| 1. |
- Bhattacharyya, Anirban, et al.
(författare)
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ESS RF Source and Spoke Cavity Test Plan
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)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. |
- Bhattacharyya, Anirban, et al.
(författare)
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Precise measurements of hot S-parameters of superconducting cavities : Experimental setup and error analysis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Superconducting accelerating cavities used in modern particle accelerators change their intrinsic properties when excited to very high field levels close to the critical field where the superconductivity is affected. In this report we describe a test-bench and data analysis procedure to determine the so-called hot S-parameters from strongly driven cavities and use them to quantify the properties of the cavity at varying field levels. The method is based on analysing reflection coefficient for a large number of configurations in a self-excited loop setup and determining the cavity coupling coefficient $\kappa=Q_0/Q_{ext}$ as a function of cavity voltage to high accuracy. Since $Q_{ext}$ is determined independently and is a constant, from the information of $\kappa$ the Q-slope can be determined.
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| 3. |
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| 4. |
- Fedotov, Alexei, et al.
(författare)
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Experimental studies of the magnetized friction force
- 2006
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1539-3755 .- 1550-2376. ; 74:6
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Tidskriftsartikel (refereegranskat)abstract
- High-energy electron cooling, presently considered as an essential tool for several applications in high-energy and nuclear physics, requires an accurate description of the friction force which ions experience by passing through an electron beam. Present low-energy electron coolers can be used for a detailed study of the friction force. In addition, parameters of a low-energy cooler can be chosen in a manner, to reproduce regimes expected in future high-energy operation. Here, we report a set of dedicated experiments in CELSIUS aimed at a detailed study of the magnetized friction force. Some results of the accurate comparison of experimental data with the friction force formulas are presented.
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| 5. |
- Goryashko, Vitaliy, 1982-, et al.
(författare)
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Proposal for Design and Test of a 352 MHz Spoke RF Source
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)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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| 6. |
- Goryashko, Vitaliy, 1982-, et al.
(författare)
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RF Power Consumption in the ESS Spoke LINAC : ESS TDR Contribution
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the ESS LINAC the transition energy between the DTL and the spoke LINAC was changed by adding the fourth DTL tank in order to match the spoke LINAC in terms of the velocity acceptance. We present calculation of the RF power required to be fed to each spoke cavity to achieve the nominal acceleration gradient. The RF power overhead needed to compensate the beam loading and the Lorentz detuning is calculated and the peak and average values of the total RF power are presented. Overhead in terms of the power averaged over the pulse is only a few percents whereas the peak power overhead can reach 20\% and lasts for around 200 microseconds. It turns out that the power overhead is mainly determined by the strong beam loading because of a high beam current whereas the Lorentz detuning is weak due to high stiffness of the spoke cavity and almost does not require extra power to the cavity. In our simulations the cavity voltage and phase are stabilized within nominal tolerances by feedback and feed-forward.A slow feed-forward is used to cure the Lorentzdetuning whereas a fast feedback through a signal oscillator is applied to compensate the beam loading effect.
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| 7. |
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| 8. |
- Hoang Duc, Long, et al.
(författare)
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Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators
- 2019
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 90:10
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the first results of an in-house developed low-level radio frequency (LLRF) system and a 10 kW solid state power amplifier (SSPA). The design approach for the SSPA is based on eight resonant single-ended kilowatt modules combined using a planar Gysel combiner. Each of the single-ended modules is based on a two-stepped impedance resonant matching, allowing for harmonic suppression, simple design for massive production, and high-performance design. A design methodology to tune SSPA modules for optimum combining efficiency is presented thoroughly in the time domain. We characterize the power droop due to capacitor banks in the time domain. In open loop of compensation, it is about 1 kW within the pulse of peak value 10 kW and a duration of 3.5 ms. This may lead to the beam instability of the accelerator as particles are not provided with the same energy during the pulse. By incorporating our LLRF system, it is demonstrated that the objective of amplitude and phase stability is satisfied, as required in the European Spallation Source proton accelerator. The presented design also offers the advantages of compact form factor, low complexity, and better performance. In closed loop compensation, the variation of amplitude (pulse droop) is measured on the order of 20 W, which is equivalent to 0.2% at 10 kW peak output power.
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| 9. |
- Li, Han, et al.
(författare)
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Characterization of a beta=0.5 double spoke cavity with a fixed power coupler
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 927, s. 63-69
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Tidskriftsartikel (refereegranskat)abstract
- ESS, the European Spallation Source, will adopt a single family of double spoke cavities for accelerating the beam from the normal conducting section to the first family of the elliptical superconducting cavities. It will be the first double spoke cavities in the world to be commissioned for a high power proton accelerator. The first double spoke cavity for the ESS project was tested with high power in the HNOSS cryostat at Uppsala University. A pulse-mode test stand based on a self-excited loop was used in this test. The qualification of the cavity package involves a double-spoke superconducting cavity, a fixed fundamental power coupler, tuner, a low-level radiofrequency (LLRF) system and a high-power radiofrequency (RF) station. The test represents an important verification milestone before the module assembly. This cavity had unfortunately a high dynamic loss of 12W @ 9 MV/m, where potential causes for such a high value have been studied and corresponding suggestions are listed. This paper presents the test configuration, RF conditioning history, first high power performance and experience of this cavity package.
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| 10. |
- Li, Han, et al.
(författare)
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First High Power Test of the ESS Double Spoke Cavity
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The first double spoke cavity for ESS project was tested with high power in the HNOSS cryostat at FREIA Laboratory. This cavity is designed for 325.21MHz, a pulse mode with 14 Hz repetition rate, up to peak power of 360 kW. The qualification of the cavity package in a high power test, involved a spoke superconducting cavity, a fundamental power coupler, LLRF system and a RF station, represented an important verification before the module assembly. This report presents the test configuration, RF conditioning history and first high power performance of this cavity package.
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| 11. |
- Li, Han, et al.
(författare)
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First High Power Test of the ESS High Beta Elliptical Cavity package
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The first high-beta elliptical cavity for ESS project was tested with high power in the HNOSS cryostat at FREIA Laboratory. This cavity is designed for 704.42 MHz, a pulse mode with 14 Hz repetition rate, up to peak power of 1.5 MW. The qualification of the cavity package in a high power test, involved an elliptical superconducting cavity, a fundamental power coupler, cold tuning system, LLRF system and klystron system, represented an important verification before the module assembly. This report presents the test configuration, RF conditioning history and first high power performance of this cavity package.
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| 12. |
- Li, Han, et al.
(författare)
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RF Performance of the spoke prototype cryomodule for ESS
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)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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| 13. |
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| 14. |
- Miyazaki, Akira, 1986-, et al.
(författare)
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Millimeter-Wave WISP Search with Coherent Light-Shining-Through-a-Wall Toward the STAX Project
- 2024
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Ingår i: Annalen der Physik. - : John Wiley & Sons. - 0003-3804 .- 1521-3889. ; 536:1
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Tidskriftsartikel (refereegranskat)abstract
- A dark photon is one of the simplest extensions of the Standard Model of particle physics and can be a dark matter candidate. Dark photons kinetically mix with ordinary photons. The mass range from 10(-4) to 10(-3) eV of such dark photons is underconstrained by laboratory-based experiments and a new search is therefore motivated. In this mass range, dark photons behave like waves rather than particles and the corresponding electromagnetic waves are in the millimeter-wave range. The technical difficulties of the millimeter waves have prevented so far dark photon experiments in this mass range. The use of coherent millimeter waves to search for dark photons in a Light-Shining-through-a-Wall (LSW) experiment is proposed. The merits and limitations of coherent wave detection are clarified and the potential of single photon sensors at microwaves is investigated. Development of millimeter-wave technology is not only limited to dark photons. Technically, an experiment for dark photons by using electromagnetic waves resembles that for axions, another light dark matter candidate, with static magnetic fields. This paper represents an essential step toward axion LSW in the millimeter-wave range (Sub-THz-AXion experiment; STAX) as a potential successor of an on-going experiment in infrared.
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| 15. |
- Miyazaki, Akira, 1986-, et al.
(författare)
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Ultra narrowband detection scheme for dark photon / axion around 30 GHz
- 2022
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Ingår i: 2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz 2022). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781728194271 - 9781728194288 ; , s. 1-1
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Konferensbidrag (refereegranskat)abstract
- We demonstrated that ultra narrowband filtering at 30 GHz dramatically enhances the signal-to-noise ratio to search for dark matter candidates which couple to millimeter waves. A coherent signal relatively locked between a synthesizer and a signal analyzer can be clearly distinguished from incoherent blackbody radiation after real time FFT over a long period. We propose a novel experiment for studying dark matter candidates.
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| 16. |
- Olvegård, Maja, et al.
(författare)
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PROGRESS AT THE FREIA LABORATORY
- 2015
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Ingår i: Proceedings of IPAC'15. - JACoW : The Joint Accelerator Conferences Website.
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Konferensbidrag (refereegranskat)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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| 17. |
- Ruber, Roger, et al.
(författare)
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Accelerator development at the FREIA Laboratory
- 2021
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 16:7
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Tidskriftsartikel (refereegranskat)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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| 18. |
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| 19. |
- Santiago-Kern, Rocio, et al.
(författare)
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Cryogenic Performance of the Spoke Prototype Cryomodule for ESS
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report gives an account of all the cryogenic tests performed on the prototype spoke cryomodule, which housed Romea (cavity 1) and Giulietta (cavity 2) with all their ancillary equipment, such as static and dynamic heat loads under different circumstances.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Wedberg, Rolf, 1947-, et al.
(författare)
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Power Supplies for Tetrode High Power Amplfiers at FREIA : ESS TDR Contribution
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)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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| 24. |
- Yogi, Rutambhara, 1968-, et al.
(författare)
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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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Rapport (övrigt vetenskapligt/konstnärligt)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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| 25. |
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