» RCA Photomultiplier (0261)
Immagini
DESCRIPTION
Exhibit 261 is an RCA photomultiplier tube that converts photons into electrical signals. It consists of an evacuated glass tube with the top face coated on the inside with a layer of material that favors the photoelectric effect and an internal structure which amplifies (multiplies) the number of electrons released by the incident photon that freed the original electron. The multiplying effect is realized by a structure of electrodes, called dynodes, each one held at a potential greater than its predecessor so that the incident electrons accelerated by the potential difference release additional electrons to be accelerated to the next dynode, and so on. The accumulated effect is a cascade of one photoelectron leading to many and a strong electrical signal. The tube must be shielded in two ways. It is wrapped in black tape so that the photoelectric effect is limited to the top face which is the origin of the desired light signal. It must also be shielded from stray magnetic fields which would disturb the internal trajectories of the cascading electrons. The latter shield is provided by two layers, an outer one of soft iron and an inner one of mu-metal that has a high magnetic susceptability even though it saturates at low fields. That the field is low is guaranteed by the external shield. The base of the tube is made of a special plastic, galalite, a composition of casein and formaldehyde. This tube was manufactured in the period 1950-1960. See exhibit 532 for another type.ISCRIZIONI
- RCA, Made in U.S.A., CRC-5819
- Scritta vicino ai piedini: Licensed only to extent indicated on carton
Dati Catalografici
| Data di costruzione: | posteriore al 1950 |
|---|---|
| Data di carico: | sconosciuta |
| Nr. Inventario: | Ignoto (Ignoto) |
| Costruttore: | RCA |
| Materiale: | vetro, metallo, galalite |
| Dimensioni: | Diametro: cm 5,6; Altezza: cm 14 |
| Conservazione: | buono |