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April 21, 2023 Snowmass Workshop
Instrumentation of the Very Forward Region of a Linear Collider
Detector
Wolfgang Lohmann, DESY
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QD0
Inst. Mask
HCAL
ECAL
YOKE
WW
46mrad
113mrad
Support Tube
Pair-LuMon
BeamPip
e
LowZ Mask
Exit radius 2cm @ 3.5m
WW
5 Tesla
SiD Forward Masking, Calorimetry & Tracking,20 mrad crossing angle
Simulation studieson several
designs
Used by H. Yamamoto
IP
VTX
FTD
300 cm
LumiCal
BeamCal
L* = 4m
Design for 0-2 mrad crossing angle (FCAL
design)
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Functions of the very Forward Detectors
•Fast Beam Diagnostics
•Detection of electrons and photons at small polar angles- important for searches (see talk by Philip&Vladimir
•Measurement of the Luminosity with precision O(<10-3) using Bhabha scattering (see talk by Halina)
LumiCal: 26 < < 82 mradBeamCal: 4 < < 28 mradPhotoCal: 100 < < 400 rad
IP
VTX
FTD
300 cm
LumiCal
BeamCal
L* = 4m
PhotoCal downstram
•Shielding of the inner Detectors
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•Measurement of the Luminosity (LumiCal)
Goal: <10-3 Precision
Gauge Process:
• Technology: Si-W Sandwich Calorimeter
• MC Simulations
e+e- e+e- ()
Optimisation of Shape and Segmentation,Key Requirements on the
Design
Physics Case: Giga-Z , Two Fermion Cross Sections at High Energy, e+e- W+W-
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Inner Radius of Cal.: < 1-4 μm
Distance between Cals.: < 60 μm
Radial beam position: < 0.7 mm
Requirements on Alignment
and mechanical Precision(rough Estimate)
LumiCal
LumiCalIP
< 4 μm
< 0.7 mm
Requirements on the Mechanical Design
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Decouple sensor framefrom absorber frame
Sensor carriers
Absorber carriers
Concept for the Mechanical Frame
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)]}ln()([,0max{T
ibeami E
EEconstW
i
ii
W
WXX
Constant value))(_( radmean genrec
))(( rad
value of the constant
0.11e-3 rad
0.13e-3 rad
30 layers 15 rings
20rings
10ring
s
4 layers
15 layers
11 layers
10rings
Performance Simulations for e+e- e+e-()Event selection: acceptance, energy balance, azimuthal and angular symmetry.
Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread
•More in the talks by Halina Abramowicz
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X- angle background
Christian Grah, DESY-Zuethen
Beamstrahlung pair background
using serpentine field
0.E+00
1.E+09
2.E+09
3.E+09
4.E+09
5.E+09
6.E+09
8 9 10 11 12 13 14 15 16
R min (cm)
Nm
ber
of
Bh
abh
a ev
ets
per
yea
r
0
500
1000
1500
2000
2500
3000
3500
Bac
kgro
un
d (
GeV
)
Events per year
Background (GeV)
250 GeV
Number of Bhabha events as a function of the innerRadius of LumiCal
Background from beamstrahlung
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•Fast Beam Diagnostics (BeamCal and PhotoCal)
e+ e-
• 15000 e+e- per BX 10 – 20 TeV
(10 MGy per year)
• e+e- Pairs from Beamstrahlung are deflected into the BeamCal
GeV
• direct Photons for < 200 rad
Zero crossing angle
20 mradCrossing
angle
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total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries
Observables
QuantityNominal Value
Precision
x 553 nm 1.2 nm
y 5.0 nm 0.1 nm
z 300 m 4.3 m
y 0 0.4 nm
Beam Parameter Determination with BeamCal
Head-on or 2 mrad
√s = 500 GeV
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QuantityNominal Value
Precision
x 553 nm 4.8nm
y 5.0 nm 0.1 nm
z 300 m 11.5 m
y 0 2.0nm
Beam Parameter Determination with BeamCal
PRELIMINARY!
20 mrad crossing angle
total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries
Also simultaneous determination of several beam parameter is feasible, but: Correlations!Analysis in preparation
Observables
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nominal setting(550 nm x 5 nm)
>100mIP
L/R, U/D F/B asymmetriesof energy in the angulartails
QuantityNominal Value
Precision
x 553 nm 4.2 nm
z 300 m 7.5 m
y 0 0.2 nm
Heavy gas ionisation Calorimeter
and with PhotoCalPhotons from Beamstrahlung
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Heavy crystalsW-Diamond sandwich
sensorSpace for electronics
Technologies for the BeamCal:
•Radiation Hard
•Fast
•Compact
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•Detection of High Energy Electrons and Photons√s = 500 GeVSingle Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’)(talk by V. Drugakov and P. Bambade)
Detection efficiency as a function of the pad-size (Talk by A. Elagin)
Message: Electrons can be
detected!
Red – high BGblue – low BG
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Includes seismic motions, Delay of Beam Feedback System, Lumi
Optimisation etc.(G. White)
Efficiency to identify energetic electrons and photons(E > 200 GeV)
Fake rate
√s = 500 GeV
Realistic beam simulation
•Detection of High Energy Electrons and Photons
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Sensor prototyping, Crystals
Light Yield from direct coupling
Similar results for lead glassCrystals (Cerenkov light !)
and using a fibre
~ 15 %
Compared with GEANT4Simulation, good agreement
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Sensor prototyping, Diamonds
ADC
Diamond (+ PA)
Scint.+PMT&
signal gate
May,August/2004 test beams
CERN PS Hadron beam – 3,5 GeV
2 operation modes:
Slow extraction ~105-106 / s
fast extraction ~105-107 / ~10ns (Wide range intensities)
Diamond samples (CVD):
- Freiburg
- GPI (Moscow)
- Element6
Pm1&2
Pads
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Linearity Studies with High Intensities
(PS fast beam extraction)105 particles/10 ns
Response to mip
Diamond Sensor Performance
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Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell.
Univ. Cracow,JINR, Dubna,
NCPHEP, Minsk,FZU, Prague,
IHEP, Protvino,TAU, Tel Aviv,DESY, Zeuthen
Workshop on the Instrumentation of the Very Forward Region of the ILC Detector Tel Aviv, Sept. 15.-20. 2005. http//alzt.tau.ac.il/~fcal/
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Summary• Many (and promising) results in
simulations/design studies • Concept for a Luminometer for small crossing angle is advanced, 20 mrad needs a different design
• Studies with sensors started- needs more effort
• High energy electron detection down to small polar angles is feasible with compact and fine segmented calorimeters; easier for small crossing angle • Prototype tests mandatory
Remarks
• The instrumentation of the forward region is relatively independent of the detector concept,
• Mechanics design work ongoing
• calorimeters in the very forward region deliver very valuable information about beam parameters
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Backup Slides
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Shower in LAT (TDR design)
Shower LEAKAGE in old (TDR) and new LumiCal design
Shower in LumiCal (new design)
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Diamond performance as function of the absorbed dose
Linearity of a heavy gas calorimeter (IHEP testbeam)
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Comparison SamplingHeavy Crystal
Comparison SamplingHeavy Crystal
Comparison 500 GeV - 1TeV
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Depositions on the calorimter frontface
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Headon 20mrad
BeamPar MPIresolution
MPI resolution
σx σx’ σy σy’ σz σz’ offx
offy
wy
N
σx (ave) 26.789 20.471 1
σx (diff) 11.201 16.615 0.720 1
σy (ave) 0.893 2.196 -0.182 -0.271 1
σy (diff) 1.648 1.839 -0.520 -0.369 0.700 1
σz (ave) 13.018 17.781 0.290 0.101 0.852 0.441 1
σz (diff) 18.780 14.747 -0.032 -0.527 0.080 -0.143 -0.101 1
Beam offset x 5.918 6.652 0.004 -0.488 0.127 -0.125 -0.036 0.887 1
Beam offset y 0.536 6.767 0.414 0.237 -0.803 -0.927 -0.577 0.168 0.144 1
Vertical waist shift
327.312 159.172 -0.496 0.434 0.901 0.713 0.623 0.017 -0.016 -0.748 1
N per Bunch (ave)
0.109 0.080 0.581 0.316 0.619 0.016 0.869 0.039 0.056 -0.161 0.395 1
N per Bunch (diff)
0.043 0.054 0.481 0.631 -0.048 -0.119 0.066 0.149 0.018 0.030 -0.209 0.275