Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solution to the ion feedback problem in Hybrid Photon Detectors and
  Photo Multiplier Tubes   A general solution to the positive ion feedback problem in Hybrid Photon
Detectors (HPD), photo multipliers (PM) and other similar detectors was found
in the insertion of a permanent electrostatic potential barrier which prevents
drift of positive ions from the anode, or the first dynode, towards the
photocathode. In this paper we present the method as applied to the Intevac
HPD.

20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin