| 1. |
- Bhattacharyya, Anirban, et al.
(author)
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ESS RF Source and Spoke Cavity Test Plan
- 2015
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Reports (other academic/artistic)abstract
- This report describes the test plan for the first high power RF source, ESS prototype double spoke cavity and ESS prototype cryomodule at the FREIA Laboratory.
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| 2. |
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| 3. |
- Goryashko, Vitaliy, 1982-, et al.
(author)
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Proposal for Design and Test of a 352 MHz Spoke RF Source
- 2012
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Reports (other academic/artistic)abstract
- More than a dozen of spoke resonators prototypes (SSR, DSR, TSR) have been constructed and tested worldwide. None have accelerated beam until now and the ESS LINAC will be the first accelerator to operate with spoke cavities. Experience with other types of superconducting cavities indicates that high-power test is vital for reliable operation of the cavity in an accelerator. Although characteristics of a bare cavity can be obtained in a low-power test some important features of a `dressed' cavity like the electroacoustic stability and tuning system can be studied only in a high-power test stand. The ESS LINAC is a pulsed machine and the Lorentz detuning originating from the electromagnetic pressure on the cavity walls is expected to be strong. The Lorentz force along with the cavity sensitivity to mechanical excitations at some resonant frequencies may lead to self-sustained mechanical vibrations which make cavity operation dicult. Practical experience shows that increasing the boundary stiness will decrease the static Lorentz force detuning but not necessarily the dynamic one. Therefore, the FREIA group at Uppsala University is building a high-power test stand able to study performance of the ESS spoke cavity at high power. The RF test stand will be able to drive the cavity not only in the self-excitation mode but also with closed RF loop and fixed frequency. The later technique will be used to reproduce the shape of the cavity voltage pulse as it is expected to be in the cavity operating in the ESS LINAC such that the cavity tuning compensation system will be tested under realistic conditions.
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| 4. |
- Jobs, Magnus, 1984-, et al.
(author)
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DB Science 400 kW RF Station Site Acceptance Test
- 2017
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Reports (pop. science, debate, etc.)abstract
- The manufactured and delivered DB-Science 400 kW RF station was tested on site at FREIA during 2016. The station can successfully deliver continuous pulse-trains with a power-level up to 400 kW, however during most of the on-site measurements and testing the total combiner output power was limited to 360 kW due to unusually high G2 currents measured in one of the spare TH595 tetrode tubes used in the station. Each of the stations 200 kW tetrode based amplifier sections were mounted with TH595 tetrode tubes from Thales and tuned for optimal performance. The gain of the tetrode amplifiers were roughly 15 dB with some variation between the two amplifier sections and the overall gain was approximately 74 dB maximum. Amplitude and phase pulse variations were within the specified levels.
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| 5. |
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| 6. |
- Jobs, Magnus, et al.
(author)
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Itelco-Electrosys 400 kW RF Station Site Acceptance Test
- 2015
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Reports (pop. science, debate, etc.)abstract
- The manufactured and delivered Itelco-Electrosys 400 kW RF station was tested on site at FREIA, in Uppsala August 31 through September 4 2015. The station could successfully deliver continuous pulsetrains with a power-level up to 400 kW. Each of the stations 200 kW tetrode based amplifier sections were mounted with TH-595 tetrode tubes from Thales and tuned for optimal performance. The gain of the tetrode amplifiers were roughly 15 dB with some variation between the two amplifier sections andthe overall gain was approximately 85 dB maximum.Some droop and phase distortion on the combined output pulse was measured caused primarily by a limited response time of the screen-grid power supply.
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| 7. |
- Li, Han, et al.
(author)
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RF Performance of the spoke prototype cryomodule for ESS
- 2019
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Reports (other academic/artistic)abstract
- The European spallation source (ESS), as a world-class high power proton accelerator facility, will be the first one to adopt 26 double spoke resonators (DSR) at its low energy section. As a new superconducting accelerating structure, these DSRs are therefore considered as a key technology and challenge of the whole project. They will be the first D SRs in the world to be commissionedfor a high power proton accelerator. As a milestone, the first DSR prototype cryomodule for ESS project was successfully tested at the FREIA Laboratory. In this qualification of the prototype cryomodule, the whole chain of RF station, RF distribution, fundamental power coupler (FPC), DSRs, cold tuning system (CTS) and low level radio frequency (LLRF) system, as well as the testing procedure have been verified on preparation for the industrialized cryomodules. Both cavities in the prototype cryomodule achieved nominal accelerating gradient, with the maximum gradient of 15 MV/m and 10.5 MV/m for cavity 1 and cavity 2 respectively. Based on the calorimetrical method, the dynamic heat load measurement showed that the cavity power consumption is around 0.5 W and therefore the intrinsic quality factor is consistent with the vertical test. This report presents the test configuration, RF conditioning history and first high power performance of this cryomodule.
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| 8. |
- Olvegård, Maja, et al.
(author)
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PROGRESS AT THE FREIA LABORATORY
- 2015
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In: Proceedings of IPAC'15. - JACoW : The Joint Accelerator Conferences Website.
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Conference paper (peer-reviewed)abstract
- The FREIA Facility for Research Instrumentation and Accelerator Development at Uppsala University, Sweden, has reached the stage where the testing of superconducting cavities for the European Spallation Source (ESS) is starting. The new helium liquefaction plant has been commissioned and now supplies a custom-made, versatile horizontal cryostat, HNOSS, with liquid helium at up to 140 l/h. The cryostat has been designed and built to house up to two accelerating cavities, or, later on, other superconducting equipment such as magnets or crab cavities. A prototype cavity for the spoke section of the ESS linac will arrive mid 2015 for high-power testing in the horizontal cryostat. Two tetrode-based commercial RF power stations will deliver 400 kW peak power each, at 352 MHz, to the cavity through an RF distribution line developed at FREIA. In addition, significant progress has been made with in-house development of solid state amplifier modules and powercombiners for future use in particle accelerators. We report here on these and other ongoing activities at the FREIA laboratory.
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| 9. |
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| 10. |
- Ruber, Roger, et al.
(author)
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Accelerator development at the FREIA Laboratory
- 2021
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In: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 16:7
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Journal article (peer-reviewed)abstract
- The FREIA Laboratory at Uppsala University focuses on superconducting technology and accelerator development. It actively supports the development of the European Spallation Source, CERN, and MAX IV, among others. FREIA has developed test facilities for superconducting accelerator technology such as a double-cavity horizontal test cryostat, a vertical cryostat with a novel magnetic field compensation scheme, and a test stand for short cryomodules. Accelerating cavities have been tested in the horizontal cryostat, crab-cavities cavities in the vertical cryostat, and cryomodules for ESS on the cryomodule test stand. High power radio-frequency amplifier prototypes based on vacuum tube technology were developed for driving spoke cavities. Solid-state amplifiers and power combiners are under development for future projects. We present the status of the FREIA Laboratory complemented with results of recent projects and future prospects.
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| 11. |
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| 12. |
- Wedberg, Rolf, 1947-, et al.
(author)
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Power Supplies for Tetrode High Power Amplfiers at FREIA : ESS TDR Contribution
- 2012
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Reports (other academic/artistic)abstract
- This paper select the topology of the power supplies to the RF power amplifier to one spoke cavity to be tested at FREIA Uppsala University.The power supplies are thought to fulfill the requirements of ESS in Lund.The amplifiers pulsed operation will have a strong impact of the choice of topology. The RF amplifier will have two tetrodes in the final stage.The anode power supply is studied for different topologies and number of anodes to supply.Storing the energy for pulse current to the anodes at high voltage or at low voltage is considered.The short circuit protection can be with a crowbar or a series switch. The series switch is selected for reasons of short interrupts in case of temporary short circuits.The grid and filament supplies are thought to be standard of the shelf power supplies.Cost estimate and comments on maintenance in the end of the paper.
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| 13. |
- Yogi, Rutambhara, 1968-, et al.
(author)
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Selection of RF Power Source and Distribution Scheme at 352 MHz for Spoke Cavities at ESS and FREIA
- 2012
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Reports (other academic/artistic)abstract
- The report describes selection of RF power source and distribution scheme for spoke cavities at ESS and FREIA. The European Spallation Source (ESS) is the world’s most powerful neutron source, which contain 36 superconducting spoke cavities at 352MHz and provide power of 0.5MW to the beam. The baseline for the RF system is a point-to-point generation and distribution from a single source to a single accelerating cavity.The RF system that has to generate this power and distribute it to the accelerating cavities, is a main resource driver for linear accelerators in form of investment, operation and maintenance. Therefore the technical alternatives are compared to minimize capital and running cost of the accelerator, without compromising its reliability. At 352 MHz and 350 kW RF power output, tetrode amplifiers are selected because of their advantages of being cheap, reliable, simple and efficient as compared to the other RF power amplifiers. The tetrodes, due to their low gain, need a pre-driver. The solid state amplifier technology is selected as a pre-driver due to its simplicity, reliability and efficiency. Half height aluminum WR2300 wave guides shall be used for RF distribution. This solution makes it possible to discard the circulator from the RF distribution chain, thus improving system efficiency.
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| 14. |
- Yogi, Rutambhara, et al.
(author)
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Tetrode Based Technology Demonstrator at 352 MHz, 400 kWp for ESS Spoke Linac
- 2014
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In: IEEE International Vacuum Electronics Conference. ; , s. 113-115
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Conference paper (peer-reviewed)abstract
- The European Spallation Source (ESS) will be the world's most powerful spallation neutron source when it comes in operation at the end of this decade. The ESS linac will accelerate 50mA of protons to 2 GeV in 2.86 ms long pulses at a repetition rate of 14 Hz on a tungsten target for neutron spallation. The linac contains 26 superconducting spoke cavities, which are being developed by IPN Orsay, France, and which accelerate the protons from 90 to 220 MeV. The FREIA laboratory at Uppsala University (Sweden) has developed the required RF power sources, procured the RF distribution and will test the cavities at nominal power. As no suitable amplifier was available at the ESS specifications (352MHz, 400kWp / 20kWavg, pulse width = 3.5 ms, pulse repetition frequency = 14 Hz), various technologies were compared and tetrode technology was selected for the first technology demonstrator RF power station at FREIA. We discuss the design of the technology demonstrator and present the first test results.
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