Phase II: HF Replacement? Aldo Penzo, INFN-Trieste HCAL Working group, CMS Upgrade Workshop FNAL, 19 Nov 2008 HF designed as “intrinsically” rad-hard; The detectors are however result of some compromises (hopefully not affecting their performances at LHC); At SLHC “zero tolerance” : HFs can and should be upgraded at “full bullet-proof” level… How and when?

From Wizard(s) to Strawman (HF – Related, SLHC Phase 2) Areas of exposure in current HF - At high luminosity charged particle flux will be unmanageable - Charged particles radiate Cherenkov light in PMT glass - PMTs will be degraded due to high radiation levels - HF is 40% of CMS calorimetry! Drew Baden, NSF/DOE JOG, 11-Sep-08 Timing info will reduce Beam Halo background in HF Timing info will reduce Beam Halo background in HF – Long/Short fiber background cleanup in HF requires low occupancy; – Long/Short fiber background cleanup in HF requires low occupancy; no async. timing rejection is possible in current system no async. timing rejection is possible in current system – Use of SiPM in HF region will also be investigated – Use of SiPM in HF region will also be investigated Chris Tully- SLHC Workshop, CERN (May 21-22, 2008) HCAL –HF may be blocked by potential changes to the interaction region –Direct impact mainly in the case of looking for WW scattering… Jordan Nash - CMS Upgrades, 21 May 2008 It is not worth preserving the matrix (radiation risks as well as time table constraints) – a complete HF replacement is the only possibility Andris Skuja, HF at the SLHC Report (October 2007)

LHC Operating Conditions (2013?) Luminosity cm -2 s -1, bunch crossing interval 25 ns, run-time 10 7 s/year. Inner part of HF (4.5 < |  |< 5): flux ~2.0x10 6 cm -2 s -1, dose ~ 100 Mrad/year. Large neutron fluxes (~ 10 9 n cm -2 s -1, at shower maximum) Activation of HF absorber ~10 mSv/h (60 days LHC run/1 day cool-down)

LHC → SLHC Luminosity A realistic scenario? See J. Nash report

Upgrade scope See J. Nash report

One good reason to go SLHC…. If “low-energy” Higgs not found Will need to look at WW scattering –Some mechanism required to avoid unitarity violation Forward Jet Tagging Essential 3000 fb -1 (SLHC) [HF - inspired] See J. Nash:

SLHC Scenarios for IR upgrade Various schemes: early separation, crab crossing, Piwinski angleVarious schemes: early separation, crab crossing, Piwinski angle Goal: Enable focusing of the beams to  *=0.25 m in IP1 and IP5, and reliable operation of the LHC at 2 - 3x10 34 cm -2 s -1.Goal: Enable focusing of the beams to  *=0.25 m in IP1 and IP5, and reliable operation of the LHC at 2 - 3x10 34 cm -2 s -1. Planning: 2013 operational for physicsPlanning: 2013 operational for physics Implications of Early Separation Very small  *(8 cm)Very small  *(8 cm) Beam elements (quads, dipole) inside CMSBeam elements (quads, dipole) inside CMS Implications on BX-ing timeImplications on BX-ing time ( * ) Could we do this without replacing HF? –No way without obscuring part of HF –But perhaps lower eta region still usable Will the HF still be useful at SLHC? ( * ) 50ns: larger number of particles in fewer bunches, large pile-up in each crossing, no modification of IR 25ns: smaller pile-up, requires substantial modification to the IR “Early separation”

’’Early beam separation’’ scheme In this case HF may be obstructed HF Triplet closer to IP Dipole inside end disks

HF Cross-section

Special HF properties Čerenkov Calorimeter – Quartz fibers –Č light yield ≈ 0.1 ionization (scintillator) –mainly e ± (T ≥ 0.2 MeV;  ≥ n -1 ≈ 0.7) Strongly non-compensating : e/h ≈ 5 (e/  ≈ 1.4) Light yield ~ 0.3 phe/GeV ~ 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)  ~ 0.03   ~ 0.03 rad] Uniformity (transverse) ± 10%

HF MAPS of fluence/dose Fluence of hadrons (E>100 keV) in cm -2 s -1 (upper plot) Radiation dose in Gy (lower plot) in the HF and its surroundings. (Values for pb -1 )

HF summary radiation budget Recent radiation background simulations show improvement in the design of the shielding around the PMT region by a factor of ~two. There is no issue with the radiation dose or neutron flux where the PMTs are located. All neutrons2.54x10 12 Neutrons (E>100KeV) 1.63x10 12 Neutrons (E>20 MeV) 5.12x10 11 Ch. Hadrons2.26x10 10 Muons4.65x10 9 Photons1.53x10 12 Dose7 krad Activation of absorber ~10 mSv/h (60 days LHC run/1 day cool-down) Servicing HF will be hard…!!

HF Radiation Environment Erchov, A.: Radiation monitoring in the HF area CMS WEEK, Tuesday 03 December 2002

Radiation Damage Quartz Fibers (QF) : QF with fluorine-doped silica cladding (QQF) can stand ~20 Grads, with ≤ 10% light loss; but plastic-clad fibers (QPF) may have ≥ 75% losses after 5 years at luminosity 10^34 / cm^2 /s. HF now equipped with QPF (cost-driven choice: QQF cost ~5 times more than QPF ) Photodetectors (PMT) : The HF PMTs Hamamatsu R7525HA are well shielded. The PMT would receive a radiation dose of about 10 krad/year, mainly ~ 10^11 n /cm^2/year PMT windows (borosilicate glass) have significant damage (induced absorption with ≥ 30% loss of transmission at 420 nm) after ~120 krad (gamma-irradiation); for neutrons, effects are similar for ≥ 10^12 n /cm^2. UV glass and Silica windows are much more rad-hard: for silica windows, no loss is observed in transmission up to ~1.4x10^14 n/cm2 Other effects of irradiation are for instance increased dark current, fluorescence emission, etc. that will increase significantly background noise. These effects are also larger in borosilicate glass than in UV, or quartz windows.

Fiber Damage and Recovery A typical spectral response of QF shows that the damage effects are reduced in the region around the maximum (420 nm) of the PM sensitivity (Quantum Efficiency); this is an important asset of quartz-fiber calorimetry. There are also quite interesting recovery mechanisms, both for fibers and PMT, reducing the effects of radiation damage, either in a natural way (self-repair in a quiet period after exposure), or artificially, for instance like thermo- (or photo-) bleaching. These need to be well understood (in particular the first one) to describe accurately the behaviour of the detector, and its history, but do not seem robust enough to be the base of a survival strategy for HF in extreme radiation conditions such as at SLHC.

Raddam monitoring Blue light is injected through a capillary tube in a 2.5 m HF long fiber (ends polished). The ratio of reflected signals S1 and S2 at each fiber end relates to fiber transparency measured by the attenuation A (dB/m). IrradiationRecovery S1 first reflection S2 second reflection

HF deterioration

Some references V. Hagopian - Radiation Damage of Quartz Fibers - CMS CR 1999/002 J.-P. Merlo et al – Radiation-hardness measurements… CMS NOTE 2007/003 V.Gavrilov et al - Study of Quartz Fiber Radiation Hardness CMS TN 94/324 Y. Onel - R&D for HCAL detectors at SLHC CMS HCAL Meeting, Oct 2003, Iowa City, IA General: G. Anzivino et al., Nucl. Instr. and Meth. A360 (1995) 237. N. Akchurin et al., Nucl. Instr. and Meth. A399 (1997) 202.

Y.Onel One of the Photodetector Candidates QE peaks at 400 nm with 45% (ultra bialkali) within the range of nm. The metal envelope eliminates Cherenkov light in the walls. A very thin window (0.6 mm) which also eliminates Cerenkov light production due to head on muons. It gives possibility to assign two channels per tower (or equivalently per light-guide.) 11/19/ CMS Upgrade Workshop, Nov 19-21, 2008 HF upgrade plan includes changing PMTs with new generation PMTs. The replacement will help to tag “PMT Events” have better energy resolution Increase muon signal efficiency Hamamatsu 16- Anode PMT R7600U-200)

[no-frills/no-hassle solution…] HF Repair/Upgrade for SLHC Phase 2 (if so decided…) A replacement of (at least fraction of) QPF with QQF and PMTs may be feasible, provided safe procedures for manipulation of the HF activated parts are implemented, and with investments comparable to the original costs of HF fibers and PMTs (~2.5 M and ~1 M respectively in CHF; at that time 1 USD was ~1.7 CHF). The cost for QQF fibers assumes replacement of about 20% of the QPF, at about 5 times their original price. If manipulation of activated components, for fiber extraction and stuffing, turns out to be prohibitive, replacement of the absorber matrix could be considered, possibly including finer-grained configuration, for instance to provide smaller trigger tower size, if useful. The price tag in year 2000 of original steel wedges with electro-etched grooves and diffusion welding assembly was ≤ 1 MCHF. It may be not worth preserving the matrix (radiation risks as well as time table constraints) – a complete HF replacement is better

Alternatives… If reconfiguring HF layout is not necessary, than an improved replica would be sufficient; If IR configuration changes drastically and HF is squeezed towards IP, then a complete new design would be necessary: New photodetectors (B-field immune): SiPM? Higher granularity, density, etc. Maybe a totally different technology?

Some very high luminosity options Rad-Hard detectors (see also ILC Forward Calorimetry) GeAs CVD Diamond [P. Weilhammer et al] Gas Ionization (PPAC) [Y.Onel, E. Norbeck] Secondary emission [Y.Onel, D.Winn] Disposable active media [???]: –Liquid Č Radiator / Scintillator [S. Buontempo et al, E. Norbeck] –Gas Č Radiator [M. Albrow, N. Akchurin/J. Hauptman]

Very Forward Region & BeamCal for the ILC Under investigation so far: W/diamond sandwich calorimeter A Forward Calorimeter in which machine elements are embedded

CVD Diamond vs Si Silicon starts to degrade at 30 kGy. High leakage currents. Not recoverable. CVD diamonds still operational after absorbing 7MGy. ~0.6MGy/s (E6_4p)~0.6MGy/s (FAP5) ~0.6MGy/s (E6_4p)~0.6MGy/s (FAP5)

CVD Diamond vs Si 5%/E + 19%/E 1/2 + 2% Diamond 4%/E + 18%/E 1/2 + 0% Silicon

Backup slides [Some properties of semiconductor-based calorimeters]

SICAPO: Silicon Calorimeter Another hanging file reconfigurable calorimeter prototype

Assembling the Si detectors

A “compensating” hadron calorimeter

PAMELA