An Easy Technique for Focus Characterization and Optimization of XUV and Soft X-ray Pulses

Round 1

Reviewer 1 Report

The manuscript “An easy technique for focus characterization and optimization of XUV and soft x-ray pulses” by Muschet et al. reports on the characterization and optimization of the focus of light beams in the XUV and soft x-ray spectral regions by using a common CMOS camera.

Experiments in the XUV and soft x-ray regimes are very challenging and setups are cumbersome, so methods providing alternatives to the current state of the art and especially on optimizing the focus are more than welcomed.  This manuscript is well written, the experimental description and specifics are given in detail the results seem promising on the development of a smart alternative to the current methods used. Overall definitely merits publication after addressing some minor issues.

1. The introduction is well written and presents nicely the strong and week points of the current state of the art but dedicates only a few lines to the presented method. The authors could mention in a more direct manor the improvements of the method presented here with respect to the ones commonly used.
2. If I understood correctly by the given setup, the position where the CMOS intercepts and collects the focused beam is where the laser-matter interaction will take place. Usually, this place is quite packed with detectors and nozzles etc. Is there enough space to translate in and out of the beam path the CMOS and run the measurement? Because if it is not the case, and for instance they have to manually remove it etc. then this is a weakness of the method and needs to be mentioned.
3. The experimental setup sketched although in principle contains all necessary details, is not so nice. It would strengthen the readability of the manuscript if a better drawing is given.

Author Response

Thank you for the very helpful review.

Point 1: We extended the introduction to explain the improvements of our method in more detail. We added:

"With this method, the 2D fluence distribution of an XUV and soft x-ray focus is acquired within a single light pulse of the source. Hence, the characterization of an XUV and soft x-ray focus becomes almost as simple as for common laser beams and much easier than the traditional methods."

Point 2: The ion detector in our beamline is moveable without breaking the vacuum. We explain this now in more detail by adding:

"The ion microscope that is used in the focus for linear and nonlinear ionization measurements can be shifted out without breaking the vacuum to make space for the CMOS camera."

Point 3: We improved the figure of the setup

Reviewer 2 Report

Applied Sciences

Article

An easy technique for focus characterization and optimization of XUV and soft x-ray pulses

The authors described the measurement and optimization of the XUV focus of an ellipsoidal mirror by the use of a slightly modified low-budget CMOS camera, which is commonly used for NIR or Vis light measurements.

English is good, a literature survey is also fine.

The required number of figures were there.

Seems short and tedious work, well presented.

Figure 1. The experimental setup could have been in more detail and elaborated in the text as well.

This manuscript can be accepted for publication with minor mandatory changes.

Author Response

Thank you for the positive review.

Point 1: We improved the figure of the setup. It is now more scientific and more understandable.

Reviewer 3 Report

The authors describe single-shot focal spot characterization for three different spectral range in EUV.  The article is interesting and provides an alternative to the existing techniques. I recommend the publication of the article in it's current form.

Author Response

Thank you for the positive review.

Reviewer 4 Report

In this paper the authors described how a common complementary-metal-oxide semiconductor (CMOS) camera can be easily modified to observe extreme ultraviolet (XUV) and soft x-ray beams. It is demonstrated that the sensitivity of this camera is high enough to acquire single-shot images of an XUV focus. The presented technique is a simple and powerful tool to measure foci of XUV and x-ray beams in all types of sources including high-harmonics, synchrotrons, and free-electron lasers.

I think this paper is interesting and valuable contribution to the field. The article is well written and articulated. The paper can be accepted for publication in Applied Sciences without any further changes required from the authors.

Author Response

Thank you for the positive review.