The invention refers to a gas-monitor detector for quantitative detection of highly pulsed and very intense radiation in the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV). This detector is free from saturation effects and is mostly indestructible. The fundamental concept has proofed itself as an evolution view of gas detectors based on the secondary parts proof. The detector is ideally suited as an online monitor due to its high transparency since the radiation is not significantly diminished or otherwise affected.

The team of inventors

Fields of application

The gas-monitor detector could also serve as a standard monitor for the radiation power at the EUV lithography for production of semiconductor devices, in addition to its utilization in FELs.


The detector has originally been developed for the quantitative determination of high-intensity EUV radiation of the free-electron laser FLASH and has been used successfully for years. In the medium term, however, in the field of EUV lithography for manufacturing semiconductor devices, there is an urgent need for intense EUV radiation sources, which

  • emit highly pulsed radiation in every case or
  • may even be based on the free-electron laser principle (FEL).

Precise control of radiation doses and monitoring of the radiation power is inevitable for the industrial use of such highly intense sources of pulsed radiation in EUV lithography. The developed concept of the gas-monitor detector could be the basis for solving these metrological problems.


Moreover, this concept includes, through the precise measurement of the employed gas pressure, a defined adjustment of the dynamic range of the detector, which is particularly essential and new for its calibration with monochromatic synchrotron with low performance radiation.


The basic method of operation of the gas-monitor detector was initially shown during calibration measurements (PTB BESSYII) and measurements at the Tesla Test - Facility. Since 2005, a total of 4 gas-monitor detectors have been in permanent use in FLASH and provide performances with calibrated radiation measurement uncertainties of <10%. In addition, the detector has been continuously developed, so that radiation in X-rays can be detected quantitatively. Several round-robin tests at various radiation sources, such as the free electron laser in Japan and the USA and even in “classical laser technologies”, have established the detector as one of the (transfer) standards by now.