Beamline Concept for New g2 Experiment

1
Beamline Concept for New g-2 Experiment

• P. Debevec, S. Knaack, P. Kammel
• University of Illinois at Urbana-Champaign
• P. Pile
• Brookhaven National Laboratory
• ALD Review February 8, 2006

E969 requirements 5 x
increase in data rate 2 x reduction of
systematic uncertainties Reduction
of major background critical
2
Improvement Strategy

• Three main ideas
• Collect backward decay m in p CMS rate x 1 or
  more Prompt Hadronic Flash eliminated
• Double (triple) quads in decay channel rate x
  2 or more Smaller b function increases
  acceptance
• open ends of inflector (W. Meng) rate x 2
  Eliminate multiple scattering in superconductor

Prompt flash Requires gating of PMTs
Introduces slow background Restricts fit range
3
Existing Beamline
Pions _at_ 3.115 GeV/c
Decay Muons _at_ 3.094 GeV/c
80 m
beam envelope y plane (vertical) x
plane (horizontal)
4
E821 Design Report H. Brown btraf calculation

• horizontal and vertical beam envelopes

in
103 in
5
E821 used forward decay beam, which permitted a
large p component to enter ring
Pions _at_ 3.115 GeV/c
Decay muons _at_ 3.094 GeV/c
This baseline limits how early we can fit data
6
Inflector mismatch to storage ring

• direct coupling of storage ring to beam line to
  illustrate mismatch

once around ring
twice around ring
inflector
K3K4 slits
weak vertical focusing
Dp/p 1/4 Dp/p 1/2
at inflector horizontal waist small vertical
divergence
7
Forward Decay
Decay muon in Lab Frame
measured particles after K3/K4 slit
p? (Gev/c)
pm
? 4 mrad
g-2 operating point
p (GeV/c)
m
p
Ideally Pp 1.005 pm but Pp 1.017 pm
Magic momentum pm 3.094 GeV/c
 
8
Forward vs. Backward Decay
Pp 5.22 GeV/c 1.687 pm Ideally Pp
5.35 GeV/c
plab
?
p? (Gev/c)
m
p
p (GeV/c)

• Scaling for m PS
• p g (p cos? b E)
• dN/dp ? 1/g
• dN/d? ? g or ?g
• ?0 accepted

 
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Beam Simulations

• Goals
• Implement all new features
• Verify basic principles
• Optimize beam line configuration
• Optimize new beam elements (cost/performance)
• Tools
• Phase space Monte Carlo program
• TRANSPORT (global beam properties)
• DECAY TURTLE (Monte Carlo trajectories)
• COSY Infinity

2nd order
 
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Beamline conceptual design report in preparation
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Backward Tune Issues
collect 5.2 GeV/c p
match to inflector acceptance
3.1
1st order
5.2
transport 5.2 GeV/c p AND 3.1 GeV/c m in decay
channel
transport and inject wide ( 3) p momentum
bandin decay channel
 
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p Collection, pp Selection

• Requirements
• accept 5.3 GeV/c
• accept 3 ?P/P
• Modifications
• increase Q1 length
• increase Q2 aperture
• replace Q3-Q6 with larger aperture standard quads
• new D1, D2
• new poles for D3, D4

Q1Q2D1D2Q3Q4 K1K2 Q5Q6D3D4
Q7Q8Q9Q10
Q1 Q2 D1 D2 Q3Q4Q5Q6 D3 D4
 
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Field requirements of new magnets
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Decay Channel Matching for 3.1 5.2 GeV/c
F O D O F
Beta function
FODO cell
xmax
L12.4 m
Pp 5.22 GeV/c pm 3.09 GeV/c
bmax
bmin
both momenta can be transported efficiently

m
p
 
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Doubling of Quads in FODO
Smaller x, larger x bmax ? L for fixed f/L
(f focal length, L/2 quad spacing) Reduce L to
reduce bmax
5.563 m
E969
E821
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Turtle
p channel acc.
p Q11 FODO match
forward
back
back?3
 
17
Turtle
infl/ring acc
p Q19
m Q19
forward
back
m phase space for backward decay very similar to
forward. Infl/ring match should be ok
back?3
 
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Status Task List

• Status
• Basic understanding and baseline beam design
  is developed
• Backward decay
• Quad doubling (or quadrupling)
• No flash, flux increase additional
  increase from inflector, kicker

• Tasks
• Engineering design injection
• Study and integration of inflector/ring
  matching, inflector optimization
• Recovery of lost p with 2nd order correction
  elements

it works
 
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additional slides
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K.L. Brown four cell achromat
COSY optomized achromat
from S. Knaack
Transport through achromat Dp/p 1, 2, 4
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max and min of beta function vs quad field
L 12.446 m forward 3.15 GeV/c backward 5.35
GeV/c
22
muon lab angle vs muon lab momentum
/- 0.5
1 mr
E821 operating point
x at every five degrees in com
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g-2 Beam
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Back decay
PBp5.22
PFp3.152
0.66
Sanford Wang