LGP-30 Memory Drum Update

[Paul Koning]

> On Jan 4, 2017, at 2:48 PM, Kyle Owen <kylevowen at gmail.com> wrote:
> 
> On Wed, Jan 4, 2017 at 12:06 PM, Jon Elson <elson at pico-systems.com> wrote:
>> 
>> Previous messages suggested the LGP-30 drum was plated with nickel. If
>> there are amateur astronomers with a vacuum evaporator, it might be
>> possible to get them to adjust their setup slightly to vacuum evaporate
>> nickel on your drum, after refinishing the base.  You'd need a rig to
>> slowly turn the drum while evaporating the nickel. Some other research labs
>> at universities might have the necessary equipment, also - check with the
>> Physics department (or electrical engineering).
> 
> 
> Will the desired thickness be enough with sputtering or evaporation? For
> modern hard drives, sure, but my gut instinct is that you'd want a thicker
> coating on the drum. I'd suggest sputtering over evaporation since it will
> probably adhere to the surface better. I'd think nickel electroplating
> would take less time and effort, though.

Electroplating sounds ok, I don't know about procedures.  You'd have to be careful that the electrolyte doesn't damage the drum body.

Evaporation and sputtering are used to make well controlled thin films, but there's nothing I can think of that limits how long you continue.  A mirror is coated only to the point that its reflection coefficient reaches the limit of the metal used, more is not useful.  But here you could just keep going however long you need.

As for adhering, both should produce good coatings if the substrate is clean.  I remember a test for good evaporative coating technique: coat a test piece, then try to rip off the coating with scotch tape.  It shouldn't be affected at all by that test.

There are reasons for using sputtering vs. evaporation, but I don't remember them.  I think the Strong book I cited discusses the subject. 

	paul