RF System

RF system is based on 10 MW Thales klystron and Scandinova modulator

Block scheme of the RF System up to 150 MeV

The high power part of the TOP IMPLART RF system foresees the use of a number of identical RF plants each based on a Thales 10 MW klystron (TH2157A) and its power supply (modulator). The power is split in 4 or 2 parts depending on the needs of the fed structures.

Tight controls are used to stabilize the phase among the several klystron outputs.

2157A 10 MW Thales Klystron with Scandinova Modulator

At 2017 we are running only the first SCDTL part of the system (up to 35 MeV), and only a single klystron is needed, as the total power requirement for SCDTL is around 7 MW.

Being still not available the modulator for the first plant (while the klystron ihas been acquired), we are using an old plant based on a TH2090 Klystron, which is powered by a line-type modulator unit. Since the repetition frequency is not an issue now, this solution is considered adequate for the scope at a repetition rate of maximum 30 Hz.

RF Pulses from have a 4 us flat-top, that however shows some ripple, contained by a careful action on the PFN inductances.

Also this is not a serious issue by now.

Low level RF is composed by a master Rohde & Schwarz oscillator amplified by a 200W AM85 Microwave amplifier.

The RF split in 4 branches is achieved by a a first split in two by means of a MEGA variable power divider, and then by two home-made very efficient riblet based splits the first delivering power to SCDTL-1 and 2 and the second to SCDTL-3 and 4.

Several -55/-60 dB calibrated directional couplers are placed in the RF line to retrieve information on the phase and amplitude of the signals driving the structures, and so letting a stabilization loop.

Each structure is also provided with a cavity field sensor, whose info is also included in the RF control system.

A Flex RIO (containing the controller and some boards for acquisition, timing and RF signal generation, measures phase and amplitude of RF power in suitable parts of the WG RF plant and structures cavity fields

These signals are analogically demodulated at an intermediate frequency (12.5 MHz) e digitally detected by a base band IQ demodulation.

The control is done by a PXI controller that emulated a PDI controller in order to act on phase shifters and tuners.