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Crystal Detector Development and Testing for Gerda Collaboration | November 2005 Updates

This document outlines the progress made in crystal detector development and testing for the Gerda Collaboration in November 2005, including crystal types, test-stands, MC simulations, and outlook for future tests. Learn about crystal performance, suspension systems, cabling tests, MaGe simulations, dominant background sources, and key conclusions drawn from the test results.

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Crystal Detector Development and Testing for Gerda Collaboration | November 2005 Updates

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  1. Task Group 2 Iris Abt, Michael Altmann, Kevin Kroeninger, Bela Majorovits, Franz Stelzer, Xiang Liu • Detector Development • Suspension & Cabling • MC Simulation • Outlook & Conclusion

  2. 2 Canberra crystals (n-type) • Mikesch-I : non-segment • Mikesch-II: 18 segments, 6 x 3z (end of year) • 3 DSG crystals (p-type) • Roland-I : true coaxial, non-segment • Roland-II : 6 segments • Roland-III: 18 segments, 6 x 3z (end of year) Prototype Test-stands & Crystals • 3 test-stands: • Milchkanne: LN2 • Gerdalinchen: LN2 • Galatea: Vacuum Gerda Collab. , Nov. 9-11, 2005 Page 2

  3. 1st: Milchkanne & Mikesch crystal • Canberra n-type crystal • Non segment • Non-true-coaxial Mikesch-I Eurysis Gerda Collab. , Nov. 9-11, 2005 Page 3

  4. Mikesch in LN2 13 LN2 & 1 LAr cooling-warming cycles FWHM~3.5keV (electronic noise dominated) Rise-time vs. crystal angle (241Am) Crystal axis affects electron-hole drift velocity Gerda Collab. , Nov. 9-11, 2005 Page 4

  5. Mikesch in LAr In LAr In LN2 Eu152 spectrum Gerda Collab. , Nov. 9-11, 2005 Page 5

  6. 2nd: Gerdalinchen & DSG Roland-I II • Similar to Gerda setup & environment • Multi-purpose, test suspension strings • Multi-crystals. IR shielding Gerda Collab. , Nov. 9-11, 2005 Page 6

  7. 2nd: Gerdalinchen & DSG Roland-I II Roland-I Roland-II IR Shield Gerda Collab. , Nov. 9-11, 2005 Page 7

  8. DSG Roland-I & II performance Roland-I leakage current Roland-II A V_bias Infrared increases leakage current, shielding very important Gerda Collab. , Nov. 9-11, 2005 Page 8

  9. Suspension system design Kapton cable suspension string (Cu) bond pads holders (cu, teflon) Gerda Collab. , Nov. 9-11, 2005 Page 9

  10. Cabling tests with optical crystal Gerda Collab. , Nov. 9-11, 2005 Page 10

  11. Materials & MaGe MC • Cu: • Cresst, Gerda, Majorana • Majorana Cu stress test: ok for 35kg MaGe simulation • Kapton-cable: • pure K, K-Cu, K-Cu-Ni-Au • contamination measurement in HADES Need MC for contamination limit Gerda Collab. , Nov. 9-11, 2005 Page 11

  12. MaGe simulation results () (,) Gerda Collab. , Nov. 9-11, 2005 Page 12

  13. MaGe simulation results Dominant backgrounds: • 68Ge in crystals • 238U, 232Th in crystals <0.4 Bq/kg • 210Pb on crystal surface <0.2 Bq/kg • 238U, 232Th in Kapton cable <2 mBq/kg • 238U, 232Th in junction box <0.5mBq/kg Upper limit on other materials: Gerda internal note (GSTR-05-019) ready Gerda Collab. , Nov. 9-11, 2005 Page 13

  14. 3rd Test-stand: Galatea 3 stages for source inside Vacuum tank for laser,  &  sources Gerda Collab. , Nov. 9-11, 2005 Page 14

  15. Outlook Milchkanne Test-stand: More cycles, more lAr test Gerdalinchen Test-stand: Mikesch-II, Roland-I & II & III: resolution, mirror charge, pulse shape, crystal axis Galatea Vacuum Test-stand: with laser,  &  sources. all of the above, plus thickness of dead layers Gerda Collab. , Nov. 9-11, 2005 Page 15

  16. Conclusion • Learned from test-stands: • Crystals sensitive to IR radiation (both n,p-types) • Need axis orientation of each crystal (for pulse shape) • Crystals fragile with water • Learned from MC: • Dominant internal background sources located (68Ge in crystal, 238U 232Th in Kapton) • Upper limit for all suspension and cabling materials. • Complete prototype design of support & cable for Phase-II available. Gerda Collab. , Nov. 9-11, 2005 Page 16

  17. Backup: Co60, Ge68, Pb210 contamination Co60 in crystal: 4/kg/day above ground, assume 10 days above ground, 40 atoms/kg first year, 4.9 decays per kg,  0.16 Bq/kg Ge68 in crystal: 1/kg day, saturation 400 /kg assume 180 days from enriching to storage undergd., 145/kg 60% decay in first year,  2.7 Bq/kg Pb210 on surface: 4000 Rn/crystal during installation 45 decays/year/crystal  0.26 Bq/kg Gerda Collab. , Nov. 9-11, 2005 Page 17

  18. MaGe simulation • Contaminations: • Th232 • U238 • Pb210 • Co60 • Ge68 • Components: • Crystal • Cu holder • Teflon holder • Cu suspension string • kapton cable • bonding pads • electronic Junction box Gerda Collab. , Nov. 9-11, 2005 Page 18

  19. Crystal axis effect Rege Gerda Collab. , Nov. 9-11, 2005 Page 19

  20. Materials & MaGe MC • Cu: • Cresst, Gerda, Majorana • Majorana Cu stress test: ok for 35kg MaGe simulation • Holder • Suspension string • Kapton cable • Junction box • crystals • Kapton-cable: • pure K, K-Cu, K-Cu-Ni-Au • contamination measurement in HADES Need MC for contamination limit Gerda Collab. , Nov. 9-11, 2005 Page 20

  21. Mikesch in LAr In LAr In LN2 Gerda Collab. , Nov. 9-11, 2005 Page 5

  22. Roland-I pulse shapes & resolution s ns Gerda Collab. , Nov. 9-11, 2005 Page 21

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