Download - Stopped K beam at J-PARC
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Stopped K beam at J-PARC
Designed by J.Doornbos1) Optics design of a K0.8 branch2) Performance3) Pion contamination 4) Comments on K1.1
Nov. 4, 2005Korea J-PARC seminar
- A branch option of K1.1 -
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LoI’s with stopped K beam
LoI-04 Study of the Rare Decay K +→+ with Stopped Kaon Beam at J-PARC
LoI-05 Measurement of the K0L→ Branching Rati
o
LoI-16 Study the Kaon Decay Physics at JHF
LoI-19 Search for T-violation in K + decays
LoI-20 Precise Measurement of the K +→ 0e + (Ke3) Branching Ratio
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Possibility of a stopped beam in Phase 1
K0 Line( KL beam)
E391a detector
K0.8 Line( stopped K±) as a branch of K1.1 Use of K1.1 by lowering
beam momentum
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Phase-2 Hall
Hall size = 60m (W) x 100 m (L) More than 2 target stations
K0.8
Use of T2
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Can we use K1.1?
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A branch option of K1.1designed by J.Doornbos
• A branch of K1.1 at B3• Common use of the upstream part up to MS1• Macroscopic time sharing with K1.1• Effective use of IFY• Single-stage DCS
• Moderate beam intensity -> Feasibility to start the T-violation experiment with minor upgrades of the Toroidal Detector
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Layout of the K0.8 branch
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Design principle
Effective use of wedge focus to make HFOC Suppression of slit-scattered pions at HFOC Cloud pion source definition by IFY
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Replacement of B3
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Beam optics
First order beam envelop@ 0.8 GeV/c
x’= 43 mr y’= 9 mr
x = 3.5 mm y = 2.0 mm
p/p = 0
Length = 19.06 m
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Momentum dispersion
R16(FF) = 0R26(FF) ≠0
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Beamline elements
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IFY profile
ZGOUBI calculation
Source size x = 2 mm y = 2 mm
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MS1 profile
DCS = 550 kV/10cmPion kick = 2.2 mr
ZGOUBI calculation
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HFOC profileZGOUBI calculation
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Final focus
ZGOUBI calculation
R16 = 0
cf. R16≠0 @ K5 → source of systematic errors
R26 ≠0• less problematic• longer target
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p/p momentum acceptance
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Angle acceptance
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Pion contamination
1. Higher order aberration2. Slit scattering3. Cloud pions from Ks (c=2.7 cm)
simulation by ZGOUBI
Aberration: y = R33y0 + R34 + A1 + A22 + B1 + B22 + ・・
A1, B1 = 0 by adjusting the sextupoles S1 and S2 A2, B2 were minimized by optimizing the octupole O1
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Rejection of slit-scattered pions
Slit scattering simulation with REVMOC
IFY and MS1
with 30 cm thickness tapered (20 mr at both ends)
x-profile at HFOC
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Rejection of cloud pions
Accepted y region at the production target
IFY = 5 mmMS1 = 4 mmHFOC = 1.6 cm
HFOC is effective !
Pion source of x = -2 ~ +2 cm y = -1 ~ +3 cm was assumed. ( c.f. c = 2.7 cm)
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Kaon yield and /K ratio
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Cloud pion contamination
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Summary of the K0.8 beam
Acc = 6 msr % p/p c.f. Acc (K1.1) ~ 4 msr % p/p Acc (LESB3) ~ 50 msr % p/p IK+ ~ ( 1~ a few) × 106/s
+/K+ < 0.5 assuming /K = 500
Beam spot : dx ~ dy ~ 1 cm << @K5
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Further studies
Realistic source distribution in T11. rotating target angle2. cloud pion source
Effects of proton beam halo /K ratio optimization
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Comments on the K1.1 optics
Sector type B4 with HFOC
effective suppression of +
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/K separation at MS1
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MS2 profile
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Final focus of the new design
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Rejection of cloud pion by HFOC
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Conclusion
The C-type branch of K1.1 for stopped beam is feasible
The intermediate vertical focus IFY plays an important
role.
The installation of an IFY slit is very necessary.
A switching mechanism has to be considered for B3+Q7. We will propose this option of the low momentum separate K-line together with the experiment proposal
There is no concrete plan yet for funding.