outline lhc ( → slhc): huge radiation challenge quartz: radiation – hard material
DESCRIPTION
LHC. Yasar Onel (Univ. of Iowa, USA). Aldo Penzo (INFN – Trieste, Italy). (On behalf of CMS HCAL). CALOR 2008 – Pavia, Italy (26- 30 May 2008). IN F N. Presented by Aldo Penzo, Calorimetric Techniques Session, 26 May 2008. The CMS - HF Calorimeters: Radiation hard Quartz Calorimetry. - PowerPoint PPT PresentationTRANSCRIPT
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Outline•LHC ( → SLHC): Huge radiation challenge•Quartz: Radiation – hard material•Cherenkov light: Filter – out junk•HF calorimeters in CMS: Forward physics at LHC•Rad – hard Quartz R&D for SLHC
INFNCALOR 2008 – Pavia, Italy (26- 30 May 2008) Presented by Aldo Penzo,Calorimetric Techniques Session, 26 May
2008
Aldo Penzo (INFN – Trieste, Italy)
Yasar Onel (Univ. of Iowa, USA)
(On behalf of CMS HCAL)
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LHC (SLHC) Experimental Challenges
For LHC:• Luminosity L = 1034 cm-2 s-1, • Bunch Crossing (BX) interval = 25 ns,
• High Interaction Rate– pp interaction rate ~109 interactions/s
• Large Particle Multiplicity ~ 20 superposed events in each BX ~ 1000 tracks into the detector every 25 ns
• High Radiation Levels– radiation hard detectors and electronics
In forward CMS region ( ~ 3-5) ~ 100 Mrad/year (~ 107 s) [Activation of HF ~10 mSv/h (60 days LHC run/1 day cool-down) ]
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LHC to SLHC
• Assume SLHC luminosity L = 1035 cm-2s-1 (10 x LHC)• Possible bunch crossing intervals: 25 ns, 50 ns • Some parameters for comparison are (1 LHC year = 107 s) :
LHC SLHC
L (cm-2s-1) 1034 1035 1035
BX interval (ns) 25 25 50Nint / BX-ing ~20 ~ 200 ~ 400 dN/d / BX-ing ~100 ~1000 ~1000
∫L dt (fb-1) 100 1000 1000
• In forward CMS region ( ~ 3-5) ~ 10 MGy/year
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Rad – hard Quartz Fibers • Quartz Fibers (QF) with fluorine-doped silica
cladding (QQF) can stand ~20 Grads, with ≤ 10% light loss;
• Plastic-clad fibers (QPF) may have ~75% losses after 5 years at LHC luminosity in high region
• Quartz Fibers respond to fast charged particles by producing Cherenkov light
• PMT Photodetectors (low B) are sensitive to radiation mainly through PK windows with ≥ 30% transmission loss at 420 nm (glass)
• Recovery mechanisms, for fibers and PMT, may reduce the effects of radiation damage, either in a natural way (self-repair in quiet periods after exposure), or artificially, for instance like thermo-(or photo-)bleaching.
• Need to be understood to describe accurately the behaviour of the detector, and its history
• Robust enough for a survival strategy of detectors in extreme SLHC radiation conditions…???
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Typical spectral response of QF shows reduced damage effects in the region around maximum (420 nm) of PMT sensitivity (Quantum Efficiency); this is an important asset of quartz-fiber calorimetry.
Quartz Fibers
05
1015202530
200 300 400 500 600 700
Wavelength (nm)
Att
enu
atio
n (
dB
/m)
10 Mrad
100 Mrad
500 Mrad
1 Grad
QE-PM (%)
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Characteristics of Cherenkov light from
Quartz Fibers• In quartz (n=1.45) charged particles with >1/n (0.7) emit Cherenkov light (Threshold 0.2 MeV for e, 400 MeV for p)
• Cherenkov angle c such that cos c = (n)-1 (~45o for =1)
• Optical fibers only trap light emitted within the numerical aperture of the fiber (~20o with axis of fiber)
T ~ 20o
C ~ 45o
> 0.7
DRDC P54 (1994) - Development of quartz fiber calorimetry (A. Contin, P. Gorodetzky, R. DeSalvo et al.)
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Sharper shower profiles
L. R. Sulak – Frascati Calorimetry Conf., 1996
R. Wigmans – Lisbon Calorimetry Conf., 1999
N. Akchurin and R. Wigmans – Rev. Sci. Instr. 74 (2003)
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Fast time response
Y. Onel, Chicago Calorimetry Conf. , June 2006
25 ns
CMS HF Calorimeter 2003 Test Beam
Intrinsically very fast
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CMS – HF Calorimeters • 2 Quartz Fiber Calorimeters for the forward
region (3< <5) of CMS
~ 250 tons iron absorber (8.8 I)
~ 1000 km quartz fibers (0.8mm diam)
~ 2000 PMT read-out • 36 wedges azimuthally; 18 rings radially
(Segmentation x = 0.175x0.175)Test beam results of CMS quartz fibre calorimeter prototype and simulation of response to high-energy hadron jets - N. Akchurin et al. - Nucl.Instrum.Meth.A409:593,1998
Design, Performance and Calibration of CMS Forward Calorimeter Wedges – G. Bayatian et al. – Eur. Phys. J. C53, 139, 2008
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Assembling the wedges
• Manual insertion of the fibers
• Wedges completed with fibers
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HF at SX5 ready for lowering to the
cavern
• Completely assembledHF module
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HF in UX5 – at beam level
• Since lowering to UX5, HFs were in garages, while the rest of CMS was lowered to UX5 & assembled;
• in the garages HFs were commissioned
• one module seen here was extracted and was brought to beam level temporarily
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HF structure and properties
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Energy resolution of HF
• Electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form. The stochastic term a = 198% and the constant term b = 9%.
• Hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the EM case, a = 280% and b = 11%.
• Highly non-compensating: e/h ~ 5• Light yield ~ 0.3 phe/GeV • Uniformity (transverse) ± 10%• Precision in ~ 0.03and in ~ 0.03 rad
E
cb
E
a
E
E
)(
a – Statistical fluctuations
b - Constant term (calibration, nonlinearity)
c - Noise, etc
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2007 CMS Global Runs
As 2007 progressed an increasing number of the following subsystems participated in the global runs (in order of entrance) :
• HF: forward hadron calorimeter • DT: drift tubes • EB: barrel electromagentic
calorimeter • RPC: resistive plate chambers• CSC: cathode strip chamber • Trk FEDs/RIB: tracker front-end
drivers/rod-in-a-box• Lumi: luminosity monitor • HB: barrel hadron calorimeter • HO: outer hadronic calorimeter• HE: endcap hadron calorimeter• HLT: high level trigger
HF in all global runs, since beginning 2007
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HF calibrations solo and in GR
Events’ display of the HF+ calibration data (by Ianna Osborne).
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HF monitoring and calibration tools
• Pedestals – long/short term stability; light-leaks
• LED – stability, photoelectron response
• Laser – timing • HV scans – gain
• Co60 Source scan – calibration ~ ± 5%• Rad-dam monitoring – fiber attenuation
damage by radiation
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HF in CMS
Total weight : 12500 tOverall diameter : 15 mOverall length . 21.6 mMagnetic field : 4 T
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Almost completerapidity coverage
at LHC
HF: 3. < < 5.
T1:3.1 << 4.7
T2: 5.3 < < 6.5
10.5m
14m
HF
-8 -6 -4 -2 0 2 4 6 8
2
HF- HF+CASTOR
CASTOR
CMS
ZDC ZDC
HF in the forward region of CMS
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HF Physics Benchmark Processes
High Luminosity: • Higgs production via WW fusion :
• pp → j j (WW) → H j j (tagging jets in HF)
• Higgs decays to vector bosons :
• H → ZZ (WW) → l l j j
• - SUSY → jets + ETmiss (hermeticity)
• Rapidity coverage needed: || up to 5 for ETmiss , 3 < || < 5 for ‘tagging’ forward jets
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“Tagging” jets
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Forward di-jets probe low-x QCD
Salim Cerci, David d’Enterria:
“Mueller-Navelet” Jets separated by several Δη
Moderate Luminosity
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Luminosity Monitor • Real time lumi monitoring with HF
– Count minimum bias events at low luminosity– Count “zeroes” at design luminosity– Use linear ET sum, which scales directly with luminosity.– Bunch by bunch – Update time: 0.1 s to 1.0 s or slower*
– “Always on” operation, independent of main CMS DAQ• Offline
– Robust logging– Easy access to luminosity records– Dynamic range (1028 ~ 1034cm–2s–1)
• Absolute Calibration– Target 5% (or better)– Offline: TOTEM, W’s & Z’s
• Simulations: Full GEANT with realistic representation of photostatistics, electronic noise and quantization, etc.
Minimal hardware requirements•Mezzanine board to tap into HF data stream Autonomous (mini) DAQ system to provide “always on”operation
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SLHC R&D on Rad-hard Quartz
• As a solution for SLHC conditions quartz plates are proposed as a substitute for the scintillators at the Hadronic Endcap (HE) calorimeter.
• Castor uses Quartz Plates• A first quartz plate calorimeter prototype (QPCAL - I)
was built with WLS fibers, and was tested at CERN and Fermilab test beams.
• Geant4 simulations are completed • R&D studies to develop a highly efficient method for
collecting Cerenkov light in quartz with wavelength shifting fibers.
• • We are also constructing a prototype calorimeter, first 6 layers have been tested at Fermilab test beam. This summer whole prototype will be at Cern test beam.
University of Iowa
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Extracting Cherenkov lightfrom Quartz plates
• Studies and simulations
• The real thing…
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Blue : Clean QuartzGreen : ZnO (0.3 micron)Red : PTP (2 micron)
Light Enhancement Tools:
• PTP and Ga:ZnO (4% Gallium doped) enhance the light production almost 4 times. OTP, MTP, and PQP did not perform as well as these.
• PTP is easier to apply on quartz, we have a functioning evaporation system in Iowa, works very well. We also had successful application with RTV. Uniform distribution is critical!!
• We tested 0.005 gr/cm2, 0.01 gr/cm2, and 0.015 gr/cm2 PTP densities on quartz surfaces, looks like 0.01 gr.cm2 is slightly better than the others.
• ZnO can be applied by RF sputtering, we did this at Fermilab- LAB7. We got 0.3 micron, and 1.5 micron deposition samples. 0.3 micron yields better light output.
Readout Options:
• Single APD or SiPMT is not enough to readout a plate. But 3-4 APD or SiPMT can do the job.
Test Beams: We have opportunity to test our ZnO and PTP covered plates, at CERN (Aug07), and Fermilab MTest (Nov 07, and Feb 08).
Preliminary results