NLC - The Next Linear Collider Project Linear Collider IR Options Tom Markiewicz / SLAC LC Workshop 2002, U. Chicago 07 January 2002

Tom Markiewicz NLC - The Next Linear Collider Project Outline Bunch Structure Crossing Angle Time Packaging of Detector Backgrounds Beam-Beam Feedback Schemes (RB) IP Beam Parameters Luminosity (RB) Luminosity Sensitivity (RB) IP Backgrounds IR Options IR Layout Choices Site Layout Choices Detector Occupancies & Acceptances Beam Delivery & IR Choices ~Accelerator Technology Independent

Tom Markiewicz NLC - The Next Linear Collider Project Bunch Structure vs. X-Angle TESLA -500 JLC/NLC- 500 CLIC- 3TeV BB 337 ns1.4ns0.67 ns c  B 100 m 4.2m2.0 m NBNB Train 950  s 269 ns103 ns f5 Hz120/150 Hz100 Hz 1/f200 msec 8.3/6.6 msec 10 msec MIN  C 0 mrad~4 mrad~12mrad Chosen  C 0 mrad Could be anything JLC=8 mrad NLC=20 mrad 20 mrad Crab Cavities Beam Steering “r<20cm” Hardware –Lum Monitor –Magnet Technology –L* (IP to 1 st Quad = QD0) Beam Extraction –Beam Diagnostics –Beam Dumps “Maximum” E cm –Minimize bends Compatibility with other designs

Tom Markiewicz NLC - The Next Linear Collider Project Beam Separation Required Before 1 st Parasitic Collision at c  B /2 IP Luminosity Loss vs. Crossing Angle for CLIC,  B =0.67 ns D. Schulte, LCWS 2000

Tom Markiewicz NLC - The Next Linear Collider Project NLC Detector Masking Plan View w/ 20mrad X-angle 32 mrad 30 mrad Large Det.- 3 TSilicon Det.- 5 T

Tom Markiewicz NLC - The Next Linear Collider Project Elevation View Iron magnet in a SC Compensating magnet 8 mrad crossing angle Extract beam through coil pocket Vibration suppression through support tube JLC IR 8 mrad Design

Tom Markiewicz NLC - The Next Linear Collider Project TESLA IR Instrumented W Mask & Pair-LumMon w/ Low Z Mask

Tom Markiewicz NLC - The Next Linear Collider Project Maximum Crossing Angle Crab Cavity Transverse RF cavities on each side of IP rotate the bunches so they collide head on Cavity power req. and relative voltage & phase stability limit maximum crossing angle: 2%  L/L when bunch overlap error  x ~ 0.4  x Since  x = (  C /2)  z, at  C =20mrad phase error  z corresponds to ~10  m ~ 0.2 degree of X-Band phase  C < 40 mrad xx

Tom Markiewicz NLC - The Next Linear Collider Project Crossing Angle Considerations Interaction with Detector’s Solenoid Beam Steering before IP: Transverse component of solenoid changes position and angle of beams at the IP 1.7  m, 34.4  rad at 1 TeV, L*=2m, B s =6 T,  C =20mrad Dispersion and SR cause spot size blow up Dispersion adds 3.1  m to vertical spot size SR contribution tiny; goes as (L * B s  C ) 5/2 Beam steering and QD position adjustment make this a NON-PROBLEM Beam Steering after IP: Energy dependence of angle of extraction line Steering: position (410  m) & angle (69  rad) different from B=0 case at 1 TeV Only run with solenoid ON and Realign extraction line when necessary

Tom Markiewicz NLC - The Next Linear Collider Project Luminosity Monitor Detail Non cylindrically symmetric geometry for inner detectors

Tom Markiewicz NLC - The Next Linear Collider Project Baseline Magnet Technology Choices Extraction outside QD0 Permanent Magnets (NLC) Compact, stiff, few external connections, no flowing fluids Adjustment more difficult Extraction in QD0 Coil Pocket Conventional Iron in SC Tube (JLC) Adjustable, familiar Massive, SC tube shields magnet from solenoid Extraction through QD0 Bore Superconducting (TESLA) Adjustable, large aperture bore Massive and not stiff

Tom Markiewicz NLC - The Next Linear Collider Project TESLA SC Final Doublet Quads Mature LHC based Design QD0: L=2.7m G=250 T/m Aperture=24mm QF1: L=1.0m

Tom Markiewicz NLC - The Next Linear Collider Project NLC Final Doublet Quad Options Permanent Magnet Option: compact, stiff, connection free 5.7cm BNL Compact SC MagnetApertureGradientRmaxZ_ipLength QD01.0 cm144 T/m5.6cm3.81 m2.0m QF11.0 cm36.4 T/m2.2cm7.76 m4.0 m

Tom Markiewicz NLC - The Next Linear Collider Project NLC Extraction Line 150 m long with chicane and common  and e- dump X-Angle allows separate beam line to cleanly bring disrupted beam to dump and allows for post-IP Diagnostics 0.2% of beam ~ 4kW 1 TeV % beam ~ 0-20W 500 GeV

Tom Markiewicz NLC - The Next Linear Collider Project TESLA Vertical Extraction at 0º Electrostatic separators at 20m Shielded septum at 50m (c  B /2) Dipoles to e-/+ dump at z=240m Calculated losses OK Challenging problem No space for diagnostic equipment Photons to separate dump at 240m with hole for incoming beam

Tom Markiewicz NLC - The Next Linear Collider Project TESLA Pre-IP Polarimeter and Energy Spectrometer No TESLA plans for post IP diagnostics NLC plans pre-IP diagnostics but no work yet begun No detailed work on post-IP diagnostics done yet

Tom Markiewicz NLC - The Next Linear Collider Project Energy Flexibility Energy Dependence of Luminosity Final Focus magnet apertures set by lowest energy Highest energy operation limited by magnet strength, synchrotron radiation and system length For fixed geometry

Tom Markiewicz NLC - The Next Linear Collider Project Luminosity Scaling with Energy Luminosity increases linearly with energy at High and Low E IRs Above maximum design energy, L drops quadratically 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

Tom Markiewicz NLC - The Next Linear Collider Project NLC & TESLA both have Minimal Angles to Primary IR & ~  20mrad to IR2 30 km Bypass Lines 50, 175, 250 GeV IR1 (250 GeV to multi-TeV) Length for 500 GeV/beam Injector Systems for 1.5 TeV IR2 (90 GeV to ~TeV)

Tom Markiewicz NLC - The Next Linear Collider Project TESLA Post-Linac Layout

Tom Markiewicz NLC - The Next Linear Collider Project Skew Correction / Emittance Diagnostics e+ e- Interaction Region Transport (High Energy) Collimation / Final Focus (High Energy) Collimation / Final Focus (High Energy) IR Hall (High Energy) IR Hall (Low Energy) IP1 IP2 Interaction Region Transport (Low Energy) Collimation / Final Focus (Low Energy) Collimation / Final Focus (Low Energy)

Tom Markiewicz NLC - The Next Linear Collider Project Pros & Cons of a Crossing Angle Cons: Beam Steering CorrectionEasy Crab cavity RequiredOK as long as  C <~40 mrad LUM not cylindrically symmetricWho cares? Net p T to interaction Pros Separate Extraction Line –Post IP DiagnosticsPre-IP Diagnostics –Single ,e beam dumpHigher P e-dump anywhere Allows for future reduction Who cares? in beam spacing Dig later if really needed

Tom Markiewicz NLC - The Next Linear Collider Project Backgrounds and IR Layouts Most important background is the incoherent production of e+e- 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 TESLA-500JLC/NLC-500 N 2.0 x x xx 550 nm243 nm yy 5 nm3 nm zz 300  m110  m

Tom Markiewicz NLC - The Next Linear Collider Project Beams attracted to each other reduce effective spot size and increase luminosity H D ~ Pinch makes beamstrahlung photons:  /e- with E~3-5% 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 Beam-Beam Interaction SR photons from individual particles in one bunch when in the E field of the opposing bunch

Tom Markiewicz NLC - The Next Linear Collider Project Pair Production Photons interact with opposing e,  to produce e+,e- pairs and hadrons Pair P T : SMALL Pt from individual pair creation process LARGE Pt from collective field of opposing bunch –limited by finite size of the bunch   e+e- (Coherent Production) e   ee+e-   e+e- ee  eee+e- 500 GeV designs

Tom Markiewicz NLC - The Next Linear Collider Project e+,e- pairs from beams.  interactions # pairs scales w/ Luminosity 1-2x10 9 /sec B SOL, L*,& Masks

Tom Markiewicz NLC - The Next Linear Collider Project NLC/TESLA Beam-Beam Comparison NLC500TESLA500 DyDy 1425  nn bb 4.6%3.2% HDHD # pairs/bunch49,000130,000 _pair e5.5 GeV2.8 GeV #pairs/ sec1.1E91.8E9 Larger  z 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

Tom Markiewicz NLC - The Next Linear Collider Project Pairs as a Fast Luminosity Monitor Also, Pair angular distribution carries information of beam transverse aspect ratio (Tauchi/KEK) TESLA

Tom Markiewicz NLC - The Next Linear Collider Project Pair Stay-Clear from Guinea-Pig Generator and Geant

Tom Markiewicz NLC - The Next Linear Collider Project e, ,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

Tom Markiewicz NLC - The Next Linear Collider Project Design IR to Control e+e- Pairs Direct Hits Increase detector solenoid field Increase minimum beam pipe radius at VXD Move beampipe away from pairs ASAP Secondaries (e+,e-, ,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

Tom Markiewicz NLC - The Next Linear Collider Project Detector Occupancies are Acceptable fcn(bunch structure, integration time) LCD=L2 Hit Density/Train in VXD &TPC vs. Radius TESLA VXD Hits/BX vs. Radius

Tom Markiewicz NLC - The Next Linear Collider Project Photons  in LD TPC 1 TeV  in LD Endcap CAL 1 TeV  in SD Endcap CAL 1 TeV TESLA #  /BX in TPC vs. z r=1.0cm, B=3T Extraction Line (6m) “shines” thru shield here, but not here r=2.2cm, B=4T

Tom Markiewicz NLC - The Next Linear Collider Project Neutron Backgrounds The 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 <x10 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 R min down x2 Fluence UP x40

Tom Markiewicz NLC - The Next Linear Collider Project Neutrons from the Beam Dump Geometric fall off of neutron flux passing 1 mrad aperture Limiting Aperture Radius (cm) z(m) # Neutrons per Year Integral

Tom Markiewicz NLC - The Next Linear Collider Project Neutron hit density in VXD NLC-LD-500 GeV NLC-SD-500 GeV Tesla-500 GeV Beam-Beam pairs1.8 x 10 9 hits/cm 2 /yr 0.5 x 10 9 hits/cm 2 /yr O(10 9 hits/cm 2 /yr) Radiative Bhabhas1.5 x 10 7 hits/cm 2 /yrno hits <0.5x10 8 hits/cm 2 /yr Beam loss in extraction line0.1 x 10 8 hits/cm 2 /year 0.1 x 10 8 hits/cm 2 /year Backshine from dump1.0 x 10 8 hits/cm 2 /yr 1.0 x 10 8 hits/cm 2 /yr negligible TOTAL1.9 x 10 9 hits/cm 2 /yr 0.6 x 10 9 hits/cm 2 /yr Neutron Backgrounds Summary Figure of merit is 3 x 10 9 for CCD VXD

Tom Markiewicz NLC - The Next Linear Collider Project Detector Occupancies from e+e- 500 GeV DetectorPer bunchR. O.Eff. #B OccupancyComment VXD-L136E-3/mm 2 50  s / mm 2 1.5cm, 4T VXD-L23.1E-3/mm  s / mm 2 2.6cm, 4T TPC 1336 , 5trks55  s 160Few per mil Barrel ECAL 1176 , 0.63GeV 150 ns10.63 GeV 101  >3MeV Endcap ECAL 1176 , 1.92GeV 150 ns11.92 GeV 91  >3MeV VXD-L138E-3/mm 2 8 ms1907.2/ mm 2 1.2cm, 3T VXD-L23.1E-3/mm 2 8 ms1900.6/ mm 2 1.4cm, 3T TPC 1377 , ?trks 8 ms190“Few per mil”Needs Study Barrel ECAL 547 , 0.73 GeV 8 ms GeVNeeds Study Endcap ECAL 597 , 0.9 GeV 8 ms GeVNeeds Study TESLATESLA NLCNLC

Tom Markiewicz NLC - The Next Linear Collider Project Synchrotron Radiation from 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, …….  X =450  rad  Y =270  rad  X =32  rad  Y =28  rad BE SURE YOU NEED IT!

Tom Markiewicz NLC - The Next Linear Collider Project HALO Synchrotron Radiation Fans with Nominal 240  rad x 1000  rad Collimation (Similar plots for TESLA)

Tom Markiewicz NLC - The Next Linear Collider Project Muon Backgrounds from Halo Collimators No Big Bend, Latest Collimation & Short FF If Halo = 10 -6, no need to do anything If Halo = and experiment requires <1 muon per e- add magnetized tunnel filling shielding Reality probably in between 18m & 9m Magnetized steel spoilers Betatron Betatron Cleanup Energy FF

Tom Markiewicz NLC - The Next Linear Collider Project LD Muon Endcap Background #e- Scraped to Make 1Muon Calculated Halo is Efficiency of Collimator System is 10 5 Bunch Train =10 12 Engineer for Halo

Tom Markiewicz NLC - The Next Linear Collider Project  IR Differences w.r.to e+e- IR Annular Mirror system 10 mrad exit aperture instead of 1 mrad 30mrad  C to accommodate exit aperture Larger inner radius of VXD as first 2 layers of LD/SD VXD look in direct line of sight w/dump

Tom Markiewicz NLC - The Next Linear Collider Project Independent Systems Model for e- Injection on e+ Arm RED=New Stuff

Tom Markiewicz NLC - The Next Linear Collider Project Fixed Target Options

Tom Markiewicz NLC - The Next Linear Collider Project Your IR Options ARE Open! Beam Delivery and IR Choices are ~ Independent of RF Technology And while each regional machine design group has a CONCEPTUAL DESIGN (in my view at least) We are far from needing to freeze any parameter which can impact either the PHYSICS PROGRAM Or the DETECTOR DESIGN There is a wealth of work to be done, particularly in the areas of diagnostic detector development and performance simulation (at SLC experimental physicists did this) Groups from U-Mass, UBC, Oxford, Brunel, NW,U.Hawaii…. are participating “Machine-Teach IN” tomorrow 4:15-6:00 Room 208