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Lofnes, Tor
Publications (10 of 18) Show all publications
Li, H., Jobs, M., Santiago Kern, R., Goryashko, V. A., Hermansson, L., Bhattacharyya, A., . . . Ruber, R. (2019). Characterization of a beta=0.5 double spoke cavity with a fixed power coupler. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 927, 63-69
Open this publication in new window or tab >>Characterization of a beta=0.5 double spoke cavity with a fixed power coupler
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2019 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 927, p. 63-69Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Double spoke cavity, High power test, Self-excited loop
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-382240 (URN)10.1016/j.nima.2019.02.003 (DOI)000462142700008 ()
Funder
EU, Horizon 2020, 730871
Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-05-16Bibliographically approved
Santiago-Kern, R., Li, H., Miyazaki, A., Gajewski, K., Hermansson, L., Fransson, K., . . . Ruber, R. (2019). Cryogenic Performance of the Spoke Prototype Cryomodule for ESS.
Open this publication in new window or tab >>Cryogenic Performance of the Spoke Prototype Cryomodule for ESS
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2019 (English)Report (Other academic)
Abstract [en]

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.

Publisher
p. 48
Series
FREIA Report ; 2019/05
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-397744 (URN)
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-11-26Bibliographically approved
Hoang Duc, L., Jobs, M., Lofnes, T., Ruber, R., Olsson, J. & Dancila, D. (2019). Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators. Review of Scientific Instruments, 90(10), Article ID 104707.
Open this publication in new window or tab >>Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators
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2019 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, no 10, article id 104707Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-402616 (URN)10.1063/1.5110981 (DOI)000504078300062 ()
Available from: 2020-01-17 Created: 2020-01-17 Last updated: 2020-01-17Bibliographically approved
Santiago-Kern, R., Gajewski, K., Hermansson, L., Jobs, M., Li, H., Lofnes, T. & Ruber, R. (2018). Cryogenic Synopsis from the Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part I).
Open this publication in new window or tab >>Cryogenic Synopsis from the Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part I)
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2018 (English)Report (Other academic)
Publisher
p. 20
Series
FREIA Report ; 04
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-365758 (URN)
Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-11-14Bibliographically approved
Santiago-Kern, R., Gajewski, K., Hermansson, L., Jobs, M., Li, H., Lofnes, T. & Ruber, R. (2018). Cryogenic Synopsis from the Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part II).
Open this publication in new window or tab >>Cryogenic Synopsis from the Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part II)
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2018 (English)Report (Other academic)
Publisher
p. 27
Series
FREIA Report ; 06
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-365761 (URN)
Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-11-14Bibliographically approved
Li, H., Santiago-Kern, R., Jobs, M., Hermansson, L., Gajewski, K., Lofnes, T., . . . Ruber, R. (2018). First High Power Test of the ESS High Beta Elliptical Cavity package. Uppsala University
Open this publication in new window or tab >>First High Power Test of the ESS High Beta Elliptical Cavity package
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2018 (English)Report (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala University, 2018. p. 60
Series
FREIA Report ; 2018/07
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-371627 (URN)
Available from: 2018-12-21 Created: 2018-12-21 Last updated: 2019-01-09Bibliographically approved
Santiago Kern, R., Bhattacharyya, A., Gajewski, K., Goryashko, V., Hermansson, L., Jobs, M., . . . Ruber, R. (2017). Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea. Uppsala
Open this publication in new window or tab >>Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea
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2017 (English)Report (Other academic)
Place, publisher, year, edition, pages
Uppsala: , 2017. p. 29
Series
FREIA Report ; 2017/12
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-333037 (URN)
Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-09Bibliographically approved
Li, H., Santiago-Kern, R., Jobs, M., Bhattacharyya, A., Goryashko, V., Hermansson, L., . . . Ruber, R. (2017). First High Power Test of the ESS Double Spoke Cavity. Uppsala
Open this publication in new window or tab >>First High Power Test of the ESS Double Spoke Cavity
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2017 (English)Report (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: , 2017. p. 60
Series
FREIA Report ; 2017/10
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-335434 (URN)
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-06Bibliographically approved
Bhattacharyya, A., Dancila, D., Ekelöf, T., Eriksson, J., Fransson, K., Gajewski, K., . . . Ziemann, V. (2015). ESS RF Source and Spoke Cavity Test Plan.
Open this publication in new window or tab >>ESS RF Source and Spoke Cavity Test Plan
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2015 (English)Report (Other academic)
Abstract [en]

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.

Publisher
p. 13
Series
FREIA Report ; 2015/01
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-246774 (URN)
Available from: 2015-03-10 Created: 2015-03-10 Last updated: 2017-01-25Bibliographically approved
Olvegård, M., Bhattacharyya, A., Dancila, D., Ekelöf, T., Eriksson, J., Fransson, K., . . . Yogi, R. (2015). PROGRESS AT THE FREIA LABORATORY. In: Proceedings of IPAC'15: . Paper presented at IPAC'15, the sixth International Particle Accelerator Conference, Virginia, USA, May 3-8, 2015. JACoW: The Joint Accelerator Conferences Website
Open this publication in new window or tab >>PROGRESS AT THE FREIA LABORATORY
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2015 (English)In: Proceedings of IPAC'15, JACoW: The Joint Accelerator Conferences Website , 2015Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
JACoW: The Joint Accelerator Conferences Website, 2015
National Category
Accelerator Physics and Instrumentation Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-263956 (URN)
Conference
IPAC'15, the sixth International Particle Accelerator Conference, Virginia, USA, May 3-8, 2015
Available from: 2015-10-05 Created: 2015-10-05 Last updated: 2017-01-25Bibliographically approved
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