Detection & Imaging Tubes

Photomultipliers and photocells are light-detecting tubes used in electric eyes, video cameras and various astronomical applications. Photocells are simple gas-filled devices consisting of a photocathode and anode, while photomultipliers, or PMT's are more complex high-vacuum devices. PMT's are extremely sensitive, some capable of detecting single photons. They amplify their photocathode's extremely small signal by passing the discharge through a chain of specialized electrodes called dynodes, which are each held at a successively higher voltage potential. In 9-stage PMT's, the voltage difference between photocathode and anode are typically in the range of 1000V, though they can be operated at lower voltages with a corresponding decrease in signal amplification. The sensitivity of a PMT is expressed in the form of quantum efficiency, a percentage describing the ratio between the number of incoming photons versus the number of electrons produced by the photocathode.


EMI 9826B

The EMI 9826B is a small end view photomultipler tube designed for use in the scintillation counters used within positron emission (PET) medical scanners. The 9826B has a peak wavelength of 420 nanometers and is characterized as having a high speed response and immunity to magnetic fields within a relatively compact package. The unusual base is designed to facilitate testing; even though the tube is a flying lead type, it's long gold leads have been welded to a 14 pin button base. This is so the customer can insert the tube into a test fixture for characterization prior to installation in a final device, at which point the button base would be clipped off.


EMI 9826B Photomultiplier
General Electric 1P24

The 1P24, manufactured by General Electric, is a small cartridge type phototube in a cylindrical envelope. This device takes the word 'vacuum tube' to a literal level... the interior of the tube is little more than empty space. One end of the device contains the anode, while the other end contains both the photocathode and evacuation nipple. The photocathode has a small hole in the center, which allows air to escape the tube during the pump-down process. The interior of this tube is a complete vacuum, unlike many other photocells which are filled with an inert gas such as argon. The 1P24 has a recommended anode voltage of 135 volts and a sensitivity of 40 microamps per lumen. According to the manual Tube Lore, this device has no known commercial installations and was used in no products, despite having been manufactured in quantity.

RMA 1P24 Phototube Datasheet (PDF, 55kb)


General Electric 1P24 Photocell Tube (VT-280)
Sylvania P607

The Sylvania P607 is a fairly common UV sensitive photocell designed for use in flame detection systems. Flame detectors are typically used in boilers and furnaces to detect the presence of a flame in the combustion chamber. Flame detectors also see some use in fire suppression systems, where they can be used to sound an alarm or activate a sprinkler system when a flame is detected. The internal construction of the P607 is extremely simple and contains only two small loops of wire; one loop acts as a light sensitive cathode, and the other receives the electrons which are released from the cathode when it is struck by UV light.

Boilers and furnaces have long lives and as a result, this device is still in common use. Honeywell produces a part, the Honeywell 18838, that is generally considered a safe replacement for this tube.


Sylvania P607 UV Photocell Tube (Honeywell 18838)
EMI 9536

The EMI 9536A is a large, 10 stage photomultiplier tube intended for use in scintillation counters and similar equipment. Of note is the tube's use of 'venetian blind' dynodes, which increase resistance to magnetic fields as well as giving the tube a very distinct appearance when viewed through its end window. The tube has a 14 pin diheptal base similar to the type used on many large end-window photomultipler tubes. The 9536A is considered to be a direct replacement for the Dumont 6292, RCA 6342 and Hamamatsu 7696 and can be used interchangeably with these parts

The example shown here was originally the property of the Ohio State University physics department. New tubes were shipped from EMI in a ridiculously oversized padded carton, which locked the tube in place with 5-inch foam baffles on all six sides.

EMI 9536A Datasheet (PDF, 2218kb)


EMI 9536 Photomultiplier (9536A)
Honeywell 113228

This long narrow device is a special type of phototube, designed to detect UV light. Unlike most phototubes which have an argon fill, this tube is filled with neon, which can be seen through the tube's clear tip if the tube is ionized. The 113228 is used almost exclusively in Honeywell Purple Peeper and Mini Peeper industrial flame sensors. It can be difficult to find sockets for the small three-pin base.


Honeywell 113228 Purple Peeper Phototube
RCA 1P21

The 1P21 is a circular cage side-viewing photomultiplier designed for extremely low light applications. The tube has nine photomultiplier stages contained within a lime glass envelope mounted on a humidity-stable beige base. The RCA 1P21 outputs its maximum amplification at 380 nanometers. This tube is capable of detecting single photons, and will be destroyed if powered up while exposed to ambient light.


RCA 1P21 Photomultiplier Tube
Hamamatsu R1250

The R1250, with a length of 10 inches and a diameter of 130mm, is a monster of a photomultiplier. This tube, designed for use in scintillation counters, is a 14 stage device with a peak spectral response of 420nm. The outside surface of the device has bee wrapped in a black plastic coating to prevent light contamination when the tube is installed in a piece of equipment. The tube uses a large 20 pin base; sockets are undoubtedly hard to find.


Hamamatsu R1250 Photomultiplier Tube
RCA 1P40

The RCA 1P40 is a fairly standard example of a cold cathode photocell tube. The tube contains a centrally located anode and a curved photosensitive cathode, most likely coated with cesium. The 1P40 has an argon fill gas and an octal base, though only five of the pins on the base have been populated. The 1P40 is sensitive to red and infrared light - an S1 spectral response.


RCA 1P40 Photocell Tube
GM Labs #2 Visitron

'Visitron' is yet another brand name concocted by tube companies to take a pedestrian argon filled phototube and make it sound new and exciting to the consumer. Despite the cloying name, the tube itself is actually quite attractive, with a large curved envelope and a four-pin phenolic base. Interestingly, these tubes appear to be individually serial numbered; the example shown here is numbered 304,279, which would represent a shockingly large production run if it is to be believed.


GM Labs #2 Visitron Tube
RCA 1P41

The 1P41 is an end-viewing miniature phototube with a small phenolic three pin base. The tube has a spectral response of S-1 and is filled with a low pressure argon gas. According to RCA, this tube is intended for relay applications and is optimized to detect infrared light in the 800 nanometer range. This tube uses the same 3 pin socket as those used by Honeywell 113228 Purple Peeper phototubes.


RCA 1P41 Photocell Tube
Teltron 1149 Orthicon

An Orthicon tube is a large camera image sensor that saw widespread use in television broadcast cameras from the 1940's to 1980s. Orthicon tubes incorporate a transparent photosensitive plate that is scanned from behind by an electron gun; this allows all the components of the tube to be arranged linearly, a significant advantage over the unwieldy Iconoscope tubes they were designed to replace. Iconoscope camera tubes had an opaque photocathode material that required the scanning electron gun to be placed in front of the point where light entered the tube. This example, an 1149 tube made by Teltron, is fairly representative of the construction style used in Orthicon tubes. Though Teltron is best known nowadays for their physics and educational tubes, they were prolific producers of camera imaging tubes during the Cold War.


Teltron 1149 Orthicon Tube
RCA 7038

A Vidicon tube is a sort of 'reverse CRT'. Instead of sweeping a beam of electrons across a phosphor coating to display a picture, Vidicon tubes sweep an electron beam across a photosensitive target to generate an image from the light striking the target. The 7038 is a fairly standard Vidicon tube, with a length of 5.6 inches and a diameter of 1.1 inches. Vidicon tubes were a staple in the construction of security cameras up until the 1990s, many of which are still in service to this day. Whenever grainy, crummy security camera footage is preposterously enhanced in a TV crime drama, a Vidicon tube likely was to blame.


RCA 7038 Vidicon Tube
RCA 921

The 921 is a cartridge style side-viewing phototube with an argon fill gas. The tube has an unusual form factor, with two metal caps fritted to the ends of a glass tube. Each cap acts as one pin for the device, with one cap being equipped with a snap connector. As with the 1P41, this tube is intended primarily for relay applications.


RCA 921 Photocell Tube
Varian 0981-82850-301

The Varian 0981-82850-301 is a thoria iridium ion source for use in Varian gas detectors. The device is barely a vacuum tube, as it has no glass envelope; the envelope for the tube remains attached to the gas detector. To protect the ion source from a world of dirty humans, the device is shipped in a protective plastic cylinder, which contains stern warnings to handle the device by its base only to prevent fouling of the pre-cleaned surfaces.


Varian 0981-82850-301 Thoria Ion Source Tube
RCA 931A

The RCA 931A is a side viewing, nine-stage photomultiplier tube, an improved version of the original 931. Tubes of this type do not produce an image; instead they are designed to measure and amplify very weak sources of light for use in astronomy and nuclear physics. This tube was manufactured with both a black and tan bases. The tan base is made of a special material that is more resistant to humidity, and as such is more desirable than the black base variant. Some modern versions of the 931A are also produced with a red base, but are electrically identical.


RCA 931A Photomultiplier Tube
Raytheon A704

With an envelope size of just over an inch, the A704 is one of the smallest phototubes ever made. This tiny two pin tube does not even have any discrete internal components, the photocathode is just a chemical, most likely a lead sulfide photoconductor, painted onto the back wall of the envelope. The tube has an argon fill gas.

Raytheon A704
Cetron CE-36

The Cetron CE-36 is a cylindrical miniature phototube with a three pin base. This tube has a side viewing photocathode and is filled with low pressure argon gas. According to the reference book Tube Lore, the CE-36 is a spectral response S-1 tube commonly used for sound reproduction in movie projectors.


Cetron CE-36 Photocell Tube
Hamamatsu R488

The R488 is an end-view phototube designed to be particularly sensitive to UV light. This tube is packaged in a small cylindrical envelope with a flat front window and a pair of flying leads. Unlike many other phototubes, which have an argon fill gas, the R488 is a hard vacuum tube. In operation, photons striking the cathode in the center of the tube would release a spray of electrons that would be collected by the mesh-shaped anode visible through the tube's front window.


Hamamatsu R488 Photocell Tube
Valvo 90AG

The Valvo 90AG is a British made argon filled phototube in a standard seven pin envelope. The 90AG is designed to be most responsive to light in the blue range of the electromagnetic spectrum. This tube has particularly good print quality on its part number and logo; it is not quite up to the standard set by Western Electric tubes, but is far better than the typical "dissolves when looked at" print used on most tubes.


Valvo 90AG Photocell Tube

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