Study of Tube Noise in Freiburg Sven Kircher University of Freiburg Noisy Tubes in Freiburg Polarity Therapy Reasons for noisy tubes

8/30/00Sven Kircher, University of Freiburg2 Noisy Tubes in Freiburg All Tubes mentioned here where build for the ageing setup Batch 2 (MPI-EP), 16 Tubes100% noisy 0% noisyBatch 1 (MPI-EP), 6 Tubes Batch 3 (FR-EP), 33 Tubes27% noisy Definition of noisy : I dark < 10 nA/m Used for Polarity Therapy

8/30/00Sven Kircher, University of Freiburg3 Countrate and current after polarity therapy Polarity therapy : (formerly know as NHVT or Sputtern) Voltage reversal for 4 minutes in Ar-CO at 3 bar 1 μA/cm (correspondes to 3,5 - 4 kV)

8/30/00Sven Kircher, University of Freiburg4 Summary of Polarity Therapy in Ar-CO Batch 2 (MPI-EP), 16 Tubes, 100% noisy 9 Tubes OK 13 out of 16 Tubes used for Polarity Therapy 13 Tubes used in Ageing Setup 4 Tubes noisy after less than 10h 4 Tubes used for second Polarity Therapy 4 out of 13 tubes are still OK after 200h but no correlation with second PT

8/30/00Sven Kircher, University of Freiburg5 Reasons for Dark Currents less than 1/500 of total I List of Reasons (not necessarily complete) Gas Mixture Wire Wall Endplug Faraday-Cageno effect seen Wire removed Cage removed Changed to current drops 80% but still far above 10 nA/m Polarity Therapynoise partly removed Batch 1 – Batch 2 Tubes in Batch 2 not cleaned after cutting => Aluminum filings

8/30/00Sven Kircher, University of Freiburg6 Conclusions Reason for high dark currents might be dirt Polarity Therapy doesnt guaranty long term stability

8/30/00Sven Kircher, University of Freiburg7 Dunkelströme in Ar-CO 2 - Unterschiede Generelle Unterschiede 1.Erbauer (Joachim / Sven) 2.Gas (Ar-CO 2 / 4-Komponenten) 3.Drahteinziehen (schaben am Twister) 4.Endstopfen (FR / MPI) Beitrag weniger als 1/500 des Gesamtstroms 5.Elektronik / Faraday-Käfig (Zylinder / Halbschalen) Kein Einfluß meßbar (Messing abgenommen) 4-Komponeten + FR-EP 10 Röhren mit I=10 nA/m und R=6 Hz Ar-CO 2 + MPI-EP 13 Röhren mit I=10 μA/m und R=10 6 Hz

8/30/00Sven Kircher, University of Freiburg8 Dunkelströme in Ar-CO 2 - Beobachtungen Dunkelstrom hängt vom Druck ab : P von 3 bar auf 4.2 bar => I fällt um 80% ± 10% Dunkelstrom hängt vom Gas ab : von 93-7 auf => I fällt um ca. 80% ± ? Deutet aufs Innere der Röhre Deutet auf die Bauweise der Röhre hin, also nicht aufs Gas