DRSH-1000 Soviet ultrahigh pressure arc mercury lamp USSR

When the lamp is cold, the internal pressure is low, but as soon as the arc is lit, a drop of mercury starts to vaporize and thus increases the pressure a lot.
In the video you can see the mercury boiling on the hot electrode.

DRSH-1000 is soviet ultrahigh pressure mercury arc lamp.

Designed to work in optical devices to obtain a narrow beam of high intensity light.

Technical specifications:
The voltage of the supply network - 220 V
Lamp voltage - 90 V
Rated power - 1000 W
Luminous flux - 53000 lm
Average duration of burning - 100 hours
Length - 232 mm
Diameter - 40 mm
Lamp weight - 115 g

Made in USSR, MELZ (Moscow Electrolamp Plant), 1972.