nlc - the next linear collider project linear collider ir options tom markiewicz / slac lc workshop...
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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 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
NLC - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
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 - The Next Linear Collider Project
NLC Detector MaskingPlan View w/ 20mrad X-angle
32 mrad
30 mrad
Large Det.- 3 T Silicon 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 IR8 mrad Design
Tom Markiewicz
NLC - The Next Linear Collider Project
TESLA IRInstrumented W Mask & Pair-LumMon w/ Low Z Mask
Tom Markiewicz
NLC - The Next Linear Collider Project
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
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, 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
NLC - The Next Linear Collider Project
Luminosity Monitor DetailNon 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 QuadsMature 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
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 - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
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
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 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
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 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
NLC - The Next Linear Collider Project
TESLA Post-Linac Layout
Tom Markiewicz
NLC - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
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
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-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
NLC - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
e+,e- pairs from beams. interactions
# pairs scales w/ Luminosity
1-2x109/sec
BSOL, L*,& Masks
Tom Markiewicz
NLC - The Next Linear Collider Project
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
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
Beampipe @ r=1.0cm, B=3T
Extraction Line (6m) “shines” thru shield here, but not here
Beampipe @ r=2.2cm, B=4T
Tom Markiewicz
NLC - The Next Linear Collider Project
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
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
1.00.5
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 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
NLC - The Next Linear Collider Project
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
NLC - The Next Linear Collider Project
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
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 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
NLC - The Next Linear Collider Project
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
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
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
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 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