NLC IR Overview

1
NLC IR Overview

• Tom Markiewicz / SLAC
• LC02, SLAC
• 04 February 2002

2
Outline

• IR Design and Backgrounds
• Takashi Maruyama, Lew Keller, Rainer Pitthan
• Tor Raubenheimer, Andrei Seryi, Peter Tenenbaum,
  Nan Phinney, Pantaleo Raimondi, Mark
  Woodley, Yuri Nosochkov
• Stan Hertzbach (U. Mass)
• Jeff Gronberg, Tony Hill (LLNL)
• RD Efforts
• Joe Frisch, Linda Hendrickson, Tom Himel
• Eric Doyle, Leif Eriksson, Knut Skarpaas, Steve
  Smith
• Tom Mattison Students (UBC)
• Phil Burrows, Simon Jolly, Gavin Nesom, Glen
  White, Colin Perry (Oxford)
• Brett Parker (BNL)

3
NLC IR Design Evolution

• LC99
• ZDR Coll (2.7km), FF (2.5km), and EXT (0.2km)
  Optics with L2.0m, 10mrad Big Bend and
  Permanent Magnet FD
• Emphasis on 6T Small Detector w/ 1.0cm radius
  beampipe
• M1 mask 1.5m long
• LCWS-2000 (and partially at BDIR-2000)
• New Raimondi/Seryi FF (0.75km) with L4.3m
• ZDR Collimation with NO Big Bend to the HEIR
• 4 Tesla Large Detector and 6 Tesla Small
  Detector
• Short 60cm Instrumented M1 w/ extra low Z
  shielding
• Snowmass-2001
• New short collimation scheme w/ FF94(?) and
  L3.8m
• New IP Beam parameters w/ 4x Luminosity
• 3 Tesla Large Detector and 5 Tesla Silicon
  Detector

4
e
Skew Correction / Emittance Diagnostics
Interaction Region Transport (High Energy)
Interaction Region Transport (Low Energy)
Collimation / Final Focus (High Energy)
Collimation / Final Focus (Low Energy)
IR Hall (High Energy)
IR Hall (Low Energy)
IP1
IP2
Collimation / Final Focus (Low Energy)
Collimation / Final Focus (High Energy)
Interaction Region Transport (Low Energy)
Interaction Region Transport (High Energy)
Skew Correction / Emittance Diagnostics
e-
5
Design ParametersPost ISG (November 2001)
6
Luminosity Scaling with Energy
Yuri N. recalculation imminent
Luminosity increases linearly with energy at High
and Low E IRs Above maximum design energy, L
drops as E-2.5 due to synchrotron radiation
emittance growth Range can be extended by
changing geometry to soften bend angle
This LEIR design done when there was 80mrad of
bending to get to IR2 Now at 25mrad curves
essentially identical
7
Large and Silicon Detectors(same scale)
3 Tesla
5 Tesla
8
NLC Detector MaskingPlan View w/ 20mrad X-angle
Large Det.- 3 T
Silicon Det.- 5 T
30 mrad
32 mrad
9
NLC Baseline Permanent Magnet Quadcompact,
stiff, connection free
Andy Ringwall
Knut Skarpaas
10
NLC Extraction Line150 m long with chicane and
common g and e- dump
X-Angle allows separate beam line to cleanly
bring disrupted beam to dump and allows for
post-IP Diagnostics
Yuri Nosochkov
0.2 of beam 4kW lost _at_ 1 TeV 0-0.002 beam
0-20W lost _at_ 500 GeV
11
Backgrounds and IR Layouts

• Most important background is the incoherent
  production of ee- pairs.
• pairs scales with luminosity and is equal for
  both designs.
• Detector occupancies depend on machine bunch
  structure and relevant readout time
• GEANT and FLUKA based simulations indicated that
  in both cases occupancies are acceptable and the
  CCD-based vertex detector lifetime is some number
  of years.
• IR Designs are similar in the use of tungsten
  shielding, instrumented masks, and low Z material
  to absorb low energy charged and neutral
  secondary backgrounds

12
Beam-Beam InteractionSR photons from individual
particles in one bunch when in the E field of the
opposing bunch

• Beams attracted to each other reduce effective
  spot size and increase luminosity
• HD 1.4-2.1
• Pinch makes beamstrahlung photons
• 1.2-1.6 g/e- with E3-5 E_beam
• Photons themselves go straight to dump
• Not a background problem, but angular dist. (1
  mrad) limits extraction line length
• Particles that lose a photon are off-energy

NLC-1 TeV
13
Pair ProductionPhotons interact with opposing
e,g to produce e,e- pairs and hadrons
500 GeV designs

• Pair PT
• SMALL Pt from individual pair creation process
• LARGE Pt from collective field of opposing bunch
• limited by finite size of the bunch

14
e,e- pairs from beams. g interactions
pairs scales w/ Luminosity 1-2x109/sec
BSOL, L, Masks
15
Pairs as a Fast Luminosity Monitor
TESLA
Also, Pair angular distribution carries
information of beam transverse aspect ratio
(Tauchi/KEK)
16
NLC/TESLA Beam-Beam Comparison
Larger sz for TESLA More time for
disruption larger luminosity enhancement more
sensitivity to jitter Lower charge density lower
energy photons Real results come from beam-beam
sim. (Guinea-Pig/CAIN) and GEANT3/FLUKA
17
Pair Stay-Clear from Guinea-Pig Generator and
Geant
18
e,g,n secondaries made when pairs hit high Z
surface of LUM or Q1
High momentum pairs mostly in exit beampipe
Low momentum pairs trapped by detector solenoid
field
19
Design IR to Control ee- Pairs

• Direct Hits
• Increase detector solenoid field
• Increase minimum beam pipe radius at VXD
• Move beampipe away from pairs ASAP
• Secondaries (e,e-, g,n)
• Point of first contact as far from IP/VXD as
  possible
• Increase L if possible
• Largest exit aperture possible to accept
  off-energy particles
• Keep extraneous instrumentation out of pair
  region
• Masks
• Instrumented conical M1 protrudes at least 60cm
  from face of PAIR-LumMon
• Longer more protection but eats into EndCap CAL
  acceptance
• M1,M2 at least 8-10cm thick to protect against
  backscattered photons leaking into CAL
• Low Z (Graphite, Be) 10-50cm wide disks covering
  area where pairs hit the low angle W/Si Pair
  Luminosity monitor

20
Hit Density/Train in VXD TPC vs. RadiusTakashi
Maruyama
LD
SD
21
Photons
Beampipe _at_ r1.0cm, B3T
Extraction Line (6m) shines thru shield here,
but not here
22
Neutron BackgroundsThe closer to the IP a
particle is lost, the worse

• Off-energy e/e- pairs hit the Pair-LumMon,
  beam-pipe and Ext.-line magnets
• Radiative Bhabhas Lost beam ltx10
• Solutions
• Move L away from IP
• Open extraction line aperture
• Low Z (Carbon, etc.) absorber where space permits

• Neutrons from Beam Dump(s)
• Solutions Geometry Shielding
• Shield dump, move it as far away as possible, and
  use smallest window
• Constrained by angular distribution of
  beamstrahlung photons
• Minimize extraction line aperture
• Keep sensitive stuff beyond limiting aperture
• If VXD Rmin down x2 Fluence UP x40

23
Neutrons from the Beam Dump
Neutrons per Year
Limiting Aperture
Integral
Geometric fall off of neutron flux passing 1 mrad
aperture
1.0
0.5
Radius (cm)
z(m)
24
Neutron BackgroundsSummary
Neutron hit density in VXD NLC-LD-500 GeV
NLC-SD-500 GeV Tesla-500 GeV Beam-Beam
pairs 1.8 x 109 hits/cm2/yr 0.5 x
109 hits/cm2/yr O(109 hits/cm2/yr) Radiativ
e Bhabhas 1.5 x 107 hits/cm2/yr no hits
lt0.5x108 hits/cm2/yr Beam loss in
extraction line 0.1 x 108 hits/cm2/year 0.1
x 108 hits/cm2/year Backshine from dump 1.0
x 108 hits/cm2/yr 1.0 x 108 hits/cm2/yr
negligible TOTAL 1.9 x 109
hits/cm2/yr 0.6 x 109 hits/cm2/yr
Figure of merit is 3 x 109 for CCD VXD
Takashi Maruyama Jeff Gronberg
25
Summary LD _at_ 500 GeV
26
Summary SD _at_ 500 GeV
27
LD Detector Occupanciesfrom ee- Pairs _at_ 500
GeVfcn(bunch structure, integration time)
TESLA
NLC
28
ee-? ee- gg ? ee- Hadrons

• NLC Analysis began Spring 2001 (Gronberg Hill
  / LLNL)
• CAIN simulation plus JETSET
• Need to integrate 190 bunches
• Doesnt appear to be a problem but one detector
  element with good time resolution will help if it
  is

gg ? ee- Hadrons Energy Distributions
Endcap
Mask
Barrel
29
Synchrotron Radiationfrom Beam Halo in Final
Doublet

• At SLD/SLC SR WAS a (THE) PROBLEM
• SR from triplet WOULD have directly hit beam-pipe
  and VXD
• Conical masks shadowed the beam pipe inner radius
• geometry set so that photons needed a minimum of
  TWO bounces to hit a detector
• Background rates consistent with flat halo
  model
• 0.1 - 1 of the beam filled the phase space
  allowed by the collimator setting.
• At NLC/TESLA
• Allow NO direct SR hits ANYWHERE near IP
• Collimate halo before the linac AND after the
  linac
• VXD MINIMUM RADIUS sets collimation depth as well
  as B_s
• Pain level goes at least as square of VXD min
  radius
• Muon production, collimator wakefields,
  collimator damage, radiation, .

qX450 mrad qY270 mrad
qX32 mrad qY28 mrad
BE SURE YOU NEED IT!
30
HALO Synchrotron Radiation Fans with Nominal 240
mrad x 1000 mrad Collimation
Stan Hertzbach
31
Muon Backgrounds from Halo CollimatorsNo Big
Bend, Latest Collimation Short FF
FF
Energy
18m 9m Magnetized steel spoilers
Betatron
BetatronCleanup
If Halo 10-6, no need to do anything If Halo
10-3 and experiment requires lt1 muon per 1012 e-
add magnetized tunnel filling shielding Reality
probably in between
32
LD Muon Endcap Background e- Scraped to Make
1Muon
Bunch Train 1012
Engineer for 10-3 Halo
Efficiency of Collimator System is 105
Calculated Halo is 10-6
Lew Keller
33
Conclusions on Backgrounds

• As we have pushed up luminosity x4, shrunken L
  from 4.3 to 3.5m, and reduced length of beam
  delivery system from 5km to 1km, backgrounds have
  risen in absolute terms to a level per train
  meriting attention
• Backgrounds/Unit of Luminosity constant before
  geometry mods
• Geometry adjustment always possible
• Nanosecond level detector timing would make
  everything except neutron-dominated VXD lifetime
  a non-issue
• Large detector Neutron damage lifetime needs more
  investigation
• Conclusion to all previous background talks was
  not a problem but now I am beginning to feel we
  need to start investigating detector response and
  optimizing detector design and performance with
  respect to these processes.

34
NLC IR Design Work

• In Progress
• Conceptual Design of Compact Superconducting
  Quads
• GEANT based study of collimation/FF(114?)
  efficiency
• Impact of lost particles and synchrotron
  radiation
• To Do List
• Complete Set of mutually consistent results and
  figures
• Improvement IR masking model in simulations
• More low Z
• Thicker masks to prevent leakage
• Instrument the MC model
• Incorporate believable engineering scheme for FD
  mount stabilization, vacuum system, cooling
  system, etc.
• Begin simulation of diagnostic detectors in EXT
  or at IP

35
SC Final Doublet Quad Optionsbased on HERA
BEPC technology
Compact 5.7cm Radius Warm Bore Design
Brett Parker, BNL
36
Cold Bore NLC SC Quadrupole w/ Integrated
Sextupole Windings

Quadrupole Coil Layers
Thermal Shield and Cold Mass Support Structure
1 cm
Coil Support Tubes
LHe Flow Space
Sextupole Coil
Brett Parker, BNL
37
GEANT Beamline SimulationsTakashi Maruyama
sy2.2 nm _at_IP (2.3nm in parameter list)
38
Collimator Efficiency SR Results from GEANT
SR Photons at IP
R1cm
Ln Ng
r
1.0cm
39
NLC IR RD Evolution

• LC99
• Coupon tests at FFTB for Beam Damage
• Transfer of Optical Anchor RD from SLAC to UBC
• Collimator Wakefield expt. planned
• Conceptual Ideas about rotating cylindrical
  liquid metal spoilers
• BDIR-2000 LCWS-2000
• First collimator wakefield data -gt drives new
  model
• Engineering drawings of rotating spoilers
• Dip tests of different liquid metals
• Conceptual ideas for inertial vibration
  suppression test systems
• Conceptual Idea of Intra-Train feedback
  (F.O.N.T.FB on ns timescale)
• Discussion of new FFTB
• Snowmass-2001
• New results from fully engineered spoiler
  prototypes, both liquid not
• First results of inertial stabilization of
  aluminum cube w/ 6 external dof
• Results from optical anchor work at UBC
• Detailed FONT electronics w/ SIMULINK,
  Guinea-Pig, GEANT sim
• LINX proposal for 1nm stabilization and
  tail-folding tests

40
Very Fast Intra-train IP Feedback at NLC limits
jitter-induced DL
Concept
Design
Steve Smith Oxford U.
Performance 5 s Initial Offset (13 nm)
YIP (nm)
40ns Latency
41
Inertial Stabilization to Suppress Jitter at
NLCFrisch, Himmel, Henrikson
Block with Accelerometers/ Geophones
Electrostatic Pushers
x10-100 Jitter Suppression in Frequency Range of
Interest
42
Interferometers to Stabilize Quads w.r.to Tunnel
Sub-nm resolution measuring fringes with
photodiodes ? drive piezos in closed loop
Platform Displacement Sensor Value
UBC Setup
43
Consumable SpoilersFrisch, Doyle
First test results before Snowmass
In Vacuum Vessel
Tapered wheels
Positioning mechanism
44
Renewable Spoiler Prototype Frisch, Skarpaas
Niobium and Molybdenum Rotors
Liquid Gallium
Liquid Tin
Vacuum vessel Roller adjustment
45
Vacuum RDSLAC (Eriksson), LBL, LLNL

• Aluminum outgassing measurements
• to determine vacuum suitability

46
LINX Engineering Test Facility

• ee- collisions at SLC with 50nm beams
• Test stabilization techniques proposed for future
  linear colliders and demonstrate nanometer
  stability of colliding beams
• Investigate new optical techniques for control of
  beam backgrounds
• Provide a facility where ultra-small and
  ultra-short beams can be used for a variety of
  other experiments

NLC 250 GeV 300 / 2 360 / 3.5 same 0.11 mm
245/2.7nm 7.5E9

• Beam Energy 30 GeV
• DR emittances g?x,y1100/50E-8 m-rad
• FF emittances g?x,y1600/160E-8 m-rad
• IP Betas ?x8mm ?y0.1 mm
• Bunch length ? z0.1 - 1.0
  mm
• IP spot sizes ?x,y1500/55
  nm
• Beam currents N? 6E9

47
Nanometer Stability of Colliding Beams
Beam-Beam Deflection gives 1nm stability
resolution
BPMres
400nm

• Colliding beams provide a Direct
  Model-Independent Test of any engineering
  solution to the final doublet stability problem
• Not possible in FFTB

48
Controlling Beam Backgrounds with Non-Linear
Optical Elements

• Tail Folding via Octupole Pairs has the promise
  of relaxing collimation depths
• Confidence that comes from an Actual
  Demonstration may permit a great savings in
  collimator design, radiation shielding, and muon
  shielding

49
Fixed Target OptionsRainer Pitthan, Lew Keller,
Yuri Nosochkov
50
Conclusions

• IR Conceptual Design is well developed
• There is a wealth of work to be done
• Diagnostic detector development
• Performance simulation
• Engineering Design