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Khan The Physics of Radiation Therapy > Chapter 1-2 > Flashcards

Chapter 1-2 Flashcards

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1
Q

Charge of electron

A

1.6x10-19C

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2
Q

Explain the chemical notation (X)

A

M is mass number (# of protons and neutrons) A is atomic number (# of protons) X is chemical symbol

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3
Q

Isotope

A

atom with same # protons but different # neutrons

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4
Q

Atomic Weight What are its units? What is the basis of the units? How is atomic mass different?

A

Mass of one atom Atomic mass unit 1/12th of Carbon Same thing

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5
Q

mass defect

A

difference between mass of constituent parts and mass of atom. stems from some mass converting into binding energy of particles in the atom

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6
Q

1eV in Joules

A

1.602x10-19 J in eV

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7
Q

Rest mass of an electron

A

0.511 MeV

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8
Q

what are the 1st and 3rd electron orbitals of an atom called?

A

1st - K 3rd - M

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9
Q

How many electrons in each of the first three shells of an atom?

A

1st - 2 (1s^2) 2nd - 8 (2s^2,2p^6) 3rd - 18 (3s^2,3p^6,3d^10)

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10
Q

How does binding energy vary with: 1) Z 2) orbital

A

1) increases with increasing Z 2) increases as orbital is closer to nucleus

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11
Q

What is the Strong Nuclear Force? At what scale is it important?

A

Force that holds the nucleus together. sub-nuclear (~10-15 m)

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12
Q

What does Co-60 emit? Where does the particle come from?

A

beta minus particle decay of a neutron into a proton, electron, and neutrino

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13
Q

What is the characteristic visible spectrum range of wavelengths?

A

400 to 700 nm

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14
Q

What is an alpha particle?

A

Helium nuclei

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15
Q

What isa beta minus particle

A

electron ejected from a nucleus

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16
Q

Define Activity What are the units? What is the relationship between Activity and number of radioactive atoms present

A

rate of desinitigration Bquerel = 1 disintegration per second A = -aN where a is the decay constant and N is the number of radioactive atoms

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17
Q

Define half-life What is the activity value after n half-lifes

A

time to reduce activity or number of radioactive atoms to half their start value 0.5^n

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18
Q

What is the mean or aveage lifetime of a radioactive source

A

time for a source with activity aN0 to produce No decays if the activity does not change with time TaN0=N0 so T = 1/a

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19
Q

What is specific activity of a radioactive material?

A

activity per unit mass

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20
Q

What are the three naturally occurring radioactive series? What to they start with? What to they end with?

A

Uranium Actinium Thorium U-238, U-235, Th-232 Pb-206, Pb-207, Pb-208

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21
Q

What is the condition on the parent and daughter nuclides for equilibrium to be acheived What does equilibrium mean in this context

A

half-life of parent is longer then the child ratio of daughter to parent activity is constant and the apparent decay rate of the child is governed by the half-life of the parent

22
Q

What is transient equilibrium in a parent-daughter decay?

A

When the parent has a slightly longer half-life than the daughter. after a long time period, activity is governed by the parent’s decay and the ratio of daughter to parent activity is a constant 1-(ad/ap)

23
Q

What is secular equilibrium in parent-daughter decay?

A

When the daughter has a constant activity because it is replenished at the same rate that it decays. This occurs when the parent half-life is much longer than the daughter.

24
Q

what is the usual energy range for an alpha particle? 5-

A

5-10MeV

25
Q

Write a generic equation for beta particle production. Describe the energy spectrum of beta particles

A

AZX -> A(z-1)X + Beta + Anti- Nutrino + energy Ranges from 0 to nuclear binding energy. Mean is approx. Emax/3

26
Q

What products may be produced by electron capture?

A

auger electrons and characteristic photons

27
Q

1amu in MeV

A

931 MeV

28
Q

What is stripping? How is it used in radiation therapy?

A

when a deuteron passes close to an atomic nucleus and the proton is stripped from the deuteron and combines with the nucleus leaving only the neutron. It is one source of high energy neutrons 2H1 + 9Be4 -> 105B +1n0

29
Q

What is the energy scale of thermal (slow) neutrons?

A

0.025 eV

30
Q

Describe an effective slow neutron detector and give the formula for any reaction that takes place in the detector.

A

Fill a chamber with BF3. 10 5B +1n0 -> 7Li3 + 4He2 the alpha particle emmitted can be measured by an ionization chamber

31
Q

What is the most common neutron capture process

A

1H1+ 1n1 -> 2H1 + gamma

32
Q

Define photodisintegration

A

Interaction of a high energy photon with an atomic nucleus–often leads to emission of one or more nucleons

33
Q

define nuclear fission

A

bombardment of nucleus with neutrons that results in a nuclear split, energy, and extra neutrons

34
Q

define nuclear fusion common equation

A

combination of low mass nuclei that produce energy and neutrons 2H 1+ 3H1 -> 4He2+ 1n0+ Q

35
Q

Units of cross-section for particle collisions

A

barns 10^-24cm^2

36
Q

define saturation activity

A

when activating a sample this is when the rate ofactivation equals the rate of decay

37
Q

1) Equation relating wavelength and frequency? 2) Equation for energy of electromagnetic wave?

A

c=w*f E=h*f

38
Q

Atomic Radius

A

roughly 10^-10 cm

39
Q

Emission type and energy for Co-60

A

1.17 and 1.33 MeV Gamma

40
Q

converstion between Bq and Ci

A

1Ci (curie) = 37.0 GBq

41
Q

Define: isotope, isotone, isomer isobar

A

Different # neutrons Different #protons, same # neutrons Different# protons, same # nucleons Same neucleus, different energy

42
Q

What deterimines of an atom spontaneously decays Write a general equation

A

Energy difference between parent and daugher NUCLEUS Q = m(zXA-ze-)c2 - m(z’A’X-ze-)

43
Q

What is the Q for beta and positron decay in terms of ATOMIC weights (NOT nuclear weights)

A

Beta:(zXA-ze-)-(z+1XA-(z+1)e–e-) Positron: (zXA-ze-)-(z-1XA-(z-1)e–e-)

44
Q

What is the Q for Alpha decay in terms of ATOMIC weights (NOT nuclear weights)

A

(zXA-ze-)-(z-2XA-4-(z-2)e–24X) where the alpha is neutral because the 2 extra electrons left over from the daughter are used to balance the He. If you had the mass of a +2 Helium ion you could use that and then further subtract the mass of the left over electrons.

45
Q

What is Half Life and Gamma energy of the Tc99 metastable state

A

6 hours and 140keV

46
Q

define flourescence yield

A

probability of characteristic photon vs Auger

47
Q

Flouresence favored by high or low Z?

A

High Z

48
Q

(Alpha,proton) reaction (Alpha,neutron) reaction

A

zX-A+2He4->z+1XA+3+1H1+Q zX-A+2He4->z+2XA+3+n+Q

49
Q

Products of proton bombardment deuteron bombardment

A

daughter and neutron or daughter and proton

50
Q

Medical ultrasound frequency Audible frequency

A

2-10MHz 15-20kHz

51
Q

What is the cutoff between using a transmission or reflection target?

A

~500keV

Khan The Physics of Radiation Therapy (4 decks)

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