Excimer laser chemical problems Page: 9 of 82
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Figure* 1 through 5 compare the use of nickel electrodes and nickel
plated preionizers with Poco graphite electrodes and brats preiottizert All
of the parts are froa a Luaonics Shi laser. Each set oi electrodea and pre-
ionizers were run of the order of 10* pulses. Note in Figs. 1 and 3 that even
with nickel electrodes and nickel plated preionizers there is still noticeable
quantities of powder present. Note also in Fig. 1 that the heads oi the
nickel plated stainless steel screws on the top of the red cap.icitors are
badly eroded - this is one side of a double row of preionizers. The other
side - the nickel plated braas screws - ire eroded eery little. The power in
Figs. 1 and 3 contains primarily chlorides of nickel and iron. In Figs. 2, A,
and 5 the aaount of powder is auch more extensive. In Fig. 2 the red capacitors
are entirely ccvered with white powder. The powder is aostly zinc, copper,
■nd nickel chlorides.
Note in Fig. 2 that the eroaion of the brass screw beads on the c«pacitors
is comparable in extent to the erosion of the nickel plated stainless steel
screws in Fig. 1. Interestingly enough, there is no evidence of free carbon
froa the Poco graphite electrodea. Evidently nosl of the reaction products
fron the electrodes were a gas as intended. The erosion of the electrode not
shown was more extensive. The electrode lifetiaes for Poco graphite are not
■ueb aore than 10* pulses; however, when coupled with an x-ray preionizer the
particulate generation rate should be quite low. The larger amount of gaseous
reaction products did create some problem* For example, a carbon smudge
buildup on the optics waa difficult to eliainate by gas flushing techniques
The effect of HC1 on stainless steel is shown in Figs A and 7. Figure t
is where the laser cavity inserts into the EDS. Figure 7 is the ferrofluidu
seal package for the CDS. The rust results froa ferric chloride absorbing
water out of the air over a period of a few days. Figure 6 was taken after
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Tennant, R. & Peterson, N. Excimer laser chemical problems, report, January 1, 1982; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1092992/m1/9/: accessed May 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.