SVT Project

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The UNH Silicon Vertex Tracker Project

The UNH Nuclear Physics group will be building a test facility for the Silicon Vertex Tracker (SVT) for CLAS12. The current plan is for the SVT to be build up of 4 concentric layers. Each layer will provide x and y information from two silicon strip detectors, each detector with a different "pitch" for the strips. A scattered particle will thus go through 8 layers of silicon plus the support backing and the detector will provide 4 x,y,z points to compute a track.

Previous work performed at Jlab:

A completing solution for tracking in the inner detector is the 'micromegas detector', see: CLAS-NOTE-2007-004

Requirements for Testing

  • Positioning of the laser in the x-direction much better than 150µm.
    • Motor with a high persision needed.
  • Laser spot on the surface better than 50 µm.
    • Very high precision motor can be used to keep siber close to the surface.
    • Also can use an optical lense to focus laser beam onto the surface.
  • Pulse length of the laser much less than 132 nsec to match the clock rate of the SVX4 chip.

Pulsed Laser for Testing

  • Pulsed LASER for testing silicon strip detectors
    • This DO Note describes a pulsed LASER setup for testing silicon strip detectors at the Silicon Detector Facility (SiDet) of Fermilab supporting the related projects and, in particular, the DO Silicon Tracker Upgrade. It will be used in the measurements of the efficiency of individual strips and their coupling. The LASER wavelength is 1060 nm, at which the absorption length in silicon is about 2 mm. The LASER setup is capable of producing light pulses with rise time of less than 1 ns, allowing the measurement of charge pulse shaping at individual strips and their capacitive couplings. Due to the high power output of the LASER, safety considerations are included. Also discussed are precautions for the safety of the LASER itself, and how to limit the light to an area smaller than 50,pm of diameter.

Rail and Support System

  • The rail and support system will be based on three moving stages: one to scan across the silicon chip (x-stage), the other to focus the laser (z-stage), and the third one to move the laser to scan the chip at a different position.
  • Amrit's group had a prototype which included x and z statges, plus some railings designed to move them. This will serve as the starting point for the UNH design. The motor for x-motion was Zaber Technlogies T-LLS275 (or equivalent model), and the motor for z-motion was Zaber NA11B60.
  • One alternative is to use T-LLS275 (or equivalent model)as the y-stage, but get a new and smaller motor for x-motion since 25 cm range provided by T-LLS275 is probably too big anyway. The range and the precision of other Zaber motors might be better matched for scanning the wafer across than the relatively large T-LLS275.