Reviewer #1: This paper details the CLAS12 RICH detector system which is designed for hadron particle identification in momentum range from 3 to 8 GeV/c. The very innovative hybrid optics design and its construction are very impressive. The authors did a very good job on providing the most detailed description of the detector system, which inevitably makes this paper long. The reviewer recommends the publication of the paper assuming the authors would make the following suggested changes: 1. In abstract: "A Ring Imaging Cherenkov" -> " A ring imaging Cherenkov (RICH)" >> Done 2. Line 16: "for the beginning" -> "at the beginning" >> Done 3. Line 27: "After a gap region ..." -> "Following an expansion volume where the light cone opens up, " >> Done 4. Line 28: "the ring" -> "the RICH ring" >> Done 5. Line 30: "velocity" -> "velocity determination" >> Modified in "the determination of the particle velocity". 6. Line 32: "identify particles" -> "idenditying the partile types" >> Done 7. Line 35: "for the various" -> "of the various" >> Done 8. Line 40: "Under these ... " -> "Based on the SIDIS Monte Carlo studies, in the most of the kinematic plane, the kaon production rate is about one order of magnitude lower than the rates of pions and protons" >> Modified in "According to the SIDIS Monte Carlo studies, the kaon >> production rate is about one order of magnitude lower than the rates >> for pions and protons in most of the kinematic plane, 9. Line 50: "is silica aerogel" -> "is to use silica aerogel as the radiator. >> Done 10. Line 51: "an amorphous" -> "Aerogel is an amorphous" >> Done 11. Line 55: "Multi-Anode PhotoMultiplier Tubes were" -> "multi-anode photomultiplier tubes (MaPMTs) are" >> Done. The past is preferred as refers to the choice made by CLAS12 and is >> not valid in general. 12. Line 61: "required" -> "requires" >> Done 13. Line 75: "campaingn" -> "study" >> We keep "campaign" as is referes to a series of test-beams. 14. Line 83: "were" -> "are" >> Done 15. Line 88: "were largely utilized" -> "are chosen for the most of the elements" >> Done 16. Line 148: "inside" -> "within" >> Done 17. Line 149: "mm" -> "millimeters" >> Done 18. Caption in Figure 5: "A_0" -> transparency A_0", "L_{scatt}" -> "scattering length L_{scatt}" >> Done in the caption and in the text. 19. Are there noticeable difference between 2cm and 3cm blocks as shown in Fig. 5? >> The optical quality is pretty similar. Clarified with "The 3cm tiles feature >> similar optical quality [7]." 20. Could not follow the derivation of eqn. (1). Is there a reference? >> Clarified with "where the angular dispersion is derived from the >> 2sigma-spot radius D0/2 divided by the travelled distance 2R [11]." >> and the citation [11] to NIMA 478 (2002) 344. 21. Line 277: "H8500 ..." -> "H8500 MaPMT" >> There is where MaPMT is defined. "MaPMT" was added at line 286 accordingly >> to the suggestion. 22. Line 283: "the novel" -> "a novel" , "H12700" -> "H12700 MaPMT" >> Done 23. Line 444: "the few percent level" -> "a few percent level" >> Done 24. Line 445: "40 l/m" -> "40 liters per minute" (?) >> Done 25. Line 594" "a time" -> "a time period" >> Done 26. In Fig. 29: in top panel. Are the high count rates for the beam-off case caused by a few channels of the MaPMT? Or is every channel of these MaPMTs showing high counts? They seem persistent with beam on. >> Clarification addede in the text and in the caption. 26. In Fig. 38: change the x-axes label in the top plot from "delta t" to "delta T" to be consistent. >> Done 27. In Fig. 39: It will be helpful to have the fit function given in the text. >> Done 28. Some of the plots are missing vertical axes labes, e.g., Fig. 41 >> Vertical axis label added in Fig. 34, 39 and 41. 29. Choose a consistent use the units for momentum. In the most part of the text, "GeV" is used. However, from Figs. 42 to 45, "GeV/c" is used. The reviewer prefers the "GeV/c". >> Revised in "GeV/c". 30. Line 979: Write this sentence "Such ..." as "As it is shown in Figs. 47 to 49, the preliminary Cherenkov angle resolution is sufficient for hadron separation in the required momentum range from 3 to 8 GeV/c". At the same time, it will be helpful to describe these figures in the main text. This is indeed a long paper. However, these plots are the most important ones readers are looking for. Also, what is the tracking resolution of CLAS12? >> Sentence revised. Few description lines of Fig.47 and 49 added. A sentence on >> the tracking resolution added at 893. 31. Line 993: remove "few-GeV". >> Done 32. Line 1008: "a" -> "an" >> Done