Beam Loss at Slow Extraction of JPARC MR

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FNAL2005/03/8
Beam Loss at Slow Extraction of J-PARC MR
Masahito Tomizawa KEK ACC. Lab.
Introduction of J-PARC MR Slow Extraction Beam
Hit Rate on ESS Wires Behavior of Protons
Mutiple-Scattered on ESS Wires
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Slow Extraction of J-PARC Main Ring

• 3.3x1014 protons per pulse(15mA) full beam power
  750kW _at_50GeV
• beam loss as possible as small lt1 (7.5kW)
  level radiation safety problem
• coasting beam extraction
• third integer resonance separatrix linear
  easy to tune separatrix angle and
  step size by
  adjusting resonant sextupoles

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psext4_007.dat mad332.madenv4.com
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Septa Parameters
Parameters of Electrostatic septa (reference
design) thickness
voltage(kV) L kick angle
(mm) /gap(mm) (m)
(mrad) ESS1W/Re(3) wires 8020
170/25 1.5
-0.2 ESS2W/Re(3) wires 8020
170/25 1.5 -0.2
Magnetic septa thickness length
magnetic field kick angle (mm)
(m) (T) (mrad) SM11
1.5 1.5 0.113
1.0SM12 3 1.5
0.226 2.0 SM21-24 (4
units) 7 0.8375
0.524 2.584 SM30,31 (2 units)
30 1.14 1.432
9.61 SM32,33 (2 units) 64
1.14 1.652 22.17
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Beam Loss Mechanism of Slow Extraction
?Primary Beam hits ESS wires ---gt reduce hit
rate (1)Real Loss at ESS wires (make
radiation) (2)Protons go out of wires by
multiple scattering (a)to extracted side one
path hit on downstream components, SM,,,,
extracted from the ring (b)to circulating
side circulating in the ring hit on
other components, SM,,,, extracted from
the ring
electrode
extracted side
wires
circulating side
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50GeV primary beam hit rate on ESS wires
dynamic bump
beam hit rate on ESS wires
tri0103_090 (sca0122_2_044)
tri0103_095
w100mm, L1.5m
before 3turns
extraction
Qv20.775
min. hit rate 0.8 _at_100mm min. hit rate 0.5
_at_50mm
Circulating Beam Parameters ex6.1p mm?mrad
ey6.1p mm?mradDp/p0.25
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MARS Simulation of scattering in the ESS wires
by T.Yokoi
Head-on Hit H 80mm, 0.1mradV 20mm,
1mrad Uniformly distributed beam
Low Density Bulk Model
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Protons scattered on the ESS wires (MARS)
40cm downstream from ESS1 exit
(Reference ESS design)
sadin_foilsct_case1.dat r12_case1.com
Scattered to circulating side
Scattered to extracted side
sadin_foilsct_case1.dat r12_case1.com
Hit rate 0.01 (1), full beam 750kW real loss
rate N(hit)-N(scatt.)/N(hit) real loss
750kW x0.01 x 0.0770.58kW
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Behavior of protons mutiple-scattered at ESS
wires Tracking ? initial beam
condition by MARS ? check losses at ESS, SM and
vacuum chambers with real shape ?particles
scattered to extracted side and circulating
side ?tracked up to ring exit ? two x-y
collimators (downstream from ESS) scrape halo
of scattered particles do not scrape primary
extracted beam
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Loss of scattered particles for 750kW
beam Reference ESS design Tungsten 80mm,
effective thickness100mm, 1.25mm spacing,
L1.5m ?Slow extraction long straight section
real loss ESS1
0.64kW quadrupole 0.044kW duct
0.03kW ESS2 0.12kW Slow
collimator 1 0.11kW Slow collimator 2
0.28kW SM11 0.33kW SM12
0.053kW ?Other LSS?arc. section lt0.5W/m Total
loss in the whole ring is 1.88kW Loss is
localized at slow extraction LSS
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Loss Map of Scattered Protons
(Reference ESS design)
Loss of protons scattered to circulating side
Loss of protons scattered to extracted side
straight section
straight section
dipole
quadrupole
quadrupole
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Protons Extracted from the Ring
Primary extracted beam Sca0122_3_044
(Reference design)
99
Extraction efficiency 99.75
Survived protons (scattered to circulated
side) Sca0123_1_090
Survived protons (scattered to extracted
side) sca0122_2_044
0.41
0.34
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Ribbon foils (AGS type) ESS1 W, 30mm20mm, 1mm,
4mm spacing, L1.5m, 0.2mrad ESS2 W, 30mm20mm,
1mm, 4mm spacing, L1.5m, 0.2mrad
ESS2
ESS1
Thinner reduce hit rate Mechanically stronger
reliable Smaller deviation due to electric filed

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(No Transcript)
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Scattererribbon ESS Scatterer 30mm20mm, 1mm,
40mm spacing, L0.5m, 0mrad ESS1 W, 30mm20mm,
1mm, 4mm spacing, L1.0m, 0.133mrad ESS2 W,
30mm20mm, 1mm, 4mm spacing, L2.0m, 0.267mrad
ESS2
ESS1
scatterer
Scatterer low average mass density, no electric
field Beam hits scatterer Multiple scattering is
dominant process--gt radiation is reduced Beam
hit rate on downstream ESS foils is small
Needs more space to get same kick angle
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Summary (50GeV 750kW beam)
real loss extraction
in the whole ring efficiency 8020mm wires
1.88kW 99.75 3020mm ribbons
1.05kW 99.86scattererribbons
0.71kW 99.91
Predicted real loss is comparable with that
of existing machine (AGS..), probably
acceptable Ribbons or scattererribbons is
effective Predicted extraction efficiency is
very high Scattererribbons reduces tail
sca0122_10_044
Validity of low density bulk model Other code
(GEANT)
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Production of Slow Extraction Devices will
start from spring 2006. We have one more year
to fix ESS scheme! Scattering simulations
RD Ribbon ESS (alignment and high voltage test)