NLC 2001 Beam Delivery Layout

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NLC 2001Beam Delivery Layout

• Tom Markiewicz
• Fermilab Meeting of Detector WG Leaders
• 05 January 2001

2
Summer 2000 Configuration
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Summer 2000 Configuration

• Linacs point at each other
• One lt 1 TeV Collimation section common to two
  IRs
• Energy collimation with tune-up dumps
• Relaxed Betatron collimation with consumable
  spoilers
• 10 and 10 mrad Big Bends to get to each of two
  symmetric IRs
• 20 mrad crossing angle at each IP
• Working assumption is Large and Small
  detector
• Non-simultaneous delivery of beam to either
  detector
• 280m IP Stretch provides separation and vibration
  isolation of IR halls
• New FF with L4.3m and magnet apertures designed
  for 1 TeV
• Most magnets could be re-used up to 1.5 TeV
• Length of FF tunnels compatible with 5 TeV
• Either
• same FF lattice to each IR or
• leave tunnel to IR2 empty (Lehman cost estimate)

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Conceptual Problems with Symmetric Two IR Layout

• Experimenters seem to want full luminosity at 90
  GeV 1 TeV, be able to quickly change energy
  and continually question the maximum energy reach
  of NLC X-band technology
• Big Bend (designed for 1.5 TeV) limits upper
  range of energy for HE IR
• Emittance growth due to SR 5 by limiting
  strength of bends
• Magnet apertures set by lowest energy
• Magnet design set by aperture and highest energy
• Ambiguous physics justification for two detectors
  given symmetric layout and fact that only one
  detector gets data at a time
• As FF gets shorter, two FF tunnels merge into one
• lateral displacement of IRs shrinks (44m in ZDR,
  16m in CD4)
• No design provision for gg, which needs larger
  crossing angle

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Base Element of 2001 Layout
Emin, Enom, Emax 250 GeV(?), 500 GeV, 1000
GeV No Big Bend New FF w/ L 4.3 m Collimation
lattice with dog-leg energy collimation 20 mrad
crossing angle One IR Hall with One Large Detector
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The 2nd IR Hall in the 2001 Layout

• Assume a 2nd IR is part of the baseline package
• Questions In order of importance
• Emin, Enom, and Emax for high luminosity
  running
• Sequential or simultaneous beam delivery
• Crossing angle, hall size, and facilities
  infrastructure
• Detector staging spacing of halls for vibration
  isolation

Optimal tunnel layout for cost, flexibility,
performance?
IR2
??m
IR1
Linac and bypass
One collimation system or two?
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First Working Answers to IR2 Questions

• Transverse and longitudinal spacing of halls for
  vibration isolation
• Dx100m Dz 0m
• Emin, Enom, and Emax for high luminosity beam
  delivery
• 90, 250, 500 GeV, respectively
• Need to know Emax to before bend tunnels are dug
• Sequential or simultaneous beam delivery
• Sequential BUT supporting simultaneous operation
  if issues resolved
• Polarized beam to each IR
• 2nd INDEPENDENT collimation system allows
  possibility of simultaneous operation at
  different energies
• Crossing angle, hall size, and facilities
  infrastructure
• 30 mrad (20-40 possible keep E(LBsq)5/2 lt
  current value)
• 10mrad gg stay-free requires bigger angle
• 2nd detector? Precision?

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Site Layout Dx100m Dz 0m
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BDIR Detail Dx100m Dz 0m
FF2
27mrad
Coll2Bends
52mrad
Coll1
FF1
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An Alternative Layout

• Length of tunnels to IR2 is just that required
  for bends that maintain good emittance beam at
  500 GeV c.o.m.
• 110m of tunnel per 10mrad of bend for 5 dilution
  if Emax500 GeV
• Can we reduce IR separation and either reduce
  cost or increase program flexibility?
• Reduce Dx to 25m
• Vibration, simultaneous occupation of halls,
  etc??
• Use ONE collimation system for BOTH IRs
• Need some empty IP-Stretch tunnel to make
  geometry work
• Second collimation system in same tunnel also
  allows possibility of simultaneous operation at
  different energies
• 25 mrad big bend and NO reverse bend
• Are there advantages to ONE big IR Hall?

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Site Layout Dx25m Dz 0mOne Collimation Tunnel
per Side
FF2
Coll
0 mrad
Bend
25mrad
Stretch
FF1
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Reversed Linac Angle, IR Separation 25mand
Separate Collimation Lattices and IR lead to Big
Bend Reverse Bend Angles 21.8mrad
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Another Possibility Dx25m Dz 440mOne
Collimation Tunnel per Side
FF2
Coll
0 mrad
Bend
25mrad
Stretch
FF1
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Site layout with Dx25m Dz 440m
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VERY, VERY Rough Cost EstimateLength Scaling
Only, NOT Parts counting
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Summary

• Its really a Users choice You get what you
  pay for
• Model 0 One IR
• Cheapest option 251M
• Model 1 Dx100m Dz 0m
• Most flexible?
• Most bending, perhaps lowest maximum energy reach
• Most expensive 499M
• Model 2 Dx25m Dz 0m
• Allows for flexibility in detector/IR staging. Is
  this interesting?
• 407M plus 60M for second collimation system
  (simultaneous running)
• Model 3 Dx25m Dz 440m
• Seems best suited to a low start up cost
• Begin with one collimation system sequential
  data taking
• Better vibration isolation same cost as Model 2
• Is there another variation we are missing?

17
Conceptual Problems with Symmetric Two IR Layout

• Experimenters seem to want full luminosity at 90
  GeV 1 TeV, be able to quickly change energy
  and continually question the maximum energy reach
  of NLC X-band technology
• Big Bend (designed for 1.5 TeV) limits upper
  range of energy for HE IR
• Emittance growth due to SR 5 by limiting
  strength of bends
• 330m for 10mrad of bend at 750 GeV/beam
• Length of Big Bend scales as E_max for constant
  De
• For fixed geometry, emittance scales as E6
  Luminosity as g-2.5
• Magnet apertures set by lowest energy
• Given aperture, once max beam divergence is
  reached, since emittance scales as 1/E,
  need to scale beta function by 1/E
• Hard to meet PS sensitivity requirements (10-5)
  without limiting range
• Ambiguous physics justification for two detectors
  given symmetric layout and fact that only one
  detector gets data at a time
• As FF gets shorter, two FF tunnels merge into one
• lateral displacement of IRs shrinks (44m in ZDR,
  16m in CD4)
• No design provision for gg, which needs larger
  crossing angle

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Luminosity Scaling with Energy

• Assuming same injector, the luminosity scales as

• Luminosity in high energy FF scales
  linearly with energy between 250 and 1
  TeV
• Low energy FF scales similarly but at
  lower energy!

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Reversed Linac Angle Leads to Larger Bend and
Reverse Bend to IR2When IR Separation 100m
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Reverse Linac Angle and Common Use of Collimation
Lattice when IR Separation is 25m leads to Bend
and Reverse Bend Tunnel Angles Too Large to be
Supported by Tunnel Length
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Separate collimation systems standard linac
angle
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Another Possibility Dx25m Dz 300m
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How About Dx25m Dz 500m