Old IOT and HVPS Cabinets of Booster RF.

Last August, a major upgrade of the Booster 500MHz Radio Frequency (RF) Transmitter of ALBA was done: the IOT amplifier of the Booster based on vacuum tube technology was replaced by a Solid State Power Amplifier of 50kW (SSPA).

The designer and provider of this equipment is BTesa, a Spanish Telecommunications company located in Madrid. This company has wide experience in Broadcast and Accelerators Technology. This project has been co-funded with ERFD funds.

The RF Systems of any accelerator are required to increase the particles energy and to restore the energy they lose due to synchrotron radiation. In ALBA, the RF System of the Booster is composed of a single transmitter that ramps the energy of the electrons from 100MeV to 3GeV. In the Storage Ring, the RF systems are composed of 12 Transmitters distributed among 6 plants and they keep the energy of the electrons at 3GeV.

Up to very recently, all high power RF amplifiers of ALBA were Inductive Output Tubes (IOT). These amplifiers are vacuum tubes with electron guns were high voltages are applied (up to 40kV) and converted in RF power. The main advantages of this technology are their cost, efficiency and high power levels. In the Storage Ring there are 12 IOTs which provide enough redundancy to achieve the high reliability levels required by ALBA users. However, the RF power requirements of the Booster are much lower compared to the Storage Ring and only one transmitter is needed. In order to provide extra redundancy and reliability to the Booster RF System, the IOT amplifier was replaced by a Solid State Power Amplifier which is composed of 96 RF Power Transistors distributed among 12 modules. This equipment was designed and provided by the Spanish company BTesa. The combination scheme of this modules and transistors allows operation even if up to 15% of the components fail. They also work at low voltage (50V) which eliminates completely the discharges problems associated to high voltage of vacuum tubes. Last, the modules have been designed to allow “hot swap” replacement, i.e., the module can be replaced even if the transmitter is operating at full power.

New Booster SSPA of Booster RF.

Installation & Performance

On August 16th, the installation process of the new transmitter started and after three days work the amplifier was working at full power, 50kW continuous wave (CW). Operation with beamlines started on 5th September and the new transmitter has been working flawlessly since then. Next table shows the main characteristics of the transmitter and measurements done during the Site Acceptance Test.

Parameter
 
Frequency
500MHz
Maximum Power CW
48kW (1.1dB compression)
Dynamic range
> 30dB
Efficiency at 48kW output power
60%
Gain
78dB
Bandwidth
> 2MHz
Phase variation over all dynamic range
10º
Harmonic contents
> 40dBc at 2nd, 3rd and 4th harmonic
Disconnection of one module at full power
OK

All departments and divisions of the ALBA Synchrotron have participated in this project, starting with Administration Department that prepared the tender awarded to BTesa in 2015 for the design and construction of this Transmitter. The Engineering Division and Logistics Department analyzed the structural requirements of the new equipment, they removed the IOT and its HVPS (Highly Voltage Power Supplies) in July 2018 and they participated in the installation of the new Transmitter. The Computing Division upgraded the control system to be compatible with this new system and the RF Group & Accelerators Division coordinated all these tasks.

This project is co-funded by the European Regional Development Fund of the European Union.

TimeLapse of the Installation