PACTA die microphotography. Die area is 2 mm2

The ICCUB-IEEC delivers to University of Tokyo 10,000 purpose-designed integrated circuits for the Cherenkov Telescope Array

Source: ICCUB
Published on 30.04.2018
Documents: 180430_NewsPACTA_FINAL_4021.docx

  • The chips, 10,000 Application-Specific Integrated Circuits (ASICs), are one of the main components of the cameras to be installed in the Large Size Telescopes that will be built in La Palma.
  • The ASICs have been designed, produced and tested at the Institute of Cosmos Science of the Barcelona University (ICCUB) Technology Unit and delivered to the University of Tokyo through a contract signed by the Institut d’Estudis Espacials de Catalunya (IEEC).

The ICCUB-IEEC has delivered to Tokyo University more than 10,000 ASICs to equip the cameras of 3 Large Size Telescopes of the Cherenkov Telescope Array (CTA). These ASICs, called PACTA, were chosen among different prototypes to become a common component for both the Large Size Telescopes (LSTs) and the Medium Size Telescopes (MSTs). The ASICs have been designed, produced, and tested by the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), a unit of the IEEC.

CTA is a project to build the next generation ground-based observatory for gamma-ray astronomy at very-high energies. The observatory will consist of two arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs) of different sizes, based on proven technology and deployed on an unprecedented scale on the northern and southern hemispheres. These IACTs will detect the Cherenkov radiation coming from gamma rays that penetrate our atmosphere and disintegrate, creating cascades of matter and anti-matter particles.

The Observatorio del Roque de los Muchachos (ORM), La Palma, Spain, will host CTA-North, which will consist on 4 LSTs and 10 MSTs. The first LST is currently being built at ORM and already contains a first batch of 2000 PACTA ASICs produced by ICCUB and delivered in 2014 to Tokyo University, the institution in charge of the electronics of the cameras for the LSTs. The first LST will be inaugurated and have its first light at the end of 2018, with commissioning and first science in 2019. The 10,000 PACTA ASICs produced, successfully tested, and delivered now to the University of Tokyo, through a contract signed by IEEC, will be used to build the cameras of the 3 remaining LSTs of CTA-North.

Different groups of IEEC have been working on the CTA project since 2008. In particular, the ICCUB-IEEC team has developed several ASICs for different cameras, based on previous experience gained after participation in the Large Hadron Collider beauty (LHCb) experiment. In particular, the chip PACTA is a PreAmplifier specifically designed to readout photomuliplier tubes operated at low gain, fulfilling stringent requirements in terms of bandwidth (500 MHz), dynamic range (15 bits), input signal range (up to 20 mA peak current), low power consumption (120 mW), and low noise (single photon detection).These stringent requirements were not available in commercial off the shelf components. The quality control of the chips produced by the IEEC-ICCUB team, performed by a robotic system, showed an excellent yield: above 99% of the ASICs fulfilled all requirements.


Figure 1. PACTA die microphotography. Die area is 2 mm2

Figure 2. PACTA chip packaged in QFN32 package.

Figure 3. PACTA block diagram

Figure 4. Single photoelectron spectrum measurement at a photomultiplier tube gain of 40,000

Figure 5. Dynamic range of PACTA extends to more than 5000 photons with 0.2 photon resolution, i.e. a dynamic of about 15 bits.

Figure 6. Automated test bench for chip quality control. Each try contains about 500 chips.

Video about robot operation


David Gascon (dgascon@icc.ub.edu)