D. De Gruttola SALE-01: issues with HV supply fixed SALE-01: issues with HV supply fixed QA weekly meeting 26/04/2016

SALE-01 acquisition was stopped after replacement of freon bottle the issue was at that time ascribed to high temperature in the room after summer the problem was still there the main problem seemed to be with HV it was not possible to power on ch 2 and 3 (currents too high) a new power supply was installed (almost no difference) all the DC/DC converters were installed in another telescope and they shown to work correctly

HV issues few days ago ch 1 was ramped down  this is the current situation the main difficulty is the instability  each channel behaves in different ways at the same conditions..and it is not easy to understand what happens are the chambers problematic? They are more than 10 years old. can the problem be the DC/DC converters? status in February 2016

Acquisition with ~18 kV per chamber the rate is: some distributions in the next slides  2-5 Hz triple coincidences  ~260 Hz single (ch 2)  ~260 Hz single (ch 3)  25 kHz single (ch 1) status in February 2016

Distributions at ~4 Hz multiplicity peaked at 0 status in February 2016

SALE-01 this telescope never bubbled so well, so one possible explanation of the bad behavior was the presence of air inside the gaps the mixture flux was changed several times, but no improvement two chambers were declared bad and replacement was required before proceeding with the replacement a last attempt was done  open the chambers looking for possible damage in HV connectors  it was done last week  ch 2 was opened but no damage on HV cables was found  after closing the chamber the gas was flushed again  the situation immediately started to seem better

currents still high, but it was possible to ramp HV up acquisition was started (see next slide) Currents after chamber opening

Multiplicity ch 2 and 3 noisy (and distributions peaked at 0), but better situation wrt February February 2016 April 2016

Multiplicity ch 3 was not opened, but the gas chain was inverted (Input/Output)  the situation started to improve soon

DQM the rates were still very low, but physics quantities in DQM started to be acceptable! bad ok

Multiplicity  since few days the multiplicity is as expected

DQM all distributions are ok now usual rate

Multiplicity  some channels need to be cured (it will be done in the next days)

Conclusions the only reasonable explanation is the presence of air inside the gaps  chambers were not correctly flushed change the value of the flux does not help in this case  “shock” as inverting I/O in the chain or flushing air in the chamber seems to help SALE-01 (1 m distance between the chambers) back in acquisition SALE-02 will be soon assembled (50 cm distance between the chambers) proposal to decrease the distance between the chambers down to 50 cm in SALE-01 in order to increase the acceptance