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Purpose: Presentation of the history, status and prospects for the development of proton therapy. Material and methods: The history of proton therapy (PT) is divided into two periods. The first one – the experimental period lasted since 1954 to 1990, when proton therapy was carried out at the ten facilities in physical institutes. The research accelerators and the horizontal proton beams with a fixed direction are used. The second period is from 1990, when the first clinical proton center was commissioned in a multi-field hospital in the city of Loma Linda, USA. In the first period, the necessary technical tools were developed and the advantages of using accelerated protons in remote radiation therapy formulated by R. Wilson in 1946 were confirmed on a limited (about 9,000) patient population: halving the radiation load on the healthy tissues surrounding the tumor and on the organism as a whole compared to γ- and electron irradiation and high dose gradients at the borders of the dose distributions and the tumors. This allows to increase the dose in the tumor (target), increase the probability of the tumor resorption and at last to irradiate tumors, including small sizes, located near critical organs and structures. By 1990, in three experimental centers in Russia (JINR, ITEP, PNPI) accumulated about 30 % of world clinical experience. Today, more than 70 multi-cabin and several single-cabin clinical based proton therapy centers operate in the world. Almost all centers are equipped with gantry installations for PT for 95 % of patients. Today proton therapy is indicated and is used for the treatment of 10–15 % of all malignancies of cancer incidence structure. Results: Healthcare in Russia needs 10–15 multi-cabin proton (and ion) centers. Currently, there are one experimental PT center in the JINR, where up to 100 patients are exposed pea year. The modern proton center was commissioned at the Medical Institute Sergei Berezin in St. Petersburg with two gantry of company Varian. The IBA proton center in Dimitrovgrad is expected. The single-cabin proton complex of domestic production has been operating in Obninsk since 2017. 20th-century technologies and the horizontal beam (without the possibility of its rotation) are used in this complex for treatment of patients with small head and neck tumors. Conclusion: Equipping the Russian health care facilities with proton therapy facilities is inevitable. Russia will buy them worldwide for decades, like almost all types of high-tech medical equipment, are bought today, or can produce them locally. All the prerequisites needed for production (rich physical – technical experience, scientific and industrial potential) are available.

An analysis is made of the possibility of using intensity interferometry in obtaining images of spatially noncoherent polychromatic sources. It is shown that in the case of spectrally pure processes the propagation operator of the spatial part of the correlation function has a transformation kernel which is the temporal coherence function. Consequently, optical reconstruction with the aid of the Fourier transformation results in distortions of the image whose magnitude depends on the relative frequency bandwidth of the radiation emitted by the object. If a point reference source is used, distortions depend also on the spectral characteristics and spatial position of this source.

A theoretical analysis is made of the propagation of a space-time correlation function in a homogeneous nondispersive medium. The solution of a six-dimensional wave equation, describing the propagation of the coherence function, is found by the angular spectrum method. The relationships obtained make it possible to analyze fully the influence of the spectral composition of radiation on the spatial coherence. For example, in the case of a spatially noncoherent source there is a critical distance zcr, such that when z zcr, the polychromaticity of the field makes a negligible contribution to the spatial coherence; however, if z zcr, the linear behavior of the coherence radius, Rc z, typical of the van Cittert-Zernike theorem, gives way to the dependence Rc z. Similar conclusions apply also to a spatially coherent source.

The review considers the recording and reproduction of complete as well as partial information concerning the vector characteristics of a field. The principal methods and features of producing a complete recording of the wave polarization are indicated, namely the use of two reference beams with orthogonal polarizations, coding the reference beam with random wave fronts, and the use of three-dimensional holograms. Different aspects of the use of holographic recording of partial information concerning field polarization are considered. In such a procedure, the information on the polarization characteristics of the object wave is coded by means of other field characteristics, the amplitude and the phase. In this connection, in analogy with the phase-contrast method, the concept of polarization contrast is introduced and defined as the transformation of the changes of the state of polarization over the object into variation of the intensity of the image reconstructed from the hologram. The production of holograms by this procedure is described consistently with the aid of the correlation-matrix formalism, and also with Stokes parameters. The intensity of the virtual image is expressed in terms of the coherence matrix of the object and reference waves, or else with the aid of corresponding Stokes parameters. It is shown that the polarization state of the reference wave serves as the analyzer of the vector characteristics of the object field. The method of double exposure using orthogonally linearly polarized waves for different exposures is compared with the method of single exposure with circularly polarized fields. Certain limitations imposed on the objects and conditions of the experiment, under which both methods coincide, are indicated. Experiments with a very simple object, illustrating the procedure, are described.