Nuclear Physics - Quick Review for Graduate students

1) "Thorium" has highest half life period and "Polonium" has shortest half life period.

2) Elements lying beyond 92U238 in periodic table are called "Transuranic" elements. 

3) Effective Multiplication Factor Ke = P/(A+L); 'P' is Production of Neutrons; 'A' is Rate of absorption of Neutrons; 'L' is Rate of Leakage of neutrons.

Ke = 1   -----------------------chain reaction is "Critical"  

Ke > 1   -----------------------chain reaction is "Super-Critical"  

Ke < 1   -----------------------chain reaction is "Sub-Critical"  

Ke =NF/(A+L) as P=NF; F is rate at which Fission occur; N is average number of Neutrons emitted per Fission

Control Rods are used to keep Ke = 1

4) Slow Neutrons (Thermalized) are efficient in causing Nuclear Reaction.

5) Atoms having same 'Z' and 'A' but differ from one another in their Nuclear energy states and exhibit differences in internal structure. These Nuclei are distinguished by their different life times. Such Nuclei are called "Isomers".

6) Nuclei having same 'A' but with Proton & Neutron number interchanged  (i.e. No. of Protons in one is equal to No. of Neutrons in other) re called "Mirror nuclei". For instance, 4Be7 (Z=4 and N=3), 3Li7(Z=3 & N=4).

7) Law governing successive disintegration deals with quantity of daughter nuclei present at any instant. 

8) Formation of daughter element depends on decay constant of parent.

9) Decay of daughter element depends on decay constant of itself.

10) Condition for "Secular Equilibrium" is N₁ƛ₁ = N₂ƛ₂ ; this occurs when element-1 is long lived.

11) Condition for "Transient Equilibrium" is N₂/N₁ = ƛ₁/(ƛ₂ - ƛ₁); this occurs when element-2 has same half life as that of parent element-1 and also ƛ₁ < ƛ₂.

12) Let ‘A₀’ be the activity at time of death . Suppose this is reduced to ‘A’ after ‘t’ years. Then    
       t = 3.32 T₁/₂ log₁₀(A₀/A); T₁/₂ is 5568 yrs.

13) Age of rocks may be estimated with comparing quantities of various isotopes of Lead existing in sample.

14)  In “ GM Region",  ionization current is independent of initial ionization.

15)  35 eV is required for producing an ion pair.

14)  Proportional region is most suitable for proportional counters in which number of  pulses increases almost linearly with voltage.

15) Plateau region is most suitable for “ GM counter “ in which number of impulses remain constant. This region is function of Voltage , Resistance, nature of gas.

16) “quenching agent " should have “ Low Ionization Potential".

17)  “ Scintillation" counter depends on principle of “ fluorescence”.

18)  “ Solid state detector " depends on following principle : incoming particles into depletion region must lose all their Kinetic Energy.

19) Non integrating ionization chamber - a pulse type; Integrating Ion chamber works in  current mode.

20) "GM counter" cannot be used to detect ɑ- particles.

21)  “Cloud chamber “ cannot be used to detect ‘𝛾 ‘ rays.

22)  By counting drops in cloud track , specific ionization can be determined.

23)  Particle disintegration process ---- outgoing particle is material particle

24) Simple capture process -- outgoing particles are -γ -rays.

25) Particle disintegration process is more probable than simple capture process.

26) Nuclear Reaction Energy (Q)

Q= (M₀+M₁) - (M₂+M₃)

Q = ( E₂+E₃) - E₁

'M₀' is mass of target nucleus (A)

'M₁E₁' is Mass and Energy of projectile(B)
'M₂E₂' is Mass and Energy of product nucleus (P)
'M₃E₃' is Mass and Energy of outgoing particle(O)

If (M₀+M₁) > (M₂+M₃), Q= +VE ;  Exothermic or Exoergic; ex:Li(P,𝛼)He⁴
If (M₀+M₁) > (M₂+M₃) , Q= -VE ;  Endothermic or Endoergic; ex: ₇N¹⁴(𝛼,P)₂He⁴
If (M₀+M₁) = (M₂+M₃), Q= 0 ;  Elastic Collision

27) Threshold energy(Eth) is minimum kinetic energy to initiate endoergic reaction.

Eth = [1+(M₁/M₀)]*Q ;  M₁ is mass of incident particle & M₀ is mass of target particle.

28)  When a parent Nucleus goes from its ground state to ground state of daughter nucleus, it emits an 𝛼-particle of maximum energy.

29) 𝛼-particle is preformed inside parent Nucleus.

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