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

Sarah K. Phillips's Collection

SVT Simulation Work

Sam Meehan's Collection

Link to Page

SVT for CLAS12 - Drawing and Such

Cross Section Drawing of SVT chip

Requirements for Testing

  • Laser with wavelength λ~1100 nm to match the band gap energy of silicon.
  • The mechanical system should be able to drive a laser system over a box of approximately 1m long and 15cm wide, weighing approximately 1kg. This is what we saw in the JLab electronic room.
  • Positioning of the laser in the x-direction much better than 150µm.
    • Motor with high accuracy is needed.
  • Laser spot on the surface better than 50 µm.
    • Very high precision motor can be used to keep fiber 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 (if we want the charge measurement to be meaningful during the test).
  • If the efficiency needs to be measured we need to make sure that the laser is not fired when the pulse is be close to the end of the gate, possibly by synchronizing the laser pulser and the SVX4 clock.

Pulsed Laser for Testing

The main principle of the LASER test is the injection of charge into silicon using an infrared LASER.

Test setup at Fermi Lab

  • Pulsed LASER for testing silicon strip detectors, which was used for similar purposes at Fermi Lab.
    • 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.

Test setup for PHENIX

CLAS12 Options

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.
  • Another good option is to order all three axis assembled from a single company Velmex, Inc. The only problem I encountered with them is that they would like to build the assembly using the same type of slides without mixing different slide families, which may not be a problem but an inconvenience. Aparently the mixing drives the cost up because of various mecahnical adapters needed to match parts from different families. This option would be really nice and it would cost about $8000.

Very Brief Notes from the Wednesday Bi-weekly Tracking Meetings

Available Hardware

Our own

From Jefferson Lab