N. Anfimov (JINR) on behalf of the ECAL0 team

 Introduction  Installation and commissioning  Calibration  Data taking  Preliminary result  Plans for 2013  Summary July SPIN-Praha-20132

1. The geometrical size is ~ m 2 with a central hole ~ m 2 and the total length (thickness) of the calorimeter should be of about 50 cm. 2. Located downstream of RPD. ECAL0 should cover the polar angular range Rad. 3. A modular structure. 4. Energy resolution ≤ 10.0%/√E (GeV) or better. 5. The photodetector should be insensitive to the magnetic field. R&D of ECAL0 prototype was being performed in Final prototype had been tested in July SPIN-Praha Requirements for ECAL0

July SPIN-Praha ECAL0 in the COMPASS setup

July SPIN-Praha “Shashlyk”-type calorimeter module for ECAL0

Micropixel Avalanche PhotoDiodes – MAPD Surface-pixellated structure - Pixels are on the surface - Gain is up to Has pixel density ~ mm -2 - PDE is up to 40% (100 mm -2 ) - PDE depends on pixel density (decrease with increasing density) - Small dynamic range (depends on total number of pixels) -Typical pixel size is (25-100)x(25-100) µm Deep micro-well structure - Pixels are deep inside epitaxial layer - Gain is up to Has pixel density ~ 10 4 mm -2 (up to mm -2 ) - PDE is up to 30% ( mm -2 ) - PDE slightly depends on pixel density (decrease with increasing density) - Large dynamic range (depends on total number of pixels) -Typical pixel size is (2-5)x(2-5) µm July SPIN-Praha-20136

7 Results of beam tests for 3x3 modules prototype

8 Modules mass-production Institute for Scintillation Materials, Kharkov, Ukraine is playing major role in calorimeter production by JINR design (lead and sci plates, assembling, fiber insertion, pretests, etc) injection-molding of scintillation plates Painting scintillation plates Assembling calorimeters General view of assembled calorimeter module Joint Institute for Nuclear Research is responsible for: - Has organized and is managing production in Kharkov - MAPD production (from Zecotek’s wafers) and tests - Photodetector unit production and tests - Tests of final modules, cosmic tests - Beam tests and investigation of modules Prober setup for wafer tests Wafer of MAPD-3N chips Cosmic tests of modules Production of photodetector units Intermediate tests and studies of electronics, MAPD, photodetector units, etc MAPD casing procedure July SPIN-Praha-2013

 Aluminium frame filled with 56 modules  ECAL0 tests with cosmics performed in assembly zone (COMPASS DAQ used)  ECAL0 craned into final position in spectrometer  Air cooling installation  Power supplies(Bias voltage)&Thermostabization &monitoring(LED) elements were developed by HVSYS company (Dubna) July SPIN-Praha Installation and commissioning The first fragment of the ECAL0 consisting of 56 modules was made for 2012 Run.

The first part of ECAL0 installed in COMPASS was successfully prepared for 2012 GPD pilot run data taking and operated well during October-December. Figures show beam load over ECAL0, MAPD amplitude variation and temperature inside the ECAL0 box July SPIN-Praha The temperature stabilization system operating in a range °C. MAPD temperature is maintained with an accuracy < 0.1 °CConditions

October 12, 2013 ECAL0 calibration with muon beam For ECAL0 module deposited fraction energy e/γ E active ~16%, 1 GeV e/γ -> 160 MeV Energy deposition from muon at 160 GeV -> 34.3 MeV in cell -> muon peak corresponds to 214 MeV All channels were roughly settled in according to this procedure July SPIN-Praha Calibration energy coefficient correction based on LED_in_spill / LED_out_of_spill. This correction is different muon/pion beams due to different backgrounds. Muon beam -> average ~1.65% Pion beam-> 4.75% Muon peak in different towers Correction coefficients distribution for 504 towers. Muon beam (top), Pion beam (bottom) Nonlinearity of MAPD response at 5GeV was measured to be about 5% and it also can be taken into account on the cluster reconstruction level. ECAL0 Intercalibration

FEM LED stability studies. FEM#1÷4 stability over 1 month: November1 – Novenmber30, July SPIN-Praha Long-term stability of FEM-system Monitoring system consist of 4 Light sources. Each source supplied quarter of ECAL0-prototype channels via light distributor 1 -> 16 4 PIN-photodiodes for LED light monitoring were used LEDs amplitudes variations < 1%

MAPD response stability over 1 month: November1 – Novenmber30, 2013 MAPDs amplitudes variations ≈ 1% cell# X=15 Y=1cell# X=15 Y=4 cell# X=15 Y=22 cell# X=15 Y=25 cell# X=4 Y=13 cell# X=1 Y=13 cell# X=28 Y=13 cell# X=31 Y=13 over all cells July SPIN-Praha Long-term stability of ECAL0

MIP signal obtained in inter-calibration with muon halo (all cells together). π 0 peak in γγ mass spectrum obtained in calibration with pion beam. (π 0 mass is subtracted in X-axis) γγ mass spectrum for semi- inclusive muon events (π 0 calibration is not applied yet). π 0 peak =127.2 MeV 14 All cells Peak width is 12% ~8% -resolution of 1 cell ~8% -cell-to-cell misalignment Intercalibration of each of the ECAL0 cells with muon halo provides precision about 8% Cluster reconstruction Cluster position -position of a central cell Cluster energy -sum of energy deposition in 9 (3x3) cells Cluster position -position of a central cell Cluster energy -sum of energy deposition in 9 (3x3) cells Physical calibration: π-beam of 190 GeV/c with intensity s -1 LH target Special ECAL0-based trigger was developed. ECAL0 based trigger: total energy deposition in ECAL0 >6GeV (3 GeV) Working tracking for primary vertex reconstruction Final calibration constants were obtained by moving π0 mass peak to it’s nominal position Physical data sample collected with muon beam demonstrates well- visible π 0 peak in γγ mass spectrum. Its position is shifted from the nominal because precise π0 calibration was not used yet for production of the data. The time resolution of cluster depends on cluster energy and for energy above 1GeV is less 1 nsResults

1.Part (56 modules) of ECAL0 for 2012 DVCS PILOT RUN built up and put into operation. It demonstrated good performance: E and T resolutions, linearity and stability fully correspond to expectations. 2.The signal from π 0 decays was seen in ECAL0 3.Data for calibration with π - was taken and are being used. 4.The full scale ECAL0 is under production. 200 modules will be produced at ISMA (Kharkov, Ukraine) till the end of this year. We are going to produce Registration Units as soon as we get new batch of photodiodes. 5.Beam tests in Bonn at ELSA: studying angular dependences 6.The design of the ECAL0 modules is could be used for the NICA/SPD ECAL July SPIN-Praha Summary