ECAL status

Outline:• Signal cable connectors quality check

results:– ADC side– PM side

• ECAL PM/C-W channels commissioning status

• Access activities• Further plans

Signal cables-I

• May 2006: it has been observed that the ‘coldness’ of some readout channels is explained not by PM/C-W failures but absent connections at the level of signal cables

• May-June 2006: all signal cables including connectors for both ADC and PM sides are subject to fast check procedure

Signal cables-II

First step: check output resistance value and its stability depending on time and bending of signal cables near ADC side connector

Signal cables-III

Second step (only for problematic channels): use reflections method to identify the place where connection is broken;

(1) - normal

(2) - problem on ADC side

(3) - problem on PM side

Signal cables-IV

Results:~400 channels with low-quality connection in

connector sockets on ADC side (value of output impedance varies if touch/ bend signal cable)

~170 channels with bad quality connection on PM-side

+ 72 channels with infinite resistance, corresponding to absent connection, majority - somewhere near PM

Signal cables: ADC side

More detailed studies discovered multiple breakdowns in process during mass-production;

Final decision: All problematic connectors on ADC side will be fixed during next months (Orsay manpower: 2 technicians + 1 physicist for quality control).

Signal cables: PM side

First step: During access to ECAL crio-side (22-29.06.2006) about 80 connectors on PM side are fixed. Very bad quality has been observed. The impression was: many other connectors are unsafe and can become broken at any moment.

Next step: take 96 of PM channels in Inner ECAL section, where ADC-side connectors are fixed already and subject them to simple mechanical test: for each channels manually unplug and plug back connector on PM side 10 times. Results are: among 96 channels 9 were originally bad + 24 did not survived this test

Final decision: redo all connectors on PM side (ITEP manpower : Tengiz + one invited technician)

ECAL PM/C-W channels commissioning status-I

It has been decided to postpone any important measurements (like for regulation curves or short term stability tests) until all connectors are repaired. Instead simplified procedure seems to be reasonable in order not to waste time:

check PM response to LED for each channel with oscilloscope

check all signal/control cabling in order to identify swapped connections

ECAL PM/C-W channels commissioning status-II

ECAL PM/C-W channels commissioning status-III

384 Inner + 128 Middle + 800 Outer channels are checked. Among them: 63 bad/suspicious channels are observed (clean signal connector problems are excluded from the statistics):

no/tiny LED signal: 38 HV control problems (always zero voltage

independently on the code written) : 7 inverted PM signal: 4 unstable signal: 4 the rest: abnormal form/value of LED signal

ECAL PM/C-W channels commissioning status-IV

‘Cold’/unstable signals: partially could be also due to bad connectors quality

In addition: 9 neighboring pairs of PM channels:

signal/control cables are mixed up 1 control cable is connected reverse way

Access activities-I

June-July 2006: ECAL cryo-side is accessible for maintenance:

• Main activity: around signal cables connectors• Also: check of problematic channels discovered

during PM/C-W commissioning (see LHCb week ECAL report for details). Origins for three sorts of problems are found: ‘noisy’ channels – due to bad quality grounding in signal

connectors on PM side HV control problems – reverse connection of control twisted

pair to PM Inverted PM signals: mixed up signal and grounding pins in

signal connector on PM side

Access activities-II

• All swapped cables are corrected• All connectors with mixed up signal and

grounding pins are corrected (4 + 9 accidentally found during visual inspection)

• All reverse connection of control twisted pairs to PMs are corrected

• Control cabling for PMs on cryo-side is finished (earlier 32 channels were not plugged)

Access activities-III

• 23 PMs are taken out for detailed studies in the lab ( expert – Yu. Gilitsky). Among them:

5 C-W are repaired 3 C-W are under repair 1 phototube is found to be damaged the rest was OK

• 11 phototubes have been installed back on ECAL already

Further plans:

• ADC side: in the beginning of July 27 connectors (216 channels of Inner section) had been fixed, checked and found to be fine. Further repair has started this week. Estimated time schedule: 1-2 months

• PM side: repair is started this week. Estimated time schedule: ??? depending on accessibility of the detector. Long term access is highly required for this sort of activity;

• In parallel: – continue PM/C-W commissioning according to the simplified

procedure. Resume profound tests and measurements as signal cables are repaired

– start HV/LV/LED fire/PIN diodes output cables routing – complete protection of monitoring system fiber bundles– September: install 2 missing LED boxes on the top of ECAL