Information For Assembly And Installation Metal Center Section X-Ray Tubes; Introduction; Stator Cable And Electrical Connection; Center Section Lead Connection - Varian B-100 Manual De Instrucciones

2.0

INTRODUCTION

A. A .010" spark gap at the center section terminal on the housing prevents excessive voltage buildup in the event of
an internal sparkover between anode or cathode to center section. Reset if moved from .010". In addition, there is a
surge protector inside housing between this fourth terminal and ground for added protection.
B. NEVER operate tube with anode high voltage cable disconnected! Complete destruction of the insert is highly probable.
If disconnecting the anode high voltage cable from the tube is required for trouble shooting, consult Varian for proper
procedures.
ALWAYS connect the metal center wire to central ground point (usually H.V. transformer).
2.1 STATOR CABLE AND ELECTRICAL CONNECTIONS: Refer to Product Data Sheet
CAUTION: Do not operate with Red wire of cable disconnected or arcing will occur. With center section properly
connected, calibration and operation are same as conventional X-ray tubes.
2.2

CENTER SECTION LEAD CONNECTION

A. Center Section Current
1. Due to the physics of the electrode geometry, cathode current divides between the anode and center section. (Some
secondary electrons created at the original impact with the anode are collected at the center section rather than
recollected at the anode as in conventional glass tubes.) See Figure 2-1. For MA calibration always use the cathode
current values. For example at 80 kV, with 100 MA cathode current, only 90 MA would be collected at the anode
and 10 MA would be drawn to the center section. In generators where MA monitoring is in the cathode side of the
high voltage generator, the red wire (center section current) may be connected to ground or if a balanced anode and
cathode current is required connect red wire to anode side of monitoring circuit (M1 or M2 depending on manu-
facturer of generator).
2. In generators where MA monitoring is in anode side of the high voltage transformers connect red wire to anode side
to add current back into monitoring circuit. With center section properly connected, calibration and operation are as
for conventional x-ray tubes.
B. Single Phase Generators
1. Single Phase Generators require an additional consideration over three phase generators. The mA signal at M1 and
M2 will be AC, whereas the center section current will be rectified. This requires connecting red wire from center
section to a point after bridge rectifier that is normally installed prior to MA meter as shown in Figure 2-1. Ground
red wire if MA meter is in cathode side of high voltage transformer.
NOTE: At completion of calibration remove red lead from MA circuit and ground at high voltage transformer.
C. Connect center section (red wire) as outlined in Table 2-1.
1. An alternate procedure listed below may be used in determining the connection point of red wire (also a check to
determine if lead is located properly).
a. Three phase generators (See Figure 2-1)
i. Ground red wire.
ii. Make an exposure at 80 kV 200 mA, 0.1 sec and record MAS reading.
X-RAY
PRODUCTS
INFORMATION FOR ASSEMBLY AND INSTALLATION
METAL CENTER SECTION X-RAY TUBES
X-RAY TUBE ASSEMBLY AND
INSTALLATION MANUAL
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