Forward Calorimetry Working Group Options for HF (Phase II Upgrade) Aldo Penzo (INFN –Trieste) HF designed to be “intrinsically” radiation - hard; Technical/financial compromises may limit some HF components’ lifetime (for instance up to ≈ 5 105 pb-1) Activation of HF elements may prohibit manipulation for servicing, repair, etc. HF complete replacement may be the only practical solution for SLHC… In this case a variety of options for HF upgrade may be considered… Forward Calorimetry Working Group CMS Upgrade Workshop FNAL, 29 Oct 2009 1

CMS Forward Region HF IP HF Absorber & Fibers 2

Phase I - II Upgrades Phase I Phase II Two long shutdowns (1 year) (other shutdowns < 5 months): 2014: new linac and new low-beta quads ~2018: to be decided 2011-12, could be new PS/SPS CMS upgrades implemented before/during 2014 shutdown are Phase I. Expected luminosity before 2014 shutdown ~ 1.5 1034 Upgrades implemented after 2014 shutdown are Phase II. Expected luminosity by 2018 3 1034, eventual Phase II luminosity could be as high as 1 1035 Phase I Phase II 3

Special HF components/properties Čerenkov Calorimeter ~ 250 tons iron absorber (8.8 lI) ~ 1000 km quartz fibers (0.8mm diam) Č light yield ≈ 0.1 ionization (scintillator) mainly e± (T ≥ 0.2 MeV; b ≥ n-1 ≈ 0.7) Strongly non-compensating : e/h ≈ 5 (e/p ≈ 1.4) Light yield ~ 0.3 phe/GeV ~ 2000 PMT read-out 36 wedges azimuthally; 18 rings radially (Segmentation DhxDf = 0.175x0.175) [dh ~ 0.03, df ~ 0.03 rad] Uniformity (transverse) ± 10% 4

HF summary radiation budget Fluence of hadrons (E>10 keV) in cm-2 s-1 (upper plot) Radiation dose in Gy (lower plot) in HF and its surroundings. (Values for 5 105 pb-1) (Y. Onel, March 2009 CMS HCAL Upgrade Meeting) 5

Expected HF Fiber Exposure and Scenario These numbers are without recovery of fibers. We expect the fiber to recover at least 20% at each shutdown. QP Fibers cannot survive beyond 1 Grad. They’ll need to be replaced with QQ fibers after 10 years of LHC run (or equivalent dose). The PMTs have sensitivity range nicely fitting with Fiber “sweet range” of 380nm-580nm. PMT HV adjustment can easily make up for lost light intensity due to radiation. (Y. Onel, March 2009 CMS HCAL Upgrade Meeting) 6

HF radiation budget at PMT 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 neutrons 2.54x1012 Neutrons (E>100KeV) 1.63x1012 Neutrons (E>20 MeV) 5.12x1011 Ch. Hadrons 2.26x1010 Muons 4.65x109 Photons 1.53x1012 Dose 7 krad For 10 years @ 1034 Luminosity: Activation of absorber ~10 mSv/h (60 days LHC run/1 day cool-down) Servicing HF will be hard…!!! 7

Radiation on PMTs Almost all studies agree that after 10 years the total radiation on PMTs will be less than 100 Gy = 10 kRad This radiation primarily comes from neutrons. Charged hardons and muons will be around 1012 /cm2 for 10 year period. When a PMT is exposed to radiation, the cathode sensitivity and secondary emission ratio exhibit very little variation. The variation chiefly results from a loss of transmittance through the glass window due to coloring of the glass. This plot is for 2mm glass thickness, it shows Hamamatsu tests with neutrons Conclusion: HF PMTs will NOT have any significant light loss due to radiation !! (Y. Onel, March 2009 CMS HCAL Upgrade Meeting) 8

HF Repair/Upgrade for Phase 2 (if so decided…) A replacement of (at least a fraction of) QPF with QQF may be necessary (if feasible) provided safe procedures for manipulation of HF activated parts are implemented, with investments comparable to the original costs of HF fibers and PMTs (~2.5 M and ~1 M respectively in 2000-01 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 full absorber matrix should be considered, possibly including a finer-grained configuration, for instance to provide smaller trigger tower size, if useful. The price tag in 2000 of original steel wedges with electro-etched grooves and diffusion welding assembly was ≤ 1 MCHF. 9

Some very high luminosity options and alternatives Liquid Č Radiator / Scintillator [V. Bonvicini et al, E. Norbeck] Gas Č Radiator [M. Albrow, D. Kaefer](ILC Č Detector) Gas Ionization (PPAC) [Y.Onel, E. Norbeck] Secondary Emission [Y.Onel, D.Winn] Rad-Hard detectors (Si, GaAs, Diamond (?) /W ) (SiD/ILD Forward Calorimetry) Quartz Plate with enhancement technology ( Zn O, pTp) [Onel, Cremaldi, Winn] 10

Liquid Scintillator in Quartz Tubes [Just one example:] Liquid Scintillator in Quartz Tubes [V. Bonvicini et al.: Compensating Calorimeters for High Luminosity Experiments Based on Liquid Scintillator Contained in Quartz Tubes] (INFN –Trieste Report [FACTOR-2009]) Extreme radiation doses require use of radiation-hard materials, and/or replaceability of those parts of the calorimeter which are not radiation hard. It has been suggested (A. Artamonov et al.[1], K. Pretzl, …) that liquid scintillators would be easily refillable into calorimeters Liquid scintillators in quartz tubes would additionally allow use of both scintillation and Čerenkov light from the quartz tubes, in order to achieve event-by-event compensation in the calorimeter response. A. Artamonov et al. A Liquid Scintillator Calorimeter for the Forward region of an LHC Experiment (1991) 11

Liquid Scintillator-QuartzTube Arrays For example: 3-5mm  quartz tube 0.7mm thick wall filled with liquid scintillator See also: F. Garufi: Nuovi rivelatori di particelle a scintillatore liquido per calorimetria e tracciamento ad alta risoluzione Tesi Dott. Ricerca, Dip. di Fisica, Univ. Federico II, Napoli (1996) Grooved Absorber Plate plug/manifold Each tube is connected to a plug/ manifold which allows the liquid scintillator flow through quartz tubes, connected to distribution &purge system; photodetectors are on the transparent back side of the plugs. 12

Conclusions Baseline for HF upgrade in Phase 2 replace (about 20% of) QPF with QQF …PMT replaced earlier… (?) If HF activation prohibits manipulation construction of new modules may give opportunity for new options Should we "…leave the old road for a new one…" ? "Chi lascia la via vecchia per la nuova… …sa cosa lascia, ma non sa cosa trova…" 13