very forward region instrumentation
DESCRIPTION
Very Forward Region Instrumentation. Wolfgang Lohmann, DESY. Basic functions: Hermeticity to small polar angles Fast and precise Luminosity measuremt Shielding of the inner detectors -. Shielding function. Due to the small bunch size s x ~100nm, s y ~5 nm - PowerPoint PPT PresentationTRANSCRIPT
April 21, 2023 Valencia Workshop
Very Forward Region Instrumentation
Wolfgang Lohmann, DESY
Basic functions:
- Hermeticity to small polar angles
- Fast and precise Luminosity measuremt
- Shielding of the inner detectors-
April 21, 2023 LDC meeting
20mrad DID
Shielding function
20mrad solenoid
Due to the small bunch size
x~100nm, y~5 nmand the large bunch
charge, N x 1010/bunch,
beamstrahlung becomes important
lots of e+e- pairs
Current design
IP
VTX
FTD
300 cm
L* = 4m
Bhabha ScatteringLumiCal 26 < < 82 mrad
Beampipe
Head-on or small X-angle
BeamCal 4 < < 28 mrad
PhotoCal downstream(100 < < 400 rad
Precise Luminosity Measurement, 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-
LumCal bgr
Bhabha
N NL
Inner Radius of Cal.: < 4 μm
Distance between Cals.: < 100 μm
Radial beam position: < 0.6 mm
Requirements on Alignment
and mechanical Precision(MC simulations, BHLUMI)
LumiCal
LumiCalIP
Requirements on the Mechanical Design
< 4 μm
< 0.6 mm
Mechanical frame: Decouple sensor support from absorber support structure
Sensor carriers
Absorber carriers
Technology
Si/W sandwich calorimeter, simulations at advanced level.No hardware devolepment up to now.
Comparison head-on, 2, 20 mrad
Centered around the outgoing beam
Centered around the detector axis
Radial beam shift: 400m
For a 20 mrad design LumiCal MUST be centered around the outgoing
beam-pipe!
)]}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
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
Background in the LumiCal :(500 GeV, TDR)Zero or small X-angle: negligible20 mrad X-angle: 3-5 TeV
background
• 15000 e+e- per BX 10 – 20 TeV
(10 MGy per year)
• e+e- Pairs from Beamstrahlung are deflected into the BeamCal
GeV
Zero (or 2 mrad) crossing
angle
20 mradCrossing
angle
BeamCal
Background in the BeamCal :(500 Gev, TDR)Zero or small X-angle: 30 TeV/BX20 mrad X-angle: 60 TeV/BX
• Radiation hard sensors needed
Detection of High Energy Electrons and Photons (Detector Hermeticity)
√s = 500 GeVSingle Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’)
Detection efficiency as a function of the pad-size
Message: Electrons can be
detected!
Red – high BGblue – low BG
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 momentangular spreadL/R, U/D F/B asymmetries
Also simultaneous determination of several beam parameter is feasible, but: Correlations!Analysis in preparation
Observables
Fast Lumi estimate and feedback for beam steering
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
Heavy crystalsW-Diamond sandwich
sensorSpace for electronics
Technologies for the BeamCal:
•Radiation Hard
•Fast
•Compact
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
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
Linearity Studies with High Intensities
(PS fast beam extraction)105 particles/10 ns
Response to mip
Diamond Sensor Performance
Particle flux, N/cm2/10ns
Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell.
Univ. Cracow,JINR, Dubna,
NCPHEP, Minsk,FZU, Prague,
IHEP, Protvino,TAU, Tel Aviv,DESY, Zeuthen
look to our web-page: http//www.zeuthen-desy.de/LC/FCAL
We would be happy to welcome youto fight together!
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 – work to be done • compact and fine segmented calorimeters necessary, needs R&D
• Prototype tests mandatory
Remark:
• The instrumentation of the forward region is relatively independent of the detector concept,
• Mechanics design just started, needs effort
• radiation hard sensors for the inner calorimeter – needs R&D
• no electronics concept so far