I work with a little different alloys but in general best solution to reveal gamma prime is to do electrolytic etching using 10% oxalic acid (6V, 3 seconds, room temperature). You can see results in attached microstructure (high volume fraction of spherical gamma prime). I don't know similar method for gamma double prime but for gamma prime it works very well. Of course you can find other acids in literature but oxalic acid is cheapest and safest in my opinion.

In my opinion, this is a very good SEM image, Could you suggest me a paper where I can read the procedure that you are using for the preparation of the samples.

To be honest, I was more interested to know, if,  modern SEMs have enough resolution to see small precipitates. Based on your image, the answer is yes

Of course you need Field Emission Scanning Electron Microscope (FE-SEM).

All of these: http://www.materials.manchester.ac.uk/our-research/facilities/electron-microscopy/scanning-electron-microscopes/

SEMs are able to make such image while used by average experienced operator (as I am).

See attached file. Last image is prepared using 10% oxalic acid solution in distilled water. Use stainless steel as cathode (AISI 304 works very well). Set DC power supply on CV and set 6 V. Put connected sample to solution for 3 seconds then rinse in distilled water, alcohol and dry it using hair dryer.