Feasibility study for improving TileCal granularity

1. Feasibility study for improving TileCal granularity K. Afanaciev, A. Solin and a lot of people in TileCal LHC Days in Belarus Minsk 2017

2. TileCal structure Hadronic calorimeter, steel absorber + plastic scintillator Readout by PMTs, 2 PMTs per cell, light routed by WLS fibers. Each cell 2+1 layers, Cs source can go through each one for calibration

3. Improving granularity Now cell size is ~ 0.1, cells B and C are read out as one cell Proposal is to split A cells in 4 and split BC into B and C. Problems: fiber bundles glued, no way to separate fibers, PMTs positioning ~ 1mm uncertainty, ~2 mm airgap

4. PMTs Hamamatsu R7600, multianode PMT 64 pixels (2x2 mm) in 8x8 grid Same form-factor as PMTs used => No need to change mechanics Same level of HV needed First test was done with direct readout of the bundle. The standard drawer electronics was used to read out 46 channels out of 64.

5. Results Total of all channels corresponds to conventional PMT very well Only a small area of MAPMT used, 3 to 5 fibers in one pixel. Most of the signal in 3 pixels

6. Optical fiber lightguide Some kind of optical coupling needed to expand bundle to PMT size => <=

7. Results

8. Better optical coupling Testbench measurements show that fiber lightguide have about 50% light loss, and defocuses quickly with increase in the airgap. An alternative device was proposed, so called focon Lightloss ~10%, better focusing. We are going to order some to the TileCal requirements and do readout tests. By Lida “Optic” plant.

9. Another optic option Probably will try this too, for comparison.

10. Electronics So far only native TileCal readout (integrator part) was used for Cs tests and MAROC Chip from ALFA for testbench. Some kind of readout is needed for the Cs tests and eventually for the testbeam tests of the fast readout chain. The idea at the moment is to use off the shelf solutions or components as proof of concept (digitisers, multichannel preamps, muliplexors and FPGA control logic). If we can instrument at least a few cells in that way and show good performance in the testbeam environment, then the development of ASICs can start. The first draft of the TileCal Initial Design Report on Phase II upgrade is out, Chapter 9 is dedicated to the High granularity option.

11. Electronics Readout electronics concept from the IDR, new “prefronend” is integrated with the Phase II upgrade electronics.

12. Conclusion Proof of principle for reading out single tiles - done Proof of principle integrating MAPMT into existing mechanics - done Tests with one type of optical coupling system - done High granularity option included into IDR - done To Do Robust algorithm for tile identification and grouping Focon studies, telescope studies, optimisation studies Electronics for full readout both in integrating (Cs scans) and fast (data) modes Analog or digital summation and integration with upgrade electronics Last dynode readout as analog sum for monitoring

13. Backup THANK YOU

14. Testbench Fitting by Poisson convoluted with Gauss As per CERN-THESIS-2010-091 by Sune Jacobsen 1 pe peak ~ 24 => gain ~ 7.5X10^4 1 pe RMS ~ 15 Average phe number ~0.27 from fit and ~0.28 from pedestal to signal ratio