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• 1.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
ESS RF Source and Spoke Cavity Test Plan2015Report (Other academic)

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.

• 2.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Building an Arduino based weather station and connecting it as a slave to a control system2016Report (Other academic)
• 3.
B.I. Stepanov Institute of Physics, National Academy of Science of Belarus,.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden .
Effects of emittance and energy spread in an electron bunch on THz radiation generated by a super-radiant source: report III of the series of reports by the Swedish FEL Center and FREIA Group2014Report (Other academic)

In this report we summarize our results on simulation of a super-radiant sourceoperating at the THz spectral range. We consider an open-type undulator com-prising plane magnets but without any guiding structure for generated THz eld.The undulator is assumed to be driven by electron bunches of femtosecond durationwhich are produced by an rf Linac. Using a numerical model developed, we analyzeeects of the bunch parameters on output performance of the super-radiant sourceand reveal some surprising results. Specically, we show that degradation in bunchspatial quality (increase in the bunch emittance) should lead to decrease in angulardivergence and spectral narrowing of the THz radiation. We also demonstrate thatelectron energy spread which commonly leads to bunch broadening and radiativeenergy drop can be eventually suppressed under appropriate conditions.

• 4.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. NXP Semiconductors.
Application Note: Uppsala University’s BLF188XR single ended amplifier at 352 MHz2015Report (Refereed)
• 5.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Brightness optimization in Thomson backscatteringprocesses2015Report (Other academic)

The generation of high-brightness femtosecond x-ray pulses enables explorationof so far largely unexplored areas of atomic physics, and also enables highcontrast images of biological tissue. The use of Thomson backscattering with high energyelectrons provides a new way to produce high brightness x-ray pulses, which is considerablycheaper than other techniques. We present a general description of Thomsonscattering and take into account laser and electron focus effects. We also consider theeffect of energy spread within the electron bunches and consider collisions at arbitrarycollision angles. We also investigate flattening and chirped laser pulses, the consequenteffect on the brightness and total number of scattering events. The optimization is thenperformed with respect to electron bunch energy and energy spread; laser and electronfocus parameters; limitation of bandwidth within the laser pulse. The optimization ofthe brightness is subsequently performed with the help of a genetic algorithm technique.

• 6.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Cryosystem for DC spark experiments: Construction and acceptance tests2019Report (Other academic)
• 7.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Simulations of Magnetic Fields and Forces in Highly Adjustable Magnet (HAM) Undulator Concept Using COMSOL2019Report (Other academic)

A design for a new type of undulator insertion device has been proposed. The undulator would consist of a stack of disks that each contain a pair of magnet structures, each disk being a half period of the minimum planar case. The disks could rotate independently about the beam axis, and the distance of the magnets from the center line is adjustable, so the magnetic field is adjustable in magnitude and orientation within the transverse plane along the beam axis. This would allow the undulator to be configured for generating a wide variety of radiation. Plane polarization would be attained with undulator periods as integer multiples of the base period. In the base case the direction of magnetization alternates between each disk, and for the case of multiple periods the magnetization alternates each M:th disk. Helical polarization would be attained with a period greater than two times the base period such that an integer number of periods fit inside the undulator structure. Initial numerical simulations have been made, and are reported in this paper. Building on a previous study [1] further simulations were requested to study the behavior of the magnets closer, and to calculate the forces acting on the magnet structures for use in feasibility assessment. In the previous study simple magnetic structures with uniform direction of magnetization were simulated. In this study a more complex structure was also investigated: a type of partial transverse Halbach configuration. This structure would concentrate the magnetic flux along the beamline and could lead to a more compact design, and limit the magnetic field outside the device.The simulations were made using COMSOL Multiphysics modelling software.

• 8.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
An approach to characterization of the Lorentz transfer function of ESS spoke cavities at FREIA2014Report (Other academic)
• 9.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Giant single-cycle THz pulsesfor pump-probe experiments2016Report (Other academic)

Strong-field single-cycle THz pulses are an invaluable tool forprobing and controlling low-energy excitations in matter such asmagnons, plasmons, phonons and Josephson waves. A novel scheme isproposed to generate quasi-half-cycle GV/m THz pulses with a mutlikilohertzrepetition rate. It makes use of coherent spontaneous emissionfrom a pre-bunched electron beam traversing an optimally taperedundulator. The scheme is the further development of the novel conceptof the slippage control in free-electron lasers [T. Tanaka, PRL 114 (2015)044801]. The pump-probe THz/X-ray/optical configuration is discussed.

• 10.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Proposal for Design and Test of a 352 MHz Spoke RF Source2012Report (Other academic)

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.

• 11.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden .
Conceptual Design of an Stockholm-Uppsala THz FEL Oscillator: report I of the series of reports by the Swedish FEL Center2013Report (Other academic)

The Stockholm-Uppsala FEL center is currently studying the user interest in terahertz radiation in the M\"{a}laren region and considering the possibility of building a terahertz free-electron laser (THz FEL) in the FREIA laboratory. In this memo we present the design of an electron RF linac required to drive a superradiant THz source.

• 12.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
RF Power Consumption in the ESS Spoke LINAC: ESS TDR Contribution2013Report (Other academic)

• 13.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
RF High Power Amplifiers for FREIA – ESS: design, fabrication and measurements2015Report (Refereed)

The FREIA laboratory is a Facility for REsearch Instrumentation and Acceleratior development at Uppsala University, Sweden, constructed recently to test and develop superconducting accelerating cavities and their high power RF sources. FREIA's activity target initially the European Spallation Source (ESS) requirements for testing spoke cavities and RF power stations, typically 400 kW per cavity. Different power stations will be installed at the FREIA laboratory. The first one is based on vacuum tubes and the second on a combination of solid state modules. In this context, we investigate different related aspects, such as power generation and power combination. For the characterization of solid state amplifier modules in pulsed mode, at ESS specifications, we implement a Hot Sparameter measurement set-up, allowing in addition the measurement of different parameters such as gain and efficiency. Two new solid state amplifier modules are designed, constructed and measured at 352 MHz, using commercially available LDMOS transistors. Preliminary results show a drain efficiency of 71 % at 1300 W pulsed output power. The effects of changing quiescent current (IDq) and drain voltage are investigated, aswell as the possibilities to combine several modules together.

• 14.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Measuring mechanical vibrations using Arduino as a slave I/O to an EPICS control system2015Report (Other academic)

In this study we have assembled hardware and software to be used for measuring of mechanical vibrationsin the FREIA-laboratory at Uppsala University. We have utilized an Arduino microcontroller as a slaveI/O and equipped it with dual accelerometers to be used for vibration measurements and a serial adapterwhich was used to connect the hardware to an EPICS IOC for analysis. Data from the two accelerometershave then been cross correlated in order to find a transfer function. Our results where in good agreementwith theory.

• 15.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Analytic Space-Charge Model for Gaussian Beams with cross-plane Coupling2017Report (Other academic)

Intensities of particle beams provided by particle accelerators are raised to levels where the self-interaction of the beam particles due to electromagnetic repulsion, the so-called space-charge effect, becomes a dominant factor. It is therefore indispensable to understand the effects on the beam dynamics in the presence of strong space charge forces. As complement to existing simulation methods, we present a fully analytic space charge model valid for transverse Gaussian beams and which includes non-linear space charge forces and cross-plane coupling. We verify the validity of the model by running test simulations in a few accelerator lattice examples. Finally, we briefly explore the possibilities for future simulations regarding new insights in beam dynamics and show initial results of the development of a beam envelope (core) in a test ring, as well as the dynamics of passive spectator particles which observe the non-linear electric field generated by a beam core.

• 16.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Dark currents studies with the Uppsala X-band Spectrometer at XBox test stand at CERN2019Report (Other academic)

Vacuum arcs is the phenomenon which limits the performance of normal conducting acceleratorcavities. It closely depends on electron field emission, which is consider a precursor for the creationof a vacuum discharge. These processes are still not fully understood, but we know that theydepend on the physical properties of the surfaces and bulk materials used in the acceleratorstructures. We need to come at these problems with a multidisciplinary approach, comprisingaccelerator, material and surface physics, for both experimental and theoretical analysis.The field emission current emitted during operation of the RF cavity is typically refer to as thedark current. Behavior of the dark current can give useful information about changes inside thestructure during conditioning and thus into the physics of the vacuum arcs. The Uppsala groupuses a magnetic spectrometer to look at the changes, both spatially on the screen and by measuringthe energy spectrum of the escaping electrons during conditioning of CLIC X-band structuresin dedicated high-power RF test stand at CERN. The spectrometer was originally designedto measure the electrons from the breakdown events with much higher intensities than the darkcurrent signals. In this paper we present the attempt to measure the dark current with the samesetup.

• 17.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Estimation of radiation levels during high power RF cavity tests in FREIA2014Report (Other academic)
• 18.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Spectrometers for RF breakdown studies for CLIC2016Report (Other academic)

A e+e- collider of several TeV energy will be needed for the precision studies of any new physics discovered atthe LHC collider at CERN.  One promising candidate is CLIC, a linear collider which is based on a two-beam acceleration scheme that efficiently solves the problem of power distribution to the acceleration structures. The phenomenon that currently prevents achieving highaccelerating gradients in high energy accelerators such asthe CLIC is the electrical breakdown at very high electrical field.The ongoing experimental work within the CLIC collaboration is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. In order to validate the feasibility of accelerating structures and observe the characteristics of the vacuum discharges and their eroding effects on the structure two dedicated spectrometers are now commissioned at the high-power test-stands at CERN. First, the so called Flashbox has opened up a possibility for non-invasive studies of  the emitted breakdown currents during two-beam acceleration experiments. It gives an unique possibility to measure the energy of electrons and ions in combination withthe arrival time spectra and to put that in context with accelerated beam, which is not possible at any of the other existing test-stands.The second instrument, a spectrometer for detection of the dark and breakdown currents, is operated at one of the 12 GHz stand-alone test-stands at CERN.  Built for high repetition rate operation it can measure the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. Two new analysis tools: discharge impedance tracking and tomographic image reconstruction, applied to the data from the spectrometer make possible for the first time to obtain the location of the breakdown inside the structure both in the transversal and longitudinal direction thus giving a more complete picture of the vacuum breakdown phenomenon.

• 19.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
DB Science 400 kW RF Station Site Acceptance Test2017Report (Other (popular science, discussion, etc.))

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.

• 20.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Itelco-Electrosys 400 kW RF Station Site Acceptance Test2015Report (Other (popular science, discussion, etc.))

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.

• 21.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Design of the Cryocooled DC Discharge System with Heat Transfer Simulations in COMSOL2017Report (Other academic)

Vacuum breakdowns are major limiting factor for the development of the compactparticle accelerators. Further progress in this domain requires studies of thevacuum breakdowns in well controlled environment, where all important parameters,like mate- rial temperature, can be regulated. Cryocooled DC spark system is one ofthe projects that addresses these demands and it is first setup where temperaturewill be controlled through a wide range, from room temperatures all the way downto 4 K. The main topics of this project are simulations of the cool down time of thepulsed DC system done in the physics simulation software COMSOL. The simulationresults are bench- marked through theoretical calculations. Two design aresimulated and compared, one with a simpli?ed geometry and one with the modelimported from CAD. Both models are of comparable dimensions and bothsimulations yields similar cool down time and the simulations are thereforeconsistent. The simulations are made in order to choose a cryocooler for thesystem. The cryocooler needs to be able to cool down the system in a short enoughtime, as well as keep the system at a certain temperature. The cool down time usingtwo different cryocoolers with different cooling capacities is evaluated, and thecryocooler with the higher capacity also cools down the system quicker. The time tocool down the electrodes from 45 K to 4 K with a cryocooler of 1.5 W coolingcapacity is 7.8 hours, as opposed to the cryocooler with 0.2 W cooling capacityyielding a cool down time of 58.5 hours.

• 22.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
1 kW Solid-State Power Amplifier at 100 MHz for Use in Cyclotron2015Report (Refereed)
• 23.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
RF Test of the ESS Double Spoke Cavity2016Report (Other academic)

A bare spoke cavity has been tested at FREIA Laboratory with a Self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. This report presents the details of each measurement.

• 24.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
First High Power Test of the ESS Double Spoke Cavity2017Report (Other academic)

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.

• 25.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
First High Power Test of the ESS High Beta Elliptical Cavity package2018Report (Other academic)

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.

• 26.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Undulator Considerations in the Baseline Design of the MAX IV Soft X-Ray Laser2018Report (Other academic)

We examine the optimal parameter space for an x-ray free-electron laser (FEL) in the operation mode of self-amplified spontaneous emission (SASE). The study focuses on FEL operation with a shorter undulator period and higher undulator strength made available through recent developments in in-vacuum, cryogenic and superconducting undulators. We survey the progress on short-period undulator technologies and compute the FEL output characteristics versus the undulator parameters. We perform the study on a case of the planned soft-x-ray FEL at the MAX IV Laboratory in Sweden. An extension of the SASE mode into the harmonic lasing self-seeded mode is also analysed.

• 27.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. STFC Daresbury Laboratory, Warrington, United Kingdom.
Science Requirements and Performance Specification forthe CompactLight X-Ray Free-Electron Laser2019Report (Other academic)

CompactLight is a consortium funded by the European Union through the Horizon 2020 Research and Innovation Programme under Grant Agreement No. 777431.  This report summarizes science requirements and performance specification for the CompactLight x-ray free-electron laser.

• 28.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. CERN.

We designed a radiation shield for the vertical cryostat at FREIA. The design is dedicated to a prototype crab cavity for the High-Lumi LHC project, and is normalized with an experimental radiation dose measured at CERN in the most contaminated case ever observed. The predicted dose is below 10 $\mu$T outside the normal concrete shield made of 30 cm thick wall and 60 thick roof.

• 29.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Electro-acoustic stability of asuperconducting spoke cavity2015Report (Other academic)

This thesis describes measurement procedures and results for the measurement ofthe Q value and microphonics of a superconducting spoke cavity. The thesis starts byintroducing the background of RF electronics and how they pertain tosuperconducting cavities. We then present the cavity model and figures of meritcharacterising its performance, the theory of how electric fields cause mechanicalvibrations in the cavity walls and present an experimental setup for measurements.Four measurement procedures are presented, of which two are implemented.Measurements are carried out by running the cavity in a self-excited loop in anaccurate manner with precise calibrations. Finally, we present the measured Q valueof a single spoke cavity and the results of microphonics measurements.We find that the cavity has a Q value of 1.06*10^9 at a resonance frequency of360.215MHz. It is sensitive to microphonics of a few frequencies, most notably someclose to 14 Hz which coincides with the repetition rate of the ESS.

• 30.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
A Pion Collector Based on Superconducting Solenoids: A Feasibility Study for the ESSnuSB2016Report (Other academic)

The European Spallation Sour e Neutrino Super-Beam project (ESSnuSB) plans to use the powerful proton beam from the ESS linac to produce a neutrino super beam in a dedicated target. The super beam must  consist of either muon neutrinos or muon antineutrinos and be directed towards an underground detector 540 km from the source. A neutrino horn based on a magnetic toroid is normally employed for colle ting the pions that emerge from the target and soon after emit neutrinos as they decay. However, the horn cannot accept the nominal pulse from the linac due to ohmic heating from the high current driving the structure. As an alternative, we have studied the use of solenoids for pion colle tion. The solenoids, that would be made superconducting for continuous operation, are however blind to the pion charge wherefore a charge separation stage is needed. This report describes our efforts of combining solenoid and dipole fields in order to collect pions from the target and separate the pion charges before they have time to decay. The study indicates that focusing with solenoids is possible, but that simultaneous charge separation can only be achieved with limited efficiency and acceptance in terms of pion divergence and momentum. Further studies are required for full understanding of the limitations.

• 31.
National Science Center "Kharkiv Institute of Physics and Technology", Kharkiv, Ukraine.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden . Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Design of a Superconducting Linear RF Accelerator for a Superradiant THz FEL: report II of the series of reports by the Swedish FEL Center and the FREIA Group2013Report (Other academic)

The Stockholm-Uppsala FEL center is currently studying the user interest in terahertz radiation in the M\"{a}laren region and considering the possibility of building a terahertz free-electron laser (THz FEL) in the FREIA laboratory. In this memo we present the design of an electron superconducting RF linear accelerator required to drive a superradiant THz source.

• 32.
National Science Center "Kharkiv Institute of Physics and Technology", Kharkiv, Ukraine.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden . Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Towards a combined THz/X-ray source: report IV of the series of reports by the Swedish FEL Center and the FREIA Group2014Report (Other academic)

In the framework of development of a Free Electron Laser (FEL) by the Swedish FEL Center and theFREIA laboratory, we discuss the design of a versatile combined THz/X-ray source driven by high-brightness electron bunches produced by a superconducting linear accelerator. The ultimate goal isto build a versatile photon source for multidisciplinary research at the FREIA laboratory of UppsalaUniversity. A signicant part of equipment is potentially available via the FREIA project at UppsalaUniversity after 2018 such as the cryogenic system, the system of power generation and transportation,control and data acquisition systems. For pump-probe experiments, we discus a possibility to combinethe THz source with an X-ray source based on the inverse Compton scattering of quantum laser pulsesfrom electron bunches. The X-ray source will operate in the \water window" with an output intensitycomparable to a second generation synchrotron. The envisioned THz/X-ray source is compact andcomparable in budget to the cost of one beamline at MAX IV. The source can also be used to trainstudents in accelerator physics and applications of THz and synchrotron radiation.

• 33.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala Test Facility Project Plan2013Report (Other academic)

Uppsala University and ESS AB are creating a test facility for the ESS spoke cavities and their RF systems at the FREIA laboratory, Uppsala. The test facility will serve for the prototyping of the RF power generation systems for the ESS single spoke cavities and for the high power testing of the prototype single spoke cavities and their cryomodule. This report describes the project plan for the Uppsala test facility.

• 34.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Tests of the Spoke Cavity RF Source and Cryomodules in Uppsala: ESS TDR Contribution2012Report (Other academic)
• 35.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
The Cryogenic System at the FREIA Laboratory2015Report (Other academic)
• 36.
Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
400 kW RF Stations Overview Experience: Overview of the operation experience during 2018-2019 with the Itelco-Electrosys and DB Science stations at the FREIA Laboratory.2019Report (Other academic)

We present the operational experience with the Itelco-Electrosys and DB Science 400 kW RF stations installed at the FREIA Laboratory. From the summer of 2018 to the summer of 2019 the stations were used for the test of the spoke cryomodule prototype for ESS. Unfortunately multiple issues with both RF stations delayed or inhibited normal operation. The Itelco-Electrosys station was out-of-operation from October 2018 to June 2019, due to multiple issues, which took a long time to understand and solve.

• 37.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea2017Report (Other academic)
• 38.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Cryogenic Settings for Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part I)2018Report (Other academic)
• 39.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Cryogenic Settings for Testing of the Fully Equipped ESS' High Beta Cavity ESS086-P01 (Part II)2018Report (Other academic)
• 40.