P. Pakhlov (ITEP ) presented by G.Pakhlova

1. EKLM status • Reminder: EKLM general layout & past years activities • Key challenge of this year: assembly and installation • Future and current tasks: electronics, firmware, tests, software • Summary P. Pakhlov(ITEP) presented by G.Pakhlova B2GM @ KEK, 20 June, 2014

2. EKLM general layout The new system should fit the existing mechanical structure, including sector’s frame and cover sheets 14 forward + 12 backward layers 2 backward outermost layers are filled with shielding: not useful for physics, higher background from backward side 104 sectors should be installed + 6 spare = 110 sectors to be assembled

3. EKLM general layout The base element is a scintillator strip; Scintillator light is collected by WLS fiber and transported to the photodetector: SiPM • Scintillator strips are produced by “Uniplast” (Vladimir, Russia); this vendor produced scintillator for HERA-B & LHCb’s ECAL; near sub detector T2K; • WLS fiber is Kuraray WLS Y-11(200)MSJ multi-clading 1.2mm diameter; • SiPMs: Hamamatsu’s MPPC S10362-11-050C, 1.3×1.3mm2; specially designed for T2K near detector; chosen as the most radiation hard among several vendors; • Minor thing: optical gel SUREL(St.Petersburg, Russia); connectors are produced by “Uniplast” SiPM matrix

4. Scintillator modules mass production • production was carried out in ITEP for 1.5 years • August’12 – December’13 • 15 strips are glued to modules, convenient for transportation and assembly WLS fiber is processed (cut, milled, mirrored, glued to connector) and then glued with optical gel to the strips groove in total 16500 strips/ 1100 modules were produced

5. Strips quality • Average light yield from near & far ends is 2 times larger than assumed for TDR: • 50 p.e. from near end (average over ~8000 long strips) vs 24 p.e. achieved at R&D for TDR • Rejection threshold is 1.3 times larger than assumed TDR value # of strips long strips (>2m) short strips (<2m) rejection threshold Light yield in p.e. In total ~2% of produced strips were rejected. Improved light collection efficiency is a warranty of robustness of the system against radiation damage, high background rate and of better physics performance.

6. The main task • of the first half of 2014 was/is assembly and installation it is almost done!

7. Logistics • Frame & Al covers used from the old RPC system; important stage was disassembly of RPC • Cables & connectors purchased by KEK; crimped at assembly • Scintillator modules; support net & fixings shipped from ITEP • Preamplifiers purchased by VPI; pig tail soldering and tests at Wayne State U. • SiPMspurchased by KEK

8. Logistics Shipping from ITEP: no big problems except for loss of one sector (sent 110  found at KEK 109)? If fail to find, one spare sector less. • minor damages that are repaired at assembly: • several SiPM-fiber connectors become loose  glued with epoxy; • few nodes of I-beam support net get unstuck after many moves from place to place  glued with cold welding. Shipping of preamplifiers • Wayne State U. did not deliver the required soldering & test rate • solved with the kind help of KEK (Ushiroda & Sumisawa): • ½ is soldered at Wayne + ½ is soldered by a company, recruited by KEK; • test of preamplifiers during assembly by ITEP staff. • Much bigger problem was discovered recently: because of 5% dead preamps channels and/or insufficient amount of order, preamplifiers for the last 12 sectors lost. The new batch of missing preamps have been ordered by Wayne SU in May, but they will be produced and shipped to KEK only by the end of July. This delays the completion of assembly and installation by 3 months  interference with CDC group.

9. Preparing frames Deinstallation of forward/backward EKLM RPC modules was carried out in April’13/January’14 Dismounting RPC forward/backward was carried out in November’13/January’14 Processing & preparing frames to reuse done by ITEP technicians November’13– May’14 new holes were drilled, old ones sealed in 112 frames + 8 spare frames will be used to fix polyethylene (note: ×2 more effective than polystyrene) shield in 2 outermost backward layers

10. Assembly

11. Assembly Started November’13, still ongoing. • By now produced: • 90 (out of 110/109) sectors fully assembled; • + 12 sectors half-assembled (no preamplifiers) • will be finished in one week, • to be resumed for one more week in September

12. Installation • 2 sectors were installed in backward EKLM in May’13: test installation. • 56 sectors were installed in forward EKLM in April’14: the company worked very efficient • – it took only ~ 1.5 week; • and very carefully • – only one outer connector was broken, immediately repaired. • 46 backward sectors to be installed in fall campaign. Tests After installation test with oscilloscope that all channels are live and cosmics is seen at proper rate (>1 Hz at 20 p.e. threshold); No quantative tests of light yield is still possible.

13. The long-standing MC puzzle: Neutron background rate with conservativeTDR estimate and with MC simulation (still underestimates neutron background) are roughly consistent, while the MC neutron radiation doze accumulated by SiPMsis ~100 times smaller than in TDR: It was recognized recently (thanks to our COMET colleagues), that in MC simulation we have ignored the important Birks' law! We naively implied that ionization energy converts to scintillation light linearly independent of ionization source, while Birks' law predicts much smaller (factor of 5-7) light yield for neutron-induced (low energy proton) scintillation compared to MIP. Hopefully, this solves the puzzle!

14. DAQ & cosmics tests • Minimal firmware at DAQ boards is provided by Hawaii group, which allow to start the system: set HV, thresholds, read out to COPPER. • However, to take full advantage of the created KLM (both EKLM and BKLM) system (maximum efficiency, optimal background suppression, robustness, use of the excellent time resolution and amplitude information) much more work on implementation of extra firmware is required: • calibration, adjustment of HV and thresholds, trigger, fit of the signal • Plan to start immediately after finish of backward EKLM installation. Need to involve experts from T.Shevchenko INR (Kiev, Ukraine), who are ready to work full time for this job + cooperation with VPI (D.Liventsev).

15. Summary • The important stage is almost finished! • After final installation, a hard work on commissioning is expected. • However, it is time • to • many people, • who made good job

16. Sumisawa san Dmitry Liventsev for their daily work on assembly & • for extremely effective organization of all logistics issues at KEK, (de)installation, disassembly and many-many other important contributions without which it would be impossible to work for our group • for training of all new ITEP assembly shifts, work on electronics and after-installation tests, coordination of work between ITEP-KEK-WayneSU-VPI-Hawaii

17. Leo Piilonen Gary Varner Ushiroda san David Cinabro

18. to ITEP engineers who worked on R&D, construction, mass production…

19. to ITEP stuff & • K.Belonozhenko, B.Bobchenko, • Y.Kuznetsov, S.Mineev, • O.Kachalina, Y.Novozhlov, • E.Novikov,A.Semennikov, • A.Frolov, S.Veselov • T.Aushev, K.Chilikin, • R.Chistov, M.Danilov, • A.Drutskoy, P.Katrenko, • R.Mizuk, G.Pakhlova, • P.Pakhlov, E.Solovieva, • I. Tikhomirov, T.Uglov David Besson from MEPhI