Software Defined Radio Based Feedback System
for Transverse Beam Excitation
Philipp Niedermayer (GSI)

Bild: GSI Helmholtzzentrum
für fürSchwerionenforschung,
GSI Helmholtzzentrum
SchwerionenforschungD. Fehrenz, 2022

Philipp Niedermayer

IBIC 2023, 13 September 2023

1

Motivation▪ Beam excitation with stripline kickers▪ Tune & chromaticity measurement▪ Slow extraction (nonlinear machine)

Beam𝐵𝐸▪ RF signal generation► Arbitrary waveform generator► Custom hardware design► Software-defined radio

GSI Helmholtzzentrum für Schwerionenforschung

Image: P. Kowina / JHAASS▪ Flexible▪ Interconnectable▪ Maintainable

Stripline ExciterPhilipp Niedermayer

IBIC 2023, 13 September 2023

3

Outline▪ Software-defined radio (SDR)▪ GNU Radio▪ Digital signal processing▪ Beam excitation for slow extraction▪ Process & requirements▪ Software radio approach▪ Commissioning▪ COSY Accelerator▪ Feedback system performance

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

4

Software-Defined Radio (SDR)

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

5

Software-Defined Radio (SDR)▪ Digital signal processing on FPGA + CPU▪ Commercial front-end hardware (USRP)▪ Large flexibility & on demand changes▪ Widely used in radio communicationcontroltrig

I/O

PC

USRP

GNU RadioRFNoC

RFSignals

Universal Software Radio Peripheral (USRP)GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

6

GNU Radio & RFNoC▪ Framework for signal processing▪ Flow graph design▪ Predefined and custom blocks▪ CPU (Python, C++)▪ FPGA (Verilog, VHDL)▪ Parametrized → GUI

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

7

Software Radio for Beam Excitation▪ Generate excitation signals▪ Baseband: DC to 10 MHz▪ Triggered operation mode

▪ Process signals▪ Up to 200 MHz on FPGA
▪ Acquisition and real-time evaluation▪ Overall latency of 1 – 2 ms

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

8

Beam Excitation for Slow Extraction

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

9

Beam Excitation for Slow Extraction▪ Sextupole driven 3rd order resonance▪ Transverse excitation to control particle amplitude▪ Particles become instable and are extracted → Spill

RF Exciter► Excitation signal controls spill

Simulation

SeptumGSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

10

Software Radio Based Feedback System▪ Excitation signal controls spill
Excitation Signal

𝐾N

DUCTX

Norm

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

11

Software Radio Based Feedback System

Software-Radio

Excitation Signal

Target rateRXFeedforward

Pulse counter

𝐾N

PID−Feedback Controller

Pulse

TX

NormRF signal

Detector
Beam

GSI Helmholtzzentrum für Schwerionenforschung

DUC+ExciterPhilipp Niedermayer

Amplifier
IBIC 2023, 13 September 2023

12

Software Radio Based Feedback System▪ Portable single-device solution▪ Digitizes detector signals (ns)▪ Generate RF signals (kHz ~ MHz)▪ Spill control with feedback▪ PID controller for amplitude (ms)▪ Automatic optimizer for parameters (cyclic)▪ Open source software▪ Flow graphs & GUIs
▪ Custom blocks

GSI Helmholtzzentrum für Schwerionenforschunggit.gsi.de/p.niedermayer/exciterPhilipp Niedermayer

IBIC 2023, 13 September 2023

13

Commissioning at COSY Accelerator

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

14

Commissioning at COSY Accelerator▪ Joint beamtime in May 2023

▪ Spill detectors

Measured spill rate
Plot resolution: 50 ms▪ HADES LGAD
▪ Scintillator BC400▪ Ionisation chamber + IFC▪ Feedback system▪ Corrects drift▪ Maintains spill rate

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 202315

Commissioning at COSY Accelerator▪ Joint beamtime in May 2023

▪ Spill detectors

Measured spill rate
Plot resolution: 50 ms▪ HADES LGAD
▪ Scintillator BC400▪ Ionisation chamber + IFC▪ Feedback system▪ Corrects drift▪ Maintains spill rate

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

16

Commissioning at COSY Accelerator▪ Joint beamtime in May 2023

▪ Spill detectors

Measured spill spectrum
50 ms▪ HADES LGAD
▪ Scintillator BC400▪ Ionisation chamber + IFC▪ Feedback system▪ Corrects drift▪ Maintains spill rate
▪ Works up to ~ 5 Hz

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

17

Summary▪ Software-defined radio▪ Signal generation, acquisition & processing▪ Flexible flow graph design▪ Excitation and feedback system▪ Portable single-device solution▪ Feedback from spill detector signal▪ Commissioning▪ Spill rate maintained (≤ 5 Hz)▪ Twin system in operation at COSY Jülich
git.gsi.de/p.niedermayer/exciter

GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

18

Acknowledgements

Thank you!
COSY Control RoomSpecial thanks toTeam of the COSY accelerator in Jülich
HADES LGAD group
Beam instrumentation department at GSI
GSI Helmholtzzentrum für SchwerionenforschungPhilipp Niedermayer

IBIC 2023, 13 September 2023

19