Narrow Results

An overview is given on key physics, detector and accelerator aspects of the LHeC including its further development with emphasis to its role as the cleanest microscope of parton dynamics and a precision Higgs facility.

A proposal has been made for the construction of a new generation of high-luminosity electron-positron colliders known as the Super Tau-Charm Facility (STCF) in China. The STCF aims to achieve a luminosity exceeding $0.5\times 10^{35}$cm${}^{-2}$s${}^{-1}$ and will operate within a center-of-mass energy range of 2 to 7GeV. Given the design challenges of the STCF collider ring, swap-out injection has been proposed as an alternative method for achieving the desired luminosity. Consequently, the STCF injector will explore both off-axis injection and swap-out injection methods concurrently. This paper will detail the ongoing research progress on these two injection techniques.

A proton–proton collider at center-of-mass energy of more than 70 TeV is the second stage of the CEPC-SPPC program. As proposed, the SPPC injector chain will use a 1.2 GeV p-Linac and three synchrotrons of 10 GeV p-RCS, 180 GeV MSS and 2.1 TeV SS. Peking University is responsible for the preliminary conceptual design of the room temperature part of SPPC p-Linac. This paper is focusing on the beam dynamics studies performed with respect to the 325 MHz RFQ. As the first accelerator structure after the ion source and the front-end of the whole SPPC, RFQ plays an important role in the beam initial transverse focusing and longitudinal bunching. Based on the New Four Section Procedure strategy, as well as the matched and Equipartitioning design method, a 3 MeV RFQ designed by Parmteq code will be introduced. The cavity length of RFQ is 3.6 m and the transmission efficiency is 98%. In this design scheme, the 40 mA proton beam from the 50 keV ion source is accelerated to 3 MeV in 3.8 m length, which achieves a sixty times energy gain. The results of the analyses show that the RFQ design is reliable and meets all the SPPC p-Linac requirements well.

The Circular Electron–Positron Collider (CEPC) is a 100-km ring $e^{+}{e}^{-}$ collider for a Higgs factory. The injector of CEPC is composed of Linac and Booster. The Linac is a normal conducting S-band Linac with a frequency of 2860 MHz; it provides electron and positron beams at an energy of up to 10 GeV with 100 Hz repetition frequency of 100 Hz. The Linac design and dynamic simulation results are discussed in detail in this paper, including electron bunching system, positron source, electron bypass transport line, damping ring and main Linacs.

The CEPC includes a main ring and an injector. The injector consists of a booster and a linac. In order to meet the requirements of the booster, the baseline design of the linac is a 10 GeV electron and positron linac. Two alternative linac designs have also been introduced in this paper. For the linac baseline design, one-bunch-per-pulse is adopted. A 1.1 GeV damping ring is used to reduce the transverse emittance of positron beam. The main RF system of the linac adopts normal conducting S-band structure. Some key technologies of linac are development. The S-band structure and pulse compressor have been researched and studied. In the damping ring, two cavities used to provide 2 MV voltage. The preliminary cavity design has finished.

The simulation and optimization of an electron injector that operates a high-intensity polarized electron beam are presented. The electron injector would provide a single-bunch electron beam at a repetition rate of 1 Hz with a bunch charge of 10 nC, kinetic energy of 400 MeV and an electron spin polarization of 85$\%$. A direct current (DC) high-voltage photogun was employed to produce the 10 nC polarized electron beam with a kinetic energy of 350 keV, beam diameter of 1.44 cm (Gaussian distribution with $\sigma$ of 0.36 cm) and full bunch length of 1.3 ns (Gaussian distribution with $\sigma$ of 0.325 ns). The beam was compressed to 6 ps of RMS bunch length using one 114.24 MHz standing-wave sub-harmonic buncher, two 571.2 MHz standing-wave sub-harmonic bunchers and one 2.856 GHz traveling-wave buncher. The beam was accelerated finally to 400 MeV via eight 2.856 GHz traveling-wave Linacs. We performed the beam simulation, and the simulated results showed that the optimized RMS bunch length was 4.65 ps, RMS relative energy spread was 0.48$\%$ and normalized RMS transverse emittance was $30.13mm\cdot mrad$ at a beam energy of 400 MeV.

The Facility for Rare Isotope Beams (FRIB) Project has entered the phase of beam commissioning starting from the room-temperature front end and the superconducting linac segment of first 15 cryomodules. With the newly commissioned helium refrigeration system supplying 4.5K liquid helium to the quarter-wave resonators and solenoids, the FRIB accelerator team achieved the sectional key performance parameters as designed ahead of schedule accelerating heavy ion beams above 20MeV/u energy. Thus, FRIB accelerator becomes world’s highest-energy heavy ion linear accelerator. We also validated machine protection and personnel protection systems that will be crucial to the next phase of commissioning. FRIB is on track towards a national user facility at the power frontier with a beam power two orders of magnitude higher than operating heavy-ion facilities. This paper summarizes the status of accelerator design, technology development, construction, commissioning as well as path to operations and upgrades.

The high-intensity heavy ion accelerator facility is a next-generation advanced heavy-ion accelerator facility built by the Institute of Modern Physics, Chinese Academy of Sciences. The RFQ is designed to provide a continuous wave beam and 2mA pulse beam with high-quality longitudinal beam distribution for the injection linear accelerator. Two different designs of aiming to suppress the longitudinal emittance were studied, and the optimized scheme which composed of a three-harmonic pre-buncher and an RFQ accelerator with small longitudinal acceptance was chosen. More emphasis is put on the section between pre-buncher and RFQ, where the space charge effect becomes severe with bunched beam. The optimal design and the analysis are presented in this paper.

The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: "paint" a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

This article discusses the main building blocks of a superconducting (SC) linac, the choice of SC resonators, their frequencies, accelerating gradients and apertures, focusing structures, practical aspects of cryomodule design, and concepts to minimize the heat load into the cryogenic system. It starts with an overview of design concepts for all types of hadron linacs differentiated by duty cycle (pulsed or continuous wave) or by the type of ion species (protons, H^-, and ions) being accelerated. Design concepts are detailed for SC linacs in application to both light ion (proton, deuteron) and heavy ion linacs. The physics design of SC linacs, including transverse and longitudinal lattice designs, matching between different accelerating–focusing lattices, and transition from NC to SC sections, is detailed. Design of high-intensity SC linacs for light ions, methods for the reduction of beam losses, preventing beam halo formation, and the effect of HOMs and errors on beam quality are discussed. Examples are taken from existing designs of continuous wave (CW) heavy ion linacs and high-intensity pulsed or CW proton linacs. Finally, we review ongoing R&D work toward high-power SC linacs for various applications.

Cargo inspection by X-rays has become essential for seaports and airports. With the emphasis on homeland security issues, the identification of dangerous things, such as explosive items and nuclear materials, is the key feature of a cargo inspection system. And new technologies based on dual energy X-rays, neutrons and monoenergetic X-rays have been studied to achieve sufficiently good material identification. An interpretation of the principle of X-ray cargo inspection technology and the features of X-ray sources are presented in this article. As most of the X-ray sources are based on RF electron linear accelerators (linacs), we give a relatively detailed description of the principle and characteristics of linacs. Cargo inspection technologies based on neutron imaging, neutron analysis, nuclear resonance fluorescence and computer tomography are also mentioned here. The main vendors and their products are summarized at the end of the article.

Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators.

This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy.

The following procedure is pursued to perform a comparison between various types of accelerators:

• ⁽¹⁾The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations.
• ⁽²⁾The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified.
• ⁽³⁾A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion.
• ⁽⁴⁾Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.

The European Spallation Source (ESS), which is established as a European Research Infrastructure Consortium (ERIC), is a multi-disciplinary research facility that is currently under construction. ESS has as vision to develop to a world class facility, enabling scientific breakthroughs in research related to materials, energy, health and the environment. The ESS facility is built by a collaboration of some 100 research institutes and universities.

With its 5 MW average beam power, its linac will be the most powerful linac of all neutron spallation sources. Neutrons are obtained by delivering 2 GeV protons at a repetition rate of 14 Hz to the He-cooled solid tungsten rotating target. The Accelerator is built with a high percentage of In-Kind Contributions (IKC) with major accelerator systems being designed, prototyped and built outside ESS. The first major accelerator elements are now being assembled and tested with their first parts being installed. Future similar large-scale projects could likely be IKC-based, which is a powerful model. Within ESS, the Mechanical Engineering & Technology (MET) section is responsible for developing and maintaining mechanical engineering and design throughout the facility. The mechanical design is consolidated in the master model and available under the ESS Plant Layout, including all In-Kind Contributions as well as other related mechanical engineering content. Consequently, the MET section is also responsible for the design, development and supervision of the proton accelerator and tungsten target in terms of civil and infrastructure design for the physical plant. In parallel, ESS has set stringent goals for high availability and reliability on the machines during operations. In order to deliver these goals and monitor the aging status of critical parts of the machines, prototypes and one-of-a-kinds, the MET section has developed and currently implements Structural Health Monitoring (SHM) program on the accelerator primarily and other machines for Operations. The innovative strategy and application of Non-Destructive Testing for Machines (NDTM) is under development by the MET section with the leading benefit of utilizing the technology of Resonant Ultrasound Spectroscopy (RUS). Both reference and irradiated samples undergo RUS measurements to obtain spectral responses of the dedicated materials, for machine reliability and operations availability purposes.

Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators.

This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy.

The following procedure is pursued to perform a comparison between various types of accelerators:

• The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations.
• The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified.
• A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion.
• Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.

Cargo inspection by X-rays has become essential for seaports and airports. With the emphasis on homeland security issues, the identification of dangerous things, such as explosive items and nuclear materials, is the key feature of a cargo inspection system. And new technologies based on dual energy X-rays, neutrons and monoenergetic X-rays have been studied to achieve sufficiently good material identification. An interpretation of the principle of X-ray cargo inspection technology and the features of X-ray sources are presented in this article. As most of the X-ray sources are based on RF electron linear accelerators (linacs), we give a relatively detailed description of the principle and characteristics of linacs. Cargo inspection technologies based on neutron imaging, neutron analysis, nuclear resonance fluorescence and computer tomography are also mentioned here. The main vendors and their products are summarized at the end of the article.

The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: “paint” a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

This article discusses the main building blocks of a superconducting (SC) linac, the choice of SC resonators, their frequencies, accelerating gradients and apertures, focusing structures, practical aspects of cryomodule design, and concepts to minimize the heat load into the cryogenic system. It starts with an overview of design concepts for all types of hadron linacs differentiated by duty cycle (pulsed or continuous wave) or by the type of ion species (protons, H⁻, and ions) being accelerated. Design concepts are detailed for SC linacs in application to both light ion (proton, deuteron) and heavy ion linacs. The physics design of SC linacs, including transverse and longitudinal lattice designs, matching between different accelerating-focusing lattices, and transition from NC to SC sections, is detailed. Design of high-intensity SC linacs for light ions, methods for the reduction of beam losses, preventing beam halo formation, and the effect of HOMs and errors on beam quality are discussed. Examples are taken from existing designs of continuous wave (CW) heavy ion linacs and high-intensity pulsed or CW proton linacs. Finally, we review ongoing R&D work toward high-power SC linacs for various applications.