Yu. Guz

HCAL status and plans

12013-02-20

Yu. Guz

Finally, no dead cells in the 2012-2013 run

However: • There are unstable PMTs (mainly rate effect)• Dark current in many PMTs (increasing with time) total of ~250 PMTs do not work well, to be improved during LS1.

• A 137Cs calibration performed 2012-12-17

• light yield degradation in front tile rows of central cells is up to 25%• another 137Cs run is scheduled for today (2013-02-20)

HCAL status

22013-02-20

HCAL 137Cs scan 17-Dec-2012

Done 17-Dec. One single source passage. Also: water samples sent to RP.

3Yu. Guz2012-07-25

gain and HV change wrt previous (LED correction of 04-Dec)

significant negative HV change required! PMT annealing during MD? Otherwise may indicate a problem with the system, to be studied (e.g. calibration of integrators; last calibration of integrators was Dec 2011, found no change wrt Sep2009 within 1% in all cells).

Yu. Guz

HCAL radiation ageing in 2011 and 2012

2011

2012 TS1 TS2 29/08 TS3 TS4

42012-10-10

Yu. Guz

HCAL radiation ageing 2011-03-29 –> 2012-12-17

52012-10-10

~25% degradation in rows 0, 1 of central cells. Not symmetric, more at side C.

Yu. Guz

HCAL rate effect Nov 2012

62013-02-20

244 PMTs have rate effect >5%

The rate effect is quite significant.

Normally, stable PMTs do not become unstable during operation (next slide).

The proposal for LS1 is to equip the HCAL centre with stable PMTs and move the unstable ones to periphery (at least).

Yu. Guz

No new unstable PMTs since 2011. Hopefully it will be possible to mitigate the problem of L0 rate variations by rearranging the PMT positions during LS1.

HCAL rate effect Nov 2012 vs Sep 2011

7

replaced in 2012

no new unstable ones

2013-02-20

... in particular, the PMTs replaced during the 2011/12 shutdown remained stable in 2012 (2.2 fb-1).

Yu. Guz

HCAL dark current, 2013

82013-02-20

77 PMTs draw >50 nA, 67 of them have rate effect >5% (not all!).

No dark current developed in the PMTs which were replaced during shutdown 2011/2012 – a good news

I>100 nA: 42 PMTsI>50 nA: 77 PMTsI>10 nA: 147 PMTs

Yu. Guz

HCAL LEDs in 2013

92013-02-20

Much less rate effect in pA runs, as expected (however still noticeable in few PMTs).

Yu. Guz

• 137Cs sources (dates are tentative):• 2013-02-28

• removal and annual inspection of sources (RP procedure). • removal (replacement?) of water from the systems, for the reason of last

tests of water samples• installation of spare garages with dummy capsules, for system tests

• 2013-03-04 – one of the sources will be used for the scan of the irradiated ECAL modules, then the sources will be transported to the RP storage

• September 2014 – the sources will be transported back to LHCb and installed into the system

• during LS1, the bad PMTs (~250, dark current + rate effect) should be partially replaced, the rest moved to periphery (there are ~ 50 spares).

• can we borrow from ECAL spares? • buy from HAMAMATSU?

HCAL: plans for LS1

102013-02-20