Lecture 6 - Fundamentals of data collection

Question 1

Typical crystal sizes for X-ray

Answer 1

0.020 - 0.300 mm

Question 2

X-rays emanating from the anode pass through entrance slits and are diffracted according to wavelength at the

Answer 2

monochromator crystal

Question 3

A collimator in front of the crystal

Answer 3

limits the X-rays to a narrowly focused parallel bundle of suitable diameter

Question 4

A radio frequency generator in a synchrotron

Answer 4

compensates energy losses of the circling electrons and keeps them at constant energy

Question 5

Bending magnets and insertion devices in a synchrotron

Answer 5

produce a tangential beam of white (polychromatic) X-rays

Question 6

Polychromatic X-rays are monochromated to a narrow band within the

Answer 6

beam line optics

Question 7

Phosphor image plates readout time

Answer 7

3-5 minutes

Question 8

Charge-coupled device readout time

Answer 8

~3 seconds

Question 9

Silicon pixel detector readout time

Answer 9

real-time readout

Question 10

X-ray signals are converted to an electrical signal by the

Answer 10

photoelectric effect in silicon

Question 11

A short detector distance is good for collecting

Answer 11

high angle diffraction

Question 12

A short detector distance runs the danger of having

Answer 12

overlapping spots on the detector

Question 13

Short detector distances are practical when the unit cell is

Answer 13

small (<100 Angstroms)

Question 14

A long detector distance is good for

Answer 14

increasing the distance between spots on the detector

Question 15

A long detector distance is limited to

Answer 15

low angle diffraction

Question 16

A long detector distance is necessary when the unit cell is

Answer 16

large (>100 Angstroms)