Minutes of meeting held on 08 Oct 2020
==========================

slides are at:
https://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=8711

(1) Robyn gave an update on the wide bore cavity HOM measurements
    (i) Status: cavity needs tuner to be modified. Presently cavity
    cannot get to 53 MHz without a modified bias supply.
       (a) High power test has been completed.
    (ii) Wire measurements were done.
     (iii) Schematic of the setup was shown.
     (iv) Measured with beam pipe to mimic cavity without gaps for
    corrections to calculated  impedances from s21 measurements.
    (v) Table of measurements and comparisons are shown w.r.t. legacy.
       (a) Rsh is higher for higher frequencies than the legacy
    cavities.
       (b) This could be explained by the much higher bias on the
    ferrites which makes the ferrites less lossy.
       (c) Another suspect is only the low mu cores are used unlike
    the legacy cavities.
    (vi) A comparison of to the legacy HOMs show not much difference
    in impedance at 80 MHz. 80 MHz is the worst mode for coupled
    bunch.
    (vi) Other modes seem to have disappeared compared to legacy.
    	 (a) However, this may be due to different configuration of
    the passive of the dampers that may be different when Kathy
    H. measured them.
         (b) BIll says that these modes are not that important for
    coupled bunch modes. 
  (viii) Robyn showed the data all the up to 500 MHz. Not much
  interesting from 210MHz to 500 MHz region.  Bill Pellico commented
  that even the cavities in operation do not pose any problem above
  ~210MHz.
  (ix) Robyn told that there are no results to compare her
  measurements on shunt impedance with simulations at this time.
     (a)Chandra and Bill: Mohammed might have  done simulations for
     current cavities as well as for the 3.25'' bore cavity.
     (b) John Reid is going to contact Mohammed regarding 3.25" bore
     cavity simulations.

(2) Chandra addressed  transition crossing in Booster during PIP2
      era: issues and possible solutions
  (i) First, he talked about some confusions regarding bunch 
      population in the Booster RF bucket at 800 MeV. He urged that 
      we need realistic linac bunch profile for more realistic simulations 
      (how they are obtained). 
      Jean -Francois: Suggested to use the distribution published in PIP2 
      design report which is same as what Eduard Pozdeyev has given.
    
  (ii) Chandra has used the initial dE-dt-distributions in Booster RF
       bucket of 0.203MV  using Eduard's input parameters 
       and turning on  SC  in 550us as bunch is populated
    (a) simulations are without resistive wall impedance and
    cavity impedance.
  (iii) Simulations were from injection to
    extraction. The highlights of the simulations are:
    (a) Transition crossing in Booster only
    with standard phase jump will give rise to  ~250% emittance
    growth, which will be too large for RR injection.
    Jean -Francois: told that this is consistant with what they 
    (Jean -Francois and Valery) have seen about 2 years ago.
    (b) gammaT jump simulations were for a range of delta-gT, time of
    turn on and relaxation time.
    (c)finally Chandra claimed that delta-gT~0.5, turn on time <150us
    and relaxation time of 1-2 ms will be ideal for the Booster for PIP2
    scenario.

  Discussions:
    (i) Bill:
      (a) May be advisable to call it psudo-gammaT jump (rather than
      conventional name),  if scheme is with existing quad. He also told
      that we are currently using a Q-jump at transition.
      (b) We may still need quad damper, Chandra agrees with it.
    (ii) Jean Ostiguy:
      (a)  Including wall impedance in simulation should not be a
      difficult problem in ESME.
    (iii) Lebedev:
     (a) disagreed with the results of the simulations because
    resistive wall is the dominant effect compared to space
    charge. Also, momentum aperture needs to be taken into account. 
    (iv) Chandra:
     (a) There were quite a good agreement between his Booster
     ESME simulations just with SC effects and measurement data for PIP 
     operational conditions.  So, at the moment he did not worry 
     about other effects. But agrees that it should be done.