CINEMA AND REPRESENTATION IN INTERNATIONAL RELATIONS: HOLLYWOOD CINEMA AND THE COLD WAR

Title:
Study on Theories and Simulations of High Brightness Gamma Ray Sources based on Laser Compton Scattering (LCS) and Linear Accelerator

Introduction& Previous Researches:
X-ray is an important type of a form of electromagnetic radiation with a wavelength ranging from 0.01 to 10 nm (equivalent to frequencies ranging from 3×10^16 Hz to 3×10^19 Hz). And it is also often called “Röntgen radiation” because Röntgen has been regarded as the main discoverer. X-ray has been one of the most ideal tools to observe microscopic world for human beings because of its strong penetrability, with which X-ray can simply penetrate substances and trigger diffraction phenomena. And thus, X-ray can be applied as an extremely sensitive probe for detecting internal microscopic information and components. Typical applications of X-ray include the following: X-ray crystallography , mammography , geoscience tomography and even security check at subway stations of huge metropolises like Beijing.
On the other hand, gamma rays with MeV-level energy are considered as the candidate to study elaborate structures like atomic nucleus and dynamic substance changes . High brightness gamma rays can be utilized in the following aspects: novel gamma knives in medical therapies, management of radioactive materials including disposal of nuclear wastes and recycling of nuclear fission materials, and generator for secondary ion sources. In addition, gamma ray beams are also used in studying astrophysical phenomena . Gamma rays and X-rays are both electromagnetic radiation and they often overlap in electromagnetism spectrum. And Laser Compton Scattering (LCS) sources are considered as a novel and ideal X/gamma ray source with adjustable energies .
Many scholars have done excellent work in this field and here are some of the representative works. Hayakawa et al . have studied neutrino-nucleus interactions with LCS gamma rays to illustrate the details of Supernova neutrino process. And the authors have proposed a method using (γ, n) reactions with linear polarized LCS gamma rays to measure the M1 strength and discussed experimental techniques using LCS beams. Ohgaki et al. have developed a nondestructive inspection system for checking nuclear materials . The authors have utilized a neutron/gamma ray combined inspection system. And the system is expected to inspect cargo containers costing less time and space. Similar studies have been also conducted in paper of Zen et al. . The authors have developed an LCS gamma ray source in the UVSOR-III storage ring and the device was expected to perform a series of basic researches on non-destructive 3D isotope imaging. And experiments were also conducted to verify the reliability of numerical simulations. In addition, Barty have reviewed the LCS gamma ray sources for nuclear materials detection and imaging. Potential applications like isotope specific nuclear materials management, element-specific medical radiography can be expected if high brightness LCS gamma ray source can be developed.

Objectives& Significance:
As what have been discussed in the previous part, we know that LCS sources of gamma rays have many prominent advantages and enormous application prospects. Thus, I would like to conduct the following researches under the guidance of Prof. Ohgaki: Firstly, theoretical studies and simulations of high brightness LCS-based gamma ray sources in linear accelerator. We shall focus on analyses of unstable factors in electron beams and laser beams, especially on energy dispersive analysis, emittance of electron beams and influences from limited bandwidth, divergence degree and non-linear effects of laser beams on energy spectrum. Then we shall analyze the influences from non-ideal factors on spectrum bandwidth. To sum up, it is necessary to optimize physical parameters like electron beam size, laser size and laser pulse length. Secondly, we shall optimize the design process of LCS source gamma ray on actual devices (For example, SXFEL deployed in Shanghai or other devices in Japan). To obtain the optimized parameters for high brightness gamma ray source, it is imperative to apply computational methods like Monte-Carlo simulations to achieve our research goals. Thirdly, I hope to apply our optimized gamma ray sources to practical situations like non-destructive testing of aircraft structure components.

Research Strategies& Expected Outcomes:
The research would consist of the following aspects.
1. Study on basic theories and principles of LCS and discussion on optimization of high brightness LCS sources. Generally, there are several important factors which effect the axial maximum brightness and should be taken into consideration when designing high brightness LCS gamma sources. Thus, in this part we should discuss: a) laser bandwidth and its influences on scattering light bandwidth; b) energy spread of electron beams and its effects on scattering spectrum; and c) influences of emittance on scattering spectrum.
2. Optimization of design parameters of LCS gamma ray source with Monte-Carlo simulations.
A. Enlightened by Wu et al. , the simulation process based on Monte-Carlo methods should include the following aspects: a) Initialization of laser and electron beams and sampling of electron beams in interaction regions; b) estimation on whether the scattering events have happened and calculate LCS probabilities based on local density of collision points in laser beams; c) after the occurrence of collision events, we should sample in the Compton scattering sections and estimate information on energies, position and exit direction of scattering photons; and d) simulation of photon transfer process and then obtain the important information on energy spectrum, angular distribution and brightness of gamma ray beams in experimental regions.
B. In addition, the following parameters should also be taken into consideration when simulating the generation of LCS gamma ray source: a) incidence angle of laser; b) energy spread, emittance of electron beams and the laser, electron focus during collision process and laser bandwidth; c) non-ideal factors during laser-electron scattering process like laser-electron time/position deviation, time jitter.
C. Optimization on axial maximum brightness. For linear accelerator, electron beams have properties of low emittance and high brightness. Thus, we should make effort in the following aspects: a) how to obtain high-density electron beams stream (that is, we want electron beams with small focus size and high beam charge); b) how to obtain laser with high energy density (it is equivalent to question that “how to obtain laser beams with small focus area and high pulse energy”); c) how to obtain electron beams with small divergence angle. In this part, we may have to utilize the simulation results in part B and compare the theoretical calculation results with experimental results.
D. If there is enough time, we should also study the similar issue with LCS gamma ray source based on storage rings.
3. Test of practical applications of home-made LCS source devices. In this part, we must choose a practical platform to achieve our goals. I would like to put our novel-designed device in actual situations like nuclear physics studies, disposal of nuclear wastes and astrophysics studies, to test the effectiveness of our devices.

 
References:

1. Here is a dissertation that inspired me to this topic, please use its bibliographies to find useful informations
but not to copy the ideas please:
https://etd.lib.metu.edu.tr/upload/12606291/index.pdf
2. This is a thesis to be submitted for admission, the university I am applying has provided me a sample
thesis, the topic has nothing to do with my theme, but please do refer to its format