefully tune the frequency of the laser pulse (in other words to chirp it) so that it corresponds to the laser pulse intensity at each moment of time. For optimal effect, we proposed to use two linearly and oppositely chirped laser pulses propagating with a certain delay to each other. In my opinion, the beauty of our work is in its simplicity. To be entirely honest, we were very surprised how simply and smoothly everything worked out.
Sergey Rykovanov, Associate Professor, Center for Computational and Data-Intensive Science and Engineering, Skolkovo Institute of Science and Technology
The latest breakthrough can considerably boost the brightness of both contemporary and future synchrotron sources for research in material science, nuclear physics, and medicine.
The researchers noted that part of the simulations was carried out on “Zhores”—Skoltech’s flagship supercomputer and named after the Nobel laureate Zhores Alferov.