Thomson scattering is an important technique for plasma diagnostics in nuclear fusion facilities such as tokamaks and stellarators. It is used to measure both the electron temperature and density at many locations inside the plasma.
The measurement is conducted using a pulsed laser, typically a Ruby laser or Nd:YAG, that generate repeated pulses that are shone into the plasma. Some of the laser light (photons) is scattered of free electrons in the plasma resulting in spectral expansion due to the Doppler effect.
Avalanche photo diodes (APDs) detect the scattered photons and high-performance digitizers capture the resulting waveforms. The spectral expansion helps assess the plasma temperature whereas the number of scattered photons determine the plasma density.
Our Thomson scattering customers typically use ADQ14DC-4C in MTCA or PXIe form factor. It is a quad-channel, 14-bit, 1 GS/s digitizer with 700 MHz analog input bandwidth that provide an excellent match with commonly used detectors. It offers highly accurate backplane trigger and synchronization capabilities in order to support massive multi-channel data capture while keeping external cabling to a minimum.
Furthermore, it hosts 2 Gbyte on-board data memory capable of storing very long pulses and supports a native data transfer rate of 3.2 Gbyte/s which can be extended even more through optional firmware upgrades. The customer can also gain access to the on-board Xilinx Kintex 7 K325T FPGA if custom real-time processing is required. The optional firmware and development kits can be purchased separately at any time and upgrades can be done in place without any need for system disassembly or significant downtime.
"The combination of 14 bits dynamic range and 1 GS/s sampling rate is taking the performance of digitizers for TS system to an unprecedented performance level compared to the normally used 10 or 12 bit ADC."
Associate Professor at Hong Kong University (HKU)
who has implemented a system supporting line scan rates of 10M lines/s
prof. Jakub Čížek, Department of Low Temperature Physics at Charles University, Prague
Associate Professor at Hong Kong University (HKU)
who has implemented a system supporting line scan rates of 10M lines/s
M. Sc. Grzegorz Nitecki, Faculty of Electronics, Military Academy of Technology, Warsaw, Poland
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