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Jema Energy has been awarded with a new tender for ESS

Jema Energy has been selected to supply 5 new Klystron modulators to European Spallation Source (ESS).  With this new award Jema will deliver a total of 18 Klystron modulators to ESS. Previously, the company has already manufactured and tested 13 modulators at its facilities in Lasarte.

The main features that ESS highlighted for the modulators:

  • 660 kVA power
  • Solid state IGBT technology
  • 115 kV/100 A pulse of 3.5 ms/14Hz

The Klystron Modulator design is based on a Stacked Multi-Level (SML) topology and consists of different subsystems located in two main parts, LV part and HV tank, both mounted in frames, assembled separately and installed together as a single block. The LV part is located on top of the HV tank, which is mounted in a single frame that sits on the floor with adequate support. The HV tank can slide in and out over externally mountable rails to facilitate easy access to its interior for maintenance purposes.


The Klystron Modulator consists of the following subsystems

  • Input unit: Includes the protections and filters.
  • Three AC/DC + DC/DC converters: With pre-charging circuit and line filter. The main capacitor banks are charged by the DC/DC converters through a DC inductors with a smooth charging current. Charging diodes are also provided. Each AC/DC + DC/DC converter feeds two DC/AC converters.
  • Six DC/AC converters: They convert the DC voltage from the main capacitor banks to a High Frequency AC voltage that feeds the HVHF modules. Each DC/AC converters feeds one HVHF module.
  • Six HVHF modules: Each module consists of a transformer, a common mode inductor, a rectifier bridge, a filter inductor and a filter capacitor bank.
  • Output stage: Four high potential output connectors to feed, through load disconnectors, four klystrons in parallel. A HV divider and four current sensors are installed for regulation, monitoring and interlocking. An arc protection system is also installed to protect the klystron against arcs.
  • Oil pumping system: With a heat exchanger to recirculate and cool the oil of the HV tank.
  • Water cooling system: For water distribution to the different components and sub-assemblies.
  • Control cabinet: With control and regulation racks and touch screen HMI to manage the regulation of the different power conversion stages and the management of all the interlocks.


About ESS

The research facility ESS, under construction in the city of Lund, Sweden, will be the most powerful neutron source in the world and is expected to deliver first science in 2023. ESS is a joint project by 13 countries and 1,800 million euros of investment that will provide researchers, companies and institutions with a world-class facility for neutron research.