Minutes of the Muon Cooling meeting. Friday 19 Feb. 1999 Fermilab.
Attended: A. Bross, P. Lebrun, D. Kaplan, D. Neuffer, E. Black, J. Norem,
P. Spentzouris, V. Balbekov
(Phonelink) Steve Kahn, Rick Fernow
(Notes by Ed Black and Dan Kaplan; please reports any errors to
kaplan@fnal.gov.)
1- Rick Fernow- Wedge simulation update
Rick described his simulation of the longitudinal-transverse emittance
exchange. He used a 3.5 T bent solenoid field and 400Mhz RF phase
rotation plus a second opposite solenoid plus lithium-hydride wedges plus
more RF, covering 2 Larmor wavelengths. The longitudinal emittance was
reduced by 0.65. He optimized the transverse emittance growth by
adjusting dipole parameters - unfortunately the transverse and
longitudinal performances seem to be correlated! After 2 days of
optimization he found an increase in momentum spread of 0.3 and in the 6D
emittance of 80%. Rick will try a more complex field shape a la Norem.
Paul asked whether the transverse emittance growth is due to lattice
mismatch or due to the absorber. Rick thinks it is distributed over all
the elements, with the first 15% in the first bent solenoid, and the
absorber only one of many contributions. There is some controversy what
the dipole field r-dependence should be, or whether it should be
independent of r. Jim commented that 180* bend gives max dispersion but
Rick says it increases the transverse-emittance growth.
2- Steve Kahn- MUCOOL tracking update
Steve sees broad correlation of dy with p, believes need to correct for
the integral of Bdl seen by each particle. He pointed out that the
"reference particle" enters on-axis but leaves off-axis. It was suggested
that he could tweak p to rectify this, i.e. "reference momentum" is not
nominal.
3-Paul LeBrun- Cooling theory meeting summary
Paul compared pi/2 (closed cell) versus pi (windowless cells) mode
cavities, all at 805 MHz, found they behave equally well if pi mode can
stand 60 MV/m max on-axis field. Jim questioned what happened to Paul's
previous (preliminary) claim that pi-mode was "too good to be true,"
answer, that was mistaken and was due to his having fiddled with the
multiple scattering and forgetting at first to restore it to deault.
4- Jim Norem- Bunch possibilities update
Jim reminded us of the relationships between cos(theta) and theta and
particle energy and velocity. From these follow the bucket shapes in KE
vs. phi at various values of theta. The conclusion is that the bucket
includes larger angles at lower energies and smaller angles at higher
energies. With a stronger accelerating field, the theta-dependence is
reduced, and also a wider range of energies is covered for each angle.