• Describe the construction and purpose of the x-ray tube housing. • Identify the principal parts of the x-ray tube and their purposes. • Describe the operation of the principal parts of the x-ray tube. • Discuss anode designs and construction. • Explain the line-focus principle. • Explain the anode heel effect. • Discuss cathode designs and construction. • Trace the path of electricity through the x-ray circuit and x-ray tube connecting the selections on the operating console to the functions within the unit. • Use tube rating charts, anode cooling charts, and housing cooling charts. • Employ methods of safe x-ray tube operation and extending x-ray tube life. Chapter 1 provided a general discussion of the x-ray tube head assembly and the function of the major parts of the design. Chapter 4 discussed the components of the x-ray circuit and the events that lead to the production of x-rays in the x-ray tube. This chapter examines the x-ray tube itself (Figure 5-1), its general construction, and how it works. The sole purpose for manipulating electricity in an x-ray circuit is to create the environment in the x-ray tube necessary for x-ray production. The need for the radiographer to understand the x-ray tube is twofold. First, as was described in Chapter 4, the radiographer must have a basic understanding of how the tube works to competently and safely formulate exposure techniques and minimize patient radiation dose. Second, such an understanding is critical to extending the life of the tube and to avoid damaging it. The rotating-anode design is used in general-purpose tubes today (Figure 5-4, B
The X-ray Tube
Introduction
General Tube Construction
Housing
Protective housing with the x-ray tube situated inside. The design of the housing serves as an electrical insulator and thermal cushion for the x-ray tube in addition to being a protective device against physical damage.
Anode
A is a stationary anode removed from the glass envelope. Note the silver-colored tungsten button and the discolored area where electrons interacted with it. B is a rotating anode removed from the glass envelope. The focal track along the edge of the disc and some damage from extensive use is visible.
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The X-ray Tube
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