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

This summary outlines the critical issues and timeline for the procurement of Ge-76 for the GERDA Phase-II project, including the yield of chemical purification and logistics. It also discusses the verification of excitation functions and the production of crystals from enriched materials. The decision between baseline quality and additional purification is yet to be made.

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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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