nlc - the next linear collider project linear collider ir options tom markiewicz / slac lc workshop...

NLC - The Next Linear Collider Project

Linear Collider IR Options

Tom Markiewicz / SLAC

LC Workshop 2002, U. Chicago

07 January 2002

Tom Markiewicz


Outline

Bunch StructureCrossing Angle

Time Packaging of Detector Backgrounds

Beam-Beam Feedback Schemes (RB)

IP Beam ParametersLuminosity (RB)

Luminosity Sensitivity (RB)

IP Backgrounds

IR OptionsIR Layout Choices

Site Layout Choices

Detector Occupancies & Acceptances

Beam Delivery & IR Choices

~Accelerator Technology Independent

Tom Markiewicz


Bunch Structure vs. X-Angle

TESLA-500

JLC/NLC-500

CLIC-3TeV

B 337 ns 1.4ns 0.67 ns

c B 100 m 4.2m 2.0 m

NB 2820 192 154

Train 950 s 269 ns 103 ns

f 5 Hz 120/150 Hz 100 Hz

1/f 200 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 1st Quad = QD0)

• Beam Extraction – Beam Diagnostics– Beam Dumps

• “Maximum” Ecm

– Minimize bends

• Compatibility with other designs

Tom Markiewicz


Beam Separation Required Before 1st Parasitic Collision at cB/2

IP

Luminosity Loss vs. Crossing Angle for CLIC, B=0.67 ns

D. Schulte, LCWS 2000

Tom Markiewicz


NLC Detector MaskingPlan View w/ 20mrad X-angle

32 mrad

30 mrad

Large Det.- 3 T Silicon Det.- 5 T

Tom Markiewicz


Elevation View•Iron magnet in a SC Compensating magnet

•8 mrad crossing angle

•Extract beam through coil pocket

•Vibration suppression through support tube

JLC IR8 mrad Design

Tom Markiewicz


TESLA IRInstrumented W Mask & Pair-LumMon w/ Low Z Mask

Tom Markiewicz


Maximum Crossing AngleCrab 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 ~10m

~ 0.2 degree of X-Band phase C < 40 mrad

x

Tom Markiewicz


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, Bs=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*BsC)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


Luminosity Monitor DetailNon cylindrically symmetric geometry for inner detectors

Tom Markiewicz


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


TESLA SC Final Doublet QuadsMature LHC based Design

QD0:

•L=2.7m

•G=250 T/m

•Aperture=24mm

QF1:

•L=1.0m

Tom Markiewicz


NLC Final Doublet Quad Options

Permanent Magnet Option: compact, stiff, connection free

5.7cm BNL Compact SC

Magnet Aperture Gradient Rmax Z_ip Length

QD0 1.0 cm 144 T/m 5.6cm 3.81 m 2.0m

QF1 1.0 cm 36.4 T/m 2.2cm 7.76 m 4.0 m

Tom Markiewicz


NLC Extraction Line150 m long with chicane and common and e- dump

1

10

100

1000

10000

100000

0 100 200 300 400 500

Beam Energy

2.1% of beam with77 kWatts has E<250 GeV

NLC 1000 BX-Angle allows separate beam line to cleanly bring disrupted beam to dump and allows for post-IP Diagnostics

0.2% of beam ~ 4kW lost @ 1 TeV

0-0.002% beam ~ 0-20W lost @ 500 GeV

Tom Markiewicz


TESLA Vertical Extraction at 0º

Electrostatic separators at 20m

Shielded septum at 50m (cB/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


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


Energy FlexibilityEnergy Dependence of Luminosity

• Final Focus magnet apertures set by lowest energy• Highest energy operation limited by magnet strength, synchrotron radiation and system

length

100 1000 50000.01

0.1

1

10

Luminosity shown is single bunchand with the same bunch populationas in Parameter set A

Energy upgradabilityof new FF (ff01)

No FF geometry change with FF geometry change

e as inLC 5TeVCM

e as in CLIC 3TeVCM

"A"& b~1/E

Par.set "A"

Geo

met

rical

Lum

inos

ity L

/L10

00G

eV C

M

Energy CM, GeV

limited) (SR :EnergyHigh

limited)length (bunch :Energy Mid

limited) (aperture :Energy Low

5.2

2

L

L

L

xxx

xxx

yxL

be

be

/

)/(1

*

6e SRxFor fixed geometry

Tom Markiewicz


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 & TESLA both have Minimal Angles to Primary IR & ~20mrad to

IR2

30 km

Bypass Lines50, 175, 250 GeV

IR1 (250 GeV to multi-TeV)

Length for500 GeV/beam

Injector Systems for 1.5 TeV

IR2 (90 GeV to

~TeV)

Tom Markiewicz


TESLA Post-Linac Layout

Tom Markiewicz


Skew Correction / Emittance Diagnostics

Skew Correction / Emittance Diagnostics

e+

e-

Interaction Region Transport (High Energy)

Interaction Region Transport (High Energy)

Collimation / Final Focus(High Energy)

Collimation / Final Focus(High Energy)

IR Hall (High Energy)

IR Hall (Low Energy)IP1IP2

Interaction Region Transport (Low Energy)

Interaction Region Transport (Low Energy)

Collimation / Final Focus(Low Energy)

Collimation / Final Focus(Low Energy)

Tom Markiewicz


Pros & Cons of a Crossing Angle

Cons:• Beam Steering Correction Easy• Crab cavity Required OK as long as C<~40 mrad• LUM not cylindrically

symmetric Who cares?• Net pT to interactionPros• Separate Extraction Line

– Post IP Diagnostics Pre-IP Diagnostics– Single ,e beam dump Higher P e-dump anywhere

• Allows for future reduction Who cares? in beam spacing Dig later if really needed

Tom Markiewicz


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-500 JLC/NLC-500

N 2.0 x 1010 0.75 x 1010

x550 nm 243 nm

y5 nm 3 nm

z300 m 110 m

Tom Markiewicz


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 /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 InteractionSR photons from individual particles in one bunch when in the E field of

the opposing bunch

Tom Markiewicz


Pair ProductionPhotons interact with opposing e, to produce e+,e- pairs and

hadrons

Pair PT:• 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


e+,e- pairs from beams. interactions

# pairs scales w/ Luminosity

1-2x109/sec

BSOL, L*,& Masks

Tom Markiewicz


NLC/TESLA Beam-Beam Comparison

)(

2

YXY

ZeeY

NrD

c

bunch

YXZ

ee

B

BNr

)(6

5 2

NLC500 TESLA500

Dy 14 25

0.11 0.06

n 1.17 1.6

b 4.6% 3.2%

HD 1.4 2.1

# pairs/bunch 49,000 130,000

<E>_pair e 5.5 GeV 2.8 GeV

#pairs/ sec 1.1E9 1.8E9

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


Pairs as a Fast Luminosity Monitor

Also, Pair angular distribution carries information of beam transverse aspect ratio (Tauchi/KEK)

TESLA

Tom Markiewicz


Pair Stay-Clear from Guinea-Pig Generator and Geant

Tom Markiewicz


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


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


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


Photons

in LD TPC

1 TeV

in LD Endcap CAL

1 TeV

in SD Endcap CAL

1 TeV

TESLA #/BX in TPC vs. z

Beampipe @ r=1.0cm, B=3T

Extraction Line (6m) “shines” thru shield here, but not here

Beampipe @ r=2.2cm, B=4T

Tom Markiewicz


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 magnetsRadiative 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 Rmin down x2 Fluence

UP x40

Tom Markiewicz


Neutrons from the Beam Dump

Geometric fall off of neutron flux passing 1 mrad aperture

Limiting Aperture

Radius (cm)z(m)

# Neutrons per Year

1.00.5

Integral

Tom Markiewicz


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)

Radiative Bhabhas 1.5 x 107 hits/cm2/yr no hits <0.5x108 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

Neutron BackgroundsSummary

Figure of merit is 3 x 109 for CCD VXD

Tom Markiewicz


Detector Occupanciesfrom e+e- Pairs @ 500 GeV

Detector Per bunch R. O. Eff.#B

Occupancy Comment

VXD-L1 36E-3/mm2 50 s 148 5.3/ mm2 1.5cm, 4T

VXD-L2 3.1E-3/mm2 250 s 742 2.3/ mm2 2.6cm, 4T

TPC 1336, 5trks 55 s 160 Few per mil

Barrel ECAL 1176, 0.63GeV 150 ns 1 0.63 GeV 101>3MeV

Endcap ECAL 1176, 1.92GeV 150 ns 1 1.92 GeV 91>3MeV

VXD-L1 38E-3/mm2 8 ms 190 7.2/ mm2 1.2cm, 3T

VXD-L2 3.1E-3/mm2 8 ms 190 0.6/ mm2 1.4cm, 3T

TPC 1377, ?trks 8 ms 190 “Few per mil” Needs Study

Barrel ECAL 547 , 0.73 GeV 8 ms 190 139 GeV Needs Study

Endcap ECAL 597, 0.9 GeV 8 ms 190 171 GeV Needs Study

TESLA

NLC

Tom Markiewicz


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, …….

X=450 rad

Y=270 rad

X=32 rad

Y=28 rad

BE SURE YOU NEED IT!

Tom Markiewicz


HALO Synchrotron Radiation Fans with Nominal 240 rad x 1000 rad Collimation

(Similar plots for TESLA)

Tom Markiewicz


Muon Backgrounds from Halo CollimatorsNo Big Bend, Latest Collimation & Short FF

If Halo = 10-6, no need to do anything

If Halo = 10-3 and experiment requires <1 muon per 1012 e- add magnetized tunnel filling shielding

Reality probably in between

18m & 9m Magnetized

steel spoilers

Betatron

BetatronCleanup

EnergyFF

Tom Markiewicz


LD Muon Endcap Background #e- Scraped to Make 1Muon

Calculated Halo is 10-6

Efficiency of Collimator System is 105

Bunch Train =1012

Engineer for 10-3 Halo

Tom Markiewicz


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


Independent Systems Model for e- Injection on e+ Arm

e- Source

Target6 GeVS or CBand

SharedTunnel

6 GeVS or CBand

SharedTunnel

2 GeVL Band

e+ MAIN LINAC

e+ Turnaround

e+ Pre-Damping

Ring

Main e+Damping

Ring

e+

e-

SpinRotator

Polarizede- Sourcee- Turnaround

Q-LatticePi Shift

BC2600MeVX-Band

Polarimeter

RED=New Stuff

Tom Markiewicz


Fixed Target Options

Tom Markiewicz


Your IR Options ARE Open!

Beam Delivery and IR Choices are ~

Independent of RF TechnologyAnd 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

nlc - the next linear collider project linear collider ir options tom markiewicz / slac lc workshop...

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