| 研究実績の概要 |
Together with the UK collaborators, we finalized the design of the experiment to achieve the Project Goals, namely to perform time-resolved optical diagnostics of relativistic plasma singularities emitting bright coherent x-rays via the BISER mechanism. These include the following main diagnostics: a ~50-100 femtosecond, 2-3 micrometer resolution Kerr-Gated optical imaging and ~10 femtosecond, 2-3 micrometer resolution optical probe; a soft x-ray flat-field 3-channel spectrograph and a soft x-ray imaging spectrograph. Further, these include additional diagnostics such as electron spectrometer, transmitted beam profile and spectrum, etc.
Our experiment was initially planned to FY2020 with the Astra laser (CLF RAL, UK) but was postponed by one year to FY2021 due to the COVID-19 pandemic. We used this extra time to prepare more thoroughly for the experiment, including preliminary tests of diagnostics, online meetings, making realistic 3D experiment setup drawings, etc.
Some of the ideas for the Astra experiment's diagnostics were tested during another experiment held in Japan with the J-KAREN-P laser within the framework of the Root Project: Kiban (A) 19H00669. Adding time resolution to these diagnostics in the next Astra experiment, we will achieve the Project Goals.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
4: 遅れている
理由
According to the initial plan, the experiment was to be performed in the CLF RAL, UK with the Astra laser in May-October 2020 (3 parts: 4 weeks + 5 weeks + 3 weeks, 12 weeks total). However, due to the COVID-19 pandemic, the experiment was postponed by one year to June-October 2021 (2 parts: 7 weeks + 5 weeks, 12 weeks total, i.e. the same duration).
We used this extra time for better preparation for the experiment. In particular, we (together with the UK colleagues) held 5 formal full-scale experiment planning meetings (online) with the experimental scientists, laser scientists, target fab scientists, and engineers. Further, we held many smaller-scale meetings. We tested offline separate diagnostics and their parts (high-resolution optical imaging, high-resolution optical probe, 3-channel flat-field soft x-ray spectrograph), and made detailed 3D drawings of the experimental setup.
Within the framework of the Root Project, Kiban (A) 19H00669, we performed an experiment with the J-KAREN-P laser (Japan). During this experiment, we tested high-resolution optical diagnostics setups similar to the planned Astra experiment. The 2-3 um imaging without time resolution was tested, with a similar setup with 50-100 fs time resolution is planned in Astra (the standard refractive microscope objective will be replaced with an all-reflective one to minimize dispersion). The 2-3 um, 50 fs optical probe was tested, with a similar setup with <10 fs probe is planned in Astra.
Thus, although with the delay, we expect to get excellent experimental results and achieve the Goals.
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| 今後の研究の推進方策 |
The updated plan is to perform the experiment in the CLF RAL, UK with the Astra laser (CLF experiment number 19210005, "Time-resolved diagnostics of relativistic plasma singularities and BISER"), in two parts: 28 June - 13 August 2021 (7 weeks) and 30 August - 1 October 2021 (5 weeks). The total duration of 12 weeks will be enough to field and tune the complex diagnostics, including unique ones available with the Astra laser: the Kerr-Gated optical imaging and sub-10 fs optical probe.
These diagnostics will allow to detect and separate relativistic plasma singularities: the motion blur is c*10 fs = 3 um (here c is the speed of light) and the spatial resolution is also 2-3 um, which are smaller than the predicted separation between the singularities of 6-10 um. We will correlate these time-resolved high-resolution optical data with the BISER soft x-ray spectra and spectral images, and achieve the Project Goals.
Before the start of the experiment, we will have one more full-scale online experiment planning meeting at the end of May. Apart from this, we will hold tens of small-scale online meetings (typically 2-3 participants) on various particular experiment-related questions; these meetings are planned to be held ~twice per week.
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