Teledyne SP Devices

Thomson Scattering

Overview

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.

What to consider when selecting a digitizer for Thomson scattering
  • Thomson scattering systems often consist of several hundred channels commissioned over several stages. It is therefore beneficial to use modular instruments to create a compact yet scalable solution that easily can be expanded over time to host more measurement channels.
  • High dynamic range is required to accurately measure pulse characteristics and determine plasma density
  • High analog bandwidth and sampling rate is required to match the performance of the detectors and to provide high spatial resolution
  • High board-level channel density helps keep the overall size down and total number of required boards reasonable
  • A flexible and accurate trigger input is crucial to ensure that it shares a common time reference with the laser
  • Synchronization capabilities is required for accurate multi-channel data capture and form factors such as MTCA and PXIe helps keep external cabling reasonable since triggers and clocks are distributed in the backplane
  • The on-board memory need to be sufficient to store the entire scattered waveform
  • Data throughput needs to be high enough so that waveforms from all channels can be transferred to a central processing unit in the time slot between consecutive triggers
  • An open on-board FPGA offers a future-proof solution where calculations can be performed in real-time to achieve data reduction and therefore lower the data throughput requirements
Commonly Used Products and Features

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.

Further Reading / Next Steps
  • For a quick overview of available ADQ14 models please watch the short 2-minute video here
  • For a list of key benefits and specifications please visit the ADQ14 product page here
  • For information about the optional firmware packages and development kit see here
  • "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."


  • Thomson Scattering
    Click to show more images
  • Thomson Scattering
    Click to show more images
  • Thomson Scattering
    Click to show more images





RELATED PRODUCTS

HARDWARE
  • ADQ14
    • Single/dual channel
    • Up to 2 GSPS sampling rate
    • Up to 1.2 GHz input bandwidth
    • DC-coupled

    Learn More

"The technical and intellectual support from the team at Teledyne SP Devices has been playing an important role in our research."

Associate Professor at Hong Kong University (HKU)
who has implemented a system supporting line scan rates of 10M lines/s

  • CONNECT WITH US
Send us an email, call our headquarters or check our Contact page to find your local sales representative.
Email Us 
  • NEWS FROM US
Sign up for our newsletter and stay up-to-date on new products and updates.
Sign Up For Newsletter 
ISO logo

We use cookies on our website. Some of them are essential for the operation of the site, while others help us to improve this site and the user experience (tracking cookies). You can decide for yourself whether you want to allow cookies or not. Please note that if you reject them, you may not be able to use all the functionalities of the site.

Ok