Re: ?? Ra-226 in computor tubes

[Free Spirit <FRANK@rover.bsd.uchicago.edu>]

>From:	SMTP%"radsafe@romulus.ehs.uiuc.edu" 23-OCT-1995 20:00:25.12
>From: gfeldman@uci.edu (Gerald Feldman)
>
>By the way, George Philbrick is best known as the inventor of the
>"operational amplifier", the basic building element of the _analog_ computer
>(as opposed to the digital computer).  Philbrick's invention allowed the
>construction of stable DC amplifiers which were used in many of our
>dosimetry instruments.

	They were called "operational" amplifiers because they could
	easily be configured with a few external components to do various
	mathematical operations, such as multiplication, division, and
	INTEGRATION, an important part in any modern linac.

	In my early days I designed an op-amp based dosimetry circuit for
	the old linac here. Before that, the Victoreen Radacon-I used to
	control dose actually integrated dose by mechanical means. 

	The dose-rate meter signal was amplified and drove a small DC
	motor (thru a tachometer feedback) at a speed proportional
	to dose rate. The motor drove a mechanical counter in reverse. You
	dialed in the number of counts, and when it reached 000, a switch
	opened and shut off the linac.

	IMHO, the operational amplifier, (and more importantly its conversion
	to integrated circuits bye guys like Bob Widlar,) has made just as
	much or more of an impact on our lives as digital circuits.