What is done to avoid electron cloud formed due to secondary emission from Phosphor in a cathode ray tube?

Answer 1

The sides of the CRT close to the phosphors are coated with a conductive film ( something like graphite) which has a positive voltage on it to catch the secondary electrons. I believe it's called an aquadag

Answer 2

The CRT face is the only part of the envelope which is covered by Phosphorus. The rest of the tube is covered with a thin film of Aluminum a small fraction of a millimeter thick. This aluminum coating reflects the emitted phosphorus rays. Normally the graphite used in manufacturing is eliminated during the heating cycle of manufacture.