Long irradiation at the side 22 hrs Gas flow Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source at 71.6 cm (~100nA) Flow direction reversed Gas passes volume @ middle print Conclusions: We can damage the side Due to gas flow direction? Just due to longer duration? … Linear? Almost -20% in 46 hrs, -60% in 136 hrs 22+24 hrs 22+24+23 hrs 22+24+23+67 hrs 9 May 2006

Damage vs time – F-module 3 Conditions: 20 l/hr Plot relative current vs netto irradiation time Corrected for atmospheric pressure ΔI/I=-7.5Δp/p Conclusions: Gain drops linear with irradiation time Gain drop vs irradiation time shown for 6 points Relative gain Irradiation time (hrs) 9 May 2006

Irradiation with reverse bias at -1350 V Irradiated area Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source at 30 cm height Uniform irradiation (~50nA) 60 hours Position 1 265cm L-wire 64 U L After 60 hrs of irradiation Zoom of spot with recovery: Before irradiation with rev bias Ratio 9 May 2006

Irradiation with reverse bias at -1350 V Gas flow 22 hrs Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source at 30 cm height Uniform irradiation (~50nA) Conclusions: No gain loss Gain recovery at the spot that was irradiated most heavily 22+17 hrs 22+17+21 hrs 9 May 2006

Irradiation with normal bias (after 60 hours of irradiation with reverse bias) Test to prevent ageing Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source on module surface Conclusions: Ageing as usual. Irradiation with reverse bias does not prevent ageing Gas flow 21 hrs 21+22 hrs 9 May 2006

Heidelberg ageing test module A typical scan ~80 cm x 16 straws ~8cm Gas Connector 2mCu 90Sr 9 May 2006

Heidelberg test module Gas flow 17 hrs Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source at 14 cm from upper module edge Conclusions: Ageing goes slow for small test module 17+22 hrs 17+22+24 hrs Current profile 180nA 17+22+24+26 hrs 9 May 2006

Heidelberg test module - longer Gas flow 17 hrs Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source at 14 cm from upper module edge 300hrs@180 nA =0.2 C/cm Conclusions: Ageing goes slow for small test module 89 hrs 182 hrs 293 hrs 9 May 2006

Compare HD test module to F-module Conditions: Flow: Ar/CO2 20 l/hr VF/VHD = 45 Linear gas velocity in straw F-mod: 9 cm/min HD-mod: 72 cm/min Gas flow 15 hrs So, some ratios…: Irradiation time: x20 Linear flow: x8 Damage: x1/3 F-module 293 hrs HD-module 9 May 2006

Damage vs time – HD module Conditions: 20 l/hr Plot relative current vs netto irradiation time Corrected for atmospheric pressure ΔI/I=-7.5Δp/p Conclusions: Gain drops linear with irradiation time Gain drop vs irradiation time shown for 6 points: Relative gain Irradiation time (hrs) 9 May 2006

Module 3 is repaired – Open in the air for 14 days Did damage partially recover? For 14 days: No HV No Ar/CO2 No irradiation Just air Oxygen? H20? 9 May 2006

Module 3 was repaired – Open in the air for 14 days Re-scan module 3 side B Did damage partially recover? For 14 days: No HV No Ar/CO2 No irradiation Just air Oxygen? H20? Ratio Wire locator 9 May 2006

Module 3B – ‘Default’ Irradiation (Confirm previous irradiation results) “Normal” irradiation: HV=1600 V 20 l/hr Ar/CO2 70/30 H20 < 100 ppm 15 hrs, 90Sr, ~150 nA Source at 127cm After irradiation Current profile 140nA Before irradiation Ratio: Irr/Non-irr: Extra damage at old spots? The spots that recovered with air, degraded again? Ratio Zoom Source at 190cm 9 May 2006

Module 3 – side A Test straw length dependence Gas flow 1: 19hr Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source ~23 hours of irradiation Test 2: problem with CO2: 21 hours normal operation 15 min no CO2 with large current 2: 21hr Initially low current at repaired spot… H20? 3: 23hr Conclusions: Damage looks very similar along the straw: no straw dependence 4: 23hr 5: 23hr 9 May 2006

Module 3 – side A Test straw length dependence 3: 23hr 5: 23hr 1: 19hr 4: 23hr 1: 21hr Conclusions: Damage looks very similar along the straw: no straw dependence 9 May 2006

Module 3 – side A Test straw length dependence Distance from gas input Gain loss (scaled to 23hr) Position Irradiation time Humidity 2 20 cm 20% 22% 232 cm 21 hr 180-120 ppm 4 70 cm 16% 182 cm 23 hr 30-10 ppm 1 125 cm 35% 42% 127 cm 19 hr 150-180 ppm 5 180 cm 15% 72 cm 12-8 ppm 3 230 cm 18% 22 cm 90-30 ppm Is test 1 a hint that the outgassing of the (wet) glue increases the damage? 1: 19hr 2: 21hr 3: 23hr 4: 23hr 5: 23hr wire locator Before After 9 May 2006

Correlation gain loss & humidity - Speculation - 9 May 2006

Long term 1450V Conclusions: Conditions: Flow: Ar/CO2 20 l/hr Gas flow 18 hrs, 1450V Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source Ar/CO2 70/30 Conclusions: Running at lower HV does not save us… 18+52 hrs, 1450V Current profile during irradiation: 18+52+19 hrs, 1450V 9 May 2006

Vary HV: 1450, 1600, 1800V Current profile similar: Conditions: 21 hrs, 1450V Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source Ar/CO2 70/30 At 1800 V, source further from surface same current profile Conclusions: No HV dependence 21 hrs, 1600V (test4) 21 hrs, 1800V Current profile similar: 9 May 2006

Vary CO2: 80/20, 70/30, 60/40 Current profile similar: Conditions: 21 hrs, 80/20 Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source 1600V At 80/20 V, source further from surface similar current profile NB: 60/40 higher current, shorter irradiation… Conclusions: More argon, more damage? 21 hrs, 70/30 (test2) 16 hrs, 60/40 Current profile similar: 9 May 2006

Vary Intensity Current profile differs: Conditions: NB: different scale 19 hrs, low int Conditions: Flow: Ar/CO2 20 l/hr 2mCu, 90Sr source 1600V, 70/30 Conclusions: 3 times the intensity, same damage? 22 hrs, default (test16) 19 hrs, high int Current profile differs: 9 May 2006

Vary Source: 90Sr versus 55Fe 22 hrs, 90Sr (test16) Conditions: Flow: Ar/CO2 20 l/hr 1600V, 70/30 90Sr versus 55Fe Conclusions: 90Sr irradiation: x2 current x3/4 irradiation time Expect: 1.5x damage Observe: 1.5x damage 90Sr ages equally fast as 55Fe? 30 hrs, 55Fe Current profile differs: x2: 9 May 2006