Structure Of Matter

Question 1

A/Z X

Answer 1

X= Chemical symbol
A= mass number (protons + neutrons)
Z= atomic number (protons)

Question 2

isotope

Answer 2

Same # protons, different # neutrons

Question 3

Isotone

Answer 3

Same # neutrons, different # protons

Question 4

Isobar

Answer 4

Same # nucleons, different numbers of protons and neutrons
Same A
Different Z

Question 5

Isomer

Answer 5

Same # protons and neutrons, different nuclear energy states

Question 6

60Co gives rise to two gamma rays with ____ + ____ energies

Answer 6

1.17 MeV + 1.33 MeV

Question 7

Fermions (fundamental particles of matter)

Answer 7

Quarks (up, down, charm, strange, top, bottom)
-building blocks of neutrons, protons, and mesons
-proton = up + up + down
-neutron = up + down + down
Leptons (electron, electron neutrino, muon, muon neutrino, tau, tau neutrino)

Question 8

Free-Air Ionization Chamber

Answer 8

Absolute ion chamber for measuring exposure
Does not need calibration against another chamber or standard
Mainly used in laboratories to calibrate field instruments

Question 9

Thimble chambers

Answer 9

Beam data acquisition
Good spatial resolution and good signal-to-noise ratio
Wall should be air equivalent (graphite, Bakelite, plastics)
Temperature and pressure of air inside chamber must be at equilibrium with surrounding environment
Ionization in cavity produced by electrons crossing the cavity, not by photon interactions with air

Question 10

Farmer-Type Chambers

Answer 10

Most commonly used ion chambers for calibration of radiation therapy beams
Central electrode made of aluminum 1mm diameter
Stem effect: measurement of signal arising from ionization occurring in the chamber stem and cable

Question 11

Parallel-Plate Chamber

Answer 11

A) extrapolation chamber: variable volume, most accurate for measuring surface dose or buildup in a phantom

B) plane-parallel chamber: fixed volume, more practical so dosimeter of choice for measuring dose at the surface of a phantom or in the buildup region where the dose increases rapidly with depth

Question 12

Electrometers

Answer 12

Charge measuring device, most commonly used for ion chamber dosimetry is negative feedback operational amplifiers (OP-AMP).