CLAS12 - MVT The Micromegas Vertex Tracker is designed to improve the track reconstruction in the vicinity of the target. It is located inside the 5 T magnet where the particle flux is the highest. The MVT is composed of two elements to maximize the angular coverage: •  a Barrel tracker made of 18 cylindrical detectors arranged in 6 layers. In combination with the SVT it covers the region from 35 to 125° and greatly enhances the polar angle resolution. •  a Forward tracker made of 6 circular, flat detectors from 6 to 29°. It improves the vertex resolutions by a factor 3 to 10 compared to the Drift Chambers. MVT - TECHNICAL PARAMETERS PARAMETER Elements Micromegas technology PCB thickness Radiation length Electronic chip Sampling frequency Cables Time resolution Total active area Number of readout elements Angular coverage Number of detectors Gas mixture Drift gap Drift electric field Micro-mesh transparency Effective gain Lorentz angle Particle flux per layer Pitch DESIGN VALUE Barrel Forward Bulk with resistive strips 200 µm 0.33% / layer DREAM 20 MHz 1.5-2 m coaxial from Hitachi, 50 pF/m 10 ns 2.9 m² 0.6 m² 15,000 6,000 35-125° 6-29° 18 6 Ar+10%iC4H10 Ne+10%C2H6+10%CF4 3 mm 5 mm Z: 8 kV/cm; C: 5 kV/cm 1 kV/cm Z: 50%; C: 75% ~100% 5,000 3,000 20° NA 4 MHz 12-20 MHz Z:540 µm; C:330-900 µm 500 µm •  Construction Strategy and Project Leadership: -  The project is lead by the Service de Physique Nucléaire at IRFU, CEA-Saclay. The lead physicist is Franck Sabatié. -  The R&D, including prototypes and lab tests, was performed at Saclay. A few beam and laser tests have been organized both at CERN and JLab. -  The final detectors (PCB and bulk) will be made at CERN and integrated at Saclay. -  The whole MVT will be installed in CLAS12 in 2 phases, the first one corresponding to the integration of the Forward tracker and 2 layers of the Barrel (B2) in 2015, the rest of the barrel in 2016. -  A first integration of the MVT-B2 setup will be performed at Saclay before shipping to JLab for the final assembly. •  Significant Dates: -  2006-2007: simulations of Micromegas in CLAS12 environment, determination of the working point, and characterization of the first curved prototypes. -  2008: implementation of the MVT in GEMC. and determination of its tracking performance. -  05/2009: MVT review at JLab. -  11/2010: MVT-SVT review at JLab. -  11/2011: MVT project review at IRFU. -  2012: first test of large, curved, resistive detector. -  09/2013: choice of the resistive strip technology. -  09/2014 : tests of pre-series detectors. •  Project Status: -  Electronics: The full production of DREAM ASICs has been received. Twelve preseries Front-End Units have been tested. Tests with the Back-End Unit are in progress. Cables for the Forward have been received, and Barrel cables will arrive in Oct. 2014. -  Detectors: Pre-series for Forward and Barrel have been received during summer 2014, and are being tested. The 6 final Forward detectors and the first 6 Barrel detectors will be produced end of 2014 and sent to JLab mid-2015. The remaining 12 Barrel detectors will be produced in 2015 for later assembly. -  Integration/Mechanics: Final 2D and 3D drawings are done for the B2 setup. All mechanical parts have been ordered and a first assembly of B2 is expected early 2015. Last update: November 18, 2014 Contact: F. Sabatié, Physicist ([email protected]) +33 1 69 08 32 06, S. Procureur, Physicist ([email protected]) +33 1 69 08 39 22 S. Aune, Engineer ([email protected]) +33 1 69 08 66 48 V. D. Burkert Hall B Group Leader ([email protected]) 757-269-7540