Development of cylindrical resonator for millimeter-wave band ESR/NMR double magnetic resonance

Development of cylindrical resonator for millimeter-wave band ESR/NMR double magnetic resonance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Development of cylindrical resonator for millimeter-wave band ESR/NMR double magnetic resonance Yuya Ishikawa, Kenta Ohya, Kohei Hirozawa, Jarno Järvinen, Sergey Vasiliev, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7625537/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Oct, 2025 Read the published version in Applied Magnetic Resonance → Version 1 posted 9 You are reading this latest preprint version Abstract We have developed a magnetic resonance equipment for very low temperature and high magnetic field aiming at Dynamic Nuclear Polarization-Nuclear Magnetic Resonance (DNP-NMR) and Electron-Nuclear DOuble Resonance (ENDOR) of diluted spin system using with Electron Spin Resonance (ESR). In this study, we have developed a cylindrical resonator with a submicron-thick gold film for millimeter-wave band ESR/NMR double magnetic resonance by exploiting frequency dependence of skin depth. ESR measurements were performed using the fabricated resonator at around 130 GHz and in the temperature range of 3 K to 70 K of BDPA diluted to 100 mM in polystyrene. ESR sensitivity is obtained from the measurement. 19 F-NMR signal from the sample holder is also successfully observed. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Nuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR) are widely known as methods for investigating basic magnetism in a substance from microscopic viewpoints. NMR measures response of nuclear magnetic moments which provides information such as the structure of organic compounds and dynamics of surrounding electron spins [ 1 , 2 ]. ESR technique can provide information on the environment of unpaired electrons which gives g value, as well as information on electron-electron or electron-nuclear spin interactions [ 3 – 5 ]. ESR and NMR are generally performed independently due to the difference in measurement targets. In recent years, with the progress of high-frequency light sources, the development of measurement methods that combine ESR and NMR has attracted much attention, especially in Dynamic Nuclear Polarization (DNP)-NMR measurement methods [ 6 – 9 ]. It has been reported that the sensitivity of NMR measurement is improved due to the DNP effect caused by irradiation of the millimeter wave of ESR frequency on the substance with hyperfine structure which is the interaction between electron and nucleus [ 10 – 14 ]. This method can improve NMR sensitivity especially for systems with dilute or small magnetization of nuclear spins. However, in order to perform this measurement, the ESR frequency needs to be known in advance. Most of DNP-NMR measurement system which have been developed so far have been designed to maximize NMR sensitivity without capability of ESR measurements. It is generally known that the NMR sensitivity largely depends on the filling factor of the sample in the oscillating magnetic field created by the RF coil. In order to perform highly sensitive DNP-NMR measurement, it is necessary to bring the sample as close to the coil as possible without disturbing the millimeter wave mode for ESR. We have so far developed an ESR/NMR resonator in which a Helmholtz-type coil for NMR was installed in a Fabry-Pèrot-type resonator (FPR) for ESR, for planar samples [ 15 – 17 ]. This arrangement will be useful for electron-nuclear double resonance (ENDOR) measurements because of rather high sensitivity of ESR measurements. However, since the spatial arrangement of the Helmholtz type coil is limited in order to avoid disturbing the millimeter wave mode in the FPR, the filling factor of the sample for NMR cannot be high. Some years ago, two examples of ESR/NMR resonators using a cylindrical shape have been reported [ 18 , 19 ]. In this double-magnetic-resonance resonator, a solenoid coil with a strip of conductor for NMR serves also as a cylindrical resonator for ESR at about 140 GHz using the TE 011 electromagnetic wave mode. Weis and coworkers reported the measurement results of 13 C NMR signal and 2 H Mims-ENDOR enhanced by the DNP effect by this resonator. This resonator shape has advantages that the filling factor of the sample in the coil for NMR can be as high as that for a normal solenoid and that one resonator can provide multimode for ESR, while the Q factor (Quality factor) of the resonator for ESR is deteriorated because the millimeter wave leaks between the turns of the coil. This low Q value is acceptable for pulsed ESR/ENDOR methods like Mims-ENDOR, while it is disadvantageous for cw-ESR measurements and for efficient irradiation of incident microwave power for DNP. It is favorable if one can measure in situ cw-ESR with an ESR/NMR dual resonator in order for precise tuning of ESR frequency for DNP measurement. In this study, in order to improve the sensitivity of DNP-NMR, we have developed a cylindrical resonator using a thin film made of gold (Au) that takes use of the different skin depths of ESR and NMR frequencies. By making an Au thin film with a thickness that reflects millimeter waves and transmits radio-frequency (RF) waves inside the resonator made of insulator resin, we can stop leaking of millimeter wave. This idea of utilizing gold layer for realizing a resonator for ESR/NMR double magnetic resonance was already used for a FPR [ 16 , 17 , 20 ]. Here, we report the development of a cylindrical type resonator for the ESR/NMR double magnetic resonance and the results of NMR and ESR measurements. 2. Principle and experimental 2.1 Relation between shape of cylindrical resonator and resonance frequency The design of the resonator needs to fully consider the magnetic field and electric field patterns of various electromagnetic modes, that is, the H and E fields in the cavity and the current distribution I in the cavity wall. If patterns are carefully considered, unnecessary modes can be suppressed and desired modes can be excited. Further, it is possible to effectively position the sample insertion position and to appropriately set the sample insertion hole into the cavity and the electromagnetic wave insertion hole (iris). The resonance condition equation for the cylindrical resonator is given by the following equation [ 3 ], $$\:{\left(Df\right)}^{2}=\:{\left(\frac{c{X}_{l,m}}{\pi\:}\right)}^{2}+{\left(\frac{nc}{2}\right)}^{2}{\left(\frac{D}{L}\right)}^{2}\:\:\:\:\:\:\:\:\left(1\right)$$ where f is the resonance frequency, c is the speed of light, and D and L are the diameter and the length of the cylinder, respectively. l , m , and n are integers representing the electromagnetic wave mode TE lmn , and \(\:{X}_{l,m}\) is m -th root of the l -th order Bessel function J m ’ . For TE 0 mn modes of a cylindrical resonator, the quality factor Q representing the sharpness of resonance has a broad maximum as a function of D / L ratio around D / L = 1. 2.2 Cylindrical ESR/NMR dual magnetic resonance resonator using Au thin film In this subsection, the resonator for double magnetic resonance developed in this research is explained (Fig. 1 (a)). This resonator uses TE 015 mode, and the oscillating magnetic field distribution becomes maximum at the center of the cylinder axis (Fig. 1 (b)). Plungers at both ends of the resonator can change the length L of the cylindrical cavity, by which the resonance frequency can be adjusted. The base material of the cylindrical resonator is polyether ether ketone (PEEK), which is a highly insulating resin material, and oxygen-free copper is used for the coupling with the waveguide. The NMR coil is wound along the outside of the PEEK material. The Au thin film was sputtered to the inner wall of the resonance part using a coater (SC-701Mk II Advance, Sanyu Electron Co., Ltd). The deposited film thickness is estimated to be 0.47 µm from the sputtering time. This thickness was selected to be an intermediate value between the skin depths for ESR millimeter-wave (~ 100 GHz) and NMR RF wave (~ 100 MHz) in order that the film reflects the millimeter wave and transmits the RF. 2.3 ESR/NMR system Here we describe the cryogenic ESR/NMR measurement system which is used for measurements in the following section. Figure 2 shows the ESR/NMR measurement system used in this study. A Millimeter Vector Network Analyzer (MVNA) (Model MVNA8-350-2, manufactured by ABmillimetre) was used both as a light source and as a detection system. The magnetic field was generated by a 9-T superconducting magnet (9-T SCM, Oxford Instruments) with the magnetic field homogeneity of 10 − 5 /10 mm DSV. The sample was cooled with a variable temperature insert (VTI, Oxford Instruments). The usable temperature range of VTI is 1.5–200 K. A Cernox resistance thermometer of CX series (Lake Shore Cryotronics, Inc.) is installed just above the resonator to measure the temperature of the sample. We have performed cw-ESR by measuring reflected power from the resonator while sweeping the magnetic field. We used a conventional pulsed NMR measurement system which is almost identical to that described elsewhere [ 21 ] except that the resonance circuit was not be installed in the cryogenic part. Alternatively, we utilized a top tuning system in which the capacitance of a variable capacitor and the length of coaxial cable connected to the coil on the resonator were adjusted at outside of the cryostat. 3. Results and discussion 3.1 Manufacture and resonance characteristics of a cylindrical resonator As shown in Eq. (1), the resonance frequency of the cylindrical resonator strongly depends on the diameter D and the length L of the cavity. Furthermore, in a high frequency range above 100 GHz, high processing accuracy is required because the wavelength becomes short. The base material of the resonator needs to be an insulating material. In this study, PEEK resin, which has higher strength and heat resistance than STYCAST1266, was used. The developed cylindrical resonator uses the TE 015 mode and is designed with a resonance frequency of 128 GHz and a cylinder inner diameter D of φ 6.5 mm. In order to prevent mixing of unwanted resonance modes, the resonator body was sliced into a few parts and the plunger diameter was made to be φ 6.2 mm which is a little smaller than D . This increases electrical resistance between the parts and suppresses the TM mode in which current flows in the longitudinal direction of the cylinder [ 3 ]. The resonance characteristics of this cylindrical resonator were measured at room temperature with MVNA. The measurement method is identical to that described in our previous work [ 16 ]. As shown in Fig. 3(a), a resonance mode was observed at a frequency of 127.51 GHz, and the Q value of this mode was estimated to be about 6500. The waves of the background are attributed to standing waves in a waveguide used to connect between MVNA and the resonator. Moreover, it was confirmed that the resonance frequency can be adjusted by moving the plungers as shown in Fig. 3(b). As expected, the resonance frequency increased as the distance between the plungers which equals L was decreased. The reason why the change in resonant frequency is not proportional to the change in L is probably due to the rattling of the screw that fixes the plunger. Such processing accuracy also affects Q value because the accuracy of parallelism between the plunger surfaces is important for TE 01 n modes. 3.2 ESR measurement In order to evaluate the developed resonator, ESR measurement of BDPA radical (α,γ-bisdiphenylene-β-phenylallyl) diluted to 100 mM in polystyrene was performed. The BDPA radical is a stable organic radical molecule and its crystal is known to have a sharp ESR line [ 22 , 23 ]. BDPA is also utilized as a donor electron spin for causing ESR in DNP-NMR measurement [ 24 ]. Therefore, BDPA is suitable for evaluation in this study. Since this sample has one radical per molecule and the spin number can be adjusted by the dilution concentration, it can be used as a sample for a sensitivity evaluation. Figures 4 , 5 and 6 show the temperature dependences of the ESR spectrum, integrated intensity of the ESR line, and the resonance frequency of the resonator. In each temperature, the ESR measurement frequency was adjusted to the resonant frequency of the resonator. Note that each measurement error in Figs. 5 and 6 is within the marker. Figure 5. Temperature dependence of integrated intensity of ESR line. In the vicinity of 130.85 GHz, one ESR line was observed over the entire temperature range from 5 to 70 K. Note that the ESR spectrum at each temperature was averaged over 5 sweeps. For the ESR spectrum at 5 K, the half width at half maximum was obtained to be 2 mT (= 20 G), and the signal to noise ratio (S/N ratio) was 6. No anomalies associated with the magnetic phase transition were observed in the temperature dependence of the integrated intensity, suggesting that it is paramagnetic in this temperature region. Regarding the temperature dependence of the resonance frequency, it was found that the resonance frequency increased as the temperature decreased. This is due to the contraction of the resonator. Next, the ESR measurement sensitivity of the resonator developed in this research is estimated. The measurement sensitivity of ESR can be expressed by the number of spins observable per Gauss. Considering that the sample used in this experiment was 34.66 mg and the density of diluted polystyrene was 1.05×10 3 g/L, the number of spins contained in the sample was 2.0×10 18 spins. The measurement sensitivity at about 5 K was calculated by (the number of spins)/((half-width)×(S/N ratio)), and was obtained to be 2 ×10 16 spins/G. 3.4 19 F-NMR measurement NMR measurement has been performed at 7 K using the developed cylindrical resonator with exactly the same sample as is used in ESR measurements. Measurement was performed with 117.55 MHz under the magnetic field 2.79 T, targeting 19 F contained in a sample holder tube made of Teflon in order to prove that we can detect NMR signal of the sample inside of the resonator. Fourier transform (FT) spectrum of obtained 19 F-NMR spin-echo signal is shown in Fig. 7 . Here, the pulse width was 5 µs and the signal was averaged for 8 times. The practicality of the cylindrical resonator on NMR measurement in the very-low temperature region was confirmed. It is noteworthy that the sensitivity of NMR is possibly improved if the thickness of the Au film can be reduced without losing ESR sensitivity. The optimization of the film thickness is a future problem. 4. Summary In this research, we have developed a cylindrical resonator for double magnetic resonance of ESR/NMR with the aim of increasing the sensitivity of DNP-NMR in the high frequency and very-low temperature regions. The resonator was made of PEEK with a submicron-thick gold film on the inner wall. This film thickness is such that the millimeter wave for ESR is reflected inside the resonator and the NMR RF wave generated by the coil wound outside the resonator is transmitted across the film due to the frequency dependence of the skin depth. The Q value representing the sharpness of resonance was estimated to be 6500 at 127.5 GHz for a designed mode TE 015 . The frequency was variable at least in a range of 127.5–131.2 GHz at room temperature by moving the plungers at both ends of the resonator. As an evaluation in ESR, BDPA radical diluted in polystyrene at a concentration of 100 mM, was measured in the temperature range of 5 to 70 K and in the vicinity of 130.85 GHz. ESR measurement sensitivity was estimated to be 1.8×10 16 spins/G. As an evaluation in NMR, NMR signal of 19 F contained in a Teflon sample holder tube put in the resonator was observed at 7 K and 117.55 MHz. These results show that both ESR and NMR signals were successfully obtained at very low temperatures by using the cylindrical resonator made of submicron-thick gold film. From this result, the developed cylindrical resonator can be used for ESR/NMR dual magnetic resonance in high frequency and very-low temperature region with keeping acceptable sensitivities both for cw-ESR and for pulsed NMR. Better sensitivity will be possibly obtained by optimizing the thickness of the gold film and improving the processing accuracy. Declarations Author Contribution Yuya Ishikawa wrote the main manuscript text and prepared all of the figures and did all of these experiments.Yutaka Fujii gave us his foundation and did the experiment with Yuya Ishikawa.Kenta Ohya designed and fabricated the cavity and did the basic experiments.Kohei Hirosawa did the NMR measurements and measured resonant property.Jarno Järvinen and Sergey Vasiliev gave us the comments and support data for development of this cavity. They contributed to the succeeding the development. Acknowledgement One of the authors (Y. I.) would like to thank to Mr. Hidetomo Yamamori and everyone at the Advanced Development Center, University of Fukui, Dr. Takashi Furuya at Research Center for Development of Far-Infrared Region, University of Fukui, and Prof. Akira Fukuda at Hyogo College of Medicine for their technical support and useful discussions in carrying out this research. References C. P. Slichter: Principles of Magnetic Resonance 3rd edn. (Springer-Verlag NewYork, 1990). A. Abragam: The Principles of Nuclear Magnetism, (Clarendon Press, Oxford, 1961). C. P. Poole Jr.: Electron Spin Resonance 2nd edn. (Dover publishing 1997). A. Abragam and B. Bleaney: Electron Paramagnetic Resonance of Transition Ions, (Dover Publications, 1986). R.S. Alger: Electron Paramagnetic resonance: Techniques and Applications, 2nd edn. (John Wiley & Sons Inc., New Jersey, 1968). A. W. Overhauser: Phys. Rev. 92, 411, (1953). T. R. Carver and C. P. Slichter: Phys. Rev. 102, 4, (1956). T. Maly et al .: J. Chem. Phys. 128, 052211, (2008). Y. Matsuki et al .: J. Infrared. Milli. Terahz Waves. 33, 745–755, (2012). L. R. Becerra et al .: Phys. Rev. Lett. 71, 21, (1993). V. Vizthum et al .: J. Magn. Reson. 205, pp.177–179, (2010). Y. Fujii et al .: J. Phys. Conf. Ser. 568, 042005, (2014). J. Järvinen et al .: Phys. Rev. B. 90, 214401 (2014). J. Järvinen et al .: Phys. Rev. B. 92, 121202 (2015). Y. Ishikawa et al .: J. Infrared. Milli. Terahz Waves. 39, pp.288–301, (2018). Y. Ishikawa et al .: J. Infrared. Milli. Terahz Waves. 39, pp.387–398, (2018). Y. Fujii et al .: Appl. Magn. Reson . 49, 783, (2018). V. Weis et al .: J. Magn. Reson. 140, pp.293–299 (1999). A. A. Smith et al .: J. Magn. Reson. 223, pp.170–179 (2012). Y. Ishikawa et al .: Appl. Magn. Reson . 52, 317, (2021). Y. Ishikawa et al .: Appl. Magn. Reson . 52, 305, (2021). L. R. Becerra et al .: J. Magn. Reson. Ser. A , 117, pp.28–40, (1995). C. Caspers et al .: APL. Photonics ., 1, 026101 (2015). V. Weis and R. G. Griffin: Solid State Nuclear Magn. Reson. 29, 66–78 (2006). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 25 Oct, 2025 Read the published version in Applied Magnetic Resonance → Version 1 posted Editorial decision: Revision requested 26 Sep, 2025 Reviews received at journal 25 Sep, 2025 Reviews received at journal 23 Sep, 2025 Reviewers agreed at journal 19 Sep, 2025 Reviewers agreed at journal 18 Sep, 2025 Reviewers invited by journal 17 Sep, 2025 Editor assigned by journal 17 Sep, 2025 Submission checks completed at journal 16 Sep, 2025 First submitted to journal 15 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7625537","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":520995132,"identity":"fda7b947-038b-4b5a-b7f4-e88fb9d3e341","order_by":0,"name":"Yuya Ishikawa","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABEElEQVRIie3QsUoDMRjA8S8cxCX01txiXyFHZ+ur5DhwEnFyKnJSyFTaNUUfolLonFDIlOoD3KDgC5xLx9ZcoKKld9VNJP/lPnL3I8kBhEJ/MAwEdOGGOPIPiN0CqHpCxRGSiMx/khTHCDji3zHD4ZO01olXWsvBstszkaiQAMqsTRUM+hDdH94G0yuuZ2aZLgwaSk9WI6bA5IAeVAMhTL/iEi1e7oaAxPaWPRNHsAIk+WESW0c25flcoJq4XTzZtBC4ZPpRlNkM70h9MCRaCHVkOt7m0t0F+BPQxJprlY1z0nSX7sT23kfri7OJOHmD6gZox+bzqlr3T9OGP/Y9/mUgqfyB2DsA/TUJhUKh/9kHPhxiRbOR2QoAAAAASUVORK5CYII=","orcid":"","institution":"University of Fukui","correspondingAuthor":true,"prefix":"","firstName":"Yuya","middleName":"","lastName":"Ishikawa","suffix":""},{"id":520995133,"identity":"3bfbe532-3f5b-4542-8727-00a6176bbc61","order_by":1,"name":"Kenta Ohya","email":"","orcid":"","institution":"University of Fukui","correspondingAuthor":false,"prefix":"","firstName":"Kenta","middleName":"","lastName":"Ohya","suffix":""},{"id":520995134,"identity":"d184f4e4-6bf3-42e3-a8fa-2cf9e83f6cfa","order_by":2,"name":"Kohei Hirozawa","email":"","orcid":"","institution":"University of Fukui","correspondingAuthor":false,"prefix":"","firstName":"Kohei","middleName":"","lastName":"Hirozawa","suffix":""},{"id":520995135,"identity":"af64f4c1-e372-4ac2-9806-2399dea292a7","order_by":3,"name":"Jarno Järvinen","email":"","orcid":"","institution":"University of Turku","correspondingAuthor":false,"prefix":"","firstName":"Jarno","middleName":"","lastName":"Järvinen","suffix":""},{"id":520995136,"identity":"7085c292-ece1-49a5-9315-d971ba150d45","order_by":4,"name":"Sergey Vasiliev","email":"","orcid":"","institution":"University of Turku","correspondingAuthor":false,"prefix":"","firstName":"Sergey","middleName":"","lastName":"Vasiliev","suffix":""},{"id":520995137,"identity":"446b3718-0725-459f-863c-95fc2466bebf","order_by":5,"name":"Yutaka Fujii","email":"","orcid":"","institution":"University of Fukui","correspondingAuthor":false,"prefix":"","firstName":"Yutaka","middleName":"","lastName":"Fujii","suffix":""}],"badges":[],"createdAt":"2025-09-16 03:53:29","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7625537/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7625537/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00723-025-01814-8","type":"published","date":"2025-10-25T16:16:34+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":92538645,"identity":"3725c2f4-ff41-49fd-b363-f3845a887c2f","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5475469,"visible":true,"origin":"","legend":"","description":"","filename":"cylindricalv5.docx","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/aebbe3a0f5971b228df3d779.docx"},{"id":92539418,"identity":"1730ac56-c9b5-4f40-a643-e5b7b54dcc26","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":383434,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1a.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/f7ead36edd8e28540b7d8a4a.jpg"},{"id":92540235,"identity":"e222f275-3721-4259-9c62-93435356b088","added_by":"auto","created_at":"2025-09-30 18:30:36","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":150358,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1b.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/b4aa4716f8deda4c9e5ced49.jpg"},{"id":92538626,"identity":"a2351431-a293-4643-babc-b548cc78c658","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":40686,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2a.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/745ebdb7aecded719504468f.jpg"},{"id":92539668,"identity":"20bb8354-d47e-45fb-b3a0-ec29a4ac4ff6","added_by":"auto","created_at":"2025-09-30 18:22:36","extension":"jpg","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86603,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2b.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/06f90a6a300f9c8287d2254b.jpg"},{"id":92538634,"identity":"179575bb-1efa-4557-94d8-a9ba84fc9a67","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":160987,"visible":true,"origin":"","legend":"","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/219a6f3b0069c691f961fe18.jpg"},{"id":92540236,"identity":"a5a369f8-b0f1-4e69-bcac-0771c7987133","added_by":"auto","created_at":"2025-09-30 18:30:36","extension":"jpg","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":251119,"visible":true,"origin":"","legend":"","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/a86f5c58ea4d94094a72a73d.jpg"},{"id":92538630,"identity":"7cc277ca-aab3-44ce-8426-a700be3824b8","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":23953,"visible":true,"origin":"","legend":"","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/7a7085da54b5d7cd4f306090.jpg"},{"id":92539670,"identity":"78ad9e54-d5f0-47f6-8c26-9829f4c6d2a9","added_by":"auto","created_at":"2025-09-30 18:22:36","extension":"jpg","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":41402,"visible":true,"origin":"","legend":"","description":"","filename":"Fig6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/b4fe8907e9d3c5d80c3b4c7a.jpg"},{"id":92538637,"identity":"81ff8b91-12c9-4f14-85db-0d32d8e34881","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"json","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":7039,"visible":true,"origin":"","legend":"","description":"","filename":"f28daa4554fb48b191aeb5aee54024e8.json","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/fafd904d2a9b3b061648244c.json"},{"id":92539420,"identity":"af0214e9-44db-4161-94e6-6dc196d5010b","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"xml","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":51206,"visible":true,"origin":"","legend":"","description":"","filename":"f28daa4554fb48b191aeb5aee54024e81enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/75dba8dc5fddee80ae95b389.xml"},{"id":92538641,"identity":"0922640d-90d6-4d7b-9fb4-d113b7cfcfb8","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":383434,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1a.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/43640542b03de424fe6ff81c.jpg"},{"id":92539422,"identity":"4848a17b-3925-48e0-89c5-2569963c6b26","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":150358,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1b.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/016fbe2a907fc879fb3ffb6e.jpg"},{"id":92538656,"identity":"55ffd03b-7de3-4fea-89f6-8eb4baa9c34d","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"jpg","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":40686,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2a.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/6dd820ddc7d61f22478696d0.jpg"},{"id":92539425,"identity":"4ac0d9b9-a8c2-42f6-b422-f44e4cbc4773","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86603,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2b.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/872b553aaca60147c3ba7ced.jpg"},{"id":92539671,"identity":"987a2721-41a1-4420-9707-ab814d090510","added_by":"auto","created_at":"2025-09-30 18:22:36","extension":"jpg","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":160987,"visible":true,"origin":"","legend":"","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/4f1b2548e14fccbceaa8f3a8.jpg"},{"id":92538646,"identity":"7710bc6a-4d60-4eef-a30d-c7a1b9fdc6ad","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":251119,"visible":true,"origin":"","legend":"","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/b46b6db06d9b394373abe89e.jpg"},{"id":92538642,"identity":"3b0dfa94-c481-406b-84cc-a6b24da061d0","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":23953,"visible":true,"origin":"","legend":"","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/42364eabcb7a2b4cbee47b5e.jpg"},{"id":92538644,"identity":"96e95c9b-4e2b-4525-9f41-bc109a7f0b13","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":41402,"visible":true,"origin":"","legend":"","description":"","filename":"Fig6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/969418db2c5e404bc61b0e0e.jpg"},{"id":92539427,"identity":"67992c1a-64a1-4dc6-8a5e-267b25b75d5a","added_by":"auto","created_at":"2025-09-30 18:14:37","extension":"jpeg","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":136622,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/07beb109cdeadc30c4f41e37.jpeg"},{"id":92539421,"identity":"edafef37-97b6-45e4-86dd-3ce2c26356cc","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpeg","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":28523,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/78d90e2987aa50e1f5512597.jpeg"},{"id":92538633,"identity":"404ebf79-0af7-4de6-86d8-a689649dee46","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpeg","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":34117,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/246fa5e75f71edccd8a89fba.jpeg"},{"id":92538652,"identity":"201316c1-0f2b-4ce8-b642-2a50c4bcff15","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"jpeg","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":72881,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/94930481a1a6601ffaad6faf.jpeg"},{"id":92538650,"identity":"bc74e740-e8c9-48c5-a088-cfc425a89609","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"jpeg","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":15132,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/297dc08431a31db1239cf3f5.jpeg"},{"id":92538655,"identity":"4c7d8ac1-1815-42b7-b551-d135a2f16470","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105724,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig1a.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/7c67b6115f6db3807d43e13d.png"},{"id":92539430,"identity":"03d341d5-1375-4d4b-af27-752c45473f98","added_by":"auto","created_at":"2025-09-30 18:14:37","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":34157,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig1b.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/d791c45ec90c9a95858bb8a6.png"},{"id":92539673,"identity":"ed84bbe4-39b7-4968-9e0a-a368e9174451","added_by":"auto","created_at":"2025-09-30 18:22:37","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":32756,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig2a.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/aaef3f519a52c9b595526e5f.png"},{"id":92538648,"identity":"0efad7b4-eb00-4cf2-b434-d17dd7127751","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":28390,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig2b.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/2604d8fce2fb19dc5a33f58d.png"},{"id":92538661,"identity":"abb98ec9-b5a5-45bb-a334-d1ac38e6be8e","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":91387,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig3.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/1ff8491c840cf0b8a5ab274a.png"},{"id":92538647,"identity":"7a6c7090-5a0b-42b9-b021-66dd8cc57e84","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":28299,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig4.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/335f23ea8a461432a84719f6.png"},{"id":92539674,"identity":"98ed34dc-6515-47a1-829a-85a3201831bc","added_by":"auto","created_at":"2025-09-30 18:22:37","extension":"png","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":8108,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig5.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/a442e1385e318586f7bd1362.png"},{"id":92538649,"identity":"388cb8a5-3958-40ed-998e-d302f06dd140","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"png","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5743,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig6.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/f56589869c16594cb81a67c6.png"},{"id":92539426,"identity":"d192d7a3-1722-489a-bf4d-4493b0318263","added_by":"auto","created_at":"2025-09-30 18:14:37","extension":"png","order_by":32,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74800,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/9ae1e0520f339b38e16b62e8.png"},{"id":92539675,"identity":"fc1a8430-965d-4619-83dc-00e2c6c580c8","added_by":"auto","created_at":"2025-09-30 18:22:37","extension":"png","order_by":33,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11925,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/54cb6fc88668afd6fd22558f.png"},{"id":92539434,"identity":"47ffd246-1b26-48f3-bcc3-880613be03c7","added_by":"auto","created_at":"2025-09-30 18:14:37","extension":"png","order_by":34,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":8728,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/a518d7e3fe99a407371ad39a.png"},{"id":92539433,"identity":"660b2382-509a-4736-9e73-23e47540a425","added_by":"auto","created_at":"2025-09-30 18:14:37","extension":"png","order_by":35,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":17094,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/140fbd9cd07562670172c085.png"},{"id":92538651,"identity":"7951f0f8-fd57-4eb8-a64c-a899c569730a","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"png","order_by":36,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":13704,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/7d7f5376cb764a90f430a72a.png"},{"id":92538653,"identity":"447b4644-0c12-4fe8-ab72-0bd9a927ced8","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"xml","order_by":37,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":49510,"visible":true,"origin":"","legend":"","description":"","filename":"f28daa4554fb48b191aeb5aee54024e81structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/45165731672db4a648dc54b8.xml"},{"id":92538665,"identity":"147c1373-f537-4596-838a-5f9363c822f5","added_by":"auto","created_at":"2025-09-30 18:06:37","extension":"html","order_by":38,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":58967,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/6974bffc7693eeb6427cff6c.html"},{"id":92538621,"identity":"8dfc8dce-1cbd-4251-b5d9-f30075d0414d","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":215907,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/9703cd42ce3cb6592921dfe3.jpg"},{"id":92539413,"identity":"3afd241e-2471-4d5a-8f4e-ca277ce5edb1","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":307679,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/133789036c91f601a8bf537b.jpg"},{"id":92538623,"identity":"7c408a7c-e839-48be-bfff-907ac449a64b","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":340563,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/f2cb614293aae2274fc780b9.jpg"},{"id":92539414,"identity":"6a53e1c4-abf4-4366-85fa-60648903f453","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":76208,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/d291e3b36acb7c17577511cf.jpg"},{"id":92538624,"identity":"afdcec75-c786-443d-b389-c167b28adf9c","added_by":"auto","created_at":"2025-09-30 18:06:36","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":82499,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/2a6f017deb2691cba77857b1.jpg"},{"id":92539415,"identity":"dafec236-9893-4a39-9f46-bb5731008738","added_by":"auto","created_at":"2025-09-30 18:14:36","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":80695,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/74012963f7ace97557dbee80.jpg"},{"id":94490733,"identity":"a15a3751-0fb9-48a3-83b0-a6fccf055a53","added_by":"auto","created_at":"2025-10-27 17:14:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1644147,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7625537/v1/59c5d2b0-cec5-42e4-934d-deb1fd5dd408.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Development of cylindrical resonator for millimeter-wave band ESR/NMR double magnetic resonance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eNuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR) are widely known as methods for investigating basic magnetism in a substance from microscopic viewpoints. NMR measures response of nuclear magnetic moments which provides information such as the structure of organic compounds and dynamics of surrounding electron spins [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. ESR technique can provide information on the environment of unpaired electrons which gives g value, as well as information on electron-electron or electron-nuclear spin interactions [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. ESR and NMR are generally performed independently due to the difference in measurement targets. In recent years, with the progress of high-frequency light sources, the development of measurement methods that combine ESR and NMR has attracted much attention, especially in Dynamic Nuclear Polarization (DNP)-NMR measurement methods [\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It has been reported that the sensitivity of NMR measurement is improved due to the DNP effect caused by irradiation of the millimeter wave of ESR frequency on the substance with hyperfine structure which is the interaction between electron and nucleus [\u003cspan additionalcitationids=\"CR11 CR12 CR13\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. This method can improve NMR sensitivity especially for systems with dilute or small magnetization of nuclear spins. However, in order to perform this measurement, the ESR frequency needs to be known in advance. Most of DNP-NMR measurement system which have been developed so far have been designed to maximize NMR sensitivity without capability of ESR measurements.\u003c/p\u003e\u003cp\u003eIt is generally known that the NMR sensitivity largely depends on the filling factor of the sample in the oscillating magnetic field created by the RF coil. In order to perform highly sensitive DNP-NMR measurement, it is necessary to bring the sample as close to the coil as possible without disturbing the millimeter wave mode for ESR. We have so far developed an ESR/NMR resonator in which a Helmholtz-type coil for NMR was installed in a Fabry-P\u0026egrave;rot-type resonator (FPR) for ESR, for planar samples [\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This arrangement will be useful for electron-nuclear double resonance (ENDOR) measurements because of rather high sensitivity of ESR measurements. However, since the spatial arrangement of the Helmholtz type coil is limited in order to avoid disturbing the millimeter wave mode in the FPR, the filling factor of the sample for NMR cannot be high. Some years ago, two examples of ESR/NMR resonators using a cylindrical shape have been reported [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In this double-magnetic-resonance resonator, a solenoid coil with a strip of conductor for NMR serves also as a cylindrical resonator for ESR at about 140 GHz using the TE\u003csub\u003e011\u003c/sub\u003e electromagnetic wave mode. Weis and coworkers reported the measurement results of \u003csup\u003e13\u003c/sup\u003eC NMR signal and \u003csup\u003e2\u003c/sup\u003eH Mims-ENDOR enhanced by the DNP effect by this resonator. This resonator shape has advantages that the filling factor of the sample in the coil for NMR can be as high as that for a normal solenoid and that one resonator can provide multimode for ESR, while the \u003cem\u003eQ\u003c/em\u003e factor (Quality factor) of the resonator for ESR is deteriorated because the millimeter wave leaks between the turns of the coil. This low \u003cem\u003eQ\u003c/em\u003e value is acceptable for pulsed ESR/ENDOR methods like Mims-ENDOR, while it is disadvantageous for cw-ESR measurements and for efficient irradiation of incident microwave power for DNP. It is favorable if one can measure \u003cem\u003ein situ\u003c/em\u003e cw-ESR with an ESR/NMR dual resonator in order for precise tuning of ESR frequency for DNP measurement. In this study, in order to improve the sensitivity of DNP-NMR, we have developed a cylindrical resonator using a thin film made of gold (Au) that takes use of the different skin depths of ESR and NMR frequencies. By making an Au thin film with a thickness that reflects millimeter waves and transmits radio-frequency (RF) waves inside the resonator made of insulator resin, we can stop leaking of millimeter wave. This idea of utilizing gold layer for realizing a resonator for ESR/NMR double magnetic resonance was already used for a FPR [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Here, we report the development of a cylindrical type resonator for the ESR/NMR double magnetic resonance and the results of NMR and ESR measurements.\u003c/p\u003e"},{"header":"2. Principle and experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Relation between shape of cylindrical resonator and resonance frequency\u003c/h2\u003e\u003cp\u003eThe design of the resonator needs to fully consider the magnetic field and electric field patterns of various electromagnetic modes, that is, the \u003cem\u003eH\u003c/em\u003e and \u003cem\u003eE\u003c/em\u003e fields in the cavity and the current distribution \u003cem\u003eI\u003c/em\u003e in the cavity wall. If patterns are carefully considered, unnecessary modes can be suppressed and desired modes can be excited. Further, it is possible to effectively position the sample insertion position and to appropriately set the sample insertion hole into the cavity and the electromagnetic wave insertion hole (iris). The resonance condition equation for the cylindrical resonator is given by the following equation [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e],\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\left(Df\\right)}^{2}=\\:{\\left(\\frac{c{X}_{l,m}}{\\pi\\:}\\right)}^{2}+{\\left(\\frac{nc}{2}\\right)}^{2}{\\left(\\frac{D}{L}\\right)}^{2}\\:\\:\\:\\:\\:\\:\\:\\:\\left(1\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003ef\u003c/em\u003e is the resonance frequency, \u003cem\u003ec\u003c/em\u003e is the speed of light, and \u003cem\u003eD\u003c/em\u003e and \u003cem\u003eL\u003c/em\u003e are the diameter and the length of the cylinder, respectively. \u003cem\u003el\u003c/em\u003e, \u003cem\u003em\u003c/em\u003e, and \u003cem\u003en\u003c/em\u003e are integers representing the electromagnetic wave mode TE\u003csub\u003e\u003cem\u003elmn\u003c/em\u003e\u003c/sub\u003e, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{l,m}\\)\u003c/span\u003e\u003c/span\u003e is \u003cem\u003em\u003c/em\u003e-th root of the \u003cem\u003el\u003c/em\u003e-th order Bessel function \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u0026rsquo;\u003c/em\u003e. For TE\u003csub\u003e0\u003cem\u003emn\u003c/em\u003e\u003c/sub\u003e modes of a cylindrical resonator, the quality factor \u003cem\u003eQ\u003c/em\u003e representing the sharpness of resonance has a broad maximum as a function of \u003cem\u003eD\u003c/em\u003e/\u003cem\u003eL\u003c/em\u003e ratio around \u003cem\u003eD\u003c/em\u003e/\u003cem\u003eL\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Cylindrical ESR/NMR dual magnetic resonance resonator using Au thin film\u003c/h2\u003e\u003cp\u003eIn this subsection, the resonator for double magnetic resonance developed in this research is explained (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a)). This resonator uses TE\u003csub\u003e015\u003c/sub\u003e mode, and the oscillating magnetic field distribution becomes maximum at the center of the cylinder axis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b)). Plungers at both ends of the resonator can change the length \u003cem\u003eL\u003c/em\u003e of the cylindrical cavity, by which the resonance frequency can be adjusted. The base material of the cylindrical resonator is polyether ether ketone (PEEK), which is a highly insulating resin material, and oxygen-free copper is used for the coupling with the waveguide. The NMR coil is wound along the outside of the PEEK material. The Au thin film was sputtered to the inner wall of the resonance part using a coater (SC-701Mk II Advance, Sanyu Electron Co., Ltd). The deposited film thickness is estimated to be 0.47 \u0026micro;m from the sputtering time. This thickness was selected to be an intermediate value between the skin depths for ESR millimeter-wave (~\u0026thinsp;100 GHz) and NMR RF wave (~\u0026thinsp;100 MHz) in order that the film reflects the millimeter wave and transmits the RF.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 ESR/NMR system\u003c/h2\u003e\u003cp\u003eHere we describe the cryogenic ESR/NMR measurement system which is used for measurements in the following section. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the ESR/NMR measurement system used in this study. A Millimeter Vector Network Analyzer (MVNA) (Model MVNA8-350-2, manufactured by ABmillimetre) was used both as a light source and as a detection system. The magnetic field was generated by a 9-T superconducting magnet (9-T SCM, Oxford Instruments) with the magnetic field homogeneity of 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e/10 mm DSV. The sample was cooled with a variable temperature insert (VTI, Oxford Instruments). The usable temperature range of VTI is 1.5\u0026ndash;200 K. A Cernox resistance thermometer of CX series (Lake Shore Cryotronics, Inc.) is installed just above the resonator to measure the temperature of the sample. We have performed cw-ESR by measuring reflected power from the resonator while sweeping the magnetic field.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eWe used a conventional pulsed NMR measurement system which is almost identical to that described elsewhere [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] except that the resonance circuit was not be installed in the cryogenic part. Alternatively, we utilized a top tuning system in which the capacitance of a variable capacitor and the length of coaxial cable connected to the coil on the resonator were adjusted at outside of the cryostat.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Manufacture and resonance characteristics of a cylindrical resonator\u003c/h2\u003e\u003cp\u003eAs shown in Eq.\u0026nbsp;(1), the resonance frequency of the cylindrical resonator strongly depends on the diameter \u003cem\u003eD\u003c/em\u003e and the length \u003cem\u003eL\u003c/em\u003e of the cavity. Furthermore, in a high frequency range above 100 GHz, high processing accuracy is required because the wavelength becomes short. The base material of the resonator needs to be an insulating material. In this study, PEEK resin, which has higher strength and heat resistance than STYCAST1266, was used. The developed cylindrical resonator uses the TE\u003csub\u003e015\u003c/sub\u003e mode and is designed with a resonance frequency of 128 GHz and a cylinder inner diameter \u003cem\u003eD\u003c/em\u003e of \u003cem\u003eφ\u003c/em\u003e 6.5 mm. In order to prevent mixing of unwanted resonance modes, the resonator body was sliced into a few parts and the plunger diameter was made to be \u003cem\u003eφ\u003c/em\u003e 6.2 mm which is a little smaller than \u003cem\u003eD\u003c/em\u003e. This increases electrical resistance between the parts and suppresses the TM mode in which current flows in the longitudinal direction of the cylinder [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The resonance characteristics of this cylindrical resonator were measured at room temperature with MVNA. The measurement method is identical to that described in our previous work [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. As shown in Fig.\u0026nbsp;3(a), a resonance mode was observed at a frequency of 127.51 GHz, and the \u003cem\u003eQ\u003c/em\u003e value of this mode was estimated to be about 6500. The waves of the background are attributed to standing waves in a waveguide used to connect between MVNA and the resonator. Moreover, it was confirmed that the resonance frequency can be adjusted by moving the plungers as shown in Fig.\u0026nbsp;3(b). As expected, the resonance frequency increased as the distance between the plungers which equals \u003cem\u003eL\u003c/em\u003e was decreased. The reason why the change in resonant frequency is not proportional to the change in \u003cem\u003eL\u003c/em\u003e is probably due to the rattling of the screw that fixes the plunger. Such processing accuracy also affects \u003cem\u003eQ\u003c/em\u003e value because the accuracy of parallelism between the plunger surfaces is important for TE\u003csub\u003e01\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e modes.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2 ESR measurement\u003c/h2\u003e\u003cp\u003eIn order to evaluate the developed resonator, ESR measurement of BDPA radical (α,γ-bisdiphenylene-β-phenylallyl) diluted to 100 mM in polystyrene was performed. The BDPA radical is a stable organic radical molecule and its crystal is known to have a sharp ESR line [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. BDPA is also utilized as a donor electron spin for causing ESR in DNP-NMR measurement [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Therefore, BDPA is suitable for evaluation in this study. Since this sample has one radical per molecule and the spin number can be adjusted by the dilution concentration, it can be used as a sample for a sensitivity evaluation. Figures\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, 5 and 6 show the temperature dependences of the ESR spectrum, integrated intensity of the ESR line, and the resonance frequency of the resonator. In each temperature, the ESR measurement frequency was adjusted to the resonant frequency of the resonator. Note that each measurement error in Figs.\u0026nbsp;5 and 6 is within the marker.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;5. Temperature dependence of integrated intensity of ESR line.\u003c/p\u003e\u003cp\u003eIn the vicinity of 130.85 GHz, one ESR line was observed over the entire temperature range from 5 to 70 K. Note that the ESR spectrum at each temperature was averaged over 5 sweeps. For the ESR spectrum at 5 K, the half width at half maximum was obtained to be 2 mT (=\u0026thinsp;20 G), and the signal to noise ratio (S/N ratio) was 6. No anomalies associated with the magnetic phase transition were observed in the temperature dependence of the integrated intensity, suggesting that it is paramagnetic in this temperature region. Regarding the temperature dependence of the resonance frequency, it was found that the resonance frequency increased as the temperature decreased. This is due to the contraction of the resonator. Next, the ESR measurement sensitivity of the resonator developed in this research is estimated. The measurement sensitivity of ESR can be expressed by the number of spins observable per Gauss. Considering that the sample used in this experiment was 34.66 mg and the density of diluted polystyrene was 1.05\u0026times;10\u003csup\u003e3\u003c/sup\u003e g/L, the number of spins contained in the sample was 2.0\u0026times;10\u003csup\u003e18\u003c/sup\u003e spins. The measurement sensitivity at about 5 K was calculated by (the number of spins)/((half-width)\u0026times;(S/N ratio)), and was obtained to be 2 \u0026times;10\u003csup\u003e16\u003c/sup\u003e spins/G.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.4 \u003csup\u003e19\u003c/sup\u003eF-NMR measurement\u003c/h2\u003e\u003cp\u003eNMR measurement has been performed at 7 K using the developed cylindrical resonator with exactly the same sample as is used in ESR measurements. Measurement was performed with 117.55 MHz under the magnetic field 2.79 T, targeting \u003csup\u003e19\u003c/sup\u003eF contained in a sample holder tube made of Teflon in order to prove that we can detect NMR signal of the sample inside of the resonator. Fourier transform (FT) spectrum of obtained \u003csup\u003e19\u003c/sup\u003eF-NMR spin-echo signal is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Here, the pulse width was 5 \u0026micro;s and the signal was averaged for 8 times. The practicality of the cylindrical resonator on NMR measurement in the very-low temperature region was confirmed. It is noteworthy that the sensitivity of NMR is possibly improved if the thickness of the Au film can be reduced without losing ESR sensitivity. The optimization of the film thickness is a future problem.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Summary","content":"\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn this research, we have developed a cylindrical resonator for double magnetic resonance of ESR/NMR with the aim of increasing the sensitivity of DNP-NMR in the high frequency and very-low temperature regions. The resonator was made of PEEK with a submicron-thick gold film on the inner wall. This film thickness is such that the millimeter wave for ESR is reflected inside the resonator and the NMR RF wave generated by the coil wound outside the resonator is transmitted across the film due to the frequency dependence of the skin depth. The \u003cem\u003eQ\u003c/em\u003e value representing the sharpness of resonance was estimated to be 6500 at 127.5 GHz for a designed mode TE\u003csub\u003e015\u003c/sub\u003e. The frequency was variable at least in a range of 127.5\u0026ndash;131.2 GHz at room temperature by moving the plungers at both ends of the resonator. As an evaluation in ESR, BDPA radical diluted in polystyrene at a concentration of 100 mM, was measured in the temperature range of 5 to 70 K and in the vicinity of 130.85 GHz. ESR measurement sensitivity was estimated to be 1.8\u0026times;10\u003csup\u003e16\u003c/sup\u003e spins/G. As an evaluation in NMR, NMR signal of \u003csup\u003e19\u003c/sup\u003eF contained in a Teflon sample holder tube put in the resonator was observed at 7 K and 117.55 MHz. These results show that both ESR and NMR signals were successfully obtained at very low temperatures by using the cylindrical resonator made of submicron-thick gold film. From this result, the developed cylindrical resonator can be used for ESR/NMR dual magnetic resonance in high frequency and very-low temperature region with keeping acceptable sensitivities both for cw-ESR and for pulsed NMR. Better sensitivity will be possibly obtained by optimizing the thickness of the gold film and improving the processing accuracy.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYuya Ishikawa wrote the main manuscript text and prepared all of the figures and did all of these experiments.Yutaka Fujii gave us his foundation and did the experiment with Yuya Ishikawa.Kenta Ohya designed and fabricated the cavity and did the basic experiments.Kohei Hirosawa did the NMR measurements and measured resonant property.Jarno J\u0026auml;rvinen and Sergey Vasiliev gave us the comments and support data for development of this cavity. They contributed to the succeeding the development.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eOne of the authors (Y. I.) would like to thank to Mr. Hidetomo Yamamori and everyone at the Advanced Development Center, University of Fukui, Dr. Takashi Furuya at Research Center for Development of Far-Infrared Region, University of Fukui, and Prof. Akira Fukuda at Hyogo College of Medicine for their technical support and useful discussions in carrying out this research.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eC. P. Slichter: Principles of Magnetic Resonance 3rd edn. (Springer-Verlag NewYork, 1990).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eA. Abragam: The Principles of Nuclear Magnetism, (Clarendon Press, Oxford, 1961).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eC. P. Poole Jr.: Electron Spin Resonance 2nd edn. (Dover publishing 1997).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eA. Abragam and B. Bleaney: Electron Paramagnetic Resonance of Transition Ions, (Dover Publications, 1986).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eR.S. Alger: Electron Paramagnetic resonance: Techniques and Applications, 2nd edn. (John Wiley \u0026amp; Sons Inc., New Jersey, 1968).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eA. W. Overhauser: \u003cem\u003ePhys. Rev.\u003c/em\u003e 92, 411, (1953).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eT. R. Carver and C. P. Slichter: \u003cem\u003ePhys. Rev.\u003c/em\u003e 102, 4, (1956).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eT. Maly \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Chem. Phys.\u003c/em\u003e 128, 052211, (2008).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Matsuki \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Infrared. Milli. Terahz Waves.\u003c/em\u003e 33, 745\u0026ndash;755, (2012).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eL. R. Becerra \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003ePhys. Rev. Lett.\u003c/em\u003e 71, 21, (1993).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eV. Vizthum \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Magn. Reson.\u003c/em\u003e 205, pp.177\u0026ndash;179, (2010).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Fujii \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Phys. Conf. Ser.\u003c/em\u003e 568, 042005, (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJ. J\u0026auml;rvinen \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003ePhys. Rev. B.\u003c/em\u003e 90, 214401 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJ. J\u0026auml;rvinen \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003ePhys. Rev. B.\u003c/em\u003e 92, 121202 (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Ishikawa \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Infrared. Milli. Terahz Waves.\u003c/em\u003e 39, pp.288\u0026ndash;301, (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Ishikawa \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Infrared. Milli. Terahz Waves.\u003c/em\u003e 39, pp.387\u0026ndash;398, (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Fujii \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eAppl. Magn. Reson\u003c/em\u003e. 49, 783, (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eV. Weis \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Magn. Reson.\u003c/em\u003e 140, pp.293\u0026ndash;299 (1999).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eA. A. Smith \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Magn. Reson.\u003c/em\u003e 223, pp.170\u0026ndash;179 (2012).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Ishikawa \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eAppl. Magn. Reson\u003c/em\u003e. 52, 317, (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eY. Ishikawa \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eAppl. Magn. Reson\u003c/em\u003e. 52, 305, (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eL. R. Becerra \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eJ. Magn. Reson. Ser. A\u003c/em\u003e, 117, pp.28\u0026ndash;40, (1995).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eC. Caspers \u003cem\u003eet al\u003c/em\u003e.: \u003cem\u003eAPL. Photonics\u003c/em\u003e., 1, 026101 (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eV. Weis and R. G. Griffin: \u003cem\u003eSolid State Nuclear Magn. Reson.\u003c/em\u003e 29, 66\u0026ndash;78 (2006).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"applied-magnetic-resonance","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"apmr","sideBox":"Learn more about [Applied Magnetic Resonance](http://link.springer.com/journal/723)","snPcode":"723","submissionUrl":"https://submission.nature.com/new-submission/723/3","title":"Applied Magnetic Resonance","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7625537/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7625537/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWe have developed a magnetic resonance equipment for very low temperature and high magnetic field aiming at Dynamic Nuclear Polarization-Nuclear Magnetic Resonance (DNP-NMR) and Electron-Nuclear DOuble Resonance (ENDOR) of diluted spin system using with Electron Spin Resonance (ESR). In this study, we have developed a cylindrical resonator with a submicron-thick gold film for millimeter-wave band ESR/NMR double magnetic resonance by exploiting frequency dependence of skin depth. ESR measurements were performed using the fabricated resonator at around 130 GHz and in the temperature range of 3 K to 70 K of BDPA diluted to 100 mM in polystyrene. ESR sensitivity is obtained from the measurement. \u003csup\u003e19\u003c/sup\u003eF-NMR signal from the sample holder is also successfully observed.\u003c/p\u003e","manuscriptTitle":"Development of cylindrical resonator for millimeter-wave band ESR/NMR double magnetic resonance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-30 18:06:31","doi":"10.21203/rs.3.rs-7625537/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-26T08:49:23+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-25T20:40:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-24T03:01:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"308299323717609750488620417991100427753","date":"2025-09-20T02:25:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"29056963245842150914831070241476057110","date":"2025-09-18T06:54:27+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-18T01:48:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-17T06:22:21+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-16T14:50:53+00:00","index":"","fulltext":""},{"type":"submitted","content":"Applied Magnetic Resonance","date":"2025-09-16T03:51:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"applied-magnetic-resonance","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"apmr","sideBox":"Learn more about [Applied Magnetic Resonance](http://link.springer.com/journal/723)","snPcode":"723","submissionUrl":"https://submission.nature.com/new-submission/723/3","title":"Applied Magnetic Resonance","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"bff59aad-56f9-4860-8140-f692340c260c","owner":[],"postedDate":"September 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-27T16:41:07+00:00","versionOfRecord":{"articleIdentity":"rs-7625537","link":"https://doi.org/10.1007/s00723-025-01814-8","journal":{"identity":"applied-magnetic-resonance","isVorOnly":false,"title":"Applied Magnetic Resonance"},"publishedOn":"2025-10-25 16:16:34","publishedOnDateReadable":"October 25th, 2025"},"versionCreatedAt":"2025-09-30 18:06:31","video":"","vorDoi":"10.1007/s00723-025-01814-8","vorDoiUrl":"https://doi.org/10.1007/s00723-025-01814-8","workflowStages":[]},"version":"v1","identity":"rs-7625537","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7625537","identity":"rs-7625537","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}