Yu. Guz 2015/09/02 1

ECAL and HCAL technical status

Yu. Guz 2015/09/02 2

ECAL LED instability issue – I It happens that the ECAL LEDs get unstable and die.

now at unacceptably high rate – not infant mortalityin the Outer zone onlyAug 12: 8 dead LEDs replaced; Sep 01-02 – other 14 replaced to other type LEDs

The LEDs become unstable before they die.

Yu. Guz 2015/09/02 3

ECAL LED instability issue – II The reason is understood: this is an unfortunately wrong choice

of the LED model done in 2013. the chosen LED type (Multicomp Mega Bright OVL-5523) have very good light yield but low (lower than usual) reverse breakdown voltage (8-12 V) (easy to measure with a KEITHLEY source meter).the design of the LED driver is such that between pulses the reverse voltage of up to ~15 V can be applied to the LED

the lower is required flash magnitude, the higher is reverse voltage

therefore the Outer area suffers mostnow working on selecting a proper LED

CREE LC503FBL1 is a good candidate: also good brightness also cheap: ~ 0.15 euro/pc selection is necessary: only 60% have UBREAK>20V,

minimum is ~12 Vtotal number of LEDs is 456 (however we can choose to replace LEDs only in the Outer zone – 168)used 01-Sep for the replacement: the light yield is similar to the old LEDs (next slide). stability etc to be studied

LED driver (simplified)

Yu. Guz 2015/09/02 4

ECAL LED instability issue – III LED picture after the replacement 01-02 of September

similar light yield (even higher in some cases)two more dead LEDs since 02-Sep.

Yu. Guz 2015/09/02 5

HCAL technical status – I

One dead cell

Yu. Guz 2015/09/02 6

HCAL technical status – II : dark currents

>10 nA: 158 PMTs>50 nA: 57 PMTs>100 nA: 24 PMTs

The PMT degradation continues: in 2015 all the PMTs with dark current >50 nA were replaced to new ones. Order of 150 PMTs would need replacement in the winter shutdown (of course for some of them the replacement can be postponed to the 2016/2017 shutdown).

Yu. Guz 2015/09/02 7

HCAL technical status – II : dark currents

No degradation is seen in PMTs replaced in 2011 and 2014 (total of 183 PMTs were replaced).

Yu. Guz 2015/09/02 8

HCAL technical status – III: Cs calibration system

The previous calibration was performed on 17-Jun-2015 evening after the test, the side A Geiger counter was found not working

Geiger counter is the sensor used by the safety signalization, which is very important

The Geiger HV mezzanine of the Garage module had to be replaced

1-Sep-2015: the replacement was done, the signalization is operational againthe source run has been performed 02-Sep-2015

Yu. Guz 2015/09/02 9

HCAL Cs calibration 2015-09-02 – I

The calibration was performed on 02-Sep-2015 evening; the PHYSICS recipe updated 03-Sep

Yu. Guz 2015/09/02 10

HCAL Cs calibration 2015-09-02 – II

The calibration was performed on 02-Sep-2015 evening; the PHYSICS recipe updated 03-Sep

Yu. Guz 2015/09/02 11

HCAL Cs calibration 2015-09-02 – III

It seems that now ageing takes place even without high radiation doses

Yu. Guz 2015/09/02 12

HCAL Cs calibration 2015-09-02 – IV

For the completeness – same ageing plot, but as a function of time.