• No dead cells (yet)

• The integrated luminosity since the technical stop: 480.5 pb-1. Gain drift and PMT rate effect are seen in HCAL, as usual.

• Gain corrections: at ~ -2% on average LED response of the 56 very central cells. Performed 4 times.

• The L0Hadron rate variations within fill are seen. This is a consequence of HCAL PMT rate effect.

HCAL operation since the last technical stop

Yu. Guz 13/06/2012 1

The moment of change was determined from the average LED amplitude over 56 very central counters (10 ≤ ix ≤ 21, 13 ≤ iy ≤ 18) which contribute the most into the hadron trigger rate (shown by rectangle at the figure below). The threshold was arbitrarily set to 2-3% drop w.r.t. reference.

HCAL HV correctionThe reference LED amplitudes were chosen from the first high luminosity fill after the technical stop. The amplitudes used for correction, as well as the reference, were chosen taking into account the PMT rate effect: 1-2 h after the beginning of the fill, to let the PMT gain stabilize.

For the period between April and June technical stops, we use as a reference the saveset in fill 2583, CaloDAQCalib-114322-20120503T020756.root

Yu. Guz 13/06/2012 2

3

HCAL HV correction

four HV corrections since the technical stop: 14-May, 23-May, 03-Jun, 12-Jun

the procedure works correctly

Yu. Guz 13/06/2012

-2%TS

, sou

rce

calib

ratio

n

HV correctionssum/sumref, 56 central cells

reference

L0hadron / L0muon 2012

In general, L0Hadron is reasonably stable.

Yu. Guz 13/06/2012 4

L0Hadron stability (Richard)

HCAL PMT heat up effect?: 2h

however, HCAL PMT rate effect leads to instability within fill

Yu. Guz 13/06/2012 5

HCAL HV update-II : L0Had / L0Mu (Regis Lefevre)http://lblogbook.cern.ch/L0+Trigger/1411

Also seen by Regis before

The rate effect is present in the high luminosity data in many PMTs: 188 have >5%. The nastiest case is when the rate effect is slow (one of such is unfortunately in the centre, I_18_15).

HCAL rate effect 2012 (May 14-23)

fast slow

>5%: 188 PMTs>10%: 56 PMTs

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The magnitude of rate effect in the “bad” PMTs in 2012 is basically the same as (or even somewhat higher than) in 2011 (07-Sep – 05-Oct) (in spite of 2 times lower gain).

The PMTs looking improved are in fact those which were replaced during the shutdown (45 PMTs) or had contacts in signal path repaired (3 PMTs).

No new “bad” PMTs appeared. It looks like the rate effect is an intrinsic feature of a PMT: HCAL has ~200 “special” unstable ones.

HCAL rate effect 2012 (May 14-23) vs 2011

replaced in 2012

Then the L0Hadron behavior can be improved, by either rearranging of PMTs (moving the worst ones – to periphery) or replacing them by spares – a task for LS1.

Yu. Guz 13/06/2012 8

no new unstable ones

The distribution is similar to HCAL, but no tail at high values. Only 3 cells >10%, all suffer from contact instability, rate effect is moderate.

to compare: ECAL rate effect 2012 (May 14-23)

contact instability rate effect

>5%: 34 PMTs>10%: 3 PMTs

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