Commissioning of C-band Standing-wave Accelerator

2017

There are growing demands on low energy electron linear accelerator (linac) for industrial applications. Most of industrial electron linacs require a compact structure and limited undesirable neutron production to avoid huge lead shielding. Radiation Technology eXcellence (RTX) and Korea Atomic Energy Research Institute (KAERI) have developed a 6 MeV compact side-coupled linac by using 2998 MHz European S-band RF technology to meet those requirements. To design the linac structure, the 3D CST MICROWAVE STUDIO (CST-MWS) was used for various electromagnetic simulations, and ASTRA code was used for particle beam dynamics simulations. After various optimizations, the shunt impedance of 61 MΩ/m is obtained at 2998.38 MHz. With a peak RF power of 2.2 MW and a 47 cm-long structure, electron beam with a peak current of 150 mA can be accelerated from 25 keV to 6 MeV. For the industrial linac, the electron beam spotsize at an X-ray target, located 5 cm downstream of the linac structure exit s...

2019

We present the overview and beam parameters measurements results as well as the operational experience with the S-band pulsed linear electron accelerator with beam energy in the range of 5-10 MeV and maximum beam power of up to 15 kW. The possibility of adjusting the beam parameters in a wide range, provided by the design and control system of the accelerator, allows to use the accelerator in a wide variety of radiation technologies.

2012

Electron linear accelerator based on parallel coupled accelerating structure was developed and produced by Budker institute of nuclear physics SB RAS and Institute of Chemical kinetics and combustion SB RAS. There were short and long parallel coupled accelerating structures with frequency 2450 MHz. For easy disassembly the electrical and vacuum connections for the first structure are performed by indium. The second structure is brazed. Now accelerator is working for researching in the field of accelerating and RF technologies. In the report the features of the accelerator working are demonstrated. The test of the long parallel coupled accelerating structure is discussed. The result of dissembled of the short accelerating structure is shown. The RF antenna lead and solidstate key for beam driving of the electron gun with RF control were developed. The design and characteristics of these devices are presented. Now the short parallel coupled accelerating structure is under modernizing ...

2012

A new klystron based X-band rf power source operating at 11.994 GHz has been installed and started to be commissioned at CERN in collaboration with CEA Saclay and SLAC for CLIC accelerating structure tests. The system comprises a solid state high voltage modulator, an XL5 klystron developed by SLAC, a cavity based SLED type pulse compressor, the necessary low level rf system including rf diagnostics and interlocks and the surrounding vacuum, cooling and controls infrastructure. The system is designed to produce up to 50 MW rf pulses of 1500 ns pulse width and 50 Hz repetition rate. After pulse compression, up to 100 MW of rf power at 250 ns pulse width will be available in the structure test bunker. This paper describes in more detail this setup and the process of commissioning which is necessary to arrive at the design performance.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The RF Technology Development group at Fermilab is working together with the NLC and JLC groups at SLAC and KEK on developing technology for room temperature X-band accelerating structures [1] for a future linear collider. We have built a few 60cm long, high phase advance, detuned structures (HDS or FXB series). These structures have 150 degrees phase advance per cell, and are intended for high gradient tests. The structures were brazed in a vacuum furnace with a partial pressure of argon, rather than in a hydrogen atmosphere. We have also begun to build 60cm long, damped and detuned structures (HDDS or FXC series). Our goal is to build many structures for the 8-pack test at SLAC by the end of 2003, as part of the JLC/NLC effort to demonstrate the readiness of room temperature RF technology for a linear collider. This paper describes the design, fabrication techniques, RF measurements and tuning, as well as the initial results from high gradient testing of an FXB structure.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The energy upgrade of the SPARC_LAB photo-injector at LNF-INFN (Frascati, Italy) has been originally conceived replacing one low gradient (13 MV/m) 3 m long SLAC type S-band traveling wave (TW) section with two 1.4 m long C-band accelerating sections. Due to the higher gradients reached by such structures, a higher energy beam can be obtained within the same accelerator footprint length. The use of C-band structures for electron acceleration has been adopted in a few FEL linacs in the world, among others, the Japanese Free Electron Laser at SPring-8 and the SwissFEL at Paul Scherrer Institute (PSI). The C-band sections are traveling wave, constant impedance structures with symmetric input and output axial couplers. Their design has been optimized for the operation with a SLED RF pulse compressor. In this paper we briefly review their design criteria and we focus on the construction, tuning, low and high-power RF tests. We also illustrate the design and realization of the dedicated low level RF system that has been done in collaboration with PSI in the framework of the EU TIARA project. Preliminary experimental results appear to confirm the operation of such structures with accelerating gradients larger than 35 MV/m.

2010

In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz mono-energetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedingly high quality to produce narrow-bandwidth gamma-rays. Modeling efforts will be presented, along with plans for a multi-bunch test stand at LLNL. The test stand will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The photoinjector will be a high gradient standing wave structure, featuring a dual feed racetrack coupler. The accelerator will increase the electron energy so that the emittance can be measured using quadrupole scanning technique...

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The linacs proposed for the Next Linear Collider (NLC) and Japanese Linear Collider (JLC) would contain several thousand X-Band accelerator structures that would operate at a loaded gradient of 50 MV/m. An extensive experimental and theoretical program is underway at SLAC, FNAL and KEK to develop structures that reliably operate at this gradient. The development of standing wave structures is a part of this program. The properties of standing wave structures allow them to operate at the loaded gradient in contrast to traveling wave structures that need conditioning to the unloaded gradient (65 MV/m for NLC/JLC). The gradients in the standing structures tested thus far have been limited by input coupler breakdowns. The behavior of these breakdowns is consistent with a model of pulsed heating due to high magnetic fields. New input couplers have been designed to reduce maximum magnetic fields. This paper discusses design considerations related to high power performance, wakefield suppression and results of high power tests of prototype standing wave structures.

Proceedings of IEEE International Electron Devices Meeting

2005

The MINAC series portable linear electron accelerator systems designed and manufactured at American Science and Engineering, Inc. High Energy Systems Division (AS&E HESD) are discussed in this paper. Each system can be configured as either an X-ray or electron beam source. The 4 MeV and 6 MeV linacs powered by a 1,5 MW magnetron permit operation in a dose rate range from 100 R/min to 600 R/min at 1 meter from X-ray target. Each MINAC is a self-contained source with standard radiation leakage less than 0,1% of the maximum dose. Along with these systems, an ultracompact 1 MeV MINAC has been successfully tested. The unit is tested to generate up to 100 R/min @ 1 m in energy range from 1 to 3 MeV with radiation leakage less then 0.01%. The results of low and high power test are presented.

2018

We illustrate the RF design of the X-band linac for the upgrade of the SPARC_LAB facility at INFN-LNF (EuPRAXIA@SPARC_LAB). The structures are travelling wave (TW) cavities, working on the 2π/3 mode, fed by klystrons with pulse compressor systems. The tapering of the cells along the structure and the cell profiles have been optimized to maximize the effective shunt impedance keeping under control the maximum value of the modified Poynting vector, while the couplers have been designed to have a symmetric feeding and a reduced pulsed heating. In the paper we also present the RF power distribution layout of the accelerating module and a preliminary mechanical design.

2000

During the initial phase of operation, the linacs of the Next Linear Collider (NLC) will contain roughly 5000 X-Band accelerator structures that will accelerate beams of electrons and positrons to 250 GeV. These structures will nominally operate at an unloaded gradient of 72 MV/m. As part of the NLC R&D program, several prototype structures have been built and operated at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. Here, the effect of high gradient operation on the structure performance has been studied. Significant progress was made during the past year after the NLCTA power sources were upgraded to reliably produce the required NLC power levels and beyond. This paper describes the structures, the processing methodology and the observed effects of high gradient operation.

Bhabha Atomic Research Centre in India has taken up the indigenous design & development of high power electron accelerators for industrial, research and cargo scanning applications. For this purpose, Electron Beam Centre (EBC) has been set up at Navi Mumbai, India. Pulsed RF Linacs, with on-axis coupled cavity configuration, include the 10 MeV Industrial RF linac, as well as 9 MeV linac and compact 6 MeV linac for cargo scanning applications. Industrial DC accelerators include a 500 keV Cockroft-Walton machine and 3 MeV Dynamitron. Several radiation processing applications, such as material modification, food preservation, flue-gas treatment, etc. have been demonstrated using these accelerators. Cargo-scanning linacs have been successfully commissioned and are being characterized for the required x-ray output. A 30 MeV RF Linac, for research applications, such as shielding studies and n-ToF experiments, is being designed and developed. For ADS studies, a 100 MeV, 100kW RF Linac system is proposed. This paper presents the details of the design of these accelerators, their development, current status and utilization for various applications.

2011

In a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a multi-purpose X-band accelerating structure has been designed and fabricated, used for high gradients tests in the CLIC structure testing program and in the FEL projects of PSI and ST. The structure has 72 cells with a phase advance of 5 pi/6 and includes upstream and down-stream wakefield monitors to measure the beam alignment. The SLAC mode launcher design is used to feed it with RF power. Following the CERN fabrication procedures for high-gradient structure, diffusion bonding and brazing in hydrogen atmosphere is used to assemble the cells. After tuning, a vacuum bakeout is required before the feedthroughs for the wake field monitors are welded in as a last step. We describe the experiences gained in finishing the first two structures out of a series of four and present the results from the RF tuning and low level RF tests.

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

The majority of medical accelerators for radiation therapy use frequencies in the S-band range. Having a compact accelerator allows for a wide range of treatments. The size and weight of the accelerator are substantially reduced if a higher frequency is used. X-band frequencies are suitable for such applications. X-band accelerator technology has been used in high-energy, as well as, industrial applications. In the medical field, it has already been implemented in some machines [1, 2]. To develop and manufacture reliable X-band radiation therapy machines, accurate and efficient techniques that characterize accelerator structures are needed. In this paper, we review some of the low-power testing techniques developed to characterize X-band accelerators.