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A less expensive forward endcap calorimeter as a fallback position

Discusses the possibility of replacing the BABAR CsI(Tl) endcap with a faster and more radiation-hard version using LYSO crystals, while retaining the existing mechanics. Presents cost-saving options and potential benefits.

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A less expensive forward endcap calorimeter as a fallback position

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  1. A less expensiveforward endcap calorimeteras a fallback position David Hitlin Frascati SuperB Workshop April 4, 2011

  2. The forward EMC endcap • The higher rates and radiation does of SuperB motivate replacing the BABAR CsI(Tl) endcap with a faster, denser, more radiation hard version: CsI(Tl)  LYSO • If there is pressure to reduce costs, there is a way to do this without discarding the work of the last several years: • Moliere radius of LYSO = 1/2 Moliere radius of CsI(Tl) • CsI crystals in the outer rings of the endcap should see rates and radiation doses similar to the forward end of the barrel • This leads to consideration of the following design: • Retain the mechanics of the BABAR endcap • Use 4 LYSO crystals in each existing CsI(Tl) compartment • Retain outer three rings of CsI(Tl) • A consequence is that the potential 10cm in front of the forward endcap does not become available for PID { Saves cost of new mechanics {Saves 40% of LYSO volume

  3. BABAR(SuperB)crystal layout

  4. Can we retain the existing BABAR endcap mechanics? • The current endcap consists of 20 carbon fiber modules in two ‘D’s • Each module contains 9 rings of CsI(Tl) crystals (only the outer 8 are filled)

  5. Radiation dose map • Hilger • Shanghai • Kharkov

  6. Radiation monitor positions

  7. Radiation dose (radfets) • The radiation dose as measured by anarray of radfets has been studied by Aidan Randle-Conde and David Doll • The radiation dose is a function of polar angle • The time distribution of radiation dose does not track the integrated luminosity: it appears to have both luminosity- and current- related components (unfortunately, the currents were not included in the n-tuples)

  8. Crystal response to radiation dose • The diminution of light output with radiation dose varies with crystal provider • The endcap contains some of the best crystals (SIC) and some of the worst (Hilger) Average over crystal providerwithin each ring

  9. Crystal response to radiation dose • The diminution of light output with radiation dose varies with crystal provider • The endcap contains some of the best crystals (SIC) and some of the worst (Hilger) There is a large variation in response within each ring

  10. Segmentation of the endcap Different combinationsof rings are possibleNumbers of rings can be staged

  11. CsI(Tl) endcap crystal nominal dimensions Ring QTY A B C D E F Length Volume 1 EC 120 4.555 4.685 4.345 5.395 5.805 5.135 32.5 840.4 2 EC 120 4.320 4.680 4.115 5.100 5.790 4.850 32.5 793.6 3 EC 120 4.080 4.685 3.895 4.805 5.795 4.575 32.5 749.9 4 EC 100 4.670 4.690 4.400 5.485 5.475 5.170 32.5 824.5 5 EC 100 4.390 4.690 4.115 5.160 5.475 4.840 32.5 773.7 6 EC 100 4.105 4.690 3.835 4.829 5.475 4.510 32.5 722.6 7 EC 80 4.825 4.685 4.475 5.670 5.470 5.265 32.5 845.0 8 EC 80 4.475 4.690 4.120 5.215 5.420 4.805 30.5 725.9 9 EC 80 ? ? ? ? ? ? ? ? Retain Rings 1-3360 crystals (1440 LYSO) New (Rings 4-9) 2160 LYSO Unfilled in BABAR

  12. Michel Lebeau’s email comment after Feb presentation “Clearly if budget conditions are decisive, and total saving of about 3M€ is at stake, the recycling of the Babar endcap structure and ancillaries is already 1/3 of THE solution, provided the absence of the PID is tolerable.Nesting 4 LYSO xals into one CsI alveolar is a very smart solution as it keeps the structure open to any LYSO/CsI ratio very late in design and construction. Maybe the (wall thickness x density) ratio to (xal size x number) is not as good as with my alveolar, but this is what it is !”

  13. Conclusion • A combined CsI(Tl)/LYSO solution makes an excellent fallback position, if there is not sufficient funding for a full LYSO endcap • It is straightforward to include as an option in the TDR, while an orthogonal solution does not appear as a natural evolution • Lends itself to staging, if this is necessary • All R&D work is essentially complete • Calibration system can be used as is, saving additional money • Aprroximate cost saving for 3 CsI/6 LYSO rings: €2.4M (@ € 30/cc) + €1M mechanics + €0.25M (calibration)= €3.65M

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