Patent Number: 
Section: claims

1. An electronic blackbody cavity comprising:an inner surface;a chamber surrounded by the inner surface;an opening configured to allow an electron beam enter the chamber; anda porous carbon material layer on the inner surface, wherein the porous carbon material layer comprises a plurality of carbon material particles, and a material of the plurality of carbon material particles consists of carbon atoms, and the plurality of carbon material particles defines a plurality of micro gaps. 2. The electronic blackbody cavity of claim 1, wherein the plurality of carbon material particles comprise at least one of linear particles and spherical particles. 3. The electronic blackbody cavity of claim 2, wherein a diameter of a cross section of each of the linear particles is less than or equal to 1000 micrometers, and a diameter of each of the spherical particles is less than or equal to 1000 micrometers. 4. The electronic blackbody cavity of claim 2, wherein the linear particles are carbon fibers, carbon micron-wires, or carbon nanotubes. 5. The electronic blackbody cavity of claim 2, wherein the spherical particles are carbon nanospheres or carbon microspheres. 6. The electronic blackbody cavity of claim 1, wherein the porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 7. The electronic blackbody cavity of claim 6, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 8. The electronic blackbody cavity of claim 1, wherein a thickness of the porous carbon material layer is in a range from 200 micrometers to 600 micrometers. 9. The electronic blackbody cavity of claim 1, wherein the porous carbon material layer is a super-aligned carbon nanotube array, and a height of the super-aligned carbon nanotube array is in a range from 350 micrometers to 600 micrometers. 10. The electronic blackbody cavity of claim 1, wherein a size of each micro gap of the plurality of micro gaps is less than or equal to 100 micrometers. 11. A secondary electron detection device comprising:an electronic blackbody cavity comprising:an inner surface;a chamber surrounded by the inner surface;an opening configured to allow an electron beam enter the chamber; anda first porous carbon material layer on the inner surface, wherein the first porous carbon material layer comprises a plurality of first carbon material particles, and a material of the plurality of first carbon material particles consists of carbon atoms, and the plurality of first carbon material particles defines a plurality of micro gaps; anda secondary electron detection element located in the chamber. 12. The secondary electron detection device of claim 11, wherein the plurality of first carbon material particles is selected from carbon fibers, carbon micron-wires, carbon nanotubes, carbon nanospheres and carbon microspheres. 13. The secondary electron detection device of claim 11, wherein the first porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 14. The secondary electron detection device of claim 13, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 15. The secondary electron detection device of claim 11, wherein the secondary electron detection element comprises a secondary electron probe, the secondary electron probe comprises a second porous carbon material layer, and the second porous carbon material layer is insulated from the first porous carbon material layer. 16. The secondary electron detection device of claim 15, wherein the second porous carbon material layer consists of a plurality of second carbon material particles and a plurality of second micro gaps, the plurality of second micro gaps are defined by the plurality of second carbon material particles. 17. The secondary electron detection device of claim 16, wherein the plurality of second carbon material particles is selected from a group consisting of carbon fibers, carbon micron-wires, carbon nanotubes, carbon nanospheres and carbon microspheres. 18. The secondary electron detection device of claim 15, wherein the second porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 19. The secondary electron detection device of claim 18, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 20. The secondary electron detection device of claim 15, wherein a material of the plurality of second carbon material particles consists of carbon atoms.