Front End Studies International Design Study

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Front End StudiesInternational Design Study
Muon Collider

• David Neuffer
• December 2009

2
Outline

• Front End for the Neutrino Factory/MC
• Concepts developed during study 2A
• Concern on Vrf as function of Bsol
• 200MHz, 10 MV/m B 2T
• Variations
• Need baseline design for IDS
• need baseline for engineering study
• updated version to match IDS
• lower fields medium bunch length

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Plan for IDS

• Need one design likely to work for Vrf/B-field
• rf studies are likely to be inconclusive
• B1.25T V 10MV/m is very likely to work
• B 2T V 15 MV/m should work with Be
• Hold review to endorse a potential design for IDS
  
• likely to be acceptable (Vrf/B-field)
• April 2010 ?
• Use reviewed design as basis for IDS engineering
  study

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Solutions for possible rf cavity limitations

• Potential strategies
• Use lower fields (V, B)
• 10MV/m at 1.5T?
• Use non-B constant lattices
• alternating solenoid
• Magnetically insulated cavities
• Is it really better ???
• Alternating solenoid is similar to magnetically
  insulated lattice
• Shielded rf lattices
• low B-field throughout rf
• Use gas-filled rf cavities
• same gradient with/without fields
• but electron effects?
• Use Be Cavities
• should have better B/ Vrf

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Shielded rf cooling channel (C. Rogers)

• Lattice that keeps B small within rf cavities
• Iron placed around coils
• B lt 0.25T at rf
• Problems
• rf occupancy 1/3
• larger ß (1m)
• tranverse acceptance
• Still has fair cooling
• increases µ/p by 1.7

3m
rf cavity
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Baseline IDS candidate

• ISS study based on nB 18 ( 280 MeV/c to 154
  MeV/c)
• 1.75T, 12MV/m
• Reference -shorter has nB 10 ( 280 MeV/c to 154
  MeV/c)
• slightly higher fields (2T, 15MV/m)
• Looking for candidate variation for IDS
• developing intermediate case, with a bit weaker
  fields

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Recent Studies on Lower Fields

• Adequate acceptance can be obtained by reducing
  magnetic fields and gradients
• B -gt 1.25T, V -gt 10 MV/m ??
• (10MV/m is 7MV/m real estate gradient could use
  7MV/m if space is filled.)
• Reduced B, V are relatively certain to work.
• Cost optimum?
• B1.5T ?, 12MV/m

0.75T, 14MV/m
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Look at performance if Vrf is reduced

• Muons per 10 8-GeV protons

Cooler/ Rotator 10 12 14 15 17 18 MV/m
10 0.35 (0.63) 0.55 (0.67) 0.66 0.73
12 0.57 (0.72) 0.754 0.77 0.80
14 0.776 0.80 0.82 0.84
15 0.81 0.85 0.88 0.84
(0.65cm) (0.8cm)
B2T (B1.25T 5 worse) - B 1.5T 5 better
Variation is not strong more rf still means more
muons
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Front End ReOptimization

• Change reference B-field to 1.5T
• constant B to end of rotator
• Redoing nB 12 example
• A bit longer than nB 10
• optimize with lower fields
• Vrf lt 12 MV/m
• Will see if we can get better optimum

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High-frequency Buncher and f-E Rotator

• Drift (p?µ)
• Adiabatically bunch beam first (weak 320 to 232
  MHz rf)
• F-E rotate bunches align bunches to equal P
  (233MeV/c)
• 232 to 202 MHz, 12MV/m
• Cool beam 201.25MHz

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Parameters of candidate release

• Initial drift from target to buncher is 79.6m
• 18.9m (adiabatic 20T to 1.5T solenoid)
• 60.7m (1.5T solenoid)
• Buncher rf 33m
• 320 ? 232 MHz
• 0 ? 9 MV/m (2/3 occupancy)
• B1.5T
• Rotator rf -42m
• 232 ? 202 MHz
• 12 MV/m (2/3 occupancy)
• B1.5T
• Cooler (50 to 90m)
• ASOL lattice, P0 232MeV/c,
• Baseline has 15MV/m, 2 1.1 cm LiH absorbers /cell

0.08
µ/p
cooling
0.00
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progression through system
z 1m
80m
156m
215m
112m
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NF Release Candidate

• Front End a bit longer than short example
• 50m shorter than ISS, however
• gradients no greater than ISS baseline
• slightly better performance

66m bunch window
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How Long a Bunch Train for IDS?

• ISS study alotted space for 80 bunches (120m long
  train)
• 80m or 54 bunches is probably plenty

Study 2A
80m
-20
100
nB 10
50m
40
-30
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Bunch train length

• Within IDS design could reduce bunch train to
  80m (52 bunches)
• very little mu loss
• With shorter front end, could reduce that to 50m
  or less
• For Collider scenario 12 best bunches, (18m)
  contains 70 of muons
• Reserving 80m for bunch trains should be adequate
  for IDS

Study 2A
20m
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B0 1.5T, nB 12 RC

• Muons per 10 8-GeV protons (Atlt 0.03, ALlt0.02)

Cooler/ Rotator 10 12 14 15 16 18 MV/m
10 0.35 (0.63) 0.55 (0.67) 0.66 0.73
12 0.57 (0.72) 0.754 0.84 0.77 0.856 0.88 0.80
14 0.776 0.80 0.84
15 0.81 0.85 0.84
(0.65cm) (0.8cm) 1.0cm 1.1cm 1.15
Black are old nB 10 example new version is
Green
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Varying Buncher/Rotator Voltage

• Vary buncher/rotator gradients from baseline to
  explore sensitivity to gradient limits.
• same baseline cooling channel (16MV/m, 1.15cm
  LiH)
• 15 MV/m -gt 1.1cm Li H
• Somewhat less sensitive than previous

Buncher / Rotator 0/0 3/6 4/7 5/8 6/9 7/10 8/11 9/12
µ/8GeVp at 240m (10) .136 .508 .686 .753 .797 .800 .831 .857


10/ 13 11/ 14
.821 .839


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rf requirements

• Buncher
• 319.63, 305.56, 293.93,285.46, 278.59, 272.05,
  265.80, 259.83, 254.13, 248.67, 243.44, 238.42,
  233.61 (13 f)
• 100MV total
• Rotator
• 230.19, 226.13, 222.59, 219.48, 216.76,
  214.37,212.28, 210.46,208.64, 206.90,
  205.49,204.25, 203.26, 202.63,202.33 (15 f)
• 336MV total
• Cooler
• 201.25MHz up to 75m 750MV

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Plans etc.

• Move toward realistic configuration
• More realistic B-field
• B 1.5T -gt coil-based fields
• add Be windows
• smaller number of rf frequencies
• Set up design for cost algorithm
• rf cavity design (pillbox, dielectric)
• rf power requirements
• Magnet design
• Continuing front end IDS design study
• C. Rogers, G. Prior, D. Neuffer, C. Yoshikawa, K.
  Yonehara, Y. Alexahin, M. Popovic, Y. Torun, S.
  Brooks, S. Berg, J. Gallardo
• Fermilab meeting (July)
• Biweekly phone Conference
• Meeting at RAL
• December 14-18
• April at Fermilab (IDS meeting)

dielectric
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IDS - cost issues
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Study2B June 2004 scenario (ISS)

• Drift 110.7m
• Bunch -51m
• 12 rf freq., 110MV
• 330 MHz ? 230MHz
• ?-E Rotate 54m (416MV total)
• 15 rf freq. 230? 202 MHz
• P1280 , P2154 ?NV 18.032
• Match and cool (80m)
• 0.75 m cells, 0.02m LiH
• Captures both µ and µ-
• 0.2 µ/(24 GeV p)