This is not the document you are looking for? Use the search form below to find more!

Report home > Science

The X-ray Tube

0.00 (0 votes)
Document Description
The X-ray Tube. A power point report.
File Details
  • Added: March, 30th 2011
  • Reads: 574
  • Downloads: 1
  • File size: 495.07kb
  • Pages: 10
  • Tags: xray tube, tube housing, glass envelope, cathode, anode, filament, focusing cup
  • content preview
  • Name: simone
Embed Code:

Add New Comment

Related Documents


by: shinta, 10 pages

Sources of calcium are generally widespread and quite extensive. These sources are of limestone, dolomite, marl, chalk, and oyster shell. Cement plants account for nearly half the demand while ...

How to Become an X-Ray Technician

by: michael_b, 2 pages

The article ‘How to Become an X-Ray Technician’ highlights the educational pathways and credentials which enable you for a career as an X-Ray technician. It also talks about the roles and ...

Generating An X Ray Technician Salary Normally Requires Very Specific Task S

by: hisilat874, 1 pages

an x ray technician is required to do to create that income can further aid you within putting together a

X-Ray Data Booklet

by: frediano, 457 pages

For the first time since its original publication in 1985, the X-Ray Data Booklet has undergone a significant revision. Tabulated values and graphical plots have been revised and updated, and the ...

Materials Science X-Ray Analysis Laboratory

by: clara, 5 pages

The Department of Mechanical Engineering supports and houses the X-Ray Analysis Laboratory with two Philips x-ray diffractometers, a Materials Research Diffractometer and a Multi-Purpose ...

Chapter 7: Basics of X-ray Diffraction

by: alina, 25 pages

About 95% of all solid materials can be described as crystalline. When X-rays interact with a crystalline substance (Phase), one gets a diffraction pattern. In 1919 A.W.Hull gave a paper titled, ...

Demonstration of Pulsed X-ray Machine Radiography

by: jonny, 38 pages

The goal of this project was to demonstrate a radiography technology for inspection of pipe welds that does not require the use of isotopic sources. The technical approach to be followed included (1) ...

XRD-6000 Shimadzu X-ray Diffractometer Manual

by: chang, 24 pages

The XRD-6000, an X-ray diffractometer analyze crystalline states under normal atmospheric conditions. This method is non destructive. X-rays focused on a sample fixed on the axis of the spectrometer ...

Part VIII. Nomenclature system for X-ray spectroscopy ...

by: govert, 9 pages

This document is the eighth in a series on the nomenclature for spectrochemical analysis issued by IUPAC. Part IV is concerned with spectroscopy in the X-ray region and deals with the nomenclature, ...

X-ray and Cryogenic Facility

by: daisi, 2 pages

The X-ray and Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Ala., is a unique, world class optical, cryogenic and X-ray test facility — in fact, the world's largest X-ray ...

Content Preview
The X-ray Tube
Tube Housing
• Made of cast steel & is usually lead-lined
– Provides for absorption of most off-focus
• Purposes:
– Controls leakage & off-focus radiation
(discussed later)
– Isolates high
– Helps to cool
the tube
Glass Envelope
• Surrounds entire cathode & anode
assemblies except for the stator
– Made of several layers of Pyrex w/ varying
– Glass is fitted to the metal
of the anode & cathode
– Must be airtight to
maintain a good

Glass Envelope
• A target window is constructed in the glass
envelope to allow less scatter & attenuation
of the photons
– In most tubes - simply a thinner “cut” of glass
– In mammography - a special
metallic beryllium window
prevents attenuation of lower
energy photons
• The cathode is the negative end of the x-ray
– Made up of the filament(s) and a focusing cup.
• Most x-ray tubes have a dual filament
cathode assembly - also known as dual focus
– The two filaments sit parallel to each other in
the focusing cup & share a common ground
– Most filament coils
are 7-15mm long ,
1-2mm wide,
0.1-0.2mm thick

• Filaments must be able to:
– Boil off electrons (thermionic emission)
– Withstand great amounts of heat
• Filament materials
– Tungsten - most widely used material
• High boiling point (3,370° C)
• It is difficult to vaporize
– Rhenium (3,170° C)
– Molybdenum (2,620° C)
• Vaporization occurs over time
– When the particles vaporize (turn into a gaseous
form), they solidify on the glass of the x-ray
tube, called sun-burning or sun-tanning of tube.
• Reduce the x-ray output of the tube
• destroy the vacuum integrity of the tube, leads to
arcing and ultimately tube failure
• Thorium (a radioactive metallic element) is
added to the filament material to make the
tube last longer.
Focusing Cup
• The focusing cup helps control electron cloud
– The electrons repel each other & want to spread
out. The focusing cup forces the electrons to
form a small stream as they move toward the
target material
– Made of nickel
– Has a low
negative charge

Grid-Controlled Focusing Cups
Some x-ray procedures require exposures be
taken at quick intervals.
• Grid-controlled focusing cups have a
variable charge applied to the focusing cup
that acts as an exposure switch
– When the tube is activated, the charge increases
& decreases rapidly
– Short bursts of electrons
flowing to the target.
Grid-Controlled Focusing Cups
• May be found in:
– portable capacitor discharge units
– digital subtraction angiography
– digital radiography
– Cineradiography
The Anode is the part of the x-ray tube
where accelerated electrons move to after
kV is applied to the tube.
• Two types:
– Stationary anode (old type) - just a tungsten
button imbedded in copper bar.
– Rotating anode consists of a molybdenum
disk(target) rotated by an induction motor.

Rotating Anode Assembly
This is a diagram of a
rotating anode without &
with the tube.
Rotating Anode Stator and Rotor
Consists of two main parts:
• Stator
– Rests just outside of the glass tube
– Made up of a series of
electromagnets equally spaced
around the neck of the tube
• Designed to energize opposing pairs,
in sequence, so that they induce the
rotation of the rotor.
• Rotor
– Located within the glass tube
– Made up of copper bars & soft iron
around a molybdenum shaft
***Mutual Induction***
Rotating Anode Stator and Rotor
• When the rotor is rotating at the desired level,
the x-ray exposure may be completed.
• Most revolve at 3400 revolutions per minute
(rpm) minimum.
• By rotating the anode
we spread the
generated heat over a
larger surface area
allowing greater
technique loads.

Anode Target Characteristics
• Anode target - the point on the anode where the
electrons strike
• Tungsten – rhenium alloy is the most common
material and is plated onto the surface of the
molybdenum disk
• Tungsten has:
– High atomic number (74)
– High thermal conductivity level
– High melting point
• Rhenium added to increase thermal capacity and
tensile strength
The Line-Focus Principle
• Actual focal spot - the area of the target material
being bombarded by electrons from the filament.
• Effective focal spot - the imaginary geometric line
that can be drawn based on the actual focal spot
size vs. the angle of the anode.
• Best described by the angle of the anode
– the smaller the angle of the anode, the smaller the
effective focal spot size (any angle <450 results in the
effective FS being smaller than the actual FS)
– 120 target angle most common because it is the
minimum that will cover a 14x17 at 40”
The Line-Focus Principle cont.

The Anode Heel Effect
• Caused by the angle of the anode vs. the intensity
of the electrons striking it.
• X-rays exiting the target on the anode side have to
traverse the “heel” of the anode
– Photons directed toward the cathode end do not have
to travel through as much of the anode because of the
angle of the target so more make it out
– Those directed toward the anode end must travel
through more material so more are absorbed
– Results in the beam being of lower intensity on the
anode side.
The Anode Heel Effect
• As much as 20% more photons at the
cathode end of the tube & as little as 25%
fewer photons at the anode end of the tube.
• Most noticeable with:
– Small focal spot
– Short S.I.D.
– Large field
Production of Off-Focus Radiation
• Radiation produced from x-ray photons or
electrons that have reflected off of the anode
• These x-rays or electrons can strike a number of
things in the tube and produce scatter photons:
– Side of the focusing cup
– Tungsten particles from sun-burn
• Because they are not produced in the focal track
they are “off-focus” and while most are absorbed
by the housing, some make it out of the tube and
degrade the radiographic image.

Extending Tube Life
• Practical methods
• Tube rating charts
– Determines if a technique is safe
– Used to test overload protection circuits
• Calculating heat units and using cooling
Practical Methods
The life of the tube is under your control!
• Proper warming extends tube life
• Avoid repeated exposures close to tube load
• Do not hold the rotor switch unnecessarily
Listen to your equipment!
Tube rating charts
• Rules for use
– Select the correct chart
– Plot the point using technical factors

Tube Rating Charts
Calculating Heat Units (hu)
kV x mA x time (s) x C x # of exposures
The heat unit rectification constants (C ) are:
– 1 φ 2 pulse (full wave)
= 1.00
– 3 φ 6 pulse
= 1.35
– 3 φ 12 pulse
= 1.41
– High frequency
= 1.45
An anode cooling curve based on
the tube’s rating chart must be
used when calculating multiple
Calculating Heat Units (hu)
If 10 exposures of 80 kVp, 200 mA & 0.43 s.
is made on a high frequency unit, how many
heat units (hu) are produced?
kV x mA x time (s) x C x # of exposures
80kVp x 200mA x 0.43 sec x 1.45 x 10 =
99,760 hu
If the anode is at its maximum how long
must we wait before making the exposures?

Anode Cooling Chart

The X-ray Tube



Your download will begin in a moment.
If it doesn't, click here to try again.

Share The X-ray Tube to:

Insert your wordpress URL:


Share The X-ray Tube as:



Share The X-ray Tube.

Enter two words as shown below. If you cannot read the words, click the refresh icon.


Share The X-ray Tube as:

Copy html code above and paste to your web page.