Results of Deceleration Studies Giulio Stancari E-835 Meeting 23 October 1999

E-835 Collaboration Meeting G. Stancari 2 Goals (a) make E-835 possible: quad magnets replaced, buses rearranged, shunts added, 8-GeV lattice modified, …  1996/97 deceleration ramps are no longer usable. (b) make whole E-835 data taking above transition: transition crossing can be very inefficient; current transition energy at 8 GeV corresponds to  s = 3.66 GeV, just below the . The plan: modify the Accumulator lattice as the beam is decelerated from 8 GeV to the E-835 data-taking energy region, so that the transition energy is shifted from just below the  to well below the  0. Keep lattice constant in E-835 region.

23 October 1999E-835 Collaboration Meeting G. Stancari 3 Charmonium spectrum and the transition energy of the Accumulator

23 October 1999E-835 Collaboration Meeting G. Stancari 4 Scheme for ramping  t slip factor  = 1/  t 2 - 1/  2 the magnet strengths determine  t

23 October 1999E-835 Collaboration Meeting G. Stancari 5 Deceleration Studies The ramp-development team (K. Gollwitzer, E. Harms, W. Marsh, D. McGinnis, G. Stancari and S. Werkema) did deceleration studies for about 8 weeks, from Aug 25 to Oct 17. Measured lattice at 8 GeV. Established maximum-aperture orbit: A x =10  and A y = 11  mm-mrad. Performed rounds of tune, orbit and frequency corrections. Minimized coupling between transverse planes. Corrected chromaticity. Checked size of RF bucket.

23 October 1999E-835 Collaboration Meeting G. Stancari 6 Tune-tracker pictures

23 October 1999E-835 Collaboration Meeting G. Stancari 7 Orbit and dp/p (revolution frequency) corrections

23 October 1999E-835 Collaboration Meeting G. Stancari 8 The emittance of the proton beams we received was much bigger than what we expect to have with stacked and cooled antiprotons. It was also variable. Emittance considerations Beam emittance  is the phase-space volume occupied by a specified fraction (ie, 95%) of particles. In the transverse degrees of freedom,   1/p. Along a ramp, the transverse emittances are expected to grow by a factor 2. In order to obtain reliable and reproducible measurements of ramp transmission efficiency, it was necessary to scrape the beam to simulate the effect of stochastic cooling.

23 October 1999E-835 Collaboration Meeting G. Stancari 9 Results (I)  a good transmission efficiency from the top to the bottom of the ramp has been achieved efficiency is 94% with beam scraped to 2  mm-mrad in both transverse planes and to  p /p  10 8 GeV 00 beam current vs momentum

23 October 1999E-835 Collaboration Meeting G. Stancari 10 Results (II)  the  t ramping scheme (aka “snowplowing  t ”) worked well. The measurements of  and  t along the ramp (Sep 13) are close to their target values.