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Thorne EMI Type 9643/4 Electron multiplier Tube


A clear glass vacuum tube with metal leads protruding from both ends. There is a shallow groove in the glass near one extremity of the tube. The object also presents a small silver and black maker’s label on the outside surface of the tube.

Accession Number:

Alternative Name:

Primary Materials: Glass, Iron alloy


Maker’s label on tube surface: “Type 9643/4”, “Serial 7902”.

Various labels on the outside of the cardboard shipping box contain the following additional information:
“Our order number: 71764”
“Your order number: 14008036”
“Dated 23/09/94”
“Bgd 1cps”
“OP Volts 3kv”
“GAIN 4.84 x 10^7”
“Resistance 15.7M OHMS”

Dimensions (cm):

Tube: Diameter = 5, length = 22; Box: Height = 42, Width = 18, Length = 18.


An electron multiplier tube is a device for magnifying a very small electric charge. A very weak signal, for instance a single electron entering the tube can be made to trigger a progressive cascade of electrons through series of charged screens—a process known as “secondary emission”.

In this case, the glass envelope is only a temporary housing. The electrical mechanism within is removed and rehoused in a high-vacuum system.

Condition: Excellent: This artifact is unused.

Associated Instruments:

Manufacturer: Thorne EMI

Date of Manufacture: c. 1994


This Venetian blind type electron multiplier tube was made in England around the time that the part was purchased in 1994. It was acquired from tube Derek York’s Potassium-Argon dating lab where it was meant to be used in the detection of particles passing through a mass spectrometer. It was apparently never used because it was the wrong kind of tube—a mistaken purchase.

Additional Information and References:

Historical Notes:

  • Donated to UTSIC