A Hard Copper Open X-Band RF Accelerating Structure Made by Two Halves

This communication focuses on the technological developments aiming to show the viability of novel welding techniques [...]

Experimental Studies of a High-Gradient X-band Welded Hard-Copper Split Accelerating Structure

Recent research on high-gradient radio frequency (RF) accelerating structures indicates that the use of hard copper alloys provides improvement in high gradient performance over annealed copper. Such structures are made by bonding individually manufactured parts. However, there are no well-established bonding techniques that preserve the hardness, surface finish and cleanliness required for high gradient operation. To preserve the copper hardness, RadiaBeam has developed a joining technique based on electron beam welding. This technique provides efficient bonding with strong, clean welds and minimal thermal loading, while maintaining a clean inner RF environment. Our RF design and fabrication methodology limits the small heat affected zone to the outer cavity envelop, with virtually no distortions or thermal loading of critical RF surfaces. It also incorporates provisions to precisely control the gap despite conventional issues with weld joint shrinkage. To date we have manufactured and validated an RF accelerating structure joined by electron-beam welding that incorporates a novel open split design to significantly reduce the assembly complexity and cost. In this paper, we will present the electromagnetic design of this structure, discuss bonding, and present the results of high-power tests, where the accelerating gradients of 140 MV/m with surface peak fields of 400 MV/m were achieved for flat-top pulse length of 600 ns with an RF breakdown rate of 10-4 1/(pulse∙m).

EXPERIMENTAL RESEARCH AND WORK DEVELOPMENT ON THE HELIUM IONS LINAC

The paper provides a brief summary of the experimental research carried out at the present time at the materials science complex developed at the NSC KIPT. The main directions for the development of the work carried out have been determined. The complex is based on a linear accelerator of helium ions. The features and advantages of the accelerating structure of the accelerator, which is based on the principle of APF, are described. A technique was de-veloped and irradiation of candidate materials for the divertor and the first wall of the TNR was carried out. The damageability of the irradiated samples could create from 3 to 80 dpa.

Racetrack Microtron—Pushing the Limits

We consider three types of electron accelerators that can be used for various applications, such as industrial, medical, cargo inspection, and isotope production applications, and that require small- and medium-sized machines, namely classical microtron (CM), race-track microtron (RTM), and multisection linac. We review the principles of their operation, the specific features of the beam dynamics in these machines, discuss their advantages and weak points, and compare their technical characteristics. In particular, we emphasize the intrinsic symmetry of the stability region of microtrons. We argue that RTMs can be a preferable choice for medium energies (up to 100 MeV) and that the range of their potential applications can be widened, provided that the beam current losses are significantly reduced. In the article, we analyze two possible solutions in detail, namely increasing the longitudinal acceptance of an RTM using a higher-order harmonic accelerating structure and improving beam matching at the injection.

Relativistic versus Nonrelativistic Approaches to a Low Perveance High Quality Matched Beam for a High Efficiency Ka-Band Klystron

Advanced technical solution for the design of a low perveance electron gun with a high quality beam dedicated to high power Ka-band klystrons is presented in this paper. The proposed electron gun can be used to feed linear accelerating structures at 36 GHz with an estimated input power of 20 MW, thus achieving an effective accelerating electric field in the (100–150) MV/m range. Additionally, in the framework of the Compact Light XLS project, a short Ka-band accelerating structure providing an integrated voltage of at least 15 MV, has been proposed for bunch-phase linearization. For the klystron, a very small beam dimension is needed and the presented electron gun responds to this requirement. An estimate of the rotational velocity at beam edge indicates that the diamagnetic field due to rotational currents are small compared to the longitudinal volume. A detailed analysis of how this has been achieved, including compression of the beam, rotation in the magnetic field, and analysis of the subsequently generated diamagnetic field has been discussed.

ENGINEERING OF THE LOW-ENERGY BEAM TRANSPORT LINE IN THE Не⁺ IONS LINAC

The design of a low-energy beam transport line in the helium ions linear accelerator is proposed. For experiments with the low-energy helium ions the vacuum chamber in a transport line is in addition included for an irradiation of investigated materials. The mathematical modeling method investigates coordination variants of an injector beam output emittance with an accelerating structure acceptance with use of electromagnetic quadrupole lenses, electrostatic lenses and the focusing solenoid. It is shown that the optimal variant, ad hoc, is the focusing solenoid application. The calculated value of a current of the helium accelerated ions makes 4.5 mА.