[고려대학교 보건환경융합과학부 방사선안전분석] Final Report

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[고려대학교 보건환경융합과학부 방사선안전분석] Final Report
수업내용, 실험결과 및 여러 자료를 바탕으로 작성한 레포트입니다.
한 학기 방사선안전분석 14개의 레포트 모두 유일하게 감점 단 1점도 없이 만점으로 A+를 받은 레포트입니다.

목차

1. What is the element (atom) of body emitting radiation? (Lab 1)
2. Quenching Gas (Lab 1)
3. Plot a GM operation curve (Counts vs. High voltage) (Lab 1)
4. Conditions from Binomial distribution -> Poisson distribution Poisson distribution -> Gaussian (Lab 2)
5. Which distribution is easiest and hardest to calculate? (Binomial vs. Poisson vs. Gaussian) (Lab 2)
6. Write the sources of ionizing background radiation. (more than 2) (Lab 3)
7. Write the sources of non-ionizing background radiation. (more than 2) (Lab 3)
8. Plot the signal of GM tube with dead, resolving and recovery time with Vth. (Threshold voltage) (Lab 4)
9. Explain two-source-method to calculate resolving time. (Lab 4)
10. If the measured count is 1000 cps and resolving time is 500 sec, what will be the corrected counts? (Lab 4)
11. If you measure counts using GM tube, what kinds of corrections should be done to measure the efficiency of the GM tube? (Lab5)
12. Is the efficiency you calculated for each isotope valid only for that isotope? (Lab5)
13. If there was 5 minutes difference between experiment A and B (with same isotope and GM tube), the results (efficiencies) will be different or not in general? Why? (Lab5)
14. What are the shelf ratios? (Lab6)
15. If the beta source is changed with alpha source and gamma source, the shelf ratios will be changed or not? And Why? (Lab6)
16. What is the relationship between backscattering and atomic number (Z) of supporting material? (Lab 7)
17. What is the relationship between backscattering and thickness of supporting material? (Lab 7)
18. Normally when we thick of thickness, we thick of linear thickness that can be measured in a linear unit such as inches and centimeters. However, in nuclear and particle physics, thickness refers to area thickness. This is the thickness of the absorbers in mg/cm2. Why we should use mg/cm2 instead of cm in radiation application? (Lab 7)
19. When the source to detector distance was 10 cm, the counts were 100. If the source to detector distance is 5 cm, how any counts would it be? (Lab8)
20. Explain the difference between Helium and alpha particle? (Lab9)
21. Define mean, extrapolated and maximum range of alpha particle and draw the graph (Counts(%) vs. Range of alpha particle) – 2 point (Lab9)
22. Draw the graph (Energy vs. Range of alpha particle) (Lab9)
23. Define beta decay. (Lab10)
24. Why the straggling of beta decay is longer than that of alpha decay? (Lab10)
25. Why is the beta energy continuous? (Lab11)
26. What are the same and different properties between visible light and gamma ray? (Lab12)
27. Derive relationship between half-life and decay constant. (Lab13)

본문내용

4. Conditions from Binomial distribution -> Poisson distribution
Poisson distribution -> Gaussian (Lab 2)

Poisson distribution은 시행 횟수는 아주 많으면서 성공 확률은 아주 낮은 경우 사용되는 확률 분포이며, N이 충분히 크고 p가 충분히 작아서 Np가 적당할 때 binomial distribution의 값을 근사적으로 구할 수 있다. Binomial distribution에서 Np=λ를 유지하면서 N→∞일 때, 그 분포는 Poisson distribution에 수렴한다.
λt≪1,N≫1 and Np≪N^(1/2)일 때 Binomial distribution은 근사식을 이용해 Poisson distribution으로 쉽게 바꿀 수 있다.

Poisson distribution에서 n ̅=Np≫1을 만족하면 Gaussian distribution을 유도할 수 있는데, Gaussian distribution의 기댓값과 분산이 Poisson distribution의 n ̅과 같다는 것을 이용한다. Poisson distribution의 확률 질량 함수와 Gaussian distribution의 확률 밀도 함수가 서로 유사하다는 사실을 이용하여 Poisson distribution을 Gaussian distribution으로 근사할 수 있다. 이를 Poisson approximation이라고 한다.

5. Which distribution is easiest and hardest to calculate?
(Binomial vs. Poisson vs. Gaussian) (Lab 2)

Binomial distribution은 N번의 독립 베르누이 시행(한 번의 시행에서 결과가 O or X 로 나오는 시행)에서 성공 확률이 p일 때 확률 분포이다. N번의 시행 중 n개가 성공일 확률 W(n)은 다음과 같다.

참고 자료

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