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Study of Long-Range Collisions and Wire-Compensation for the Tevatron. Frank Zimmermann February 21 – March 8. Thanks to: Bela Erdelyi, Paul Lebrun, Tanaji Sen, Vladimir Shiltsev, XiaoLong Zhang. motivation. wire compensation is under study for the LHC with - PowerPoint PPT Presentation
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Study of Long-Range Collisions and Wire-Compensation for the
Tevatron
Frank Zimmermann
February 21 – March 8
Thanks to: Bela Erdelyi, Paul Lebrun, Tanaji Sen, Vladimir Shiltsev, XiaoLong Zhang
motivationwire compensation is under study for the LHC with3 prototype wire-devices in the SPS
is there a potential for wire-based compensation of long-range collisions at the Tevatron?
situation is more difficult: helix (both transversedimensions), many betatron phases, differences between bunches and between injection & collision,dispersion, coupling, etc.
is it helpful to compensation a few “most harmful”long-range collisions? can I confirm the efficiencyof wire correctors found at injection?
which parameter can guide the compensation?
I looked at • bunch A1 at injection “cog0” (A1 stays longest in the
machine and was studied by B. Erdelyi and T. Sen) • bunches A6, A1 and A12 in collision
injection parameters
collision parameters
Phase-Space Positions of the Long-Range Collisions
Image of all LRBB collisions mapped into normalized phase space.
x-px y-py
x-px y-py
injection, A1
collision, A6
injection, A1
collision, A6
Normalized distance versus index of LR collision.
Ax Ay
AxAy
injection, A1
collision, A6
Distance Ay vs Ax (left) and total distance Atot(right) vs. index of LR collision.
Ax
Ax
Ay
Ay
Atot
Atot
LR encounters below 7 for bunch A1 at injection:
LR encounters below 7 for bunch A6 in collision:
6
3
Tracking is performed usingan extended version of WSDIFF
described at LHC99.
15 trajectories with random start amplitudes between 0 and 10 over 500 turns.
phase spacex-px y-py
coordinates vs time
injection, A1
xy
Tune Footprints
tune footprint for start amplitudes up to 6in each plane
all LR encounters without the 6 closest
injection, A1
not much difference…
injection, A1
comparison of footprints from WSDIFF with BBSIM
tune footprint for start amplitudes up to 6in each plane
all LR encounters without the 3 closest
collision, A6, w/o head-on
a large difference!
collision, A6, A12, A1
w/o head-on
Bela’s solution for wire compensation at injection (4 wires,which optimized dynamic aperture and/or minimized normof the nonlinear map)
tune footprint for start amplitudes up to 6in each plane
LR encounters only with 4 wires
injection, A1
footprint ‘rotates’, but keeps similar extent
Diffusion
launch group of particles at the same amplitude with a random phase and
compute increase of the average action variance per turn
(scheme of John Irwin for the SSC)
injection, A1
X Y
X Y
all LR encounters
without the 6 closest
dynamic aperture ~6 dynamic aperture ~5
injection, A1with 4 wires
~0.5improvement in Y
(note different horizontal scale on this plot)
dynamic aperture ~5.6dynamic aperture ~5.6
collision, A6
all LR encounters
without the 3 closest
X Y
X Y
dynamic aperture ~8
dynamic aperture ~8
~8.5 ~8.5
collision, A6
all LR encounters
with only the 3 closest!
X Y
X Y
dynamic aperture ~9.0 dynamic aperture ~9.5
dynamic aperture ~8 dynamic aperture ~8
collision
all LR encounters, A1
all LR encounters, A12
X Y
X Y
dynamic aperture ~6 dynamic aperture ~6
dynamic aperture ~5dynamic aperture ~5
Analytical estimates
tune shift, chromaticity, coupling,chromatic coupling, diffusion
tune shift & coupling
horizontal & vertical tune shift
A6
A1
A12build upover allLRencounters
injection
collision
collision
collision A1
real & imaginary coupling
A6
A1
A12build upover allLRencounters
injection
collision
collision
collision A1
chromaticity &chromatic coupling
horizontal & vertical chromaticity
A6
A1
A12
injection
collision
collision
collision
build upover allLRencounters
A1
real & imaginary chromatic coupling
A6
A1
A12build upover allLRencounterscollision
collision
collisioninjection A1
Total tune shifts, chromaticities, coupling driving terms, and chromatic couplings induced by long-range collisions for various pbar bunches in collision:
and for A1 at injection:
diffusion coefficient in 4D
no analytical solution yet for this double integral…
Future Plans
• extend simulations to 6D andcompute diffusion at 1
(chromaticity & chromatic coupling most likely important)• continue analytical calculations• study effect of unequal beta on
compensation• other suggestions welcome!