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SciFi 2

SciFi 2. B. Leverington, on behalf of the SciFi One group. Points for today:. I will focus on Upgrade 2. It's a completely new detector, SciFi 2 . (Forget about cutting SciFi 1 modules shorter, reusing frames , etc.) Highly integrated with the “Mighty” silicon tracker.

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SciFi 2

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  1. SciFi 2 B. Leverington, on behalf of the SciFi One group

  2. Points for today: • I will focus on Upgrade 2. • It's a completely new detector, SciFi 2. (Forget about cutting SciFi 1 modules shorter, reusing frames, etc.) • Highly integrated with the “Mighty” silicon tracker. • I will present a summary of our brainstorming discussion from last Wednesday. • Geometry and mechanics concept • Developments in Scintillating Fibres • SiPMs, Cooling, and Readout B. Leverington - SciFi 2 for LHCb Upgrade 2

  3. Radiation 1 MeV n eq. (no shielding) (50 fb-1) Ionising Radiation • Plots by Matthias Karacson for Upgrade 1 https://cds.cern.ch/record/2235317/files/LHCb-TALK-2016-380.pdf M0 M1 M2 M3 M4 M5 Shielding reduces 1MeV eq. fluenceby a factor of2.5 (T1) to 3.4 (T3) T1 3.3*1011neq/cm2 T3 4.2*1011neq/cm2 B. Leverington - SciFi 2 for LHCb Upgrade 2

  4. Slide from Lucia Grillo Occupancy correlated with ionizing dose… Maximum dose is about half in Upgrade 2 with current MT plan B. Leverington - SciFi 2 for LHCb Upgrade 2

  5. Ionising dose/Occupancy • Cut away the part of SciFi that sees too much dose and occupancy. • Build the Mighty tracker. • What defines the boundaries? • Not determined by the new 35 kGy line, but the average dose over the length • Losses due to ionising radiation equal to natural attenuation losses around 1000 Gy Plots by C. Joram B. Leverington - SciFi 2 for LHCb Upgrade 2

  6. The all-seeing tracker... B. Leverington - SciFi 2 for LHCb Upgrade 2

  7. We would like to avoid this. B. Leverington - SciFi 2 for LHCb Upgrade 2

  8. A hybrid module fibre silicon Services Services fibre B. Leverington - SciFi 2 for LHCb Upgrade 2

  9. A hybrid scint. fibre/silicon module • Remove the support structure of the silicon tracker from the material budget in the acceptance (use the existing SciFi module). Minimise the rest. • . • Proof of concept could be tested in Upgrade 1b for some beampipe modules • Interconnection of the silicon tracker box, Scifi sandwich and services will be challenging. • Needs a group with strong engineering and technical support to lead this part. Carbon Fibre 2 cm • Core cavities for cables, cooling pipes, data • Stiffness comes from the core not compressing or shearing and the skin not stretching or wrinkling 2 cm Scint.Fibre Carbon Fibre Bootstrap to the outside if access is required. B. Leverington - SciFi 2 for LHCb Upgrade 2

  10. Hit Efficiency and S/N • Reduced hit detection efficiency is the “aging” effect of the SciFi and is directly coupled to the S/N ratio. • For 50 fb-1 a reduction of efficiency of 1-2% is expected. Precise numbers are difficult to obtain before a few years of operation. • What are the knobs that we can turn? • Another photodetector? • Unlikely, given the geometry and properties of the fibre mats. B. Leverington - SciFi 2 for LHCb Upgrade 2

  11. Fibres - the NOL idea • Can we (LHCb) improve the fibre performance to start with a ‘better’ fibre in the beginning? • Energy loss dE/dx is given • Fibre construction, i.e. cladding, no suitable material with n < 1.42 • Activation and wavelength conversion  NOL idea NOL: Nanostructured Organo-silicon Luminophores Act Act WLS Act Act “Conventional” S.A. Ponomarenko et al., Nature Sci. Rep. 4 (2014) 6549 • Activator and WLS are chemically coupled using silicon links • Non radiative energy transfer (Förster mechanism) • Faster and more efficient than radiative emission See Lukas’ slides for more details. https://indico.cern.ch/event/808850/ B. Leverington - SciFi 2 for LHCb Upgrade 2

  12. NOL fibre Emission spectra (@ 15 cm from excitation point) • Peak wavelengths: • Blue NOL: 430 nm • Green NOL: 470 nm • Blue standard: 440 nm • Green standard: 530 nm Blue NOL fibre Green NOL fibre • 8 iterations of NOL fibres • Best were 50% faster than standard fibres, 1ns. • Best light yield about 15% lower than standard fibres. • Might be a material impurity problem. • No control over the production of the materials. • NOL WLS bars to be used for ALICE Diffractive detector upgrade • NOL11 fibres were considered for Mu3e. • Green fibres (emission peak 500 nm) might be still interesting to test. • No hadron irradiation done yet!!! X-ray results are ok. • Optimise for an irradiated detector Blue standard fibre Green standard fibre B. Leverington - SciFi 2 for LHCb Upgrade 2

  13. Other plastic scintillator developments Emmission spectra with QD https://doi.org/10.1016/j.jlumin.2013.09.051 • Most of the scintillators used in HEP were developed in the 60 and 70’s. • Is the marketbiased towards scintillators that match conventional PMTs? • Quantum Dot (QD) enhanced scintillators • nsdecay time, longer wavelengths possible • Still problems with attenuation length, non-trivial to dissolve in plastics • Testing new scintillating polymers (PEN, PET) • blue emission, no wavelength shifter yet • Slow decay times ( 10ns), good light yield • Red based dyes such as Nile Red as Wavelength shifter • <3ns decay time, dissolves easily in polymer • (Light) stimulated radiation damage recovery. The fluorescence spectra of PEN https://doi.org/10.1140/epjc/s10052-019-6810-8 The fluorescence lifetimes of Nile Red in polymers. https://doi.org/10.1016/j.cplett.2009.06.088 B. Leverington - SciFi 2 for LHCb Upgrade 2

  14. SiPM developments • For upgrade 2 (300 fb-1) : • 2.5*1012neq/cm2 • The SiPM characteristics ( gain, PDE, x-talk, After-Pulse) remain unchanged and the detector is still fully functional at this fluence. • Shielding in front of the calorimeter probably can’t be increased, but it’s not the only source of neutrons. • Development of radiation optimized SiPMs • Study optical focusing system on pixels with micro-lenses to reducing active surface and increase over-all PDE. • Study more radiation hard SiPM implementations (silicon structures) and the use of smaller pixels Shielding in Upgrade 1: Fluencereduction by a factor of2.5 (T1) to 3.4 (T3) Micro-lens simulation https://infoscience.epfl.ch/record/256964/files/EPFL_TH8842.pdf B. Leverington - SciFi 2 for LHCb Upgrade 2

  15. Cooling Dark Count Rate (unirradiated) • Need to go below -80C to achieve the same DCR with a factor 6 more neutron fluence • Going below -40C without vacuum “nearly impossible” • Reaching that Dew point is already difficult with dry gas • A vacuum based package for the 128 channel SiPM without dead regions on the edges is expected to be extremely challenging (impossible?). • A vacuum based cooling system with a clear fibre interface could be the solution. • A vacuum vessel with a clear fibre feedthrough and a 40cm long Kapton flex for thermalisation and feedthrough. • Cooling to -140°C (133K)is possible from the SiPM operation point of view. Upgrade 1 After-pulse probability Upgrade 1 B. Leverington - SciFi 2 for LHCb Upgrade 2

  16. Vacuum cooled + fibre guide solution 16 arrays in cryogenic box • Clear fibre guides • Wound with the same fibre pitch as mats for 1:1 matching • 10% light loss in preliminary tests • Length ~ 0.5 – 1 m • Separates the module from the SiPMs and cooling • No more dry “cold box”, just a light shielded connection • Light-injection for calibration moved out of the module 4 flexible clear-fibre lightguides Scintillating fibre mats B. Leverington - SciFi 2 for LHCb Upgrade 2

  17. Readout Electronics • Currently available FPGAs won’t work in the increased radiation environment. • Will require a clustering ASIC (+ raw mode for Light injection) • Probably smart to keep this separate from a refreshed PACIFIC • Most of SciFi 2 will be a “high-occupancy” region relative to the beampipe modules of Upgrade 1. • Many clusters, requires a different (SFV) data format • Time-of-arrival with the SciFi technology. • Application in LHCb unlikely (power consumption, too little direct light, mirror reflected light) B. Leverington - SciFi 2 for LHCb Upgrade 2

  18. Summary • SciFi-2 is a new detector. No chance to reuse SciFi-1. • Will integrate the silicon tracker with the SciFi-2 • This a very significant engineering effort. Start early with a strong team and leadership. • Standard scintillating fibres will work in Upgrade 2 • The increased loss due to higher average radiation damage would benefit greatly from fast, longer wavelength emission (green, red) • NOL fibres are faster, but lower light yield. Will check comparison after irradiation. • Still need experience from Upgrade 1 for better predictions. • Standard SiPMs will work in Upgrade 2 in a cryogenic bath down to 133K. • Some small benefits could be gained from extra shielding • Requires the development of clear fibre guides (10% light loss). • Gains from reduction of active silicon area B. Leverington - SciFi 2 for LHCb Upgrade 2

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