This photo shows some members of the Medical Counting lab in about 1965.
From left to right Rear: Tony Wilde, Unknown, Unknown, George Loveday, Bob Hubbard.
Front: Russy Narielwalla, Pat Saunders (with pipe), C.J.Tirion (visiting Philips engineer).
I was initially put to work under the watchful eye of Pat, developing the N600 Linear Ratemeter and N610 Automatic Scaler.The N610 replaced the earlier N530 Scaler and employed Trochotron beam switching tubes in the first two counting stages. These were thermionic valves having a 27-pin base and a glass envelope surrounded by a powerful cylindrical permanent magnet. The electron beam within the tube was capable of being switched to any one of ten targets (or anodes) at rates up to 1MHz (1Mc/s in those days).
The targets were (externally) connected to a standard (gas filled) indicator tube (similar to a Dekatron) for the display of the count and a single double triode was all that was required to provide a suitable drive waveform, unlike the earlier N530, which employed a 'hard valve decade' formed by four double triode bi-stable circuits, two double diodes and a host of resistors.
By using Trochotrons, a significant reduction in components was made coupled with a counting speed improvement. But there was a drawback. If a Trochotron was left on a bench, it would invariably roll towards any nearby lump of steel (the mains conduit at the rear of the bench was favourite) and attach itself. If left overnight the magnetic field became sufficiently distorted to render the tube unusable. So they needed a little TLC and were best stored in their original boxes or plugged into their associated equipment!
Robin Cornish, a graduate, also started on the same day as me, worked on the N616 Vibrating Reed Electrometer, an instrument for the measurement of very small currents (of the order of femtoamps) produced by Ionisation Chambers.
George Loveday, a former apprentice, joined the lab at some point (possibly early 60's) and worked on a new medical diagnostic unit, the N668 Gamma Camera. The early versions of this unit contained valves and some germanium transistors but later models, I believe, were fully transistorised.
The Gamma Camera was essentially 'a pin-hole camera made of lead'. Gamma rays, from a radioactive tracer in the subject, entered a large area thallium-activated sodium iodide crystal mounted inside a lead shield. An array of 9 (or later 23) photomultiplier tubes 'looked' at the rear of the crystal and signals from these provided deflection and brightness modulation signals for a storage cathode ray tube mounted in a control console. The resulting CRT image provided an 'in vivo' view showing radioactive tracer build-up and distribution in the subject.
Sodium iodide crystals used in the Gamma Camera and Scintillation Counters were all grown, tested and prepared in Ekco chemical labs. For Scintillation Counters used in high-resolution gamma spectroscopy work the crystal was permanently bonded to the associated photomultiplier tube.
Most equipment built in the labs was tested at some point with a radioactive test source.
Ron Glover was the Nucleonic Radiation Safety Officer whose primary job was to keep tabs on all radioactive sources in the Company, some of which were stored in the Applications lab. He was also responsible for the Radiation Safety Badges issued to all lab staff.
Occasionally, some prankster would leave his radiation badge in close proximity to a radioactive source say, over the weekend, resulting in an apparent massive overdose, indicated when the badge film was subsequently developed. Needless to say, the perpetrator would receive an 'earful' from Ron!
Norman Jerrum designed the mains transformers used in the power supplies of these units, which provided +300V and -105V (regulated) D.C supplies. The transformer had numerous secondary windings and usually included a 450-0-450V winding. This was not very 'finger friendly' if you were a bit careless during testing!
Production quantities of these units were manufactured and tested in the Special Products dept, which occupied the former lamp factory, behind and to the right of the 'hanger' shown in the Dev and Eng photo.
Louis Schymocha (was there a 'z' in it?) was in charge of the Test dept. He later changed his surname to Sheldon!
John Dowding, of Test Engineering dept, was responsible for the manufacture of any special test jigs needed by the Production Test dept.
George Oxley, brother of John Oxley in Ekco Plastics, ran the Packing dept, providing an essential service to all depts in Dev and Eng.
The instruments described so far formed part of a large range of medical counting equipment being developed at this time using thermionic valves. In those early days, reliability of such equipment was often impaired by the poor performance of so called 'high stability' carbon film resistors. Resistor values above about 50k ohms had a tendency to drift high or even go open circuit. It was not until metal oxide resistors became available (in the late 50's?) that this problem disappeared.
Transistors and ultimately integrated circuits were yet to come and would make dramatic changes to the size and performance of this range of equipment.
As transistors became more readily available, a new range of counting equipment was started and known as the M5000 series. This range employed 'plug-in' circuit boards and was smaller and modular so you could 'mix and match' units to create a counting system suited to specific tasks.
Around the mid 60's integrated circuits (IC's) were available and in particular a BCD decade counter in a 14 pin DIL package appeared. This device could count at speeds beyond 10 MHz and could replace 8 transistors, numerous diodes and resistors, needed to create a decade counter circuit, used in the earlier M5000 units. In conjunction with a BCD-to-decimal decoder (IC) it could directly drive a numerical indicator tube (or Nixie) with no additional components, again dramatically reducing the component count.
A new breed of IC based instruments thus evolved, which employed one double-sided PC board housing all components, mostly IC's. These were 'slim line' units weighing one fifth of the weight of the earlier valved units.
The first of these was the M5024B Scaler-Timer. This was followed by the M5183 Digital Ratemeter, which also employed, probably one of the first, Ekco Thick Film Circuits designed and produced by Joe Phelan of the chemical labs. This circuit contained a ladder network of matched resistors used in the digital-to-analogue circuit of the Ratemeter.
Other (non-medical) nuclear instruments were developed in the Industrial lab. These included Radiation monitors, Thickness, Fluid Density, Metal Wall and Moisture gauges. More recent units were the M3182 Mineral Analyser and M8524 Bore Hole Logger. Details of some of these can be seen in the Ekco Nucleonic Gallery.
Sadly, in the late 60's the Nucleonic group was bought out, with, I believe, some other nucleonic companies, by Nuclear Enterprises. In 1970 the Ekco Electronics name was changed to Ekco Instruments. I remained with the Company, developing Crane Safe Load Indicators until 1982. But that is another story.
