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XR 50
V3.1 | May 02, 2016
circumstances, e.g. after changing the filament, the emission current in standby mode may
exceed this value.
In order to ensure safe operation of the source, two concurrent regulation circuits are activ-
ated in standby mode. Thus two limits are used for standby mode:
Standby filament current.
Standby emission current.
These two limits are not exceeded at any time. The limit of the emission current in standby
mode is factory set to 0.1 mA.
7.3.4
Water Current
Cooling water is used to transport heat away from the anode and source housing. The cooling
water at the water output of the source has the same potential as the anode and the source
housing. Due to the water conductivity, there is a leakage current, called the water current (I
W
),
which flows through the water to ground. The amount of this current depends on the water con-
ductivity, as well as the length and thickness of the water hoses.
The water current is calculated in the UXC 1000 from the relation:
(1)
I
I
I
=
−
W
A
E
The net power of the anode consists of X-ray radiation and heat dissipation. The anode gross
power additionally includes the voltage drop caused by the water current.
The difference between gross and net anode power will increase as water conductivity
increases. At a certain conductivity, the water current where the sum of the emission current
and water current is higher than the available power rating for the UXC 1000. In this case, the
power supply will fail.
If the water resistance is too large (I
W
< 2 mA at 15 kV), there is a danger of electrochemical
corrosion.
Normal values are in the range 2…10 mA for the water current at 15 kV anode voltage. In order
to ensure stable operation, there needs to be a water current in this range.
7.4
Magnetic Fields
The source is constructed mainly from copper, aluminium and other non-magnetic or dia-
magnetic materials. There is a small residual magnetic field of >0.5 μT.
Summary of Contents for XR 50
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