Monthly Archives: December 2007

Sixty today

On on Dec. 16, 1947 – sixty years ago today – the world’s first transistor was constructed and tested at Bell Labs, New Jersey, USA. Those responsible for the device were William Shockley, the theorist and John Bardeen and Walter Brattain who actually constructed the first one.

What started life as a heap of precariously balanced parts…

Replica Transistor

…ended up kick-starting the microelectronics revolution.

Today’s equivalent to Bardeen and Brattain’s part is one of the myriad sub-millimeter sized black specks you’ll find on the PCB of just about any modern electronics. Yet even these dwarf their tiny sibblings on the silicon die of a CPU, where they are packed with more than 150 million to the square centimeter.

Lost Dagenham

Another image from the archives this week: Clay Cottages of Marston Avenue. You won’t find them there now though, these last two were demolished in 1962, razed to make room for garages.

Clay Cottages - Dagenham ~1960

These particular cottages were around 500 years old – some of the oldest dwelling places in Essex. They originally had no first floor, this being added fairly recently. In our enlightened times there would probably be a cry to save them from destruction. In the 1960s however, the low ceilings and lack of modern facilities condemned them.

I’ve reason to believe even the garages that replaced them are now gone.

High-voltage coincidence

I’m in need of a high-voltage, low current DC power supply temporarily for an experiment in the lab, prices for these from the usual suppliers run into the hundreds of pounds. Given that all (all but the very best ones anyway) they consist of is a string of diodes and capacitors in a Cockcroft-Walton configuration, I decided to build one.

C-W generators are reasonably safe devices unlike their very similar cousins, the Marx generator. The voltage developed by the generator might be very high in both cases, but the C-W generator supplies very little current, whereas the Marx gen will deliver something more fatally akin to a lightning bolt. That’s not to say you can’t hurt or kill yourself with a C-W gen, just that you’ll have a bit of a harder time managing it. If you have an ioniser in your house, it will be very little more than a few stages of a CW gen and some resistors for further current limiting.

So, that’s the high-voltage, where does the coincidence come in? It happened that yesterday while flicking though my copy of the December CERN Courier, I spotted a feature on Cockcroft and Walton splitting the atom using equipment based around the generator bearing their name. I may going into the details of their achievement in another post, but for now a photo of them in their finery (and not just because I can then count this as an EDW post. Oh no…)

Walton-Rutherford-Cockcroft

Ernest Walton, Ernest Rutherford and John Cockcroft.