Silicon Telescope

Telescope Overview

The FTBF facility hosts an all silicon tracking telescope, providing a precision position measurement of less than 5μm using the primary 120GeV proton beam.

This facility adds to other operating test-beam facilities equipped with high precision tracking telescopes.

The main distinguishing features are:

  • A high-energy bunched proton beam (limited multiple scattering and precise time localization of the incoming particles)
  • Full beam time synchronization with the Data Acquisition System (DAQ)
  • Fast readout capable to accumulate up to 150,000 beam tracks per minute during the 4.2s spill
  • Beam tracking with better than 5μm precision at the DUT
  • Triggered and/or timestamped (with a 3.125ns, 40MHz, resolution) readout
  • An easy to use trigger board for a quick integration of the DUT DAQ stream with the telescope data stream
  • Low material budget in the beam (11% total radiation length)

Telescope characteristics

The telescope is placed along the FTBF beamline and consists of 4 detector planes, each made of modules leftover from the CMS Forward Pixel detector production-mounted on a carbon fiber frame and 6 XY strip stations mounted on an aluminum frame, covered with a carbon fiber sheet.

The main characteristics of the pixel part of the telescope are:

  • 4 Planes measuring X and Y (2 tilted in X and 2 tilted in Y for better resolution)
  • Pixel cell size is 100x150x320μm3
  • Overlap coverage area of ~1.6 x 1.6 cm2
  • Resolution on the DUT ~8μm (achieved tilting the stations)
  • Minimal material in the path of the beam (each plane is 1.19% radiation length)\

The main characteristics of the strip part of the telescope are:

  • 6 Stations measuring X and Y (each station has 2 strip planes orthogonally oriented to measure X and Y)
  • Strip pitch is 60μm, strip length is 9cm, thickness is 320μm
  • 640 strips for an overlap coverage area of ~3.84 x 3.84 cm2
  • Resolution on the DUT ~5μm
  • Minimal material in the path of the beam (each station is 1.06% radiation length)

Figure 1 shows the telescope configuration while figure 2 shows a pixel module and two strip stations.

Silicon Telescope

Figure 1 The strip and pixel tracking telescope at the FTBF

Silcon Pixel and Strip Modules

Figure 2 Left: Pixel module. Right: two strip stations

Trigger Synchronization

The trigger is formed using 1 scintillator detector placed behind the pixel telescope and can be put in coincidence with other scintillators that the facility has placed along the beam line.

The telescope can reconstruct tracks at about ~40KHz rate without losing triggers.

The strip telescope also offers a 6.6MHz timestamp counter (~150ns resolution).

The time resolution can be also improved using a 40MHz counter (3.125ns) running in the trigger board.

Trigger number and timestamp counters are saved in the data stream and can be used to match events between the telescope and the DUT DAQ.

Data Acquisition System

The data acquisition system is based on a DAQ developed at Fermilab called OTSDAQ (

Users can synchronize their operations sending or receiving UDP messages, to OTSDAQ, to start and stop the runs with a click of a button.

Users can also establish a procedure to make sure that the telescope and the DUT DAQ will start off spill when no triggers are present.

The telescope data stream and the DUT data stream are then merged offline using the trigger number or the timestamp.

The telescope data is organized by tracks to which is associated the trigger number and/or the timestamp.

The data format is a Root Tree with as much information as the user needs. The default data format is based on the XY slope-intercept of the tracks and the associated trigger number.

Updated May 26, 2020.