Study on 9x9 standard single cell prototypes in Ferrara G. Cibinetto – INFN Ferrara BaBar Coll. Meet. – Elba May 22, 2003 Outline HV training Plateau curves measurements

May 3, 6 prototype arrived from Pol. Hi. Tech. already conditioned. All of them with good plateau under binary gas mixture, measured @ PHT. 2 days under high gas flow (~12 volumes/day) – then ~2 volumes/day. Additional HV training: ~24 hours to reach 4500V ~48 hours to go up to 4900V 3 more days with HV applied (4900V) ~48 hours to go up to 5100V (only profile 4 failed) Plateau measurements.

Each tube is trained individually. Limit on drawn current 1uA. HV training Each tube is trained individually. Limit on drawn current 1uA. During the first 3 days of conditioning the Voltage variations are very smooth. After 5 days we can turn on a tube from 0 to 4900V in about one minute without causing any trip. 4000V   4500V 4000V   4500 - 4900V   4900V   5100V   4900V

Plateau curves of the 9x9mm single layer Prototypes Gold coated wire Profiles with golden wires have ~400V wide plateax. Silver-wire chambers have shorter plateau. Silver coated wire Gas mixture: CO2/C4H10/Ar(88/8.5/2.5) Vthreshold = 35mV dead = 400ns

Some comments The HV training seems to be good, all the profiles (except one) are stable in the plateau region. No plateau curves for silver-wire tubes. Similar results in Princeton and Ohio. The plateau curves for golden-wire prototypes look larger than the ones measured in Princeton and Ohio. What is different? electronics? conditioning? transportation? The signal amplitude looks higher with the Ferrara setup, this might suggest differences with gas mixture.

Short term plans Measure plateau with lower thresholds (5 - 10 mV) Measure plateau with slightly different gas mixture (varying Ar from 2% to 4%) ADC spectra and efficiency plateau curves Study with the final strips prototypes and readout electronics (with Angelo) Crush test Other R&D issues Influence of the gas flow on resistivity Test with humid gas mixture