All the exposures below were for 8s; the standard arc exposure is 2s, but only one out of four lamps was plugged in.
All the following plots have the same vertical scale, and show
every 40th spectrum on the image.
The single red, yellow, blue, green, and black traces are spurious.
Four images are shown for each of three wavelength ranges: one "existing" Ne-only lamp exposure, and three exposures from the new lamps. The existing Ne lamps are relatively stable, but the new lamps change significantly between exposures. Note that at the dimmest (exposure 39112, the middle exposure), the new lamp Ne lines are dimmer than those in the existing lamps, and at brightest are twice as bright. The new lamps do show Ar lines.
I do not know how long the new lamps had been on when the first exposure was started, but the three exposures were taken in quick succession.