{"id":21,"date":"2026-08-05T19:16:22","date_gmt":"2026-08-05T19:16:22","guid":{"rendered":"https:\/\/fplab.ek.hun-ren.hu\/index.php\/references\/extruders-punchers\/"},"modified":"2026-09-03T11:35:57","modified_gmt":"2026-09-03T11:35:57","slug":"extruders-punchers","status":"publish","type":"reference","link":"https:\/\/fplab.ek.hun-ren.hu\/index.php\/references\/extruders-punchers\/","title":{"rendered":"Extruders & Punchers"},"content":{"rendered":"\n

EXTRUDERS & PUNCHERS<\/h2>\n\n\n\n

Cryogenic pellet production technologies for fuelling and controlling the plasma in present and future fusion devices.<\/strong><\/h4>\n\n\n\n

Pellet injection is one of the key technologies for fuelling magnetically confined fusion plasmas.<\/strong> Instead of introducing hydrogen only as a gas, small pellets of frozen hydrogen isotopes can be accelerated directly into the plasma. This allows the fuel to penetrate deeper and makes pellet injection an attractive solution for the controlled fuelling of large fusion devices.<\/p>\n\n\n\n

At HUN-REN Centre for Energy Research, we develop several of the core technologies required for the complete pellet production chain. Our work covers cryogenic hydrogen extrusion, pellet cutting and punching, pellet handling and acceleration<\/strong>, with experimental systems developed and tested in-house. The aim is to create reliable technologies capable of producing well-defined pellets repeatedly and at the frequencies required by future fusion machines. This includes systems relevant to EU-DEMO, JT-60SA and other large fusion experiments.<\/strong><\/p>\n\n\n\n

Cryogenic extrusion<\/h3>\n\n\n\n

The first step is the production of a continuous or semi-continuous rod of solid hydrogen. Our laboratory has developed a batch-type cryogenic extruder<\/strong> capable of producing solid protium or deuterium rods for pellet production.<\/p>\n\n\n\n

The current system was designed specifically to support the development and testing of the EU-DEMO pellet puncher<\/strong>. It has a nominal solid-hydrogen capacity of more than 5,000 mm\u00b3<\/strong> and produces a 3.2 mm diameter ice rod<\/strong>, corresponding to the planned DEMO-relevant pellet geometry. The target operating point is compatible with pellet production at up to 15 Hz<\/strong>.<\/p>\n\n\n\n

The extruder is installed in our Large Flexible Cryostat<\/strong>, a dedicated experimental platform for cryogenic research. The system combines a two-stage cryocooler, hydrogen gas handling, vacuum technology, controlled heating and extensive diagnostics. During operation, temperatures at several locations, piston position, extrusion force, pressure and heating power can all be measured. These data are also used to improve numerical models of the extrusion process and to guide future design upgrades.<\/p>\n\n\n\n

Experimental campaigns have already demonstrated the successful extrusion of 3.2 mm diameter solid deuterium<\/strong> using both straight and curved nozzle configurations. The modular construction of the system makes it possible to investigate different nozzle geometries, extrusion parameters and cooling configurations.<\/p>\n\n\n\n

Pellet cutting and puncher development<\/h3>\n\n\n\n

Once the hydrogen rod is produced, it must be divided into accurately sized pellets. This sounds simple, but the process becomes challenging when pellets must be produced repeatedly at high frequency without disturbing the continuous movement of the ice rod.<\/p>\n\n\n\n

Our group develops different electromechanical pellet cutter and puncher concepts<\/strong> for batch and continuous extrusion systems. For step-wise ice feeding, a single-action cutter can be used, while continuously moving hydrogen rods require mechanisms that obstruct the extrusion path for only a very short period of time.<\/p>\n\n\n\n

One of our current developments is a pellet puncher for EU-DEMO<\/strong>, developed in collaboration with KIT. Its integration with the HUN-REN batch extruder provides a dedicated experimental environment for studying the complete pellet production process under realistic cryogenic conditions.<\/p>\n\n\n\n

From ice production to pellet injection<\/h3>\n\n\n\n

Our research is not limited to individual components. The long-term objective is to develop and validate the complete chain from hydrogen ice formation through extrusion and pellet cutting to acceleration and injection<\/strong>.<\/p>\n\n\n\n

In addition to the extruder and puncher systems, the laboratory is developing compact centrifugal acceleration technology. The TATOP table-top accelerator, for example, uses an acceleration arm with a radius of only 10 cm and can reach pellet velocities of up to approximately 450 m\/s<\/strong>. Together, these developments provide a flexible platform for studying future pellet injection technologies at laboratory scale.<\/p>\n\n\n\n

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TATOP rendered picture 2026<\/figcaption><\/figure>\n\n\n\n

Key capabilities<\/h3>\n\n\n\n