The LSD2 is a specialised flash tube for high speed photography. The flash duration is given as 1 μS and the discharge is 35 Joules. The flash should be fired once a minute at maximum by a 5,000 V pulse to the trigger electrode.
The cathode and trigger. Presumably the outer ring is the trigger. The filling gas is probably xenon.
The wide glass tube envelope is 30 mm in diameter and, excluding the ES base, is 125 mm tall.