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.
Micromegas technology
PCB thickness
Radiation length
Electronic chip
Sampling frequency
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
Bulk with resistive strips
200 µm
0.33% / layer
20 MHz
1.5-2 m coaxial from Hitachi, 50 pF/m
10 ns
2.9 m²
0.6 m²
3 mm
5 mm
Z: 8 kV/cm; C: 5 kV/cm
1 kV/cm
Z: 50%; C: 75%
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
-  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