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

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Presentation on theme: "Results of Deceleration Studies Giulio Stancari E-835 Meeting 23 October 1999."— Presentation transcript:

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

2 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.

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

4 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

5 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.

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

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

8 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.

9 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

10 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.


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