1. 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 Aldo Penzo (INFN – Trieste, Italy) Yasar Onel (Univ. of Iowa, USA) (On behalf of CMS HCAL)

2. LHC (SLHC) Experimental Challenges For LHC: Luminosity L = 10 34 cm -2 s -1, Bunch Crossing (BX) interval  = 25 ns, High Interaction Rate –pp interaction rate ~10 9 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 (~ 10 7 s) [Activation of HF ~10 mSv/h (60 days LHC run/1 day cool-down) ]

3. LHC to SLHC Assume SLHC luminosity L = 10 35 cm - 2 s - 1 (10 x LHC) Possible bunch crossing intervals: 25 ns, 50 ns Some parameters for comparison are (1 LHC year = 10 7 s) : LHC SLHC L (cm - 2 s - 1 ) 10 34 10 35 10 35 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 (  ~ 3-5) ~ 10 MGy/year

4. 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…???

5. 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.

6. 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 (~45 o for  =1) Optical fibers only trap light emitted within the numerical aperture of the fiber   (~20 o with axis of fiber)  T ~ 20 o  C ~ 45 o  > 0.7 DRDC P54 (1994) - Development of quartz fiber calorimetry (A. Contin, P. Gorodetzky, R. DeSalvo et al.)

7. 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)

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

9. 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  = 0.175 x 0.175) 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

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

11. HF at SX5 ready for lowering to the cavern Completely assembled HF module

12. 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

13. HF structure and properties

14. 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  ~ 0.03  and in  ~ 0.03 rad a – Statistical fluctuations b - Constant term (calibration, nonlinearity) c - Noise, etc

15. 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

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

17. HF monitoring and calibration tools Pedestals – long/short term stability; light-leaks LED – stability, photoelectron response Laser – timing HV scans – gain Co 60 Source scan – calibration ~ ± 5% Rad-dam monitoring – fiber attenuation damage by radiation

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

19. Almost complete rapidity 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2  HF- HF+ CASTORCASTOR CASTORCASTOR CMS ZDC HF in the forward region of CMS

20. 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

21. “Tagging” jets

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

23. 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 (10 28 ~ 10 34 cm –2 s –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 requirementsMezzanine board to tap into HF data stream Autonomous (mini) DAQ system to provide “always on”operation

24. 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

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

26. Blue : Clean Quartz Green : 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/cm 2, 0.01 gr/cm 2, and 0.015 gr/cm 2 PTP densities on quartz surfaces, looks like 0.01 gr.cm 2 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