Frontier Detectors for Frontier Physics 13 th Pisa

Frontier Detectors for Frontier Physics 13 th Pisa Meeting on Advanced Detectors MPD / NICA and BM@N / Nuclotron Experiments Picosecond Cherenkov detectors for heavy ion experiments at LHEP/JINR Vladimir Yurevicha and Oleg Batenkov b a Joint Institute for Nuclear Research, Dubna, Russia b V. G. Khlopin Radium Institute, St. Petersburg, Russia The modular Cherenkov detectors with picosecond time resolution are developed as main start and L 0 trigger detectors for Au + Au collisions in future experiments MPD and BM@N at JINR for study of highly-excited and dense baryon matter in Au+Au collisions at energies of NICA collider and Nuclotron. The modular arrays FFD/MPD and T 0/BM@N detect high energy photons and charged particles via registration of induced Cherenkov radiation by MCP-PMTs in the modules. The detectors provide start pulse for TOF detector with time resolution σ t < 50 ps and effective L 0 trigger of Au+Au collisions. MPD experiment with beams of NICA collider Au + Au, = 4 ÷ 11 Ge. V Fixed target experiment BM@N with beams of Nuclotron Au + Au , 2. 0 ÷ 4. 5 A Ge. V, 10 7 ion/s The MPD is 4π-setup and it consists of various detectors for study of characteristics of numerous secondary particles produced in IP within a wide pseudo-rapidity interval. ZDC DC ST The key element of BM@N setup is multilayer tracking system (silicon, GEM, straw tubes, drift chambers) placed behind the target. IP T 0 detector RPC (TOF) In both experiments the TOF detector is based on large area RPC arrays. The start signal comes from Fast Forward Detector (FFD) in MPD and T 0 detector in BM@N. The TOF method is used for particle identification. FFD Fast Forward Detector (FFD) Experiment MPD BM@N The FFD consists of two arrays of Cherenkov modules at z = 75 cm from IP. The aim of the FFD is to provide • Start signal for TOF detector • Selection of Au+Au collisions at |z| ≤ 25 cm from IP • L 0 trigger Detector FFD T 0 2 1 Number of modules 12 × 2 12 Number of channels 48 × 2 48 At the present some different arrays with 12 and 20 modules are considered to define a final version of FFD modular array. The initial version used for study of detector performance has 12 modules with 48 channels per array. Required time resolution, σ t < 50 ps Min. bias trigger Yes Central collision trigger Yes Operation in magnetic field, B 0. 5 T Number of arrays SP- 41 magnet Target T 0 detector The T 0 detector is modular Cherenkov detector on a base of the same modules used in FFD/MPD. The aim of T 0 detector is to provide • Start signal for TOF detector • L 0 trigger with selection of events on centrality at high intensity of Au beam with absence of any materials in beam line except Au target. To define a final detector design some different versions are considered. The initial version of T 0 detector for study of detector performance has 12 modules placed around a target with 48 independent channels. Detector Module Beam Tests The module contains of aluminum housing, 10 -mm Pb converter, quartz radiator with 4 bars 26. 5× 15 mm each, MCP-PMT XP 85012/A 1 -Q, FEE board, and HV divider. The anode pads of MCP-PMT are joined into 2× 2 cells. The FEE has 4 channels for processing pulses from anode pads and a single channel for pulse from MCP output. Each the chain consists of amplifier, shaper, and discriminator and produces analog and LVDS signals which are fed to SMA and HDMI connectors respectively. Pulse height, m. V MCP-PMT XP 85012 /A 1 -Q 500 400 25 μm pore 8× 8 anode pads 53× 53 -mm photocathode Quartz window 300 200 100 2 4 6 8 10 Time, ns Typical pulses on an oscilloscope screen The characteristics of detector modules were studied with deuteron beam of Nuclotron at energies from 2. 0 to 3. 5 Ge. V/u. Two pairs of detector modules D 1 – D 2 and D 3 – D 4 were used in the test measurements. Three different readout electronics were applied: 1. DRS 4 Evaluation Board V 4 digitizers (PSI), 2. 5 GS/s digitizer CAEN mod. N 6742, 3. VME module TDC 32 VL, 32 -channel 25 ps multihit time stamping TDC (JINR). 1 2 3 4 5 6 1 – Pb plate / converter 2 – quartz radiator 3 – MCP-PMT 4 – FEE board 5 – module housing 6 – HV connector 7 – SMA outputs of analog signals 8 – HDMI cable (LVDS signals + LV) Study of detector performance with MC simulation 7 8 Layout of detectors on MPD-test beam line and the Cherenkov modules D 1 – D 4 (without Pb converter) D 1–D 2 D 3–D 4 LAQGSM + GEANT 4 S. Lobastov FFD performance FFD L IP FFD R π p TOF measurements with two pairs of the modules and DRS 4 E. B. V 4 TOF result (sigma) Single detector resolution, σt Pulse form measured with DRS 4 Evaluation Board V 4 Pulse height distributions for photons with energies of 50, 100, 200, and 500 Me. V Current FFD design with 12 module arrays Pulse height distribution via time of arrival in FFD for charged particles, Au+Au at = 7 Ge. V The efficiency of photon detection Eγ (Me. V) εγ (%) 50 100 200 500 32 52 67 74 The measurements with LVDS pulses and TDC 32 VL give time resolution of single detector channel of 35÷ 40 ps. The time resolution of start signal improves as where N is a number of hits depending on beam energy and centrality of Au+Au collisions. = 5 Ge. V Test in magnetic field of BM@N magnet T 0 detector Energy spectrum of photons coming to FFD array from Au+Au at = 5 Ge. V Photon multiplicity in FFD array at = 9 Ge. V as a function of centrality Efficiency to trigger Au+Au collisions by registration of photons and charged particles ( threshold =1000 Ch. ph. ): ONE - a single FFD array, OR - any of two arrays, and AND - both FFD arrays T 0 detector performance photons + pions Detector modules Vacuum pipe Au + Au, 2 A Ge. V Target 33. 5 ps 24 ps Au + Au, 4 A Ge. V Beam Layout of T 0 detector inside BM@N magnet and a view of detector modules A constant shift of pulses in time scale is observed due to an influence of magnetic field on electron path inside MCP-PMT. February – March 2015 Current design of T 0 detector Trigger performance of T 0 detector for Au+Au collisions at different centrality for two beam energies 2 and 4 A Ge. V 100% efficiency to trigger central and semi-central Au+Au collisions. The central collisions correspond to events with the largest number of hits and they can be selected by L 0 trigger. Operation of modules in magnetic field with B = 0. 5 T was tested with a prototype of T 0 detector. The pulse height distributions and time resolution were studied with 3. 5 -Ge. V/u carbon beam. The C ions interacted with Cu target 10 mm diam. × 7 mm. The modules detected secondary photons and charged particles. A beam Cherenkov detector with 11 -mm quartz radiator generated start signals for TOF measurements. The time resolution of the start detector was σt = 27 ps. To restore the gain of MCP-PMT in magnetic field, HV was increased (+20 V for modules at 0° and 180°, and +250 V for modules at 60° and 120°). The time resolution obtained with CAEN digitizer and MCP output pulse is 57 ps and 110 ps for modules at 0° (180°) and modules at 60° (120°) respectively. The data analysis is in progress. References 1. V. I. Yurevich, Nuclear Instruments & Methods in Physics Research A (2015), http: //dx. doi. org/10. 1016/j. nima. 2015. 01. 006 i. 2. V. I. Yurevich, O. I. Batenkov, et al. , Physics of Particles and Nuclei Letters 10 (3) (2013) 258. Contact info: E-mail: yurevich@jinr. ru