The increased efficiency of the helium cryogenics system, achieved by installing a new helium liquefaction system, makes it possible to plan the construction and installation of a dedicated test bed for superconducting microwave cryomodules, independent of the main line of the PolFEL laser accelerator. Its construction will greatly facilitate and expand the possibility of carrying out research work in areas 8, 9 and 10, indicated in the application for funding and in the feasibility study of the project. This will be because these studies can be performed without interfering with the accelerator line, as a result of which their preparation time will be significantly shortened, and the effective research time - extended.

One of the main research tasks envisaged for the test bed utilises the International Test Cryomodule, owned by NCBJ and acquired in collaboration with the STFC Daresbury laboratory. Research conducted with it to date has focused on adapting the TESLA structure technology commonly used in superconducting accelerators to accelerate high-current electron beams with a high accelerating field gradient. This research, thanks to the construction of the test bed, will continue. It should be pointed out that the eventual development of the high-current acceleration technology opens the way for future expansion of the PolFEL accelerator to improve its performance (and increase the intensity of photon beams), but also allows planning to extend the use of the electron beam for research in the field of nuclear physics, foreseen for the second phase of the PolFEL project, with an experimental photoproduction station for radioisotopes important in medical diagnostics and therapy, such as 99Mo. In this way, the construction of the station will become one of the elements of the implementation of the priority research direction within the smart specialisation of the Mazowieckie Voivodeship (consistent with KIS No. 1): Solutions enabling diagnostics and internal isotope therapy in cancer and other civilisation diseases.

The development of a functioning solution based on the International Test Cryomodule also envisages its installation and testing in the main line of the PolFEL laser accelerator. In this way, the results of the research programme will allow the energy of the electron beam to be increased and thus broaden the spectral range of the radiation generated by PolFEL towards shorter wavelengths, contributing to increasing the research areas available with the device. The construction of the test bed will also contribute to facilitating the economic exploitation programme of the PolFEL by making it more flexible to test commercially available particle acceleration technology solutions. NCBJ has signed a cooperation agreement with one manufacturer providing, among other things, for paid testing of prototypes of its products. The test bed will allow these and other future similar commercial tasks to be performed without overburdening the basic infrastructure of the facility and limiting its primary research function.

The research agenda of the Polish Free Electron Laser has identified National Intelligent Specialisation No. 1 as the lead for the project: Healthy Society, particularly in the areas of Research and Development of Medicinal Products and Medical Technologies. One of the tools for the implementation of research in this direction is the IR research station envisaged for implementation as part of Phase 1 of the construction of PolFEL, directed towards research in biochemistry and biophysics. However, its applications are limited to the infrared spectral range. During the planning and implementation of Phase I, it was revealed that an equally interesting research programme in the field of bio-medical sciences could be carried out in the ultraviolet and THz spectral range available to the PolFEL laser. Its implementation, however, requires the construction of a separate research station dedicated to this range and meeting the technical requirements specific to it, which is not and has not been possible due to the budget and programme constraints of Phase 1. The proposed research station fills this gap. The biomedical research station will be equipped with the following measurement systems:

• THz imaging system for biomedical samples
• system for measuring the kinetics of biochemical reactions (Stopped-Flow/Pump-Probe system)

The system for imaging biomedical samples in THz radiation will be equipped with a Scanning Near-Field Optical Microscopy (SNOM). This type of device allows the diffraction limit found in optics to be broken. The electromagnetic wave frequency of 0.5 THz to 3 THz generated in the PolFEL facility corresponds to a wavelength of 600 µm to 100 µm. In typical optical microscopy, the diffraction limit of imaging is half the wavelength, i.e. in our case from 300 µm to 50 µm. Imaging details that are smaller than 50 µm would be impossible using a 3 THz wavelength. The size of most biological cells ranges from a few hundred nanometres to a few micrometres, so well below the imaging capabilities of an ordinary THz microscope. These limitations are not present in SNOM microscopes, where microprobes are used to read electromagnetic fields in the close vicinity of an object. The size of the microprobes varies from a few hundred nanometres to a few micrometres, so that the resolution of the scanned image is proportional to the size of the microprobe and the wavelength of the incident radiation. For THz frequencies, a resolution of a few to several micrometres is possible, allowing biological cells to be imaged.

THz imaging is an excellent tool for cancer diagnosis, as it allows not only the imaging, but also the identification of cancerous tissue surrounded by healthy tissue, due to the different water concentrations in the two tissues. The SNOM microscopy device, with the help of a THz laser beam generated at the PolFEL facility, will allow cancer cells in tissue to be imaged with greater resolution than before. The SNOM device will also assist in the development of techniques and methods that can be used to detect and track nanoparticles in biological cells. The method can be used to quantitatively map the local concentration of a carrier in biological cells.

The system for measuring the kinetics of biochemical reactions will consist of several sub-modules:

• Stopped-Flow system with detection system(s) to measure fluorescence when excited with a PolFEL beam from a VUV undulator, equipped with additional small auxiliary apparatus: pH-meter, thermostat, centrifuge, etc.
• a Pump-Probe spectroscopy system for measuring fluorescence fading, working with a PolFEL beam from a VUV undulator as an excitation beam for a biochemical sample
• an additional system of parametric amplifiers (OPA - Optical Parametric Amplifier) for an optical laser, cooperating with both above-mentioned systems allowing: preliminary calibration and measurements preparing for measurements with a PolFEL beam and for the excitation of a non-linear crystal in a pump-probe spectroscopy system with up-conversion.

Both systems will be equipped with appropriate laboratory/optical tables, spare and consumable parts (cuvettes, electrodes, plastics) and reagents for test experiments (proteins/peptides, ligands, etc.).

The stopped-flow method is a commonly used research technique to follow the progress of a (bio)chemical reaction occurring more than 1 ms after mixing the reactants. Most biochemical reactions are accompanied by a change in the state of the system parameters observable over a wide range of electromagnetic radiation (from UV through Vis to IR). However, the main limitation is the sensitivity of the measurement, which is a direct consequence of the low concentrations used in the predominantly aqueous solutions of bimolecular systems. For this reason, it is essential to use extremely powerful pulsed optical sources that will not destroy the sample, but allow efficient excitation of electron and/or oscillatory transitions. Due to the aforementioned dilution of the samples, their interaction with radiation is negligible. Synchronisation of the stopped-flow system with pulses from the FEL laser and pulses from the OPA amplifiers will allow both a wide range of sample excitation from the deep ultraviolet range (from about 170 nm from the VUV line of the PolFEL laser) and preservation of the high energy of the laser pulses.

The pump-probe spectroscopy system will be used to measure fluorescence decay times from a few picoseconds to a few microseconds. In this system, the sample will be excited either by a VUV pulse from the PolFEL laser (from about 170 nm onwards) as well as from one of the OPA parametric amplifiers. In the measurement range of a few picoseconds to a few nanoseconds, the fluorescence excited in the sample will be mixed in a non-linear crystal with a gating signal from a second parametric amplifier delayed relative to the excitation pulse by a delay line. The electromagnetic radiation thus mixed together will fall on the detector. This type of spectroscopic investigation is called up-conversion pump-probe spectroscopy, where detection is performed on a fluorescence signal mixed with a gating signal at the appropriate moment in time. In the measurement range of a few nanoseconds to a few microseconds, fluorescence is measured using Time Correlated Single Photon Counting (TCSPC), where the delay time is selected electronically on very fast detectors. The above system will allow fluorescence decay to be measured in the spectral range from the ultraviolet (from about 300 nm) to the near infrared (up to about 1500 nm for upconversion and up to about 800 nm for TCSPC).

Research topics of the system for measuring the kinetics of biochemical reactions, which will be enabled or enhanced by the creation of the above apparatus, include:

• protein and peptide aggregation processes underlying ageing and civilisation-related diseases, including Alzheimer's and Parkinson's disease, as well as type II diabetes;
• mechanisms of protein folding and protein/protein and protein/nucleic acid intermolecular interactions relevant to the search for therapies for genetic diseases such as cystic fibrosis and genetically determined cancers;
• protein/small molecule interactions for modelling mechanisms of drug action;
• interactions of physiological and toxic metal ions with proteins for understanding the molecular basis of civilisation diseases related to environmental contamination, such as allergies and cancer.

The construction of the biomedical research station as designed will also allow the PolFEL infrastructure to be used to conduct research on the structure and interaction of viruses, including< coronaviruses such as SARS-CoV-2 and its variants.

One of the identified directions of work could be the use of the phenomenon of soft (weak) ablation of biological or biochemical material occurring under the influence of an intense beam of non-ionising laser radiation on free electrons (such is the nature of the PolFEL radiation in the entire spectral range available to it), especially the THz beam, combined with the use of spectroscopic techniques, multidirectional measurement techniques (including - imaging techniques) and the pump-probe method to analyse the released aerosol. The use of metamaterials for the construction of terahertz biosensors is also a promising research direction developed worldwide in recent years. The common denominator of the aforementioned methods and research directions is a significant improvement, at least by an order of magnitude over other experimental methods, in the sensitivity of detection and analysis of biochemical material. This provides a potential opportunity to develop new rapid, in situ and sensitive methods for the detection of viral genetic material at the nanoscale.

To ensure the implementation of this research direction, the National Centre for Nuclear Research signed a Letter of Intent on cooperation with the Institute of High Pressure Physics of the Polish Academy of Sciences, which, within the CENTERA Project, is developing research competencies in the area of THz radiation, combining them with knowledge and manufacturing capabilities in the area of solid state physics and metamaterials. This opens up the possibility to carry out a full cycle of research, starting with basic research, through concept verification, construction and testing of successive versions of biosensors, up to the production of complete sets enabling, for example, the identification of virus material, ready for use in laboratory practice.

The construction of a clean laboratory will improve the efficiency of the use of the research infrastructure of the Polish Free Electron Laser, while contributing directly to some of the goals of the research agenda. The laboratory will have rooms of varying cleanliness classes, including - in a limited area - ISO Class 4 rooms, an ultra-pure water treatment plant and a range of auxiliary and measurement equipment. This design will allow for research in its area on electron source technology, in particular the fully superconducting electron gun, which is key to one of PolFEL's objectives - its continuous wave mode operation. Superconducting technology requires high cleanliness requirements and both elements of the laboratory: the ISO Class 4 clean room and access to ultra-pure water are absolutely essential in this respect. The research infrastructure implemented as part of Phase I did not provide for a clean laboratory for budgetary reasons. All activities, whether of a research and development or operational nature, which might require the opening of the vacuum-tight superconducting structure of the launcher, were foreseen to be performed externally, either by the manufacturer of the structures or by using the infrastructure of laboratories cooperating with the National Centre for Nuclear Research specialising in superconducting acceleration technologies, such as DESY in Hamburg or HZB in Berlin. It is obvious that such a solution, although allowing the launch of the PolFEL laser accelerator with superconducting launcher, significantly limited the possibility of conducting own research in this, so important area (research tasks 10 and 11 - indicated in the application for funding and in the project feasibility study).

In addition, in the event that any maintenance operations are required on the superconducting launcher, in particular the technologically required regular (with a frequency of approximately six months) replacement of the photocathode plug, the lack of in-house clean laboratories and the need to use external laboratories inevitably prolongs the time required to perform such operations and thus contributes to reducing the availability time of the PolFEL device. Thus, the construction of clean laboratories, by extending this time, will contribute to improving the implementation of the research agenda in all directions.

One of PolFEL's key research directions is the study of biochemical processes and their dynamics. For practical applications in this area, the ability to use the clean room and, in particular, the ability to access ultra-pure water is critical to the process of preparing biological samples for conducting research with them using the radiation emitted by the PolFEL laser. The cleanroom laboratory expands the range of biochemical and biomedical tests available at PolFEL by installing, independently of the ultra-pure water treatment station, also a specialised deioniser and washing-deionising machine.

Proper sample preparation of biological or biochemical material is a key element for success in this field. The possibility of using the resources of a clean laboratory will significantly facilitate this process, both in the case of the IR research station that is being implemented in Phase 1 and in the case of the biomedical research station, the construction of which is one of the components of the currently proposed Phase 1.1. In some cases, having a clean laboratory and, in particular, access to ultra-pure water, the purity of which degrades rapidly, if only through contact with the air or the walls of the container, will make it possible to carry out research that would not otherwise be possible.