A CERN contribution to the dual readout calorimeter concept

1. A CERN contribution to the dual readout calorimeter concept Paul Lecoq CERN, Geneva

2. Outline • Contribution based on a CERN R&D effort by • E. Auffray, P. Lecoq, G. Mavromanolakis, K. Pauwels • In liaison with the Crystal Clear collaboration • Metamaterials • LuAG:Ce & undoped LuAG • GdScAG:Ce & undoped GdScAG • Heavy Fluoride Metal glasses • AFG, ZFG, HFG

3. A different detector concept Excitation Scintillation Cerenkov “Unit cell” • PFA provides an attractive approach for a 3D imaging calorimeter • Integration issues with huge number of channels • Dual readout is appealing for fem determination • DREAM approach: sampling fluctuations • Bulk scintillator approach: coupling between scintillation and Cerenkov light • Can scintillators provide a solution • Combining the merits of PFA and Dual Readout • Minimizing their relative drawbacks

4. Scintillating crystals for homogeneous calorimeters Since L3, Babar, CMS (testbeam),… systematics can be controlled to give excellent energy resolution at high energy (0.5%) 2004 TB 0.5%

5. Scintillating crystals for homogeneous calorimeters Considered however to have poor performance for hadronic calorimetry • Homogeneous calorimeters are intrinsically non compensating • In addition quenching effects limit scintillation efficiency in high ionization density regions • e/h >> 1 • e/ decreases with energy (as fem increases) inducing non linearities

6. Proposal • New technologies in the production of heavy scintillators open interesting perspectives in: • Design flexibility: detector granularity • Functionality: extract more information than simple energy deposit • The underlying concept of this proposal is based on metamaterials • Scintillating cables made of heavy scintillating fibers of different composition ➱ quasi-homogeneous calorimeter • Fiber arrangement in such a way as to obtain 3D imaging capability • Fiber composition to access the different components of the shower

7. Micro-pulling-down crystal fiber growth BGO F=400mm YAG:Ce F=1mm LYSO:Ce F=2mm YAP:Ce F=2mm Courtesy Fibercryst, Lyon

8. Industrial oven Open pulling chamber and RF coil Courtesy Fibercryst, Lyon and Cyberstar, Grenoble Pulling chamber Pulling System Crucible and fiber RF Generator Control

9. UV excitation Some crystal fibers YAG up to 2m BGO ( : from 0.6 mm to 3 mm ; Length up to 30 cm) LYSO:Ce ( : from 0.6 mm to 3 mm ; Length up to 20 cm)

10. Thin pixels, compact array Pixels diameter 350 µm Array surface 10 mm x10 mm Alpha particles detector (both ends detection) Some applications: LuAG:Ce

11. Concept of meta-cable • Select a non-intrinsic scintillating material (unlike BGO or PWO) with high bandgap for low UV absorption • The undoped host will behave as an efficient Cerenkov: heavy material, high refraction index n, high UV transmission • Cerium or Praesodinum doped host will act as an efficient and fast scintillator • ≈ 40ns decay for Ce • ≈ 20ns decay for Pr • If needed fibers from neutron sensitive materials can be added: • Li Tetraborate: Li2B4O6 • LiCaF: LiCaAlF6 • elpasolite family (Li or B halide of Rb, Sc and rare earth) • All fibers can be twisted in a cable behaving as a pseudo-homogeneous active absorber with good position and energy resolution and particle identification capability • Readout on both sides by SiPMT’s

12. Concept of a Meta-cable for HEP SiPMTs SiPMTs MOEMS diffractive optics light concentrator MOEMS diffractive optics light concentrator

13. Material Selection The host is required to have: - a high density, a high refraction index and high UV transmission (Cerenkov) - good performances in pulling-down technologies - good doping capabilities (leading to fast and intense scintillation) Investigated materials are: LYSO LuAG GdScAG Excellent light yield Short decay time Easy to grow But Still to large attenuation along the fiber Excellent light yield Short decay time But Uneasy to grow Similar to LuAG Expected to be more easily grown Attenuation under investigation

14. Lutetium Aluminum Garnet LuAG (Lu3Al5O12) Physico-chemical properties Optical properties

15. Different Cerenkov materials * For  =1 particles. But lower  Cerenkov threshold for high n materials should further improve the photon yield in showers

16. LuAG:Ce and LuAG:Pr excitation & emissionspectra LuAG:Ce LuAG:Pr Measured on sample of 2x2x8mm from A. Petrosyan

17. LuAG:Ce and LuAG:Prdecay time

19. Preliminary results More in the talk from G. Mavromanolakis on Friday

20. First results on GdScAG

21. Heavy Fluoride glasses • Extensive studies in the 90es in the frame of the Crystal Clear collaboration as a possible alternative to crystals for a high precision ECAL at LHC • Motivations • Easy and cheap to produce: • ≈350°C to 570°C melting point (1000°C to >2000°C for crystals) • Can be cast in any shape with minimum of mechanical processing • Generally ternary compounds with large flexibility in composition • Main drawbacks at LHC • Weak scintillation (before the development of APDs) • Less radiation hard than crystals Not necessarily showstoppers for CLIC/ILC

22. Properties of Fluoride Glasses

23. HFG decay time

24. HFG radiation damage

25. HFG temperature dependence

26. Conclusions • Metamaterialapproach based on the DREAM concept • Added value: quasi-homogeneous calorimeter • scintillating and Cerenkov fibres of the same heavy material allowing to suppress sampling fluctuations • Additional neutron sensitive fibers can be incorporated • Very flexible fiber arrangement for any lateral or longitudinal segmentation: for instance twisted fibers in “mono-crystalline cables” • em part only coupled to a “standard” DREAM HCAL or full calorimeter with this technology? Simulations needed • Bulk material approach • L(Y)SO, LuAG, GdScAG • Well known technology • Expensive • Heavy fluoride glasses (HFG)