Calliope ENEA Casaccia MON = monitor MWPC (CH1) T1 = test MWPC (CH3) T2 = test MWPC (BTF,CERN1,CERN2) T = temperature sensor P = atmospheric pressure sensor gas mixture: Ar / CO2 /CF4 = 40 / 40 / 20 gas flow ~ 6 l/hr = 100 cc/min (1 volume in 20 min) Source Co60 (~25,000 curie) MON T2 GEM PC Co60 BOTTLES HV CONTROL ROOM 4.5 m P T window T1 GAS RACK

CERN chambers CERN1: in Closed loop Active area ~ 875 cm 2 (B 1.5 mm pitch, others 2 mm) B=reference (every day ON 2-3 hrs) Total Wire length ~ 4300 cm I ~ 990  A/gap HV(A, C, D) ~ 2.65 kV HV(B) ~ 3 kV CERN2: in Open Mode Active area ~ 480 cm 2 (all gaps 1.5 mm pitch) C=reference (every day ON 2-3 hrs) Total Wire length ~ 3200 cm I ~ 670  A/gap HV(A) ~ 3.14 kV HV(B) ~ kV HV(C) ~ kV HV(D) ~ kV Gaps C,D are asymmetric (wire is at 3.65 and 1.35 mm from cathode)

MWPC-LNF chambers CH1 = MONITOR CHAMBER (1.5 mm pitch) active area 500 cm 2 Total Wire length ~ 3330 cm I ~ 20  A/gap Gaps A,B in OPEN Mode; Gaps C,D in Closed Loop. CH3 = TEST CHAMBER 1 (1.5 mm pitch) active area 500 cm 2 HV=3.2 kV (reference A ON for ~5 hrs every 2-3 days) Total Wire length ~ 3330 cm I ~ 160  A/gap Gaps A, B, C, D in Closed Loop. BTF = TEST CHAMBER 2 (2 mm pitch) active area 1200 cm 2 HV=2.75 kV (reference D ON for ~5 hrs every 2-3 days) Total Wire length ~ 6030 cm I ~  A/gap Gaps A, B, C, D in OPEN Mode.

Layout of chamber positions and gas MWPC-CH3MWPC-BTF GEM-LNF-TEST1 GEM-LNF-TEST2 GEM-CA-TEST1 GEM-LNF-MONIT MWPC-CH1 P1P Gy/hr P Gy/hr P Gy/hr GEM-CA-TEST2 MWPC-CERN1 MWPC-CERN2 3 m rack Closed loopOpen modeGEM (open mode) AB CD position

Atmospheric pressure vs. Time

Temperature of source room vs. Time

Gas system One bottle for each gas (Ar, CO2,CF4) Gas from bottle to Mass flowmeter (connected to MKS) Total gas flow: 40/40/20 cc/min = 6 l/hr to mixer (little cylinder) Typical flows: Open Mode ~ 5-6 l/hr Closed loop: fresh gas ~ 1.35 l/hr circulating gas ~ 6.5 l/hr Fresh gas should be 10% of circulating gas, but below the 20% (i.e l/hr) the system is unstable. First purifier used from 16/6 to 3/7 (~ 17 days). May be too long ? Third purifier (asked 24 th june) arrived only on July 9 th !!!!!! Content of O2 was measured and did not change, but water content is unknown. The oil in the Open Mode bubbler is dark brown, while it’s clean for the Closed loop (this is not sufficient to state that purifier is working properly).

Saturation of gas gain HV% Sat.HV% Sat.HV% Sat. A B C D CH3CH3 w/o Resis.BTF Saturation < 10 %

Currents in BTF gaps (open mode)

Currents in BTF reference gap D

Ratio of currents BTF(A,B,C)/D

Currents in CH1 gaps A,B (open mode)

Ratios of currents BTF(A,B,C)/CH1(A+B)

Currents in CH3 gaps (closed loop)

Currents in CH3 reference gap A

Currents in CH1 gaps C,D (closed loop)

Ratios of currents CH3(B,C,D)/CH1(C)

Ratios of currents CH3(B,C,D)/CH3(A)

Integrated charges Same as above, but for 2 mm pitch.

Dark currents (first measurement: 16-jun) ONOFFONOFFONOFF A B C D CH1CH3BTF CH1 (C,D) 3.15  3.05 kV CH3 (B) 3.2  3.15 kV The power supply does not allow to measure currents < 1 uA

Dark currents (second measurement: 26-jun) SY2527N471A (nA) SY2527N471A (nA) SY2527N471A (nA) B kV CH1CH3BTF To read currents with N471A we need to switch OFF/ON all gaps CH1 (D) draws current also after switch off All BTF’s decreasing (for ex. BTF(D) 90  28 nA in ~ 1 hr)

Integrated charge in CH3

Integrated charge in BTF

Currents in CERN1 (closed loop)

Currents in CERN 2 (open mode)

CERN 1 ratios

CERN 2 ratios

I_ref (closed) / I_ref(open)

Integrated charges in CERN 1

Integrated charges in CERN 2

Conclusions MWPC-LNF Integrated charges: BTF (2 mm) mC/cm (> M1R3) CH3 (1.5 mm) mC/cm (>M2R3) No aging in Open Mode chamber (within ~5%) Analysis of Closed loop chamber requires more work MWPC-CERN Integrated charges: CERN 1 (2 mm) ~340 mC/cm (> M1R3) CERN 2 (1.5 mm) mC/cm (>>M2R3) No aging in both chambers (within ~8%) Several problems with gas mixture: low CO2 content for ~ 10 days ?) Lower currents in all chambers after change of CO2 bottle Undefined purity of mixture and H2O content  More time for an accurate data analysis, especially for closed loop

Spare transparencies follow

Source pool window irradiated panels

TEST CHAMBER 2

MONITOR CHAMBER MON TEST GEM PC Co60 BOTTLES HV CONTROL ROOM 4.5 m

MWPC prototypes Test chamber 1 and monitor chamber : chambers are 4-gaps with active area ~ 251 x 208 mm 2 wire pitch 1.5 mm (8 pads x 17 wires) Operating voltage = 3200 V Typical currents: test ~ 160  A/gap monitor ~ 20  A/gap

Dose rates (still to be measured) CH1 dose rate < Gray/hr CH3 dose rate ~ 0.1 – 0.2 Gray/hr (~0.3  A/cm 2 ) BTF, CERN1, CERN 2 dose rate ~ 0.3 – 0.6 Gray/hr (~1  A/cm 2 )