Enhancement of Gain Coefficient of Li-Like Ion 3d-4f Soft X-ray Laser Oscillation by a Single Resonator
, Noboru Hasegawa 2, Thanhhung Dinh 2, Masahiko Ishino 2, Takeshi Higashiguchi 3 and Masaharu Nishikino 2Round 1
Reviewer 1 Report
This manuscript reports the study of the enhancement of soft X-ray laser with 15.5nm Li-like Al 3d-4f transition in laser produced plasmas. The optimized time interval of pulse train is obtained, which as a good way to the enhancement of gain coefficient. In addition, a single resonator method is introduced for a high gain obtained. Those work gets some valuable research findings for obtaining a high gain soft X-ray laser in experiment, and I recommend publication after a minor revision.
Comments and revision suggestions:
1. Why the spectral line of 15.5nm Li-like Al 3d-4f transition is selected as the research for the soft X-ray laser? What are the other possible options of transition?
2. The author of the manuscript involves two organizations, but three institutions are listed.
3. Most of the references are relatively early, hoping to present some latest research progress.
4. The reference numbered 21 is mentioned in the text of the manuscript, but it is not in the reference.
Author Response
Responses to reviewer1 comments
Thank you very much for reviewing our paper. We greatly appreciated your valuable comments and suggestions. According to them, we have revised the paper, and herewith submit the revised version for your review. Our responses to the comments/suggestions are as follows:
1. Why the spectral line of 15.5nm Li-like Al 3d-4f transition is selected as the research for the soft X-ray laser? What are the other possible options of transition?
⇒ Around 10-20 nm wavelengths, some lasing actions have been observed so far. For example, Al XI 3d-5f (10.57 nm) and Al X 3d-5f (12.35 nm) shows the laser oscillations with very weak gain coefficient. In this study, we focus on the lasing transition of Al XI 3d-4f (Li-like ion, 15.47 nm) having higher gain coefficient. Much shorter wavelengths lasing action by using He-like and H-like ions are possible, but much larger pump laser is required.
2. The author of the manuscript involves two organizations, but three institutions are listed.
⇒Thank you very much. We revised it.
3. Most of the references are relatively early, hoping to present some latest research progress.
⇒The reason for no recent paper can be explained by that the different X-ray laser pumping scheme (Transient electron excitation scheme, TCE) has much shorter pulse width. To observe fast phenomena, recombination scheme X-ray laser with a pulse width of ~10 ns is not sufficient short, whereas the TCE scheme provides ~ps or sub ps pulse duration. Therefore, the major research became the TCE scheme X-ray laser. Thus, lately the paper on recombination X-ray laser was not published so often.
4.The reference numbered 21 is mentioned in the text of the manuscript, but it is not in the reference.
⇒ Reference 21 was the same as Ref.20. So, we removed Ref. 21 in the manuscript.
Reviewer 2 Report
This paper reports the authors' recent efforts to enhance the gain coefficient of a soft X-ray laser at 15.5 nm by double path amplification with a soft X-ray multilayer mirror. The system is constructed based on the so-called recombination plasma scheme for highly charged aluminum ions. The improvement of the gain coefficient was much lower than expected from the geometry due probably to insufficient alignment of the optical path of the reflected soft X-ray beam.
Though the actual gain coefficient is lower than expected, the reviewer judges that the contents of the paper should be worth publishing as a conference proceedings. However, the reviewer suggests some minor amendments including grammatical errors listed below.
lines 16, 57, 77: Is the word "pass" correct? The reviewer is not sure about the terminology, but isn't it a mistype of "path"?
line 26-27: Is the term "amplified stimulated emission" correct? The reviewer imagines that it might be "amplified spontaneous emission".
line 38: experience -> experiences
line 42: After this line, the reviewer suggests an addition of a sentence to explain the mechanism of the population inversion in more detail. For example, "The population of the lower excited states is more rapidly decayed by the enhanced spontaneous emission".
line 53-54: The authors gave two values (3.2 and 8.3) of gain coefficients. What is the difference between them?
line 72: Reference [21] does not exist.
Figures 3 and 5: The size of the characters for the axes are too small. It would be better if they are a little bit larger.
line 118: plot the intensity ratio of with ... -> plots the intensity ratio with ...
line 126: were -> was
line 134: increase soft X-ray ... -> increase the gain coefficient of soft X-ray ...
line 138: further enhancement ... -> for the further enhancement ...
Author Response
Thank you very much for reviewing our paper. We greatly appreciated your valuable comments and suggestions. According to them, we have revised the paper, and herewith submit the revised version for your review. Our responses to the comments/suggestions are as follows:
1. lines 16, 57, 77: Is the word "pass" correct? The reviewer is not sure about the terminology, but isn't it a mistype of "path"?
⇒ “pass” is commonly used in this field, so that we did not revise them in the manuscript.
2. line 26-27: Is the term "amplified stimulated emission" correct? The reviewer imagines that it might be "amplified spontaneous emission".
⇒ Thank you for the reviewer. That is right. “amplified spontaneous emission” is correct. We revised it, accordingly.
3. line 38: experience -> experiences
⇒ Thank you for the reviewer. We revised it, accordingly.
4. line 42: After this line, the reviewer suggests an addition of a sentence to explain the mechanism of the population inversion in more detail. For example, "The population of the lower excited states is more rapidly decayed by the enhanced spontaneous emission".
⇒ Thank you for the reviewer. We revised this sentence as follows:
Subsequently, the electrons captured into high Rydberg levels decay into the lower excited states through the ladder-like collisional de-excitation, while the population of the lower excited states suffers from fast radiative decay, terminating into the ground state. (resonance transition).
5. line 53-54: The authors gave two values (3.2 and 8.3) of gain coefficients. What is the difference between them?
⇒ The gain coefficient of 3.2 cm-1 was earlier value, and 8.3 cm-1 has been obtained recently. Thus, we remove the gain coefficient of earlier values, 3.2 cm-1 in the revised manuscript.
6. line 72: Reference [21] does not exist.
⇒ Thank you for the reviewer. We revised it.
7. Figures 3 and 5: The size of the characters for the axes are too small. It would be better if they are a little bit larger.
⇒ Thank you for the reviewer. We used larger fonts for horizontal and vertical axes.
8. line 118: plot the intensity ratio of with ... -> plots the intensity ratio with ...
⇒ We revised it.
9. line 126: were -> was
⇒ We revised it.
10. line 134: increase soft X-ray ... -> increase the gain coefficient of soft X-ray ...
⇒ Thank you very much. You’re right. We revised it accordingly.
11. line 138: further enhancement ... -> for the further enhancement ...
⇒ Thank you very much. You’re right. We revised it accordingly.
