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Summary of TG2-Meeting New Detectors for GERDA Phase-II

Summary of TG2-Meeting New Detectors for GERDA Phase-II. - Procurement of 30 kg of Ge-76 enrichment to 86%. Critical issues: - minimization of activation by cosmic rays / logistics - yield of chemical purification to 6N purity. Crystal production from enriched material.

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Summary of TG2-Meeting New Detectors for GERDA Phase-II

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  1. Summary of TG2-Meeting New Detectors for GERDA Phase-II - Procurement of 30 kg of Ge-76 enrichment to 86% Critical issues: - minimization of activation by cosmic rays / logistics - yield of chemical purification to 6N purity • Crystal production from enriched material • Verification of excitation functions by n-beam experim. • Detectors, suspension, integration into GERDA

  2. Ge-procurement Will happen in two steps: • Step-I: 15kg of Ge-nat, 6N purity • Purpose: Verify quality of purification process Test of transport, customs, handling, QC-measurements, ... Test-Sample for crystal pulling • Status: Arrival in Munich expected for end february • Step-II: 30kg of Ge-76 (99,8%-purity)Option: 40kg of Ge-76 plus additional purification (= approx. 30kg of 6N-purity)

  3. Ge-procurement step-II: Enriched Ge-76 Production and delivery of 30kg of Ge-76 • Baseline: 30 kg of purity 99.8% (insufficient purity for Crystal production  chemical purification required) • Option: delivery with purity 6N (would require production of approx. 40kg of Ge-76 (depending on yield of purification procedure), question of money) • Decision baseline vs. Option to be taken after analysis of Ge-nat and conclusion of discussions with Umicore

  4. Ge-procurement step-II: Enriched Ge-76 (ctd.) Timeline: - administrative tasks preceeding start of production essentially concluded - production time: 6 months delivery until mid-September expected - will be stored underground until beginning of crystal fabrication

  5. Yield of Chemical Purification Necessary (critical issue): • material purity of approx. 6N required • guaranteed after enrichment: 99.8% purity • Problem with chemical purification: Yield of standard procedure: only approx. 70% Investigation of process optimization to increase yield: Promising first results (see talk by V.Kornoukhov)

  6. New scheme of GeO2 purification:expected results • Duration ~ 9 days • total waste – 27.5% • recoverable waste – 22% in form of metal ~ 3 kg in form of solution ~ 800 L • unrecoverable waste – 5.5%

  7. FIRST RESULT AFTER SYSTEM TUNINGSVETLANA, January 200599.8%  99.98% (?)

  8. Crystal Production • Visit to Umicore, Olen (Belgium) in December 2004 • Umicore will investigate possible options and prepare a proposal • Ge-76 handling causes interference to their standard processing (in order to avoid contamination of our sample) • process steps: reduction to metal  polyzone refinement  monozone refinement  crystal pulling  shaping of the crystal

  9. LNGS GERDA meeting 03.02.2005Validation of excitation functions of 60Co and 68Ge production on germanium isotopes • V.F. Batyaev, I.V. Kirpichnikov, V.N. Kornoukhov, R.D. Mulambetov, • Yu.E.Titarenko, A.A.Vasenko, V.M. Zhivun • ITEP (Moscow, Russia) • A.Caldwell,… • MPI (Munchen, Germany) • S.Schoenert,... • MPIK (Heidelberg, Germany)

  10. Motivation • Various codes used for calculating excitation functions, results do not agree • Never measured with a neutron beam • Measurement with a neutron beam can be done at ITEP accelerator

  11. LNGS GERDA meeting 03.02.2005A schematic of arrangement of the Ge-samples around the proton-irradiated W target

  12. LNGS GERDA meeting 03.02.2005Strategy of the experiment Two approaches to do the irradiation: • Three sets of the Ge targets are placed at three different positions/angles. 2. Single set of the Ge targets are placed at one position (30o – 60o) and irradiated with three different energy of protons: 115 MeV, 256 MeV and 800 MeV. Measurement of Ge-68 and Co-60 decay to be done by Germanium spectrometry

  13. LNGS GERDA meeting 03.02.2005Measurement 68Ge/60Co activity • Ge detector: CANBERRA GC2518 • Efficiency: 25% of NaI(Tl)) • Efficiency is about 2% for 1077keV of 68Ge (for the minimal distance between a sample and the detector)

  14. Being discussed: • what do we finally learn, i.e. is accuracy high enough? • time scale of the experiment, manpower needed • which priority with respect to other activities? • budget (estimated 50-100 k$, depending on strategy), who is to provide the required funding? • Issue for discussion in the collaboration board

  15. Points for Discussion (Ge-procurement) Logistics for step-I: Natural Ge: who needs samples (quality control, etc.) ? Which amount? Conclusions to be drawn from step-I: QC-results: when available? storage place for Ge-76 which samples to be taken from Ge-76 feedback from Umicore decision baseline vs. option for Ge-76; should we prepare for going immediately for even more Ge-76, i.e. definition of priority w.r.t. other proposals?

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