ZDD installation and performance

BESIII Collaboration Meeting, December 2011

A. Calcaterra, for the ZDD group (LNF+TO)

Talk outline

• ZDD performance in Frascati, Spring 2011– Cosmic rays– Single-electron beam

• ZDD installation, August 2011• ZDD tests with cosmic rays at IHEP, Fall 2011• Outlook

– Short term– Next weeks

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The ZDD in the East area

A. Calcaterra

(2m)

ZDD: Pb/Sci.Fi Array, scintillating material 60% of total (in volume), two modules (up and down the beam) dimensions:14x4x6cm3

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γ beam axis

Fiber bundles

W screen

Gearbox for minical movement

1

62

7

3

8

4

9

5

10 beam

14 cm4

cm

Each sector is sent to a PM, sectors 1&2 (6&7) are sent to the same PM (for now)

ZDD module segmentation

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One (out of two) ZDD module tested at BTF with 450, ~300, ~200 MeV e- bunches (Ne-=1,2,3)

Final Pb-scifi ZDD module, bundles guides,PM’s, TDC, at the moment not FADC but ADC caen V792N

Small scintillator (60x11x4) mm3 used to trigger and select electrons impact point

BTF test beam at LNF (may 16-22 2011)

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Setup in Cosmic rays (LNF)

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Setup in Cosmic rays

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Top “finger” scintillator, (11x5x50) mm3

Bottom “paddle” scintillator

Trigger coincidence rate = (2-3 minutes)-1

Purpose of cosmic rays DAQ

• 2 types of data taking: integrated charge (QDC CAEN V792N) and lineshape (Flash ADC CAEN V1721). Timing information is also present (TDC CAEN V1190) but not systematic.

• QDC data used for:– inter-channel calibration – resolution studies– absolute scale, comparing cosmics to single-electron

• FADC data used for MeV/mV calibration

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Run 224: QDC cts for each PM

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HV correction table for “up” calorimeter

Ch Ped(pC) Peak(pC) Delta(pC) G/Gref oldV newV0 15.962 38.968 46.011 0.978 1.434 1.4271 15.611 63.125 47.514 0.947 1.442 1.4262 13.941 63.929 49.988 0.900 1.432 1.4013 15.491 60.51 45.019 1.000 1.349 1.3494 15.059 37.434 44.75 1.006 1.399 1.4015 15.793 55.505 39.712 1.133 1.405 1.4436 14.558 58.434 43.876 1.026 1.451 1.4597 13.895 64.744 50.85 0.885 1.427 1.391

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Find passing tracks (left side)

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4Q passing tracks (“up” calorimeter)

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Absolute scale and E/E

• According to Montecarlo a passing cosmic track leaves 16 MeV of energy in the scintillator

• QDC scale (when “Happy Box” is used) is approximately 170 pC / 16 MeV = 11 pC / MeV.

• For E/E we find 20/180 = 11%, consistent with simulation (no shower fluctuations).

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Number of photoelectrons

• Assuming a PM gain ≈ 1.2·106, the number of photoelectrons per cosmic track is:

• The factor 2 in the denominator is due to the “Happy Box”

• Approximately 1/7th of these 443 p.e. develop in the first PM, 2/7th in each of the other 3 PMs

443102.1106.12

10170619

12

peN

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Photoelectrons/MeV (cosmics)

• According to Montecarlo 16 MeV are deposited in the scintillator by cosmic track, 50 MeV in all. This means:

• 28 photoelectrons/MeV in the fibers (14 cm)• 9 photoelectrons/MeV in the whole

calorimeter

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2011/11/30

ZDD as a new luminometer(luminosity monitor)

• The old luminometer on east side of BESIII was uninstalled and replaced by ZDD.• ZDD signal is fanned out as luminometer. The electronics and DAQ for luminometer are kept the same.• Tested by the noise, the new luminometer system is working properly. Its performance as a luminometer

shall be checked under colliding mode of BEPCII.

Frascati cosmic ray test shows:

The time resolution is 0.97ns, which meets the requirement of a luminometer （ <4ns） The signal width is only 5.2ns, so dead time is very little.

Slide by Xue Zhen16

Tests at the BTF

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• The BTF: few-electrons, 50Hz pulses from DANE Linac

• Minicalorimeters rotated, fibers vertical• Trigger on AND of RF signal and «finger»• Data taken mostly with QDC (FADC electronics

available only at the end of our beam time)

trigger (6.0x1.1x0.4)cm3

finger scintillator

Single-electron beam from Frascati Beam Test Facility

Purpose of single-electron DAQ

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• Study response to single electrons of different energies

• Study • resolution with single electrons• absolute scale factor, MeV/pC• photoelectron statistics

• How does these data compare to cosmic-rays ones?

QDC 8Q, 450 MeV, PM equalized

38.43/294 = 13%

36.84/296 = 12.4%

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Absolute scale

• According to Montecarlo a 450 MeV electron leaves 12%·450 = 54 MeV of energy in the scintillator

• If the absolute scale from cosmics is right, we should see 54 MeV·5.5pC/MeV=297 pC (“Happy Box” X2 preamp was not in use yet)

• ….and we do! Perfect!

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Number of photoelectrons

• Assuming a PM gain ≈ 1.2·106, the number of photoelectrons at 450 MeV is:

• According to MC (12%·450 = 54 MeV deposited in the scintillator) this means 30 photoelectrons per MeV (28 in cosmics)

• How are these divided among the strata?

1600102.1106.1

10300619

12

peN

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Run 4 at 450 MeV

22

32/300=10% 150/300=50%

86/300=30% 31/300=10%

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The ZDD installation war!

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Arrival at IHEP

The ZDD installation war!

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The ZDD installation war!

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The ZDD installation war!

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The ZDD installation war!

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Thanks Mario and Zhen for a fantastic effort!

Cosmic rays at IHEP• There is no external trigger• Auto-generated trigger: ≥2 out of 8 FlashADC

channels must have a minimum below some threshold (baseline-3cts = baseline-12mV)

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Analysis still very preliminary• Fitting the waveforms we obtain for each

channel a minimum and a time of minimum– Noise shows up mainly in 2-hits events (peak

times differ randomly)– 3-hits events are much cleaner

• …still, very difficult to define a passing track, due to the very small solid angle

• No control over the track length, many different track lengths in the samples

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Tue 2011/11/22, 6.5 hours of data

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Horizontal scale ns, 1bin=2ns.We plot t if majority=2, or the biggest time difference out of 3 (majority=3) or out of 6 (majority=4)

Next steps (very soon)

• Use BESIII signals into our own DAQ instead of auto-generated one but read data onto our separate PC.

• Implement the TDC (100 ps resolution)• Estimate data size in real running conditions

– Expected size = 1 byte per channel per BESIII trigger per window size (1 sample/2 ns)

– 200 ns window 16 bytes*100 samples

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Next steps (not much later)

• After data size is known (and accepted )…• …and we demonstrate that the data may be

useful…• …then, we will finally ask to incorporate VME

readout into BESIII general dataflow• At this point, help will be needed from expert

BESIII DAQ- and offline-reconstruction persons

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Conclusions

• The ZDD has been designed, built, and tested in record-time

• The design is sound and the performances are acceptable given the relatively little time and effort left for data taking and analysis

• The installation was hard but the final result is satisfactory

• Next stop…….physics results

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A final thought of wisdom

“One knows very well that, in reducing ideals to practice, great latitude of tolerance is needful; very great”

T. Carlyle

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Spares

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The HV correction

• Let’s choose a “target” amplification (45 pC)• In column 5 we find the factor to correct for• According to

• We compute

)/log()log()log( 00nnnn VVGG

/)/log()log()log( 00nnnn GGVV

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PM HV calibration

• Initial 8-channel equalization done on the basis of Hamamatsu individual datasheets

• For all events, find pedestals and peaks• Choose one channel as normalization• Assuming (Hamamatsu datasheets)

• Invert formula and find new Vn’s

)/log(74.4)log()log( 00nnnn VVGG

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FADC scale calibration

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Run 228, cosmics, QDC data

Ch Ped (pC) Peak (pC) Signal (pC) (pC) /E(%)

0 16.1 (27.2±0.3) 11.1 (4.2±0.3) 38%

1 15.7 (36.2±0.9) 20.5 (7.2±1.0) 35%

2 14.1 (35.9±1.0) 21.9 (6.8±0.7) 31%

3 15.6 (37.6±0.7) 22.0 (5.5±0.8) 25%

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Run 228, cosmics, FADC data

Peak in channels 1,2,3 is a factor 2 higher than in channel 0, just as expected. This is a good thing!

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Ch Peak (mV) (mV) /E (%)

0 (142±10) (63±20) 44

1 (323±23) (109±34) 38

2 (383±25) (102±40) 27

3 (316±57) (162±91) 512011/11/30 A. Calcaterra

Conversion factors at 1.4 kV

• Run 228: no “Happy Box”: 5.5 pC/MeV of scintillator-deposited energy

• QDC+FADC cosmics data: unfortunately, a small sample (1 day only)

Ch Peak (pC) Peak (mV) Factor (mV/pC) Factor (mV/MeV)

0 11.1 142 12.8 70.4

1 20.5 323 15.8 86.9

2 21.9 383 17.5 96.25

3 22.0 316 14.4 79.2

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