Presented by Aldo Penzo, Calorimetric Techniques Session, 26 May 2008 LHC The CMS - HF Calorimeters: Radiation hard Quartz Calorimetry Aldo Penzo (INFN – Trieste, Italy) Yasar Onel (Univ. of Iowa, USA) (On behalf of CMS HCAL) 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 INFN CALOR 2008 – Pavia, Italy (26- 30 May 2008) Presented by Aldo Penzo, Calorimetric Techniques Session, 26 May 2008

LHC (SLHC) Experimental Challenges For LHC: Luminosity L = 1034 cm-2 s-1, Bunch Crossing (BX) interval D = 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 (h ~ 3-5) ~ 100 Mrad/year (~ 107 s) [Activation of HF ~10 mSv/h (60 days LHC run/1 day cool-down) ]

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 50 Nint / BX-ing ~20 ~ 200 ~ 400 dN/d / BX-ing ~100 ~1000 ~1000 ∫L dt (fb-1) 100 1000 1000 In forward CMS region (h ~ 3-5) ~ 10 MGy/year

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 h 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…???

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.

Characteristics of Cherenkov light from Quartz Fibers In quartz (n=1.45) charged particles with b >1/n (0.7) emit Cherenkov light (Threshold 0.2 MeV for e, 400 MeV for p) Cherenkov angle qc such that cos qc = (bn)-1 (~45o for b=1) Optical fibers only trap light emitted within the numerical aperture of the fiber qT (~20o with axis of fiber) qT ~ 20o qC ~ 45o b > 0.7 DRDC P54 (1994) - Development of quartz fiber calorimetry (A. Contin, P. Gorodetzky, R. DeSalvo et al.)

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)

Fast time response CMS HF Calorimeter 2003 Test Beam 25 ns Intrinsically very fast Y. Onel, Chicago Calorimetry Conf. , June 2006

CMS – HF Calorimeters 2 Quartz Fiber Calorimeters for the forward region (3< h <5) of CMS ~ 250 tons iron absorber (8.8 lI) ~ 1000 km quartz fibers (0.8mm diam) ~ 2000 PMT read-out 36 wedges azimuthally; 18 rings radially (Segmentation DhxDf = 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

Assembling the wedges Manual insertion of the fibers Wedges completed with fibers

HF at SX5 ready for lowering to the cavern Completely assembledHF module

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

HF structure and properties

Energy resolution of HF a – Statistical fluctuations b - Constant term (calibration, nonlinearity) c - Noise, etc 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 h ~ 0.03 and in f ~ 0.03 rad

HF in all global runs, since beginning 2007 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

HF calibrations solo and in GR Events’ display of the HF+ calibration data (by Ianna Osborne).

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

HF in CMS Total weight : 12500 t Overall diameter : 15 m Overall length . 21.6 m Magnetic field : 4 T

HF in the forward region of CMS HF: 3. < h < 5. T1: 3.1 < h < 4.7 T2: 5.3 < h < 6.5 10.5m 14m HF -8 -6 -4 -2 0 2 4 6 8 h 2p f HF- HF+ C A S T O R CMS ZDC Almost complete rapidity coverage at LHC

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: |h| up to 5 for ETmiss , 3 < |h| < 5 for ‘tagging’ forward jets

“Tagging” jets

Forward di-jets probe low-x QCD Moderate Luminosity Salim Cerci, David d’Enterria: “Mueller-Navelet” Jets separated by several Δη

Luminosity Monitor Real time lumi monitoring with HF Offline 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

SLHC R&D on Rad-hard Quartz University of Iowa 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.

Extracting Cherenkov light from Quartz plates Studies and simulations The real thing…

Preliminary results Light Enhancement Tools: Readout Options: 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). Blue : Clean Quartz Green : ZnO (0.3 micron) Red : PTP (2 micron)