Meeting with Makoto Chiba Univ. 2022/12/05
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Present: Alexander K., Alex E., Makoto T., Marco C., Rolf E.,
         Xiaochun H., Elke A., Murad S., Beni Z.


- mass production for experiment at Jparc with n=1.04
  14cm x 14cm x 2.5cm tiles, 100 tiles in last 2 month
  1300 tiles in total over 3 years

- maximum tile size 15cm x 15cm, near future may expand to 20cm x 20cm
  the larger the tiles the more variation on the sides and the smaller
  the maximum thickness
  for these tiles the size variation (cross section) is of order +/-1mm
  cutting (e.g. with water jet) is required to reduce size variation

- special care is not needed but long term operation should foresee
  enclosure with dry nitrogen environment.

- small tiles of 5cm x 5cm size would have much better edge quality
  and cutting (e.g. with water jet) is not needed

- also small sizes can be made thicker with not much effort

- 3cm thickness for 15cm x 15cm tiles is possible
  ("with special care" -> my interpretation)

- tiles can be cut into "any" shape, e.g. not just square

- water jet cutting has a size variation of +/- 0.25mm

- cutting by other means may be possible but has not been tested
  e.g. laser or diamond saw

- how flat are the surfaces? currently not so good but can be improved
  on by carefully designing the mold.

- the bottom surface is much flatter than the top

- n=1.03 and n=1.02 are certainly possible with 3cm thickness
  the smaller n the thicker the tiles can be with same effort.

- transparency as a function of n and wave length? at 400nm and n=1.03
  scattering length is 60mm and exhibits a maximum as a function of n
  at n= 1.03
  what about other wave length? like 300nm -> Makoto will come back to that.

- for pfRICH combination of transparency as a function of n and wave length
  is important due to QE of photo sensor with maximum at 360nm
  (well below 400nm)

- the variation in n at n=1.03 for different tiles in the production is
  of order 1.5%

- n=1.03 seems to be rather "easy" to produce compared to larger n

- there is a relationship between index of refraction n and the
  density: linear approach is n = 1 + k*rho with k = 0.21 for Russian
  Aerogel, and k = 0.25-0.3 for Japanese Aerogel.
  on that slide the term "hydrophobic" was mentioned in the context of
  Japanese Aerogel.

- what is the uniformity of n over the volume of a single tile?
  similar to the variation over tiles, +/- 1.5%