Minutes of meeting held on 04 Jun 2020 ========================== slides are at: https://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=8457 (1) Tan gave a quick verbal update: (i)Internal review of the digital LLRF system went well. There’s still a lot of work to be done, like building the electronics and stuffing them into boxes. The plan is to have the hardware built by the end of the year. (ii) Longitudinal dampers: We analyzed why the dampers did not seem to work well during the last run. We discovered that the delays were too long in the digital system and was, in fact, exciting the beam right after transition and before extraction. A new firmware will be installed with less delay (~30-40%) and better diagnostics. (iii) 2 stage collimator review went well. (2) Valery gave an update of the new 2 stage collimators (i) Conceptual design started in 2017. Preliminary design of new collimation unit for both 400 MeV and 800 MeV in 2020. (ii) The present collimators that were designed and installed in 2003-04 as 2 stage collimators but are not operated as 2 stage collimators. They are used as single stage collimators (L6 and L7) and the primary (S5) is not used. (iii) Presently, the highest losses are in the collimation region L6. (a) the high radiation at the collimators is mainly due to out scattered portons at the single scattering regime. (b) Considerable part of the halo avoids the collimator and directly hit the RF stations. (iv) Booster phase advance is 102 deg and so having collimators at L6, L7, L8 and L9 would be useful by redistributing losses at L6 and L7 to a collimator at L8 and in the future L9. (v) New collimator will be in L8. (vi) This will have the primary and collimators in a single unit. (a) Mars simulations have been performed on this new design. (b) Main idea is to use a thick primary 4 cm < t < 15 cm of copper. (b) > 90% collimation efficiency can be reached. (vii) New collimator unit will have rotatable primiary because the exact halo distribution is unknown. (ix) At 800 MeV, collimation inefficiency is due to protons "punching" through collimator. (a) Thicker primary ~20 cm or two rotated primaries. (b) Use stainless rather than copper. But stainless has other problems. (x) Next stage is to consider final design. (a) Shielding will need to be understood. (b) Fix the design. There isn't that much time before installation in end of FY22.