On page 4 we find: The test samples were made by the NatLab radio-tube workshop. The tolerances are rather tight, but can be improved when a better, steeper input pulse is used. Many of the entries in notebook deal with the issue of reproducibility.
Other members of this group are Leo Tummers and Piet Jochems. Philips, who at that time was the largest manufacturer of electron tubes in Europe, is determined in acquiring the same position in transistors. These conclusions tend to deal with some very specific issues or problems and are therefore difficult to interpret.
When van Overbeek returned with Jonker from the tubelab, a second record was made.
The last batch of test tubes mentioned in the notebooks is 38JP April The only photograph of van Overbeek that I have is pasted on his personal department h. The entry in notebook discusses the results from test tubes numbers 38AK and 38AL.
The wire grid and the aperture plate are mechanically aligned. In September van Overbeek and J. Adrianus van Overbeek is remembered as an exceptionally gifted and creative engineer.
The technological distance to Bell Labs is at that moment too large. For a perfect scan the electron beam has to follow the path between two grid wires. Apparently at that time already some test samples 38AK, 38AL had been fabricated. This will generate an error signal Fig.
Most likely it was assigned to the tube by the commercial departments at a pretty late stage. In fact it can not be found in all the notebooks and reports that I have consulted. He only finished high school 5 year H. A group of about ten people is formed who, headed by F. In December the transistor is invented at Bell labs. After a year Jonker leaves to start the tube lab at the production side at the Emmasingel.
After intense negotiations on licensing conditions an agreement is reached and in April J. So the principle of the E1T was filed in an Invention Disclosure with number One of the last series of experiments to check the correct design of the aperture screen and to measure the voltage increments between two successive stable positions.
Similar to the E1T, in the beam deflection tube from Sears the variations in slotted screen current are used to keep the electron beam in a fixed position . Test circuits are designed, and the design of the tube is optimized for a low anode voltage.
In these preliminary experiments an additional tube was needed because of an incorrect placement of the deflection plate and because the deflection electrode drew too high a current due to secondary emission electrons. When the electron beam deviates from the ideal path, it will impinge on one of the grid wires on either side of the ideal trajectory.
A similar system is used in the E1T counting tube to keep the beam fixed in one of the 10 stable positions. A number of technical issues is discussed and a division of tasks is agreed upon.
At the end of several tubes are send to other departments for evaluation. People who have known van Overbeek remember him as being rather eccentric.
Illustration from the paper by Sears which schematically shows how a screen with horizontal slots is used to keep an electron beam in an exact horizontal trajectory . Out of the series of tubes, 31 tubes were rejected because a short circuits due to getter deposition on the top mica, 12 tubes were lost due to other causes, and for the remaining tubes the anode resistor for proper operation was selected: One of the t slot eindhoven problems in this period is related to the charging of the mica isolators due to secondary electrons.
Unfortunately, the general trends and ideas, which are so much of interest to us, were largely stored in the head of van Overbeek. They return full of enthusiasm, but realize that an enormous amount t slot eindhoven work still needs to be done before Philips will be able to fabricate junction transistors on its own. Jan Slotboom, who when he joint Philips shared offices with van Overbeek, and who was by then almost retired, remembered how he would disappear for weeks.
The remaining entries of that year and of deal with two topics: The entry evaluates a set of measurements made on a batch of test tubes. To achieve this a trick is used.