Flash tubes and quench tubes

Gas discharge tubes

Optics & Photography

Flash Tubes and Quench Tubes

See also: Photoflash fundamentals (principles of electronic flash lighting).

Mazda FA7S/1
Dual flash tube with common top triggering electrode and 4-pin base.
Outer glass enclosure is open to the air via a hole in the base.

Photographs left:
© Andy Cowley 2005.

Flash tube mounted on a 14-pin CRT base.
Possibly experimental or home made.
Outer glass tube is not sealed. Enclosure once held 2 tubes.

Photograph:
© Andy Cowley
M1EBV, 2005.

Mullard Flash Tubes
Advert from 1951.
Gives short-form specs for
LSD2, 3, 5, 7, 8, 9.

Xenon quench tube.
In TTL and auto flash systems, prior to the use of GTO thyristors and IGBTs to switch off the tube current, the flash burst could be terminated by dumping the charge still remaining in the flash capacitor. This was done by triggering a small xenon arc tube, known as a 'quench tube', which was connected in parallel with the main tube. Such a tube is shown on the left, firstly with an RF induced glow discharge, and below with an arc discharge. Triggering was by means of an external copper electrode wrapped around the tube and connected to a normal trigger transformer (i.e. a miniature Tesla coil).
The quench tube shown is from a small hot-shoe mounted flash unit (Guide # 24 /m). It is only slightly larger than an ordinary mains indicator neon, and was evidently manufactured using the same simple glass-pinch technique.
The quench tube method for automatic flash exposure became immediately obsolete with Vivitar's invention of the GTO series control circuit. The reason, of course, is that the quench tube dumps all of the available energy in the capacitor, whereas the GTO conserves it. Thus, in a quench-tube system, the capacitor must always be recharged from the extinction voltage, a situation that wastes time and reduces the battery life.

Gas discharge tubes

Optics & Photography

Flash fundamentals