Photomultiplier tube

A photomultiplier tube comprising:

• a casing having a substrate which has insulating properties, the substrate having a first end and a second end opposite to the first end;
• an electron multiplying part including a 1st to an Nth stage (N denotes an integer of 2 or more) which are arrayed to be spaced away sequentially from the first end to the second end on the flat surface of the substrate, the electron multiplying part configured to multiply electrons in a direction from the first end to the second end;
• a photocathode installed at the first end spaced away from the electron multiplying part, converting incident light to emit the photoelectrons;
• and
• an anode part installed at the second end spaced away from the electron multiplying part;
• wherein grooves are formed in the substrate, each groove located between two adjacent stages of the electron multiplying part on the flat surface of the substrate, and
• the electron multiplying part is fixed on raised parts adjacent to the grooves on the substrate.