Instrumentation for the upgrade to the JET core charge-exchange spectrometers

Area of Science:

• Fusion energy research
• Plasma physics
• Spectroscopy

Background:

• Charge-exchange spectroscopy on JET faces challenges due to the ITER-like wall, resulting in weaker spectral lines and increased contamination.
• Existing instrumentation struggles with reduced signal intensity and nuisance spectral lines.

Purpose of the Study:

• To upgrade the charge-exchange spectroscopy instrumentation on JET to overcome signal reduction and contamination issues.
• To enable simultaneous measurement of impurity and fuel-ion charge exchange spectra.

Main Methods:

• Implemented upgraded imaging spectrometers with dichroic beam splitters to enhance throughput.
• Utilized CCD cameras with fast frame transfer times and optical demagnification.
• Applied the Scheimpflug condition and telecentric design for optimal spectral focusing and imaging.

Main Results:

• Achieved improved light collection efficiency for charge-exchange spectroscopy.
• Enabled simultaneous measurement of both impurity and fuel-ion charge exchange spectra.
• Successfully integrated new instrumentation rapidly for in-vessel calibration.

Conclusions:

• The upgraded instrumentation significantly enhances the capability of charge-exchange spectroscopy on JET.
• This advancement is crucial for accurate plasma diagnostics in the presence of the ITER-like wall.
• The system's design facilitates rapid assembly and alignment using commercial components.