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["Kiselev, Alexander" <ayk AT bnl.gov>]

  Thank you Bill,

  for a very comprehensive report. Few questions, for my understanding:

  (1) what is a theory behind Cr and Al layer thickness influence on the reflectivity? Chromium is only needed for bonding aluminum to a substrate, correct? Aluminum thickness should just be few times more than a skin layer thickness for a given wavelength, or am I totally wrong here? If surface roughness accumulates over deposition, it seems to be beneficial to decrease both Cr and Al thickness at the same time, which is none of the configurations in a 1^st and a 2^nd depositions. I now do not recall what the 3^rd configuration was, which is not described in this note.

  (2) what is a theory behind an expectation that going to 10^-9 torr will improve the coating quality? Are we concerned about a residual gas pressure (why?), or about something like a residual dust contamination per se, or about Cr/Al atom diffusion (and eventual dust attachment)? I mean what is a mechanism by which say abundant nitrogen molecules in the vessel can affect the deposition?

  Page 19: 300 nA. Page 20: Purdue, 300%.

  I agree with Kong that the report would benefit from adding reflectivity measurements at BNL, and comparing them to the JLab ones.

  Cheers,

     Alexander.

---

From: Wenliang Li <wenliang.b.li AT gmail.com>
Sent: Sunday, February 25, 2024 7:10 PM
To: eic-projdet-pfrich-mechanical-design-l AT lists.bnl.gov <eic-projdet-pfrich-mechanical-design-l AT lists.bnl.gov>; Kiselev, Alexander via Eic-projdet-pfrich-l <eic-projdet-pfrich-l AT lists.bnl.gov>
Cc: Prakhar Garg <Prakhar.Garg AT stonybrook.edu>; Stoll, Sean <stoll AT bnl.gov>; Tu, Zhoudunming <zhoudunming AT bnl.gov>; abhay <abhay.deshpande AT stonybrook.edu>; Thomas Hemmick <thomas.hemmick AT stonybrook.edu>; Kiselev, Alexander <ayk AT bnl.gov>; Preet Mann <preet.mann AT stonybrook.edu>; Benedikt Zihlmann <zihlmann AT jlab.org>; Woody, Craig <woody AT bnl.gov>
Subject: Mirror coating report ready

 

Dear all,

On behalf of the mirror coating team at SBU, I would like to share a report with you summarizing our findings from the first few coating attempts.

Please feel free to send us comments or suggestions. 

I must emphasize the significant contribution made by the undergraduate students at SBU.

Question to Alexander: do we have anywhere (central collection server) to document eic-related internal reports such as this report?

Many thanks

Bill on behalf of the coating team