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f. Check lamp calibration values. (Higher lamp energies or cal points means more
energy must be dumped into the lamps creating more heat.)
If all of the above items are checked and found to be normal yet, the laser still overheats, it may be pos-
sible that the water pump head is worn and not moving the water quickly enough or there may be
some flow restriction. Or everything may be normal but the system just need to be left on so the laser
would cool down. If the laser overheats, do not turn it off! Let it run and it will cool down.
BLASTSHIELD
The following section will address the subject of "blown blastshields" and the causes for this problem.
Laser energy is focused at the center of the proximal endface of the fiber. Due to the causes listed in
the following topics, the fiber endface will tend to absorb or scatter more laser energy than it trans-
mits. During laser operation, the temperature of the fiber endface will increase. When the tempera-
ture exceeds the energy handling capacity of the fiber, the heat generates a violent reaction within the
fiber and fiber endface "explodes".
This small scale "explosion" ejects sparks, hot gases, and debris away from the fiber endface. While
most of the debris is sent out of the lens cell vents, some of the debris is directed toward the blast-
shield. The blastshield sacrifices itself in the explosion, and in doing so, protects the fiber focus lens
from damage. The blastshield is now "blown", and each additional laser pulse will create another
explosion. The fiber and blastshield need to be replaced before any further laser operation takes place.
It is recommended that all customers carry additional fiber delivery devices and a spare blastshield
FRU.
1. The system is blowing blastshields.
a. Visually inspect Blastshield Optic for contamination or signs of damage. Replace if
necessary.
b. Verify fiber alignment. (See Section 3 for details)
c. Interview the customer to determine system usage to calculate the failure rate and
to collect other important information. Ask the following questions:
- What type of fiber delivery device was in use at the time?
- Who is the manufacturer?
- How many times was this device used/sterilized?
- How much energy was put into the device?
- Could the failure be handling or procedure related?
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