Author: IPPLM

In 2014, a new Laboratory (Laboratory of X-ray Diagnostics) was established at the Institute of Plasma Physics and Laser Microfusion (www.ifpilm.pl) addressing the needs of plasma fusion for new technologies development. Its main activity is related to the development of Gas Electron Multiplier(GEM) based detectors with an ultimate goal of their application in fusion. The GEM detectors were discovered at CERN and used for the first time for nuclear physics research (https://gdd.web.cern.ch/). Considering their unique capabilities, the IPPLM researchers in collaboration with University of Warsaw and the Warsaw University of Technology proposed their usage for the fusion plasma measurements. The main goal is the detection of soft X-ray radiation emitted from plasma produced in existing or future fusion devices, which delivers information about various important plasma parameters. The Laboratory is engaged in detectors design, development and testing of the final product, being equipped with modern diagnostic tools and necessary measurement equipment.

The Laboratory conducts development work on the structure and implementation of GEM detectors. Our main tasks are the design of the sensor structure, building prototype components, assembly of the detecting module and their further experimental and numerical studies towards the purpose of soft X-ray imaging of plasma structures and monitoring of plasma impurities (such as e.g. tungsten – material foreseen for the divertor material in ITER).

GEM technology is  relatively new but has been already proven as a robust one. The “engine” of the detector is a GEM foil, 50 μm thick Kapton foil, densely perforated, covered on both sides with a thin layer (5 μm) of copper. This foil becomes an effective amplifying element even in case a moderately high voltage is applied to its sides, hence reducing the probability of spontaneous discharges.

For the needs of research activities conducted within the Laboratory of X-ray Diagnostics, the IPPLM has been equipped with a modern clean room which includes professional equipment used exclusively for the preparation of detector components and their final assembly. In this room, all works connected with the assembly of detectors are performed. This ranges from the preparation of frames, gluing the window's foils, conducting all the intermediate stages of assembly works, up to the assembly of the final sensor. In addition, there is a fully equipped modern measurement laboratory where preliminary measurements and studies are conducted before the final decision is made on the constructed device as well as the conclusive tests before the detector is finally approved.

The advantages of the developed detectors allow the IPPLM researchers to apply them for plasma impurity monitoring at tokamak devices (WEST, JET, etc.), where the plasma contamination occurs due to the interaction of the plasma with the surrounding surfaces, i.e. with the materials of the first wall of the tokamak chamber. As impurities cause plasma energy losses due to an increase of radiation emission generated by partially ionised atoms such a task is extremely important for fusion devices. Therefore, an appropriate diagnostic tool is needed, which would be able not only to monitor the level of the generated impurities, but also to reconstruct their spatial distribution.

The IPPLM, together with the collaborators, contributes to the development of diagnostics on the WEST and JET tokamaks by the design, construction and installation of the GEM detectors for plasma monitoring. The detectors are currently working at the above mentioned two important research centers. The first diagnostics was built and installed in collaboration with the University of Warsaw and the Warsaw University of Technology at the JET tokamak (Culham, UK) in 2014. Another diagnostics aimed at preparation of the radiation tomography was built in collaboration with the Warsaw University of Technology. It has been under tests at the WEST device (Cadarache, France) since 2017. This research is still ongoing on the last detector, in the frame of soft X-ray tomography diagnostics, to be installed at the WEST device in the nearest future.

Thanks to the experience gained over the years in the development of diagnostics based on the GEM detectors, the IPPLM has become a part of important scientific programmes performed at JET and WEST tokamaks, ITER-oriented tokamaks, which means that the IPPLM contributes also to the development of the scientific programme for ITER.

Clean room. Image: IPPLM