ecal status

Pit activities summary;

PM and R/O cells status;

LED monitoring system status;

Gain by photo-statistics;

Plans / requests;

ECAL status

22 Sept 2008

Pit activities summary

8 Sept: all patches are installed;

17 Sept: - one malfunctioning patch is replaced. Now corresponding line

does not show dependence on MV;

- another patch on one line with ratio A(MV=60) / A(MV=80) higher than one is replaced. Nothing changed;

- 12 LEDs which showed no signal according to PMs (e.g. run 33503) are checked with oscilloscope (see below);

- several data samples are collected afterwards (see slides below + appendix);

Ratio LED amp (MV = 60V) / LED amp = 80V): 2d

R=LED amp(60V) / LED amp (80V), before access

R = LED amp(60V) / LED amp (80V), after access

Bad patch Line with R > 1, patch

has been changed

PATTERN OF LINES WITH R > 1 is reproduced !

Ratio LED amp (MV = 60V) / LED amp = 80V): 1d

INNER MIDDLE OUTER

On average - R is ~1;

(pay attention, that Y-scale is logarithmic)

R.M.S. of LED signals

NO SIGN OF NOISY LINES

There are several cells with r.m.s., higher than in neighboring cells – to be checked

LED peak r.m.s., ADC counts

ECAL cells-I 5 candidates: breakdown of capacitance on C-W.

To be checked according to the consumption from MV source. All belong to A-side – could be result of last weeks exercises with ECHVA project / LEDs switched ON at cosmic gains / … / etc

+ 7 more cells with absent LED signal

- 3 cells: narrow pedestal distribution, no C-W noise ( M 11/28; M 59/31; O 39 / 11 ) – absent contact?

- 4 cells: C-W noise is OK ( O 24/44; M 12/31; I 20/45; I 45/22)

Cosmic data: got the impression that some cells, which have to be masked, are actually not! (mostly on A-side). Anatoly, could you please cross-check?

ECAL cells-II

Reference plot:

White color: cells which are currently masked in DB (HV is set to zero)

(answer to Patrick’s question)

LED system: status-I 12 LEDs checked during the last access (just start DAQ and plug the oscilloscope to the output of PIN diode): - 4 LEDs of the group A105 - all signals are OK by scope, ergo this is problem with time alignment - 4 LEDs of the group A103 - all signals are OK, ergo this is problem with time alignment - 1 LED A202.3 - bad quality of the cable, delivering LED fire signal inside LED box. Now LED is working, but connection has to be repaired if there will be an opportunity (not urgent) - 1 LED C309.1 - OK by scope - 2 LEDs C301.1 and C301.3 - broken connection between HV box and flat power distribution cable, fixed, signal from both LEDs are OK by scope In the last data: groups A105; A103 and LEDs C309.1 are still missing. Also: no readings from C3.20.3!

Suggestion is the following: take one more LED sample but only after recipes for readout part (LEDTSB, FEBs) are checked and finalized. If after that some LEDs will appear missing, we will request access and check them once again with the scope.

LED system: status-II

Response on LED, ADC counts

Current LED intensity settings for operational LEDs: more-or-less reasonable after first iteration.

Next iteration (data are collected and processed): final fine tuning.

LED system: time alignment

Prev1 T0 Next1

???

seems to be lost…

A = k * G * N(p.e.) * e / s(adc)

N(p.e.) = f *(A/σ)² (number of photoelectrons)e – electron charge; s(adc) = 0.0195 pC/ADC count;f = 1.2 (Fano factor); k = 1/3 (clipping coeff);A is LED peak position; σ is LED peak sigma;

G = 304688 * σ² / A

Limiting factors:

a) contribution from the photostatistics should dominate other possible sources. Natural strategy is to decrease the intensity of the LED light as much as possible increasing simultaneously the gain of phototubes

BUT…b) even at zero intensity settings many ECAL LEDs produce residual light. It is not seen by

pototubes at nominal gain settings, while, for example, at cosmic gains response on LEDs for many phototubes is high enough to saturate ADC

Calibration of the gain by photostatistics

Several samples at different settings: Gain 100K, 150K, 200K LED intensities: 0.1V; 0.2V; 0.3V

Cells, accepted for analysis: > 90% of signal in one BX; signal is not saturated;

After gain change: ~10 minutes of “warming-up” under LED illumination (56 Hz);

Only last 5000 events out of 20K collected are used in the analysis;

Calibration of the gain by photo-statistics (cont)


INNER MIDDLE OUTER

Expected gain is 100K !


Expected gain

Section LV=0.1V LV=0.2V LV=0.3V

100K Inner 144K 144K 143K

Middle 139K 139K 141K

Outer 139K 139K 140K

150K Inner 198K 199K 197K



200K Inner 248K 252K 246K



Still: about 30% - 40 % difference ( ~5-6% in terms of PM HV)

1) PIN distribution – seems to be narrow (though signal values are very small, can be not signals but cross-talk…)

2) Absolute gain value is somewhat undefined due to dependence of C-W output on LV, but:

- when we measured directly output HV on one C-W base in the wall with / without patch installed, the measured value in the presence of patch was exactly equal to the expected one

May be, lab studies on the future test-bench will clarify the situation

Calibration of the gain by photo-statistics: some remarks

Request: restore LED /PIN system timing ASAP

ECAL detector activity: Check 5 cells with capacitance breakdown

+ Long term LED stability run;

--------------------------------------------------

Major work is now in the lab (C-W modification related activity);

Requests / plans

Reference:#33907: nominal HV, nominal LED LV, 20K of events; 56Hz LED trigger rate#33912…33925 LED intensities scan; nominal HV, 20K of events; 56Hz LED

trigger rate

Data for different gain settings:#33931 Gain 100K; LED LV = 0.1V; 20K; 56Hz#33936 Gain 100K; LED LV = 0.2V; 20K; 56Hz#33937 Gain 100K; LED LV = 0.3V; 20K; 56Hz#33939 Gain 150K; LED LV = 0.1V; 20K; 56Hz#33940 Gain 150K; LED LV = 0.2V; 20K; 56Hz#33942 Gain 150K; LED LV = 0.3V; 20K; 56Hz#33946 Gain 200K; LED LV = 0.1V; 20K; 56Hz#33947 Gain 200K; LED LV = 0.2V; 20K; 56Hz#33948 Gain 200K; LED LV = 0.3V; 20K; 56Hz

Time scan:#33950: nominal HV, nominal LED LV; 56 Hz; 26 steps / 800 evt per step

Appendix: data samples

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