What is the function of dynode?
A dynode is an electrode in a vacuum tube that serves as an electron multiplier through secondary emission. The first tube to incorporate a dynode was the dynatron, an ancestor of the magnetron, which used a single dynode.
What is the function of photocathode and dynode in avalanche photomultiplier tube?
Dynode Photomultiplier or PMT The photocathode consists of a photosensitive substance that produces photoelectrons when bombarded with photons of visible light. The photoelectrons produced at the photocathode are then accelerated toward a positively charged dynode in the PMT.
What is meant by dynode?
Definition of dynode : an electrode in an electron tube that functions to produce secondary emission of electrons.
How does a discrete dynode multiplier detector work?
As with the discrete geometry, electrons are made when the ion initially strikes the front of the dynode. The secondary electrons are accelerated toward the back of the detector by the potential drop, generating more electrons each time they strike the detector’s walls.
What is dynode in a PMT?
In a PMT, dynodes are electrodes in a vacuum tube that serve as an electron multiplier through SEE (see Figure 1). The dynodes are so arranged that the electric fields between them cause the electrons emitted by each dynode to strike the next with an energy of a few hundred eV.
What are the two types of photomultiplier tube?
There are two common photomultiplier orientations, the head-on or end-on (transmission mode) design, as shown above, where light enters the flat, circular top of the tube and passes the photocathode, and the side-on design (reflection mode), where light enters at a particular spot on the side of the tube, and impacts …
How does a dynode multiply electrons?
The dynodes are so arranged that the electric fields between them cause the electrons emitted by each dynode to strike the next with an energy of a few hundred eV. As a result of secondary emission, the number of electrons increases from dynode to dynode, giving the required multiplication.
What is a high energy dynode?
High energy dynodes (HED) are now commonly used to enhance the sensitivity of ion detectors by increasing the impact energy of input ions, which increases the number of emitted secondary particles. In quadrupole systems, HED’s are usually designed to collect only low energy ions.
Is photocathode positive or negative?
Photocathodes are also commonly used as the negatively charged electrode in a light detection device such as a photomultiplier or phototube.
What is the photocathode bonded directly to?
The photocathode is bonded directly to the input phosphor using a very thin adhesive layer. These layers are curved so that all of the electrons emitted from the photocathode travel the same distance to the output phosphor (Figure 14-3).