If only there were a light bulb as efficient as a compact fluorescent light (CFL), but without the ghastly green light and brain-eating  toxic mercury.   Am I asking too much?  The inventors of the Electron Stimulated Luminance (ESL) lights don’t think so.  A company called Vu1 plans to sell ESL bulbs in Europe and the Mideast in 2013.  Vu1 lights are based on cathode ray tube (CRT) technology, are dim-able and have the cozy glow of incandescent light bulbs.  How did Vu1 accomplish this magic?  It helps that I know a little bit about CRTs from the days when my brother and I repaired old televisions.

The Hard Way of Learning About CRTs

Nature Abhors a Vacuum, So Do I: It was the mid 1980s. My brother glared at me in that moment between the sound of breaking glass and the horrible bang-whoosh which tugged at our eardrums and filled the room with a greenish-white cloud, Dad is gonna be mad! I didn’t have time to say, shut up! as we bolted from the room, but I knew it was my fault.  I held my breath to avoid inhaling poisonous mercury fumes from the fluorescent light I had just dropped across the back of Dad’s television.

It was a 1940s vintage Admiral TV with an AM/FM radio, phonograph and a 12 ½ inch picture tube.  It was nearly old enough to have displayed the last time the Chicago Cubs had won the World Series in 1945.  It had been around for Elvis’s debut and the moon landings.  My father had begun to restore it the night before his wedding and my brother had fully repaired it in the mid 1980s– only a few weeks before I destroyed it.

When we mustered the courage to return to the room, we saw that the fluorescent tube was intact but the neck of the TV’s picture tube had broken off.  Air rushing into the vacuum had blown a hole in the screen’s phosphor coating.  I wondered, what we should fear more; mercury vapors, phosphorescent dust– or Dad.

CRT televisions faded into history, but fluorescent lights continue to be my bane.  Our kitchen is equipped with dimmer switches.  The prison-style bare bulb fixture in our bathroom is too fragile to support heavy CFL bulbs.  Some fixtures require screw base bulbs, others have bayonet, candelabra or T-50 floodlight sockets.  Until recently only one style of CFL light bulbs was available in Ireland, so we installed these into as many fixtures as possible.  The CFLs in recessed sockets overheated and the ones we installed in the cool damp bathroom lasted only a few months.  The ones on the dimmer switch didn’t work at all.  Soon I had a collection of dead CFL light bulbs, waiting for the environment minister to devise a disposal plan for the toxic mercury inside them.  His eventual plan was for citizens to ‘look it up on the Internet’– so here I am. Meanwhile, this became one of the first countries in the world to ban incandescent light bulbs.  Am I screwed?

How do ESL lights work?

ESLs work just like the Cathode Ray Tube (CRT) in Dad’s old TV.  There are differences but let me first explain how a CRT works.  Inside the fragile glass neck there is a piece of metal called a cathode.  The cathode is electrically heated with a filament similar to those used in incandescent bulbs. This allows electrons to ‘boil’ off of the metal’s surface.

These electrons won’t go far unless you remove the air and push many more electrons onto the cathode, giving it a negative charge.  Since like charges repel, the negative electrons leave the cathode and fly towards a positively charged piece of metal near the front of the tube called an anode. This assembly is called an electron gun.

Where Do the Electrons Go?

Once you have electrons shooting out of an electron gun, you need to give them a target. In an X-Ray machine the target is a chunk of metal which stops the electrons and forces them to give up their energy as X-Rays.  In a CRT, the electrons strike a phosphorescent powder, causing it to glow.  Electromagnets sweep the electron beam back and forth over the screen, painting a picture.

In a color CRT, three electron beams pass through a metal shadow mask, full of holes which direct the beams to red, green and blue phosphor dots.

There is Nothing Wrong With Your Television Set

During our TV repair years, my brother and I would occasionally find one with bad horizontal and vertical oscillator tubes.  This disabled the beam steering magnets which left an extremely bright dot shining in the center of the screen.  ESLs don’t use a shadow mask or beam steering magnets but they do have an electron gun and a bright phosphor screen.  Vu1 has taken advantage of advancements in phosphor chemistry and small, high voltage power supplies to make what appears to be an ecologically friendly light..

What about X-Rays?

One of the first things I thought of when I heard about ESLs was, I thought we were trying to get rid of CRTs.  My second thought was, What about X-Rays? In 1967 a General Electric manufacturing defect resulted in TVs which emitted 10-100,000 times the X radiation considered safe.  Most TVs gave off some X-Rays, color ones more so, because the electron accelerating voltage was higher, at about 25,000 volts.  The shadow mask stopped some electrons, converting their energy to X rays.  To filter these, old TV screens were made of thick leaded glass.

ESL’s lack of a shadow mask and relatively low accelerating voltage of 5000V means they are unlikely to emit many more X-rays than a typical CFL bulb and nowhere near as much as the sun.)  ESL lights have passed Underwriter’s Laboratory X-Ray testing in the U.S.

Throw Them in the Trash? You must be joking!