Michael Lalayan

Transverse deflecting structure XFEL TDS INJ

The Transverse Deflecting System XFEL TDS System INJ has been built as the part of the European X-ray Free Electron Laser for longitudinal bunch profile and slice emittance measurements. The 0.7 long Transverse Deflecting Structure (TDS), as the part of the system, has been built on base of the disk-loaded structure with hybrid EH-wave, operating frequency 2997.2 MHz and pulse input RF power up to 3 MW. The structure has been built, tuned and installed in the XFEL Injector beam line. All design parameters have been got at low RF power level. Electron beam has been passed through the whole Injector including TDS.

Structures with a transverse deflecting field for a free-electron laser

For a system for measuring the length and emittance of an electron bunch in a free-electron laser, the optimal geometry of a structure of the disk-loaded-wa veguide type with a transverse deflecting field at an E11 wave is selected. A well-known configuration of a deflector in the form of a circular diaphragmed waveguide with two holes for stabilizing the plane of wave polarization and two new deflector versions-with an oval shape of the coupling hole and with two grooves in the shell—are considered.

Development of the Hardware-Software Complex PIRS-5 for Field Measurements in Accelerating Structures

Hardware-software complex «PIRS-5» was developed to make measurements in warm accelerating structures. The idea was to create full-automatic measuring system, which can measure electrical field at the bead position with non-resonant and resonant pull techniques. PIRS-5 has postprocessor, which calculate electrical component from the frequency, reflection or transmission coefficient, shunt and effective shunt impedance. This work describes the construction of this complex, its mathematical part and possible future modifications. PIRS-5 LAYOUT AND SCHEMATICS Measurement setup PIRS-5 is software and hardware complex developed for electrodynamical characteristics measurements of accelerating structures. “PIRS” is acronym for Russian “facility for resonator parameters measurements” initially developed at MEPhI by Prof. A.Ponomarenko and his research team. After series of renovations and upgrades it became powerful tool for accelerating structures research nad development led by RF lab tem at MEPhI. Vector network analyzer being the key element of this setup is able to measure resonant frequencies and quality factors without any additional hardware or software involved. But field distribution inside accelerating structure and corresponding parameters like shunt impedance are not so easily acquired. In this paper new upgraded version is described. Algorithms and software part were substantionally altered and redesigned. Both resonant and non-resonant measurements of electromagnetic fields became possible using this implementation. New software allows computation of shunt impedance and effective shunt impedance computation based on electric field measured. Measurement setup schematics is illustrated on Fig. 1. It is quite ordinary hardware for this kind of measurements based on small perturbation technique. It includes Vector network analyzer Agilent 8753ET (1), control PC (2), accelerating structure under test (3), coupling antenna (4), small dielectric or metal bead (5), bead moving and positioning system (6) actuated by step motor (7). Latter is powered and PC controlled via step motor controller (8). It was already mentioned, that Agilent VNA is the main RF measuring device able to acquire accelerating structure parameters operated up to 6 GHz. Bidirectional GPIB interface connects it to PC and provides VNA control and data transfer. Accelerating structure under test is connected to VNA port by one or two coupling pickups chosen accordingly to particular measurement task. Small dielectric or metal perturbing bead attached to nylon string is travelling along cavity axis. Mechanical system allows precise string alignment and bead position determination. Computer controls all the hardware, provides data storage and user interface. PIRS-5 SOFTWARE Control software developed for PIRS-5 consists of two main algorithms (see Fig.2). Figure 2: PIRS-5 software. They are algorithm of data acquisition and post-processor. Let us consider algorithm features paying brief attention to the user interface implementation details. After user enters cavity length, measured quality factor and bead form-factor program starts measurement. This algorithm is illustrated on Fig. 3. Figure 1: PIRS-5 layout. THPSC073 Proceedings of RuPAC2016, St. Petersburg, Russia ISBN 978-3-95450-181-6 702 C op yr ig ht

Commissioning and First Tests of the New Standing Wave 10 Mev Electron Accelerator

A new linear electron accelerator for industrial applications was developed by the joint team of CORAD and MEPhI. It is based on conventional biperiodical accelerating structure for energy range from 7.5 to 10 MeV and beam power up to 20 kW. The use of modern methods and codes for beam dynamics simulation, raised coupling coefficient and group velocity of SW biperiodic accelerating structure allowed to reach high pulse power utilization and obtain high efficiency. The first two accelerators with the new structure have been installed and tested.

Measurement of electrodynamics characteristics of higher order modes for harmonic cavity at 2400 MHz

In the frameworks of the High Luminosity Large Hadron Collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a possible candidate, an assembly of two cavities with grooved beam pipes connected by a drift tube and housed in a common cryomodule, was proposed. In this article we discuss measurements of loaded Q-factors of higher order modes (HOM) performed on a scaled aluminium single cell cavity prototype with the fundamental frequency of 2400 MHz and on an array of two such cavities connected by a narrow beam pipe. The measurements were performed for the system with and without the matching load in the drift tube..

Optimization of electric field distribution inside CH-resonator

Distribution of the E-field amplitude on the axes inside multi-gap CH-resonators has a significant influence at the beam dynamics. High accelerating gain requires uniform field distribution on the beam axes. The field tuning task was solved using complex pilon design. Final cavity geometry, methodology and main electrodynamics characteristics are presented.

Thermal calculation of accelerating structures in electron linacs

The temperature distribution in the accelerating structures of standing-wave and traveling-wave electron linacs is calculated. The objects of consideration in the former and latter cases are, respectively, a circular iris waveguide with magnetic coupling and a biperiodic accelerating structure. Calculation data for steady and transient heating conditions are presented. The variation of the cell’s geometry and resonance frequency with the temperature of the structure is also calculated. Calculations are made for copper structures with allowance for microwave wall losses.

Higher order modes in an RF deflecting structure

RF deflectors on the basis of a disk-loaded waveguide with different methods for stabilizing the polarization plane of an EH11 hybrid wave (with two holes in the diaphragm, with an oval-shaped coupling aperture, and with two grooves in a shell) were developed for the system of measuring the length and emittance of an electron bunch in a free electron laser. The electrodynamic characteristics of higher order modes were calculated and measured for the mentioned methods for specifying the wave polarization plane.