Scintillator testing in Prague (update from Aussois) Testing station upgrade – vacuum, deltaE, electronics, magnetic properties Scintillator testing results 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Observed spectra puzzle Reminder from Aussois Distorted 207Bi spectrum is observed while electron beam spectra look normal. 207Bi Pedestal = 20-30% of entries Electron beam 1 MeV Pedestal = 2% of entries Careful check of trigger system Delta-E design improved Ruben visited Prague with alternative data acquisition No malfunction found Possible explanation Electrons interacting in the 207Bi source or somewhere else contribute to the spectrum background and to a pedestal. Conclusion: It is understandable physics effect. We can live with it. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Station upgrade – update from Aussois Vacuum Better and shorter hoses used (instead of previous “garden” type). Vacuum improved from 7 Pa to 1 Pa. Today, it degrades to 4 Pa - maintenance needed. No effect of vacuum improvement on spectra is observed -> the vacuum is sufficient Delta-E New Delta-E detector made without use of light-guide. The scintillator foil is fixed directly to PMTs with elastic glue RTV615. More light is collected (3x) – more reliable trigger signal. Absence of the light-guide prevents undesirable electron scatterings. PMTs support is black painted to minimize possible light reflections. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Station upgrade – update from Aussois Magnetic shielding The magnetic electron source is covered into a m-metal box (thickness 1mm) to avoid magnetic field impact on PMTs performance. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Station upgrade – update from Aussois Electronics Current source for the magnet equipped with a polarity switch to allow the magnet de-gaussing. New PMT HV modules installed with PC control. VME crate supply repaired. Signal attenuators purchased for work with higher PMT HV. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Hysteresis measurement de-gaussing using max. 3 A. virgin_1: 0 -> +4A series_1: +4A -> -4A, -4A -> +4A series_2: +4A -> -4A, -4A -> +4A De-gaussing using max. 3 A. virgin_2: 0 -> +4A Conclusion: de-gaussing using max. 3A is sufficient. We decided to use max. 4A to be safe in future. De-gaussing procedure 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Magnetic shielding efficiency “Spectrometer” is installed inside of mu-metallic box. Magnetic field sensor placed instead of PMT at a point between photo-cathode and first dynode, oriented parallel to B-lines. Conclusions: Measurements without shielding cylinder (blue lines) –> B generated by the spectrometer is of the order as natural B. Measurements with mu-metallic cylinder (green lines) -> remaining spectrometer mag. field as well as natural mag. field is eliminated. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Testing chronology HV modules change Ch#1 broken VME crate change Station Upgrade Attenuators installed 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Scintillators production quality 2014 The blocks produced in 2014 have better light yield and energy resolution then the ones from 2011. 2014 production is visually much better - no black specs or other visible pollution, no yellowing in contrast to the 2011 production. Remaining 8 X-wall blocks will be delivered from ENVINET this week, tested at Prague lab and send to UCL the next week. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Summary Extensive upgrade of the station done. De-gaussing procedure elaborated. Magnetic shielding improved and tested. New optimization of the apparatus settings and calibration done. Charactrization of X-wall blocks done, remaining 8 blocks next week. Measurement of reference block(s) in other laboratory(s) is desired. (Bordeaux, UCL) 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Backup 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Stability of Testing HV modules change Ch#1 broken VME crate change Station Upgrade Attenuators installed 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Vacuum system upgrade Vacuum probe installed. Spectrometer sealed – vacuum improved from 300 Pa to 7 Pa. We have to change a hoose for further improvement. Efect of sealing on spectra is significant. 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

V. Vorobel, SuperNEMO meeting, Caen Testing station setup 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen

Typical signal conditions DE left scint. block DE right Counts per 10 s deltaE left deltaE right Scint block coincidence 1439 2096 - 324 1401 405 311 2085 416 335 14.10.2014 V. Vorobel, SuperNEMO meeting, Caen