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Lofnes, Tor
Publications (10 of 16) 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., 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
Goryashko, V., Ziemann, V., Lofnes, T. & Ruber, R. (2013). RF Power Consumption in the ESS Spoke LINAC: ESS TDR Contribution.
Open this publication in new window or tab >>RF Power Consumption in the ESS Spoke LINAC: ESS TDR Contribution
2013 (English)Report (Other academic)
Abstract [en]

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.

Publisher
p. 24
Series
FREIA Report ; 2013/01
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-192108 (URN)
Available from: 2013-01-16 Created: 2013-01-16 Last updated: 2013-01-16Bibliographically approved
Wedberg, R., Yogi, R. A., Goryashko, V., Santiago-Kern, R., Hermansson, L., Lofnes, T., . . . Ruber, R. (2012). Power Supplies for Tetrode High Power Amplfiers at FREIA: ESS TDR Contribution. Uppsala: Department of Physics and Astronomy, Uppsala University
Open this publication in new window or tab >>Power Supplies for Tetrode High Power Amplfiers at FREIA: ESS TDR Contribution
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2012 (English)Report (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Department of Physics and Astronomy, Uppsala University, 2012. p. 6
Series
FREIA Report ; 2012/02
Keywords
Tetrode, FREIA, Power Supply, High Power RF Amplifier
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-182119 (URN)
Available from: 2012-10-05 Created: 2012-10-03 Last updated: 2017-01-25Bibliographically approved
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