Radon monitoring system in the Kamioka mine Guillaume Pronost on behalf of the Super-Kamiokande collaboration Kamioka Observatory, ICRR, The University of Tokyo JPS Miyazaki conference, September 21th 2016 (Supported by KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas 26104008)
Why measuring Radon? Radon is a radioactive gas which tend to accumulate indoors (and so underground). Radioactivity from Radon can lead to health issue in case of high exposure. Radioactivity from Radon is a background for high precisions experiments looking for low energy physics like the ones present in the Kamioka mine: Super-K, XMASS, CANDLES, KamLAND, etc. Monitoring the Radon concentration allows to protect the health of the researchers and technicians working in the mine and to control the background coming from Radon. JPS Miyazaki conference, September 21th 2016 2/14 pronost@km.icrr.u-tokyo.ac.jp
Radon detector Radon detector design: 10cm 1L detector 17cm USB Humidity sensor (new) RaspberryPi ADC Electronics case: 120 V H.V., ±12V input signal, RaspberryPi ADC I Data taking and upload performed by the RaspberryPi (RP) I Data analysis performed automatically on the Radon data server JPS Miyazaki conference, September 21th 2016 3/14 pronost@km.icrr.u-tokyo.ac.jp
Radon detection concept: electrostatic collection method 120 V amp. 218 Po + N P α 21X Po + RaA (α 1 ) 218 Po RaC (α 2 ) 214 Po 222 Rn RaF (α 3 ) 210 Po GND Air Filter SUS mesh Air Collection of positive ions from 222 Rn decay chain on the PIN photo-diode: 222 Rn α 218 Po + α 1 214 Pb + β 214 Bi + β 214 Po + 214 Po + α 2 210 Pb + β 210 Bi + β 210 Po + α 3 206 Pb + Concentration = RaC counts Calibration Factor(Humidity, time data taking ) JPS Miyazaki conference, September 21th 2016 4/14 pronost@km.icrr.u-tokyo.ac.jp
Data analysis: new software New analysis software developed in the past months, based on ROOT/CERN Automatically computing the radon concentration from the detector data Calibration factor determined using the current Humidity (from sensors) Radon count to Radon concentration factor Factor (Bq/m^3)/(RaC'/10min) 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 80 90 100 Relative Humidity (%) JPS Miyazaki conference, September 21th 2016 5/14 pronost@km.icrr.u-tokyo.ac.jp
Monitoring in the Mine 22 detectors in the mine for Rn monitoring (18 with RaspberryPi system) 11 dedicated to Super-K areas KamLAND CANDLES XMASS SK Atotsu tunnel ( 2 km) Rn Hut EGADS JPS Miyazaki conference, September 21th 2016 6/14 pronost@km.icrr.u-tokyo.ac.jp
Monitoring in the Mine 22 detectors in the mine for Rn monitoring (18 with RaspberryPi system) 11 dedicated to Super-K areas KamLAND CANDLES XMASS SK Atotsu tunnel ( 2 km) Rn Hut EGADS JPS Miyazaki conference, September 21th 2016 6/14 pronost@km.icrr.u-tokyo.ac.jp
Radon monitoring in the SK area: SK Dome SK Dome Right SK Dome Center SK Dome Left 1day-averaged radon concentration Radon concentration appears to be below 148 Bq/m 3 in SK Dome 148 Bq/m 3 correspond to 4 pci/l: US limit for indoor Rn concentration JPS Miyazaki conference, September 21th 2016 7/14 pronost@km.icrr.u-tokyo.ac.jp
Monitoring of the fresh air Fresh air is brought from outside by a air pipe in the mine, extracted at 100 m 3 /min We monitor the output of this air pipe in the SK dome Rn concentration from Duct Air detector fluctuates > 148 Bq/m 3 mostly around midnight Leak in the air pipe? JPS Miyazaki conference, September 21th 2016 8/14 pronost@km.icrr.u-tokyo.ac.jp
Fresh air issue: investigations New detector installed at the input of the air pipe (in the Rn Hut) Concentration in Fresh air input (Bq/m3) 200 150 100 10 1 50 1 10 0 0 50 100 150 200 Concentration in Fresh air output (Bq/m3) Visible correlations between the input and the output of the fresh air pipe We can conclude that we have no leak in the pipe Additionnal investigations needed to understand the fluctuations JPS Miyazaki conference, September 21th 2016 9/14 pronost@km.icrr.u-tokyo.ac.jp
Radon monitoring in the SK area: Entrance Room and Front of Shift room Door was let opened 20 minutes Golden week WE Official visits WE WE WE WE WE Front of SK Shift Room SK Entrance Room 1h-averaged radon concentration In front of SK Shift room c Rn < 148 Bq/m 3 In Entrance room: fluctuations between safe values and very high values Each time the Entrance door is opened, dirty air comes inside We need to minimize the time when this door is opened JPS Miyazaki conference, September 21th 2016 10/14 pronost@km.icrr.u-tokyo.ac.jp
Radon monitoring in the SK area: Atotsu tunnel Atotsu Tunnel 1h-averaged radon concentration We are monitoring the Radon concentration in the tunnel Rather high Radon concentration since the detector is running (beginning of April) However, some huge decreases of the concentration happened some times (mostly during night) JPS Miyazaki conference, September 21th 2016 11/14 pronost@km.icrr.u-tokyo.ac.jp
Radon monitoring in the SK area: Atotsu tunnel Radon concentration Temperature in Kamioka-cho Correlation between Radon concentration and outside Temperature Our hypothesis: Cold outside temperature low outside pressure Mine air going out from the vertical pit of Kamioka mine Wind in Atotsu tunnel coming from outside Need to use the data of the wind in Atotsu tunnel to verify Temperatures from Japan Meteorological Agency website JPS Miyazaki conference, September 21th 2016 12/14 pronost@km.icrr.u-tokyo.ac.jp
Radon monitoring in the SK area: Atotsu tunnel Outside Inside Inside Outside We now have the data of the wind sensor in Atotsu tunnel Unfortunately, the phenomenon did not happen again (can be expected in end of September / October when temperature will be lower) JPS Miyazaki conference, September 21th 2016 13/14 pronost@km.icrr.u-tokyo.ac.jp
New radon monitoring in the mine: Summary 22 1L Rn detectors deployed inside the mine 11 in Super-K experimental areas All the areas of the mine are monitored 75% equipped with Humidity/Temperature sensor (10 USB sensors in SK areas) New data analysis software developed, based on ROOT/CERN We demonstrated that there is no visible leak in the fresh air pipe We observed some fluctuations in the tunnel concentration which seems to be linked to the outside temperature. Future plans: Investigate the high Radon values in the input of the fresh air pipe Investigate on the fluctuations of the Rn concentration in the tunnel JPS Miyazaki conference, September 21th 2016 14/14 pronost@km.icrr.u-tokyo.ac.jp
Backup Backup JPS Miyazaki conference, September 21th 2016 14/14 pronost@km.icrr.u-tokyo.ac.jp
Fresh air issue: investigations I Analyze of the detector raw data with our new analysis software: Fresh air output Old analysis system Same day/night fluctuations, but lower concentration Issue in the way the concentration was computed with the old system However, still higher than expected JPS Miyazaki conference, September 21th 2016 14/14 pronost@km.icrr.u-tokyo.ac.jp
Fresh air issue: investigations II We proposed the following in order to investigate this issue: Settle a new radon detector in the US Radon Hut monitor the input and the output Radon concentration from air pipe Air Pipe RP RP Rn D New systems Not to scale Rn D Pump H/T H/T Super-K Dome 2 km US Rn Hut JPS Miyazaki conference, September 21th 2016 14/14 pronost@km.icrr.u-tokyo.ac.jp