METALJET D2+ MAINTENANCE AND SERVICE
Revision 19, November 2016 Page 6-6
6.2.5 Particle filter
Background: The purpose of the particle filter is to trap particles in the liquid metal loop and to allow formation
of a stable jet. Replacing the particle filter has a very high probability to produce stable jets again after the
introduction of instable jets.
Excillum recommendation: Excillum’s experience is that the particle filter does not wear out during normal
operation and we therefore suggest that service is driven by when replacement of the nozzle assembly fail to
produce a stable jet.
Manufacturer information: Manufacturer does not provide any information on expected lifetime of particle
filter.
Service instructions: Service manual under Section Replace particle filter and then:
1. Replace the nozzle assembly according to the instructions in the service manual under Section Replace
nozzle assembly.
2. Inject liquid metal into the jet system if the system has been drained during filter replacement. Follow
the instructions in the service manual under Section Inject liquid metal.
3. Put the MetalJet D2+ system in the “Ready” state and observe the behavior of the jet pump.
4. Follow troubleshooting instructions in Section 8 if the jet pump has trouble starting or maintaining a
stable jet pressure.
5. Put the MetalJet D2+ system in the “Lowpower” state and verify stable operation of the jet.
6.2.6 Exit window
Background: The exit window consists of a beryllium window and a heated carbon foil. The assembly is
designed to protect the beryllium vacuum window from being contaminated by depositions of liquid-metal
vapor or droplets. Protection is provided by passing an electrical current through a thin carbon foil, heating the
carbon foil to several hundred degrees. Any liquid-metal vapor or droplets ending up on the hot carbon foil is
immediately evaporated and the x-ray exit window is kept clean.
During normal operation of the exit window the current through the carbon foil is 1.5 A and the applied voltage
is about 4 V (±0.5 V).
The two most common failure modes are
1. Current is 1.5 A, but the voltage is only about 1 V or even lower.
2. Current is about zero and the voltage is significantly higher than 4 V.
Failure mode #1 indicates that the exit window is contaminated by liquid metal in such a way that the carbon
foil is not electrically isolated from the steel cover anymore.
Failure mode #2 indicates that the carbon foil is damaged in such a way that the electrical resistance has
increased significantly.
The functionality of the exit window cannot be guaranteed in either of the two failure modes, and the solution
is to replace the faulty exit window with a new one.
Excillum recommendation: The lifetime of the window has so far been limited by incidents related to jet
instabilities or by customer requirements on beryllium window homogeneity. We therefore suggest that
service is entirely driven by exit window failure or application requirements.
Manufacturer information: Follow recommendation above.
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