1. Active Dividers Tilecal upgrade meeting at Stockholm (3-5 June 2013) François Vazeille on 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 1

2. 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]. 2

3. 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 electronics than a scope Test Bench of batch of 10 Dividers Passive Active 3

4.  Summary of specifications ATLASsATLAS TilecalITCTilecalITC Maximum anode current(µA) 281040 Maximum non-linearity 1%  1% 4

5.  Summary of results for currents up 120 µA  Examples of comparison PMT-Passive Divider for 2 current ranges - NL can reach 40%. - NL < 1% at 2 µA PMT#AB2484, Divider#108508 PMT-Active Divider for 2 current ranges - Only 5 sets show a small NL tendency. - 15 other sets have a NL  0%. PMT#9F23Q1 Divider#2 PMT#AA0061 Divider#1 5

6.  General results from the 20 sets  Passive Dividers : Results and comparison s of the means to simulations  Active Dividers Max anode current 5 bases15 bases 50 µANL < 0.5%NL  0% 100-120 µANL < 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%. - Passive Dividers fit the ATLAS conditions: NL < 1% as requested. - Very good agreement with simulations. 6

7.  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 PMT at the same HV  Gain dispersion < 0.7%: a very good working homogeneity. 7

8. Missing electronics studies to do and 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. 8

9. Radiation hardness and next tests  Full application of the ATLAS radiation policy TID (Gammas): Gray NIEL (neutrons): 1 MeV eq.n/cm 2 SEE (protons): >20 MeV h/cm 2  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.  Most pessimistic estimates (LB) while waiting for a new ATLAS policy. 9 RadiationSFsimSFldrSFlotSRL/LHCRTC/LHCSRL/sLHCRTC/sLHC TID3.5542.501757.50525 NIEL5142.57 10 11 5.14 10 12 7.71 10 11 1.54 10 13 SEE5146.14 10 10 1.23 10 12 1.84 10 11 3.69 10 12

10.  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 stages Transistors DiodesResistors PCB to be irradiated  Special PCB to irradiate: active components within a square 7x7 cm 2.  Complete Test bench with on-line monitoring Power Supply Mux/DAQ USB interface PCB - Hardware ready. - Software almost ready + working tests to do. - Needs only the connection to a laptop under labview. 10

11.  Experimental sites for tests ?  Interest of having a whole on-line monitoring Testing up to the maximum doses with a permanent monitoring enables 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) 11 But, are there possibilities in other Tilecal Institutes ?

12. 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. 12

13. 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. 13

14.  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. 14