Instrumentation & Measurement Magazine 24-9 - 64

Control and Monitoring System
In this section, we describe the cabinet that hosts the control
and monitoring system and peripheral components, shown
in Fig. 2a. The core of the DDS is a National Instruments (NI;
Austin, TX, USA) Peripheral Components Interconnect (PCI)
eXtension (PXI) crate that hosts several cards (commercial by
NI and custom) where the control and monitoring algorithms
are implemented.
NI LabVIEW software is used to create a real-time executable
file that is run in the crate controller on the LabVIEW
real-time operation system. The program uses five cards with
Field Programmable Gate Array (FPGA) that have been programmed
to manage the data acquisition from the beam
monitors and control the treatment delivery by exchanging delivery
data between each other. The treatment plan is sent from
the oncological information system to the controller. It is then
converted into parameters that are readable by the FPGAs. The
delivery information is loaded in four memory cards, from
which they will be accessed by the FPGAs, via front panel connections.
This occurs during the delivery without the need
for data exchange between the beamline components and the
crate controller. This architecture is chosen to guarantee realtime
treatment control, with high reliability and safety.
Four FPGA cards are dedicated to controlling the intensity
monitors (IntFPGA), the strip chamber (StpFPGA), the
pixel chamber (PixFPGA) and the scanning system (ScanFPGA).
The final FPGA card (TimFPGA) is used to synchronize
the delivery with the Master Timing System (MTG), which
sends synchronization signals to all elements comprising the
accelerator. The BOX can be configured for any combination
of position detectors. At CNAO, both a strip and a pixel detector
are used.
FPGA cards control the treatment on a spot-by-spot basis,
where each beam spot is defined by the number of particles,
lateral positions and beam energy. IntFPGA receives the
planned number of particles and triggers advancement to the
next beam spot when the planned number of particles have
been delivered. This trigger is also sent to the other FPGAs to
maintain treatment synchronization. StrFPGA and PixFPGA
contain the segmented ionization chambers data acquisition,
allowing for determining the spot position, controlling the
beam position via a feedback loop to the scanning magnets,
and monitoring the spot to generate a treatment interruption
signal if an error is detected. ScanFPGA controls the scanning
magnet power suppliers to move the beam to the correct position
and uses spot position signals sent from StrFPGA, as
feedback for beam spot position corrections.
Through a direct connection to the interlock system, all FPGAs
are able to interrupt the treatment delivery if any error is
detected in the delivered spot characteristics or in the internal
Fig. 3. Interfaces of the CNAO DDS with external devices, systems, and services.
64
IEEE Instrumentation & Measurement Magazine
December 2021
Instrumentation & Measurement Magazine 24-9

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