MachineDetector Interface

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Machine-Detector Interface

• David Urner
• JAI / Oxford University

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Topics

• ILC energy spectrometer
• Force-neutral Anti-Solenoid
• QD0-Service Cryostat Prototype
• Luminosity Optimization
• Push-Pull
• Background-Driven SiD Design Decisions
• Extraction Line
• Radiation Shielding

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Proposed ILC energy spectrometer
Bino Maiheu

• Precision measurement dE/E 10-4
• Minimal impact on beam itself allowed emittance
  growth from SR
• Limited space budget in BDS 60 m
• Minimal impact on physics data taking for e.g.
  calibration runs
• Magnetic chicane with high resolution beam
  position monitors cavity BPM
• Max 5 mm dispersion at center chicane
  determines resolution
• Emittance growth determines chicane layout
• Diagnostics needed
• Gain drifts temperature
• Mechanical stability interferometer
• Magnetic fields (?B.dl ) NMR, Hall, fluxgate
  magnetometers

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T474 test experiment at ESA, SLAC

• ESA comparable repetition rate, bunch charge,
  energy spread as ILC
• Possibility to vary bunch length, energy, charge
• Easy steering with feedback system
• Build an energy spectrometer prototype, using a 4
  magnet chicane
• Goal is to demonstrate the stability of this type
  of energy measurement at 10-4 level, and
  investigate how such a magnetic chicane can be
  operated most efficiently at the ILC
• Operate at 5 mm ?X at centre chicane as in
  current ILC design
• Need lt 1mm resolution on position measurement
  (BPM) with position measurement stability over
  multiple hours of 100 nm

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QD0-Service Cryostat Prototype

• BDS RD plan stresses importance of integrated
  systems testing of an engineering prototype (QD0
  with connection to service cryostat)
• to establish the degree of coupling of external
  vibration sources to the QD0 cold mass.
• What noise is expected from technical systems?
• How well can the QD0 cold mass be isolated?
• What about bellows?
• Are there any internal modes to worry about?
• How well can QD0 be supported in the detector?
• How do we isolate the QD0 cryostat from external
  vibration sources?
• Particular attention is needed in this regard to
  the design of the cryogenic transfer line between
  the service and QD0 cryostats.

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Luminosity Optimization

• GuineaPig (beam-beam interactions)
• New features
• beam-beam effects on bhabhas
• C
• all keywords of guinea-pig are now available
• hadrons (do_hadrons)
• minijets (do_jets)
• pairs (do_pairs)
• abstract I/O interface
• separate algorithms and I/O
• plugging different format (ascii)
• plugging graphical interface

• FONT Simulation
• Fast feedback using bunch kick-angle to correct
  for y and y.
• Simulation of fast feed-back using PLACET (beam
  transport), GuineaPig (beam-beam interactions)
  and Matlab (fast feed-back)
• Simulation based on Glen Whites code
  incorporating
• Newest Lattice
• Smaller wake fields
• Similar results as
• with old code
• Ready to incorporate
• additional effects and
• other feedback loops.
• Likely Result A much worse behaviour

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Luminosity Optimization

• MONALISA
• Relative position measurement of two QD0 magnets
  with respect to each other using interferometers
• Position changes few nm (requires continuous
  uninterupted measurements)
• Absolute distance below 1mm (can be done at any
  time)
• Use as input for FONT
• Test on FONT simulation how effective this is in
  reducing convergence time particularly under bad
  beam conditions (as one would expect for startup
  or after a longer period with no beams).
• Requires light path (half inch pipe) through SiD
  yoke from QD0 to the ground.

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Luminosity Optimization

• Luminosity feedback
• Luminosity sensitive to bunch shape ? optimum at
  y?0
• After IP position and angle feedbacks (based on
  kick-angle monitor) have converged maximise
  luminosity directly using luminosity monitor
  based on BeamCal and GamCal
• BeamCal Detector
• .003 lt ? lt .02 rad
• ?3.5m from IR
• Pairs curl in the magnetic field
• Measure the ?104 beam-strahlung ee- pairs/bunch
• GamCal Detector (B Morse)
• ?180m from IR integrated into polarimeter chicane
• ?10-4 X0 to convert beam-strahlung gammas into
  ee- pairs
• Converter could be gas jet or a thin solid
  converter
• Dipole magnet with PT kick 0.25 GeV/c separates
  the pairs from beam electrons
• Calorimeters outside vacuum after magnet measure
  the 1-10 GeV positrons

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Luminosity OptimizationVertical Offset
M.Ohlerich

• complementary information from
• total photon energy vs offset_y
• BeamCal pair energy vs offset_y

ratio of E_pairs/E_gam vs offset_y is
proportional to the luminosity similar behaviour
for angle_y, waist_y
see also EUROTeV-Memo-2006-011
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Statistical Error for BX

• If at startup less than 10 nominal luminosity
• beamcal might not give much of a luminosity
  measurement from a single bunch.
• Conclusion BeamCal and GamCal provide robust
  complimentary information.

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Push pull

• Assertions - Superconducting magnet (detector
  final focus) warm-up/cool-down time scales are
  long enough that these magnets have to be moved
  while cold?
• But they may be de-energized?
• If true, this drives a need for long umbilical
  connections to each of the experiments that are
  able to accommodate 20 m motion while cold.
• In last few weeks lots of discussions about
  possible layouts

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Push Pull

• Separate cryostats for QD and QF magnets
• QD0 carried by detector at optimized L
• Cantilevered support tube concept dead
• QF never moves and z-position of QF same for
  all detectors
• Distance between the 1st and 2nd SC quads after
  IP is increased to provide sufficiently long warm
  section for push-pull design.
• For three options of L 3.51 m, 4.0 m, 4.5 m,
  the SC extraction quad QDEX1 is placed at 5.5 m,
  5.95 m and 6.3 m. The 2nd SC quad QFEX2A is at
  fixed position, 9.6 m from IP.
• A long drift after QFEX2A provides transverse
  space for crab-cavity.

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Push-Pull Alignment after Move

• Assume repositioning accuracy of detector 1mm.
• Use MONALISA system to measure remaining
  difference to O(mm)
• Realign QD0 using MONALISA information
• Unclear yet how QD0 is supported
• Use y and y kickers to steer beam correctly into
  QD0 based on MONALISA data
• From here FONT should do the trick.
• Would expect that silicon Tracker and VXD have to
  be realigned as well.
• Is some method of position monitoring for the
  tracking detectors foreseen?

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Background-Driven SiD Design Decisions
Takashi Maruyama
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Background-Driven SiD Design Decisions Current
Beam pipe is not compatible with the Low P or
High Lumi options.
R 1.2 cm ? 1.5 cm (Low P), and R 1.2 cm ? 1.8
cm (High Lumi).
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Background-Driven SiD Design Decisions New SiD
Geometry

• LumiCal
• Z156.75 168 cm
• Rinside6cm
• compatible with
• Nominal 5 Tesla
• Nominal 4 Tesla
• Low P 5 Tesla
• Beampipe
• Original 43 mrad cone cylinder
• BeamCal
• Study background as a function of BeamCal
  z-position

LumiCal
43 mrad
Move BeamCal
Cylinder
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Tracker Hits vs. BeamCal DZ
Si Tracker photons
Barrel VXD e/e- hits
Barrel

• VXD hits
• No effects from LumiCal/BeamCal changes
• Si Tracker hits
• Less photons (20) due to smaller radius LumiCal
• photons increases by moving the BeamCal
  forward.
• But the rate is acceptable if ?Z lt 30 cm.

Endcap
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Extraction Line

• The quads focus the beam to the 2nd focus at
  Compton IP with R22 -0.5 transformation.
• The diagnostic contains energy and polarimeter
  chicanes, two proposed GAMCAL bends and the fast
  kickers for sweeping the beam on 3 cm circle at
  the dump window.
• Two collimators are included in the energy and
  polarimeter chicanes, and three collimators are
  in the final 100 m drift to protect the kickers
  and limit the beamsize to within the R 15cm
  dump window.

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Extraction Line

• The original 4-bend symmetric polarimeter chicane
  is modified to increase the strengths of the 3rd
  and 4th bends by 50 which improve acceptance of
  Compton backscattered electrons in the Cherenkov
  detector.
• The 5th and 6th bends are added to the
  polarimeter chicane which close the orbit bump
  and can be used by the proposed Gamma Calorimeter
  (B. Morse).

• Fast sweeping kickers
• Without beam collision, the undisrupted nominal
  beam size is too small (2.42 x 0.29 mm2) at the
  dump window.
• A system of 5 horizontal and 5 vertical fast
  kickers is included 90 m before the dump. The
  rapidly oscillating x and y kicker field (1 kHz)
  sweep the beam on 3 sm circle at the dump window.
  This was shown to be sufficient to protect the
  dump window and prevent water boiling in the dump
  vessel (L. Keller).

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Neutrons from the Beam Dump
New FLUKA simulation (Darbha)
x (cm)
Quadrupole aperture
2.4 cm
3.7?1010 ns/cm2/y
2.4 cm
7 mrad
n
3.0 cm
VXD Layer 1 fluence (one beam) 1.8?1010
ns/cm2/y w/o BeamCal 4.3?108 ns/cm2/y w BeamCal
Be
Si VXD
W BeamCal
z (cm)
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Neutrons in VXD (FLUKA)
Neutrons from pairs
Neutron origins
BeamCal
Neutrons from radiative Bhabhas
Beampipe
M1
Z (cm)

• Neutrons that reach the vertex detector are
  mostly generated in the BeamCal.
• Anti-DID can reduce the neutron flux.
• Different L design should not affect the neutron
  flux.

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Modelling of spent beam
(Nosochkov)

• 5T post-IP solenoid including anti-DID field with
  orbit and focusing correction have been modelled.
• Disrupted beam loss on magnets small in nominal
  option
• Manageable in a large energy spread option
• High loss at diagnostic collimators if at IP
• Large y-offset
• Non-zero y-angle
• Particularly in large energy spread option
• Driven by nonlinear dispersion from dipole
  correctors
• To reduce this effect
• a) the design IP y-angle is minimized,
• b) anti-DID field is increased,
• c) dipole corrector field is brought closer to
  IP.
• In machine operation, the beam running with large
  y-offsets at IP should be efficiently detected
  and prevented.

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Radiation Shielding

• Shaft and wall between detectors
• Shielding capability of a SID
• Effects of gaps for cables and tubes
• Pacman thickness
• Inner diameter
• Requirement of penetration
• Effects from upstream part (muon etc)
• 3D Monte-Carlo simulation ? MARS15-MCNP code is
  used

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Other Topics

• Intensive discussions particularly in preparation
  of the ILC Interaction Region Engineering Design
  Workshop at SLAC 17-21 Sept.
• 4 workgroups
• WG-A Overall detector design, assembly, detector
  moving, shielding.
• WG-B IR magnets design and cryogenics system
  design.
• WG-C Conventional construction of IR hall and
  external systems.
• WG-D Accelerator and particle physics
  requirements

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The End
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Backup slides
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Preliminary spectrometer results

• Taking into account Taking into account ?B.dl and
  deflection at center of chicane, can B.dl and
  deflection at center of chicane, can
• compute correct beam energy compute correct beam
  energy
• Have to Have to subtract incoming orbit subtract
  incoming orbit in each event prove we measure
  just energy ! in each event prove we measure
  just energy !
• Further detailed analysis, Further detailed
  analysis, spectrometer stability studies
  spectrometer stability studies underway...
  underway...
• More and better data to come in July...

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Power loss for L 3.51 m with 5T solenoid

• Loss on magnets is still small or modest, but
  loss on diagnostic collimators may become high
  when both y-offset and y-angle at IP are large,
  particularly in high disruption options c14
  (c15).
• Therefore, large IP orbit offsets need to be
  efficiently controlled. Further improvement of
  diagnostic collimation system should be studied.
• The source of the higher loss is the non-linear
  dispersion created by the corrector field. It
  increases the orbits of low energy electrons
  which may be consequently lost.
• In order to reduce the non-linear dispersion, the
  corrector fields need to be lowered and,
  possibly, brought closer to IP for more local
  correction. The following may be considered
• The uncorrected IP y-angle is minimized.
• The anti-DID field is increased, so the
  correcting fields on the SC quads are reduced.

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Current SiD layout
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