active dividers
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Active DividersTilecal upgrade meeting at Stockholm (3-5 June 2013)
François Vazeilleon behalf of Roméo Bonnefoy, Michel Crouau (Now retired)
Dominique Pallin, Christian Fayard, Marie-Lise Mercier, Eric Sahuc.
Summary of previous progresses· Main results given in the Tilecal Note (Note not yet approved)· Missing electronics studies to do· Radiation hardness and next tests· First production for ITC scintillators· Conclusion
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Summary of previous progresses
Passive Dividers
Active Dividers
· Goal: To keep the Tilecal performances (Linearity, energy resolution) for the measurement of very high energies at the highest luminosities.
· Proposed solution: Replacement of present “Passive Dividers” by “Active Dividers” keeping stable the voltage repartition in between every stage Use of active components (Transistors and diodes) in the last 3 stages, in order to balance the current stream induced by Minimum Bias events.
· Preliminary results previously shown [Tilecal meeting, 17 June 2011].
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Main results given in the Tilecal Note(The Note ATL-COM-TILECAL-2013-014 is not yet approved)
¨ Pure electronics tests using the upgraded Divider Test Bench Interdynode voltage comparisons without/with injected currents of 10 Passive and 20 Active Dividers. Protocol for the certifications of productions.
Two series of tests
¨ Full tests of Dividers associated to PMTs Comparisons for a given AC light (Signal) of 20 sets ″PMT-Passive Divider-Active Divider″ in function of the injected DC light (Minimum Bias).
No other BE electronicsthan a scope
Test Bench of batch of 10 DividersPassive Active
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Summary of specifications
ATLAS sATLAS
Tilecal ITC Tilecal ITC
Maximumanode current(µA)
2 8 10 40
Maximum non-linearity
1% 1%
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Summary of results for currents up 120 µA
Examples of comparison
PMT-Passive Dividerfor 2 current ranges
- NL can reach 40%.- NL < 1% at 2 µA
PMT#AB2484, Divider#108508
PMT-Active Dividerfor 2 current ranges
- Only 5 sets show a small NL tendency.- 15 other sets have a NL 0%.
PMT#9F23Q1Divider#2
PMT#AA0061Divider#1 5
General results from the 20 sets
Passive Dividers : Results and comparison s of the means to simulations
Active Dividers Max anode
current
5 bases 15 bases
50 µA NL < 0.5% NL 0%
100-120 µA NL < 1% NL 0%- The behavior differences are likely due to the PMT behaviors.- The Active Dividers fit all ATLAS (Crack 8µA) and sATLAS (Tilecal 10 µA and Crack 40 µA) specifications, with an improved PMT working and a large safety everywhere.- Simulations at 20 µA: NL < 0.2% and measures: <NL> < 0.2%.
- Passive Dividers fit the ATLAS conditions: NL < 1% as requested.- Very good agreement with simulations.
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Gain dispersion
Comparison of absolute gains without DC currents
Active Dividers give a gain 22% higher than Passive Dividers. Precisely: (21.9 1.8) %
20 Active Dividers coupled to the same PMTat the same HV Gain dispersion < 0.7%: a very good working homogeneity.
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Missing electronics studies to doand completion of the Divider Note
As proposed by comments on the Divider Note: Noise studies Comparisons of Passive and Active Dividers on the PMT working After this Stockholm meeting.
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Radiation hardness and next tests
Full application of the ATLAS radiation policy
TID (Gammas): GrayNIEL (neutrons): 1 MeV eq.n/cm2
SEE (protons): >20 MeV h/cm2
à Requested tests of 20 Dividers following the ATLAS protocol, likely TID and NIEL only.
First indications- LHCb tests on 4 Dividers: no failure up to the maximum tested dose of 870 Gy and the whole LHCb preshower still working.- Argonne tests (See Gary’s results) on 4 Dividers: still working.
à Most pessimistic estimates (LB) while waiting for a new ATLAS policy.
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Radiation
SFsim SFldr SFlot SRL/LHC RTC/LHC SRL/sLHC
RTC/sLHC
TID 3.5 5 4 2.50 175 7.50 525NIEL 5 1 4 2.57
1011
5.14 1012
7.71 1011
1.54 1013
SEE 5 1 4 6.14 1010
1.23 1012
1.84 1011
3.69 1012
Clermont-Ferrand set-up
- 20 Dividers: whole last 3 stages + resistors simulating the other ones.- 16 Transistors alone + 8 Diodes alone (with direct/inverted polarities).- Everything supplied at the right HV and on-line monitored.
Last 3 stagesTransistors
DiodesResistors
PCB to be irradiated
Special PCB to irradiate: active components within a square 7x7 cm2.
Complete Test bench with on-line monitoringPower Supply
Mux/DAQ
USBinterface
PCB- Hardware ready.- Software almost ready + working tests to do.- Needs only the connection to a laptop under labview. 10
Experimental sites for tests ?
Interest of having a whole on-line monitoring
Testing up to the maximum doses with a permanent monitoringenables to know the Divider status at intermediate doses:- from ATLAS to SATLAS, - for Tilecal and ITC channels,- for softer new ATLAS radiation rules (Yesterday Liq Ar talk).
First considered option: X-generator at Clermont-Ferrand (250 keV max) long investigations and discussion with CERN experts (Federico Faccio and Philippe Farthouat) Big calibration difficulties in the dose estimates. Preferred option: Gamma rays smaller mis-estimates of the doses.
¨AIDA Transnational Access support for tests in 5 European sites (DESY, CERN, JSI, KIT, UCL)
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But, are there possibilities in other Tilecal Institutes ?
First production for ITC scintillators
· Batch of 350 Dividers soon delivered at CERN Clermont-Ferrand orders to selected Cies (PCB, component placements, cables) through CERN.
Certification will be made at Clermont-Ferrand.
- Set of 10 dividers takes about Half an hour for testing A quality sheet.- About 1 week for the whole production.
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Conclusion
· The Passive Dividers fit the ATLAS specifications for Tilecal PMTs, but not fully for Crack scintillators.
· The Active Dividers fit the sATLAS specifications for both Tilecal and Crack scintillators, within a wide range going well above the expected Luminosities. The linearity (and the energy resolution) will be improved /ATLAS. They could equip all the PMTs.
A very good agreement of electronic simulations and results, for both Passive and Active Dividers.
· The Divider Test bench has been upgraded and can welcome Passive/Active Dividers.
A batch of 350 Active Dividers will equip now the Crack scintillators.
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· Remaining studies to do
- Noise studies.
- Completion of the Divider Note.
- Radiation tests, despite promising results (LHCb, Tilecal Argonne) Complete radiation tests are scheduled Clermont-Ferrand radiation test bench soon operational. Ready to provide it to other Institutes for dedicated radiation tests with the on-line monitoring of the Divider working.
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