The LSD3 is a Xenon flash tube designed for studio photo-flash equipment. It is listed in the 1949 Mullard Valves for Industry and Communication case bound book.
The maximum energy is a 100 Joules the same as a mid energy studio flash of today. The maximum anode voltage is 2,700 Volts and the breakdown voltage is greater than 3,000 Volts. The trigger electrode would normally receive a pulse of 5 kV or so. The Xenon gas filling gives a colour temperature for the discharge that corresponds to noon daylight, approx 5,500 °K.
The flash duration given is between 150 and 300 μs. Modern units for studio work operate at about 400 volts and the flash duration is about 1 ms. The tube life is given as a minimum of 10,000.
The mesh surrounding the centre leg of the flash tube is the trigger electrode.
The end view.
The envelope is 30 mm in diameter, and excluding the UX4 base pins is 83 mm tall.