ATLAS Inner Tracker Upgrade (ITk)
22 Feb 2011








After ten years operation the ATLAS inner detector components (the core of ATLAS) will have become degraded by intense radiation. After this time the Large Hadron ​Collider will be upgraded to increase the intensity of particle collisions by ten-fold.

A new upgraded inner detector is required to allow continued detection, data acquisition at the higher rate and to withstand the higher radiation environment. A programme of work is considering ways to create the new inner detector.

Technical challenges:

  1. Ten times radiation tolerance
  2. Increased heat generated by front end read-out electronics
  3. Up to 200 simultaeous collisions in each bunch crossing
  4. Much higher track density
  5. More read-out channels, higher density, faster, more data
  6. Cable density must not increase
  7. Minimising the amount of material traversed by particles

RAL-PPD is part of both the pixel and strip detectors of the ITk.  RAL scientists and engineers are involved in:

  1. Mounting pixel modules onto end-cap rings
  2. Construction and prototyping of silicon strip modules
  3. Mounting of strip modules onto barrel staves
  4. Development and testing of high voltage switching circuits
  5. Development of Data Acquisition​ (DAQ) systems for pixel and strip readout
  6. Systems design and testing
  7. Signal integrity testing
  8. Component irradiations
  9. Mechanical support design and prototyping
  10. Simulation and performance studies​

The TDR (Technical Design Report) for the Strip detector has recently been published.

​Silicon Strip Modules

The ITk silicon strip module is built from a large area (97.5x97.5mm) silicon sensor with front end electronics, DC-DC converter and high voltage switching circuitry mounted on flexible polyimide circuits glued directly onto the sensor surface.  Barrel modules of both long (5cm) and short (2.5cm) strip lengths have been built and prototyped at RAL


Prototype long strip (left) and short strip (right) modules built at RAL

​​​Strip Staves

Local support, cooling and electrical connections are provided to strip modules via a 1.4m carbon fibre stave which holds 14 modules on​ either side.


A 14 module barrel stave

Modules are mounted on the stave at RAL using a 2m robotic gantry.  Full 12 module staves have been built with an old chip-set (ABCN-250) whilst a 26 module thermo-mechanical stave and 8 module electrical​​ stave have also been built using the most recent prototype ABC-130 chipset.


The 26 module thermomechanical stave (left) and the 8 module electrical prototype (right)

Pixel Rings

​​The local support structure in the pixel end-cap is based on carbon fibre rings.  Modules are mounted onto these rings at RAL using a robotic gantry system


Mounting of pixel thermomechanical modules onto end-cap rings

Simulation and Performance

Studies are ongoing to investigate the performance of different layouts in simulation, for example investigating the efficiency of reconstructing a hard scatter vertex in high density events such as those expected at the HL-LHC


The fraction of the total track transverse momentum from the true hard-scatter interaction that is used in the reconstruction of the hard-scatter vertex (left) and the fraction of the track transverse momentum used in the reconstruction of the hard-scatter vertex that comes from pile-up tracks (right)