Document Type : Research
Radiation application Department- Shahid Behehshti University
Radiation application Department- Shahid Beheshti University
Radiation Application Department. Shahid Beheshti University
Protecting the electronic components against the space radiation is an important basic requirement in satellites designing and constructing. One of the most common radiation shields for satellites is the addition of aluminum to achieve the desired radiation levels. However, in environments such as the GEO circuit where electrons are predominant, thick aluminum walls are not the most effective beam shields, as they are not able to attenuate the secondary X-rays caused by the electrons colliding with the shielding material. In general, materials with higher atomic numbers, such as tantalum, can severely attenuate X-rays, but when used as their own electron shield, they generate more secondary X-rays and impose more weight on the system. Today, polyethylene is a well-known material in the field of protection due to its high level of hydrogen, low density, ease of use and reasonable price, and is used as a benchmark for comparing the efficiency and effectiveness of other protection materials. There is a lighter method of protection called multilayer which works well in electronic environments as well as protecting against energetic protons. In designing and manufacturing radiation protection, proper selection of material and layer thickness is very important in reducing the dose and optimizing the weight. This requires experimental or computational work. Despite the accuracy of the experimental method, because practical experiments are costly, require a long time to run, and lack of access to space radiation testing laboratories using computational and simulation methods can be saved in time and budget.
In this work, the influence of different structures in space radiation shielding has been evaluated using MCNPX Monte Carlo code. Therefore, the induced dose was calculated in a silicon component. A graded-z shield consisting of aluminum, carbon and polyethylene was proposed. The operation of the graded-z shield in various dose ranges has been investigated compared with aluminum and polyethylene. Due to the importance of weight factor in the design of space systems, this factor is considered as one of the criteria for optimizing the thickness of the designed protection layers in comparison with aluminum and polyethylene protection for low-risk, medium and high-risk periods. The energy and flux of space rays for a mission in the GEO orbit that began in early 2021 and lasts for 5 years is provided by the Space Environment Information System (SPENVIS). The results showed that by replacing the conventional aluminum shield with the graded-z shield in specified dose ranges, weight reduction of 22/12% will be achieved in maximum case. For medium and low risk ranges, the use of multi-layer protection is more sensible in terms of weight than aluminum protection. In addition, if it is not necessary to use aluminum boxes to place electronic components inside the satellite, use polyethylene shield in terms of weight budget in high risk mode with 17.65%, medium risk 13.16% and low risk With 19.23% difference compared to aluminum protection is cost effective. Advantage of science in the field of manufacturing new materials such as aerogels and the placement of these lightweight materials, lighter shields can be designed.
keywords: Absorbed dose, Space radiation, MCNPX, Graded-z shield