Narrow Results

The CEPC booster needs to provide electron and positron beams to the collider at different energy with required injection speed. A 10 GeV linac is adopted as the injector for CDR. Then the beam energy is accelerated to specific energy according to three modes of operation of the CEPC collider ring ($H$, $W$ and $Z$). The geometry of the booster is designed carefully in order to share the same tunnel with the collider. The design status of the booster with the CDR lattice including parameters, optics and dynamic aperture is discussed in this paper.

A damping ring system which includes a small 1.1 GeV ring and two transport lines is introduced in CEPC linac in order to reduce the transverse emittance of positron beam at the end of linac and hence reduce the beam loss in the booster. This paper introduces the parameter choice and optics study of damping ring. The corresponding instability effect and IBS effect are also checked to make sure the design current and design emittance can be realized. Except for damping ring, two transport lines are needed to match the parameters between linac and damping ring. Both designs for energy compressor and bunch compressor including beam simulations are discussed in this paper.

We present a comparative study of magnetism and optical properties for $3d$ transition metal (TM) (Mn)-doped and $4f$ rare-earth metals (Gd and Nd)-doped ultrathin ZnO nanowires using ab-initio density functional calculation. Our calculations indicate Nd-doped ZnO nanowires with oxygen vacancies are more favorable for ferromagnetism. Calculations including spin–orbit coupling for Nd-doped ZnO nanowires reveal not only giant anisotropy where magnetism parallel to the nanowire axis is found to be favorable but also stabilized ferromagnetism. We have calculated the absorption spectra for Mn-, Gd- and Nd-doped ZnO nanowires and found that the absorption intensity increases upon increasing the concentration of dopant ions. While Mn-doped ZnO nanowire allows absorption of light in the large energy window ranging from visible to ultraviolet, Gd- and Nd-doped systems absorb light primarily in the ultraviolet region. Our result indicates transition-metal-doped as well as rare-earth-doped ZnO nanowires may be ideal for spintronics and optoelectronic devices.

A theory for the averaged optical characteristics of an ensemble of metal nanoparticles with different shapes has been developed. The theory is applicable both for the nanoparticle size at which the optical conductivity of the particle is a scalar and for the nanoparticle size at which the optical conductivity should be considered as a tensor. The averaged characteristics were obtained taking into account the influence of nanoparticle shape on the depolarization coefficient and the components of the optical conductivity tensor. The dependences of magnetic absorption by a spheroidal metal nanoparticle on the ratio between its curvature radii and the angle between the spheroid symmetry axis and the magnetic field vector were derived and theoretically considered. An original variant of the distribution function for nanoparticle shapes, which is based on the combined application of the Gaussian and “hat” functions, was proposed and analyzed.

The classic Grangier et al. (1996) experiment is revisited to suggest an alternative model of a single photon. Photon-counting experiments using spontaneous parametric down conversion (SPDC) show that not every single-photon incident on a detector triggers it, and that coincident triggering of detectors can occur during a single gate. The latter is usually interpreted as being caused by spurious photons entering the gate from different SPDC events. However, a pseudo-classical-type model is suggested which dispenses with these intruder photons. Here, a single-photon manifests as a transversely-iterated front of non-rotating screw threads. Each advancing thread has the potential to trigger a detector, and each allows the transfer of spin angular momentum (SAM). On exiting a beam splitter, a single-photon front can produce multiple triggering of detectors on different parts of the front with a probability of at most $5.02\times {10}^{-5}-3.54\times {10}^{-4}$ for the experiments presented.

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EUROPE — Radioembolization using sir-spheres significantly improves overall survival for patients with inoperable colorectal cancer.

Using no conventional measurements in position space, information extraction rates exceeding one bit per photon are achieved by employing high-dimensional correlated orbital angular momentum (OAM) states for object recognition. The correlations are shown to be insensitive to axial rotation of the target object: The information structure of an object's joint OAM coincidence spectrum is unchanged even when the object undergoes random rotations between each measurement. Additionally, OAM correlations alone are shown to be sufficient for full image reconstruction of complex, off-axis objects, and novel object symmetries are observed in the phases of OAM-object interaction transition amplitudes. Variations in mutual information rates, due to off-axis translation in the beam field, are studied, and it is shown that object symmetry signatures and information rates are independent of environmental factors sufficiently far from the beam center. The results motivate dynamic scanning applications in contexts where symmetry and small numbers of noninvasive measurements are desired.

I review some accelerator physics topics for circular as well as linear colliders, considering both lepton and hadron beams.

A number of countries have identified redundant large telecommunications antennas (TA) and indicated their intention to convert them into radio telescopes (RT). As the efficiency of a parabolic dish radio telescope depends on its surface quality and optical alignment, a careful assessment of these properties should be undertaken before conversion. Here, as a case study, we describe a laser scanning (LS) procedure we developed and used for the Warkworth 30m Cassegrain antenna. To investigate gravity-induced mechanical deformation of the antenna surfaces and structure, we conducted measurements at elevation angles ranging from 6 to 90 degrees. The ability of a laser scanner to survey its nominal $4\pi$ steradian surroundings allows for simultaneous study of the main and subreflectors, readily permitting a dynamic investigation of variation of the telescope optics as elevation changes occur. In particular, the method we present here allows determination of the surface quality of both main and subreflectors, the displacement between centers of the reflectors, their relative rotations and focal length variation as a function of elevation angle. We discuss details of settings, measurements, data processing and analysis focusing on possible difficulties and pitfalls. In our case study, no significant elevation-dependent surface deformation of the reflectors was observed, with the overall standard deviation of the postfit residuals varying between 1.0 and 1.7mm as elevation angle changes from 90^∘ to 6^∘, respectively. We, therefore, conclude that in our case both the main reflector and the subreflector, as well as the telescope optics, remain unaffected by gravitational deformation within the accuracy of the measurements, a conclusion that can possibly be extended to the similar class of TA currently considered for conversion.

We have developed a balloon-borne far-infrared interferometer, the Far-infrared Interferometric Telescope Experiment (FITE). The final goal of spatial resolution was one arcsec at 100$\mu$m. As a first step, we aimed to achieve a spatial resolution of five arcsecs at 155$\mu$m with a 6-m baseline. FITE is a two-beam interferometer like Michelson’s stellar interferometer. Positions and attitudes of all mirrors required to have their alignment checked and possibly adjusted before launch and were checked during observation. We had to satisfy three requirements: the coincidence of the phases of each beam (wavefront error), image quality of the two beams at the (common) focus, and no optical path difference between the two beams for celestial objects. In order to achieve the former two requirements, we developed an interferometer adjustment system that used a newly-developed interferometer measurement instrument. This instrument adopted a Shack–Hartmann wavefront sensor to measure wavefront errors of the two off-axis parabolic mirrors, simultaneously. With this system, the adjustment of the FITE interferometer was carried out at the Alice Springs balloon base in Australia as the JAXA’s Australia balloon experiment campaign of 2018. On-site adjustment was successful; wavefront errors of the two off-axis parabolic mirrors were 1.78$\mu$m and 4.99$\mu$m (peak-to-valley), and the Hartmann constant was 13 arcsecs. As for the optical path difference, we achieved the requirement by step-wise displacement of a folding plane mirror. Results satisfied the requirements for an interferometer designed for a wavelength of 155$\mu$m. Improvement of spatial resolution at far-infrared wavelengths is undoubtedly important for research on protoplanetary disks, circumstellar dust shells of late-type stars, and star-forming galaxies. The method we have developed is also useful for future space interferometers.

Smartphones are widely available and used extensively by students worldwide. These phones often come equipped with high-quality cameras that can be combined with basic optical elements to build a cost-effective DIY spectrometer. Here, we discuss a series of demonstrations and pedagogical exercises, accompanied by our DIY diffractive spectrometer that uses a free web platform for instant spectral analysis. Specifically, these demonstrations can be used to encourage hands-on and inquiry-based learning of wave optics, broadband versus discrete light emission, quantization, Heisenberg’s energy-time uncertainty relation, and the use of spectroscopy in day-to-day life. Hence, these simple tools can be readily deployed in high school classrooms to communicate the practices of science.

This paper is the second in a series of published solutions¹ discussing problems of the Ortvay Rudolf international competition.

The problem treated below is a simple exercise about grasping the fundamental aspects of a given phenomenon described within a qualitative “verbal” report and applying the principles learned in classical mechanics and geometric optics in order to explain its mechanism. The most important part of such problems is the interpretation of the phenomenon at hand, which naturally has a certain degree of vagueness, often allowing multiple scenarios. Similar tasks are often encountered, i.e. at the conceptual level of engineering and design.

In this case, the problem can be interpreted most straightforwardly as the description of an optical phenomenon in which a free-falling observer sees (presumably) its own delayed optical image. Here, we will focus on one concrete solution, the calculation of which does not use mathematical techniques beyond those expected of first-year university students.

We describe a simple experimental apparatus which allows the quantitative study of the classical analog of a quantum eraser. The apparatus consists of a laser diode, a thin wire, two polarizers providing the which-way information, and a third polarizer which erases that information. The experimental results are analyzed with the aid of a digital camera and the Tracker application, and are compared with a novel classical computation of the interference patterns, which is presented as well.

Deployment of quantum technology in space provides opportunities for new types of precision tests of gravity. On the other hand, the operational demands of such technology can make previously unimportant effects practically relevant. We describe a novel optical interferometric red-shift measurement and a measurement scheme designed to witness the possible spin-gravity coupling effects.

Each and every observational information we obtain from the sky regarding the brightnesses, distances or image distortions resides on the deviation of a null geodesic bundle. In this talk, we present the symplectic evolution of this bundle on a reduced phase space. The resulting formalism is analogous to the one in paraxial Newtonian optics. It allows one to identify any spacetime as an optical device and distinguish its thin lens, pure magnifier and rotator components. We will discuss the fact that the distance reciprocity in relativity results from the symplectic evolution of this null bundle. Other potential applications like wavization and its importance for both electromagnetic and gravitational waves will also be summarized.

Fluctuations in the Bose-Einstein condensate (BEC) remain a rich field of study even in the ideal gas limit. We here present the laser master equation approach to the problem in the spirit of Eugene P. Wigner who said: “With classical thermodynamics, one can calculate almost everything crudely; with kinetic theory, one can calculate fewer things, but more accurately; and with statistical mechanics, one can calculate almost nothing exactly.” The combination of kinetic theory plus statistical mechanics proves to be a powerful combination for the calculation of essentially exact BEC equilibrium results.

I review some accelerator physics topics for circular as well as linear colliders, considering both lepton and hadron beams.