Blog posts of '2014' 'June'



Today's stroll through the Mullard company's document archive threw up this rather fetching photograph which was attached to a memo from Philips BV in 1954, advising Mullard Blackburn of how operators were trained about valve componentry and assembly at Philips Heerlen.  They advocated the use of  a LARGE training aid because apparently, girls tend to be impressed by large things and the training association sticks..   

Who said it's not the size that matters but how you use it?



Isn't this exciting, this is an 'Atomic Suit' developed by GE for use at the Richland Washington Atomic plant in the US.  GE, unlike Mullard, had it's fingers in many manufacturing pies and this is just one of their other interests.    This suit was meant to protect the wearer from the effects of nuclear radiation, however, the suit potentially could have other uses.

Cue entry of the stern faced Sister Annette of the nearby Hanford based Pendlebury-McCarthy School for Girls.   As pastoral care nun and basketball coach, she was there to ensure that no impropiety occurred when the lower half of the suit was fitted to the model and of course to assess the efficacy of the lower suit area as a potential aide to modesty and chastity  if worn by some of her more high spirited charges.





Today's dip into the Mullard factory archives has come up with this photo of a suited gentleman testing valves using a Mullard High Speed Valve Tester (MHSVT).   How many people wear a suit whilst valve testing  - I wear a string vest and a lime green thong whilst testing our wares -  however, I digress.  The formal attire should give a clue for this is the MHSVT in the main transmitting room at BBC Alexandra Palace some time in 1953.  

I think this photograph was taken during valve maintenence testing undertaken immediately prior to filming an episode of Jigsaw  where a young art student from Perth, Australia, got an audition drawing cartoons  - "Can you tell what it is yet, little girl.........?." said the art student.   "Is that an 813 in your pocket or just a small digeridoo?"  innocently trilled the pigtailled young lady.  

Altogether, the BBC had 17 of these instruments, indeed, the fourth one off the production line of the first production run was bought by the BBC for use at Lime Grove studios where it was used for peridoic testing of a stock of 12000 valves.


A pal of mine, knowing I am a chemist decided to bring me this photograph from his time at Mullard Semiconductors - he thought the Dreschel bottles in the background would float my boat but in actuality it's the process being undertaken that piqued my interest.  My pal told me that this was an Orgone Accumulator - silly boy - but we know different!!

What we have here is a photograph taken in 1955 at the Mullard semiconductor materials laboratory with a Process Engineer purifying an ingot of Germanium for semiconductor manufacturing by a process known as Zone Refining, an elegant method which depends on  the concentration of impurity solutes in the liquid phase due to a low partition coefficient.  

And here's how it works: -

A germanium ingot is placed in graphite container called a boat which in turn is placed inside a silica tube under an argon or nitrogen atmosphere.  A molten zone is created in the ingot by passing it through an RF heated zone which raises a portion of the ingot to 932oC which melted the germanium and as the solubility of any impurities is higher in the liquid than the solid phase, the impurities tend to concentrate in the molten zone which gradually moves down the ingot, taking the majority of the impurities with it until they are eventually concentrated at one end of the ingot.  

The impure end is 'lopped off' and the process successively repeated until a 99.995% pure germanium ingot remains.   The process was quite slow with transit of the ingot progressing at 1cm/hour so purification could take some time.  This photograph was taken only 5 years after this process was originally invented by Dr. W Phann at Bell Laboratories in the 'States.  The process is still in use today with silicon for chip wafers being refined in the same way, however, the process has been refined (sic) over the years to be much faster as a continuous process with new material being added as the impure bit is removed rather than the slower batch process you see here.

Interestingly enough, a similar process known as Zone Remelting was used to put impurities back in to the germanium ingot with a high degree of homogeneity to 'dope' it with antimony and/or arsenic to inbue negative, n-type semiconduction or conversely aluminium and/or boron to imbue positive, p-type semiconduction.