slide1
Download
Skip this Video
Download Presentation
Properties of X-Rays

Loading in 2 Seconds...

play fullscreen
1 / 37

Properties of X-Rays - PowerPoint PPT Presentation


  • 71 Views
  • Uploaded on

Properties of X-Rays. Reference: “Elements of X-ray Diffraction”, 3nd Edition, B.D. Cullity , and S.R. Stock, Prentice Hall, NJ 2001. -- Chapter 1. http://en.wikipedia.org/wiki/X-ray http://chemistry.tutorvista.com/nuclear-chemistry/x-rays.html#. X-ray source: Tube source:

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Properties of X-Rays' - carney


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1
Properties of X-Rays

Reference:

“Elements of X-ray Diffraction”, 3nd Edition, B.D. Cullity,

and S.R. Stock, Prentice Hall, NJ 2001. -- Chapter 1

http://en.wikipedia.org/wiki/X-ray

http://chemistry.tutorvista.com/nuclear-chemistry/x-rays.html#

slide2
X-ray source:

Tube source:

http://en.wikipedia.org/wiki/X-ray_tube

http://www.youtube.com/watch?v=7Shle-b0W0E

http://www.youtube.com/watch?v=vruuVFH_Vro&feature=related

Rotation anode source

http://en.wikipedia.org/wiki/X-ray_tube

http://en.rigaku-mechatronics.com/technology/technology01.html

Synchrotron radiation source

http://www.nsrrc.org.tw/

Liquid metal jet X-ray source

http://www.excillum.com/Technology/metal-jet-technology.html

slide3
Vacuum, thermionic emission, high voltage, and a target

http://www.arpansa.gov.au/radiationprotection/basics/xrays.cfm

Braking radiation

Characteristic

X-ray

Auger electrons

slide4
Braking radiation:

Target

v2

v0

v1

V2 > V1

v

I

V2

V1

x

slide5
Characteristic X-ray

K

L

M

Auger Electrons

K

L

M

slide6
Nonradiative

transition

M

}

{

Auger

electron

Characteristics

X-Ray photon

L3

L3

L3

L2

L2

L2

Excitation

source

L1

L1

L1

K

K2

K1

Radiative

transition

K

K

k

K (L) shell excitation  K (L) radiation, etc.

slide7
K

K

I

Critical potential

 Characteristic X-ray

Cooling anode  Better heat dissipation  higher power

(applied potential  electron beam current (Typical tube source: 50 kV and 40 mA→2 kW

water

slide8
Rotation Anode Source

Rotating the anode  more cooling time for the part hit

by energetic electrons  higher power is allowed!

http://www.antonine-education.co.uk/Pages/Physics_GCSE/Unit_3/Triple_01_X-rays/triple_01.htm

Rotating anode and cooling  higher power

slide9
Target materials and associated constants

1 mil =0.001 inch = 0.025 mm

slide10
Synchrotron radiation source

Lorentz force:

http://www.nsrrc.org.tw/english/lightsource.aspx

Electromagnetic radiation produced by relativistic charged

particles accelerated in circular orbits.

slide11
Undulatorsultra-brilliant, single-wavelength radiation from the resulting interference patterns

http://www.nsrrc.org.tw/english/lightsource.aspx

slide13
Absorption:

Lambert-Beer law

Reference:

http://www.helsinki.fi/~serimaa/xray-luento/xray-absorption.html

I

I0

dx

: linear absorption coefficient

I0: X-ray intensity at x = 0

 = (/) ;  : density;

(/): mass absorption coefficient

slide14
Multicomponent system μ/ρ:

For a substance containing several elements

wi is the weight fraction of the element i

http://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

slide15
Fluorescence (longer wavelength)

I

I0

Scattering (elastic: same wavelength,

Compton scattering: different wavelength )

x

(/): true absorption; (m/): scattering

Small for Z >26

slide16
True absorption:

http://www.helsinki.fi/~serimaa/xray-luento/xray-absorption.html

For fluorescent, photoelectron is not necessary as long as the electrons at the ground state are excited to a higher energy level

slide17
Sharp discontinuities at K, LI, LII, LIII, M,… absorption edges!

http://www.helsinki.fi/~serimaa/xray-luento/xray-absorption.html

slide18
Use of absorption for filtering function

http://www.helsinki.fi/~serimaa/xray-luento/xray-absorption.html

slide19
X-Ray detectors:

Proportional Counters ()

  • Microchannel PlatesSemiconductor Detectors () Scintillators () PhosphorsNegative Electron Affinity Detectors (NEADs)Single Photon Calorimeters

http://imagine.gsfc.nasa.gov/docs/science/how_l2/xray_detectors.html

slide20
Important aspects of a detector:

(1) Losses

(2) Efficiency

(3) Energy resolution

Losses

v

Time

v

Time

v

Random loss

(Inevitable)

v

Serious loss

slide21
Random losses (always there)

Resolving time of the detector electronic: ts

the maximum rate without losses: 1/ts.

Losses  as rate .

Counting

loss

Detector 2

Use filters

Noise?

Quanta Detected /second

Detector 1

Quanta Absorbed /second

slide22
Efficiency:

fabs,w:

fabs,d: effective excitation ( signals)

flosses: counting losses

window

1

1-fabs,w

~ 1

slide23
Different detector: different wavelength range to detect!

Efficiency of a 10-cm-long gas ionization chamber as a function of energy, for different gases at normal pressure.

slide24
Energy Resolution:

For most of the detectors

Voltage produced  energy

of X-ray quanta.

Counting rate

W

V

Pulse amplitude

Resolution

R resolution 

slide25
Gas filled detector:

Proportional and Geiger counter

Wire anode

cathode

C

X-rays

R

electron-ion pairs produced:

E: X-ray energy; ei: effective ionization potential

ei for He, Ar, and Xe: 27.8, 26.4, and 20.8 eV; Using Cu

K radiation, Ar gas: n = 8040/26.4 = 304

slide26
Gain may be defines as

N: # of electrons reaching wire anode; n: # of electron

produced by X-ray quanta

slide27
Typical Gain ~ 104-105.

G = 104

Cu radiation on Ar gas filled proportional counter

304104 = 3.04106.

Typical F10-10 farad.

Small voltage  need further electronic amplification

Bias larger enough (~ several KV) avalanches (G saturated)

 “Geiger counter” (long deadtime)

slide28
Scintillation Counter detector:

http://www.bruker-axs.de/fileadmin/user_upload/xrfintro/sec1_6.html

slide30
Scintillator (usually Tldoped NaI)

UV

photoelectron

http://en.wikipedia.org/wiki/Scintillation_counter

Relatively high count rate detector (>100,000 cps is possible)

poor energy resolution

slide31
Semiconductor detector:

Excellent energy

resolution

Usually cooling

is required!

Reasonable count

rate

Find more on:

http://wwwmayr.informatik.tu-muenchen.de/konferenzen/Jass04/courses/4/Tobias%20Eggert/TalkIoffe.pdf

slide32
Si, Ge semiconductor detector (LN2 cooling required )!

Spectrometry application!

For spectrometry application without LN2 cooling

Si drift detector

http://144.206.159.178/ft/787/31793/552178.pdf

slide35
Safety Precautions

 Electric shock

 Radiation Hazard:

user’s responsibility (your own and others)

* Four main causes of accidents

(1) Poor equipment configuration, e.g. unused beam

ports not covered, interlock system is not engaged.

(2) Manipulation of equipment when energized, e.g.

adjustment of samples or alignment of optics when

x-ray beam is on.

(3) Equipment failure, e.g. shutter failure, warning

light failure.

(4) Inadequate training or violation of procedure

slide36
Failure to follow proper procedures has been the result of:

rushing to complete a job,

 fatigue

 illness,

personal problems,

lack of communication, or

 complacency

slide37
* Radiological Signs

* Everyone should participate the safety training course

offered by the University before actually doing X-ray

or other radiation related experiments.

ad