Photomultiplier apparatus and radiation detector incorporating such apparatus

1. A photomultiplier apparatus comprising:

a. a first housing;

b. window means mounted to the first housing, the window means being at least partially transparent to electromagnetic radiation of a first wavelength range;

c. photomultiplier means provided in the first housing for receiving electromagnetic radiation of said first wavelength range passing through said window means and generating an electrical output signal dependent on the intensity of said electromagnetic radiation;

d. sealing means for isolating electrical terminals of said photomultiplier means from said window means; and

e. resiliently deformable optical coupling means located between said window means and said photomultiplier means, for allowing at least some electromagnetic radiation of said first wavelength range passing through said window means to enter said photomultiplier means, wherein said resiliently deformable optical coupling means extends along a part of a sidewall of said photomultiplier means and encapsulates an end of the photomultiplier means facing said window means, and

wherein said sealing means comprises an electrically insulating material which encapsulates at least some of the electrical terminals of the photomultiplier apparatus and which at least partially overlaps said optical coupling means so that said photomultiplier means is completely encapsulated by said sealing means and said optical coupling means.

2. An apparatus according to claim 1 , wherein the optical coupling means comprises at least one mouldable material.

3. An apparatus according to claim 1 , wherein said sealing means at least partly encapsulates said photomultiplier means.

4. An apparatus according to claim 1 , wherein said sealing means is adapted to resist transmission of electromagnetic radiation in at least part of said first wavelength range.

5. An apparatus according to claim 1 , wherein said sealing means comprises at least one mouldable material.

6. An apparatus according to claim 2 , wherein at least one said mouldable material comprises a silicone material.

7. An apparatus according to claim 1 , wherein the first housing includes a first material having smaller transmissibility to electromagnetic radiation of said first wavelength range than said window means.

8. A radiation detection apparatus comprising:

a photomultiplier apparatus according to claim 1 ; and

scintillator means for converting ionising radiation into electromagnetic radiation of said first wavelength range, wherein the scintillator means is optically coupled to the window means of said photomultiplier apparatus.

9. An apparatus according to claim 8 , wherein the scintillator means comprises a second housing comprising a second material having greater transmissibility than said first material to the ionizing radiation.

10. An apparatus according to claim 8 , wherein the scintillator means or said second housing includes means for mechanically coupling the scintillator means to the first housing such that the scintillator means is optically coupled to the window means of said photomultiplier apparatus.

11. An apparatus according to claim 8 , wherein the mechanical coupling means is releasable such that the scintillator means and the photomultiplier means may be coupled together and decoupled.

12. An apparatus according to claim 11 , wherein said mechanical coupling means comprises co-operatively threaded portions provided on the second housing and the first housing, a bayonet-type coupling between the first and second housings or an arrangement of fixing points which are coupled by means of screws, bolts or clips.

13. An apparatus according to claim 8 , wherein the photomultiplier apparatus is intrinsically safe in the absence of the scintillator means.

14. A method of manufacturing a photomultiplier apparatus, the method comprising the steps of:

a) forming an assembly comprising optical coupling means located between photomultiplier means and window means, wherein the optical coupling means is resiliently deformable, extends along a part of a sidewall of said photomultiplier means and encapsulates an end of the photomultiplier means facing said window means and the photomultiplier means is adapted to receive electromagnetic radiation of a first wavelength range passing through said window means thereby generating an electrical output signal dependent on the intensity of said electromagnetic radiation;

b) mounting the assembly within a housing; and

c) providing sealing means for isolating electrical terminals of the photomultiplier means from the window means, wherein said sealing means comprises an electrically insulating material which encapsulates at least some of the electrical terminals of the photomultiplier apparatus and which at least partially overlaps said optical coupling means so that said photomultiplier means is completely encapsulated by said sealing means and said optical coupling means.

15. A method according to claim 14 , wherein the step of forming said assembly comprises locating said photomultiplier means and said window means in position relative to each other and moulding said optical coupling means there between.

16. A method according to claim 14 , wherein the step of providing said sealing means comprises at least partially filing the housing with at least one mouldable material.

17. An apparatus according to claim 2 , wherein said sealing means at least partly encapsulates said photomultiplier means.

18. An apparatus according to claim 2 , wherein said sealing means is adapted to resist transmission of electromagnetic radiation in at least part of said first wavelength range.

19. An apparatus according to claim 3 , wherein said sealing means is adapted to resist transmission of electromagnetic radiation in at least part of said first wavelength range.

20. An apparatus according to claim 2 , wherein said sealing means comprises at least one mouldable material.