The photon beam brightness of synchrotron light facilities is increased by reducing the beam emittance. For the upgrade of the storage ring of the Swiss Light Source (SLS2), the lattice achieving a low emittance foresees longitudinal gradient bending (LGB) magnets producing high peak field values and quasi-hyperbolic field profiles to minimize emittance at locations of radiation. Two types of technologies are studied: a 1.4 T peak field magnet based on permanent magnet materials (PM-LGB) and a superconducting version (SC-LGB) working at almost 5 T peak, to be upgraded to 6 T in future. The baseline scenario consists in commissioning the SLS2 with 60 PM-LGB assemblies first and exchange at a later stage three PM-LGBs by superconducting ones providing a higher peak field value. Thus, the design must foresee interchangeability. In this paper, we focus on the magnetic and mechanical design aspects of the PM-LGB and on the main mechanical constraints of the SC-LGB.

Magnet measurements at the Paul Scherrer Institute (PSI) are performed with the use of a process control tool (PCT), which is fully integrated into the PSI control system. The tool is implemented as a set of user friendly graphical user interface applications dealing with particular magnet measurement techniques supported at PSI, which include advanced Hall probe, vibrating wire, and moving wire methods. The core of each application is the state machine software developed by magnet measurement and control system experts. Applications act as very efficient assistants to the magnet measurement personnel by monitoring the whole measurement process on-line and helping to react in a timely manner to any possible operational errors. The paper concentrates on the PCT structure and its performance.

3D Hall sensors generally suffer from cross-sensitivity among measurement axes, which limits their accuracy compared to 1D Hall sensors, and complicates their calibration. To overcome these issues, a time-effective and intuitive calibration and field reconstruction method is proposed which is well-suited, but not limited, to a new type of 3D Hall sensor ("Hallcube") consisting of six orthogonally arranged 1D Hall sensors that form a sub-millimeter active volume, and pairwise compensate for the planar Hall effect. Generally, the method is applicable to 3D Hall sensors that are composed of separate 1D Hall sensors, and show negligible planar Hall voltage (inherently or after compensation). The method is based on a twostep calibration scheme: (1) determination of the relative placement of the six constituent Hall sensors, and (2) calibration of each of the six sensors analogously to a standard 1D Hall sensor calibration. From the normal vectors and the voltage-to-magnetic-field characteristic of each sensor, the full magnetic field vector can be reconstructed. The proposed method was applied to the first prototype Hallcube sensor which achieved an accuracy of 800 ppm at the 1 T level for any direction of the field vector. The accuracy limiting factor was the underperformance of the 1D Hall sensors, whose Hall voltages display a long-term instability of >600 ppm. (C) 2017 Elsevier B.V. All rights reserved.

The measurement of all three components of a magnetic field, simultaneously to high precision with Hall sensors, remains a challenge. Given the high precision of state-of-the-art conventional uniaxial Hall sensors, this is disappointing. Currently, three-axis Hall sensors suffer from either, or a combination, of the following: large spatial distribution between active areas; high signal noise; cross-sensitivity between measurement axes due to angular errors or the planar Hall effect; the inability to measure at a single point in space and time. A new type of three-axis Hall sensor is proposed, consisting of three sets of uniaxial Hall sensors in a small active volume. The feasibility of the proposed sensor has been proven in a prototype with an active volume as small as 200 mu m x 200 mu m x 200 mu m. Due to its unique configuration, the new sensor addresses current three-axis Hall sensor limitations: it provides a high spatial resolution of 30 mu m x 30 mu m x 1 mu m for each field component; full field vector measurements practically at a single point in space and time; and a reduction of the planar Hall effect by a factor of 35. Angular errors between the individual Hall sensors in the prototype lie between 0.1 degrees and 0.5 degrees, above the tolerable error for non-corrected measurements. However, once understood they can be taken into account. With proper calibration, this type of three-axis Hall sensor has great potential for high-accuracy three-axis magnetic field measurements and is particularly suitable for field mapping of magnets. (C) 2015 Elsevier B.V. All rights reserved.

We report the first observation of the annihilation of positronium from the 2S state. Positronium (Ps) is excited with a two-photon transition from the 1S to the 2S state where its lifetime is increased by a factor of eight compared to the ground state due to the decrease in the overlap of the positron electron wave-function. The yield of delayed annihilation photons detected as a function of laser frequency is used as a new method of detecting laser-excited Ps in the 2S state. This can be considered the first step towards a new high precision measurement of the 1S–2S Ps line.

In light of a 3-D Hall sensor that is being designed at the Magnet Section of the Paul Scherrer Institute (PSI), a new calibration scheme is under development. As a preparation to this, a single Hall plate is calibrated for perpendicular and in-plane field directions by rotation of the Hall plate in a calibration magnet. A piezoelectric nano rotary positioner system that fits into the 38 mm aperture of the calibration magnet will be applied. In addition, two Hall plates glued back-to-back and rotated 90 ° around the normal axis with respect to each other are used which have the clear advantage that the planar Hall effect is nearly cancelled out. It will be shown that the full 3-D field vector of a magnetic field can be extracted by rotation of the probe(s) in the to-be-measured magnetic field. Hence, the setup can be used efficiently to measure the (inhomogeneous) magnetic field of large aperture magnets. The paper describes the calibration results and the scheme to measure the full field vector using a piezoelectric nano rotary positioner system.

For the quadrupole magnets of the future free electron laser facility (SwissFEL) at the Paul Scherrer Institute (PSI), the location of the magnetic axis has to be known to be better than 50 μm, to minimize the commissioning time, and facilitate the final positioning of magnets to an accuracy of 1 μm using beam alignment. For this purpose, the PSI Magnet Section has developed a vibrating wire measurement system with a new type of detector capable of measuring large numbers of magnets in a short period of time. The system has been upgraded and improved so that the total accuracy of finding the magnetic axis is better than 10 μm. A new measurement procedure is described and a method is detailed with which a submicrometer reproducibility of a magnetic axis location is achieved. In addition to the axis offset, the proposed method is applicable to the measurements of the magnet roll angle. With temperature sensors attached to magnets, the method allows for valuable studies of the effect of thermal dilation on the position of the magnetic axis which is of a particular interest for the SwissFEL air cooled quadrupole magnets. Results of measurements performed on SwissFEL prototype quadrupoles with 12 mm aperture are shown.

High brightness electron bunches will be guided in the future Free Electron Laser (SwissFEL) at the Paul Scherrer Institute (PSI) by several hundred magnets. The SwissFEL machine imposes very strict requirements not only at the field quality but also at the mechanical and magnetic alignments of these magnets. To ensure that the magnet specifications are met, and to develop reliable procedures for aligning magnets in the SwissFEL and correcting their field errors during machine operations, the PSI magnet test system was upgraded. The upgraded system is a high precision measurement setup based on Hall probe, rotating coil, vibrating wire and moving wire techniques. It is fully automated and integrated in the PSI controls. The paper describes the main controls components of the new magnet test setup and their performance.

The Paul Scherrer Institut is building an X-ray free electron laser (SwissFEL) providing a source of intense, ultra-short pulses of coherent radiation in the wavelength range of 0.1 to 0.7 nm. In this facility, there will be 162 small aperture quadrupoles of two types (22- and 12-mm aperture), which both include horizontal and vertical steering functions, under preparation for the linac and the undulator line. Before the series production, eight full-scale prototypes of the final design were built in collaboration between Industry and the Paul Scherrer Institut. This paper describes the features of the quadrupole design and the measurement challenges and reports the main results obtained during the magnetic measurements. The integrated field gradient, the field profile, the harmonic content, and the magnetic axis are measured using four independent systems well suited for small bore apertures: an 8 mm and a 19-mm diameter rotating coil, a Hall probe, and a vibrating wire system. The results of the integrated transfer function and of the field quality are given and discussed.

Abstract SwissFEL [1] will start operation with the so-called Aramis FEL line which lases in the hard X-ray wavelength range from 1 to 7 Angstroem. First photons are foreseen for the end of 2016. In this first phase of the project only the transfer line (a dog-leg section) to the soft X-ray line will be assembled. The soft X-ray undulator line, Athos, will be completed at a later stage after 2018. The civil construction of SwissFEL has started in spring 2013 and will be completed by December 2014. Aramis line has 12 undulator segments but can host up to 20 segments. Tests of an undulator prototype have been recently completed and are described in a companion paper [2]. The layout and the design status of components are presented.

In this work we present the design, the construction and the measurements of the magnet for a so-called spin-rotator (Wien filter), a beam line device used to rotate the spin direction (and the associated magnetic moment) of muons in a beam used for condensed matter research at the Swiss Muon Source at the Paul Scherrer Institute. The design parameters-originating both from the properties of the preferred particle beam as well as the technological constraints for the high-voltage components generating the necessary electric field-were optimized for device compactness, cost and high beam transmission.

We usedGeant4 to accurately model the low energy muons (LEM) beam line, including scattering due to the 10-nm thin carbon foil in the trigger detector. Simulations of the beam line transmission give excellent agreement with experimental results for beam energies higher than ∼ 12keV.We use these simulations to design and model the operation of a spin rotator for the LEM spectrometer, which will enable longitudinal field measurements in the near future.

The SwissFEL Injector Test Facility at the Paul Scherrer Institute (PAI/Switzerland) started its operation in August 2010. This Facility represents the first stage of the 6 GeV acceleration complex foreseen for the SwissFEL X-Ray coherent light source planned at the PSI. The 250 MeV Injector consists of an S-Band RF photo injector followed by four S-Band acceleration structures of 4 m length each. For fine focusing corrections each accelerating structure is surrounded by four solenoids (WFS) of 0.8 m length and a maximum field of 0.1 T. Each solenoid consists of two coils in one yoke tube. To decrease the bunch length of the electron beam a magnetic bunch compressor chicane with four dipoles (AFBC2) providing a maximum magnetic field of 0.4 T for a length of 0.25 m was build. The central dipoles of the compressor chicane are sited on a movable girder to allow extensive compression studies with dipole angles between 0° and 5°. The preservation of a high brightness and a low emittance for the femto-second electron pulse impose severe tolerances in the field quality and in the magnet positioning. In this paper we review the design of two magnet types and discuss the results of field quality and magnetic axis measurements in terms of the specifications.

In this work we present the design, the construction and the measurements of the magnet for a so-called spin-rotator (Wien filter), a beam line device used to rotate the spin direction (and the associated magnetic moment) of muons in a beam used for condensed matter research at the Swiss Muon Source at the Paul Scherrer Institute. The design parameters-originating both from the properties of the preferred particle beam as well as the technological constraints for the high-voltage components generating the necessary electric field-were optimized for device compactness, cost and high beam transmission.

The tolerance in the alignment of the quadrupoles in the linacs and in the undulator lines of the Swiss Free Electron Laser (SwissFEL), the next project at the Paul Scherrer Institute (PSI), will be about 1 μm. This accuracy will be reached using beam alignment techniques. To minimize the commissioning time, it is also requested to install the quadrupoles with a precision of ±50 μm. To achieve this goal, the vibrating wire technique will be used in association with other systems to determine the position of the magnetic axis of the quadrupoles with respect to external fiducials. After a general introduction to the project and to the instrumentation principle, the novel approach developed at PSI is presented. The main innovation consists in the use of a phase lock loop (PLL) for maintaining the wire in its resonance condition. This approach simplifies the operation of the system in case the wire is moved or replaced and increases substantially the reliability of the measurement outcomes in the frame of a series test campaign.

The Swiss Light Source (SLS) at the Paul Scherrer Institute (PSI) in Villigen, Switzerland, is a 3rd generation synchrotron light source. With an energy of 2.4 GeV, it provides high brightness photon beams for research in materials science, biology and chemistry. The SLS storage ring contains 36 room temperature bending magnets, all of which produce light for experimental use; at the design energy of 2.4 GeV, they have a maximum magnetic field of 1.4 Tesla. Light is produced along the entire bending arc but can only be transferred to the external experimental facilities from selected short portions of the beam path. In cooperation with the Budker Institute for Nuclear Physics (BINP) in Novosibirsk, Russia, three of these magnets were replaced with new room temperature magnets with short regions of high magnetic field up to 2.9 Tesla. This enabled the production of intense light beams at shorter wavelengths than from the existing magnets. The critical energy of the 2.9 T magnet is 11.1 keV, compared to the 5.4 keV of the normal bend. This paper describes the design, including the multiple restraints, together with the measurement and commissioning of these so-called Superbends.

A radiation therapy system using carbon ions is proposed. It is based on an accelerator system of two coupled cyclotrons. The first cyclotron accelerates carbon ions (or other particles) up to 250 MeV/nucl. The second cyclotron is used to boost these carbon ions to 450 MeV/nucl for treatments at deep tumor sites. This separate sector cyclotron consists of six sector 3.5 T magnets with superconducting coils and four RF cavities. We report on our first results of a feasibility study of the superconducting sector magnets of this booster cyclotron. To prevent concave magnet pole edges and to achieve symmetry in the design of the magnet, the introduction of a radial gradient in the sector is proposed. A magnet geometry based on a configuration with tilted coils is presented. The field strength varies from 2.8 T to 3.5 T over 0.8 m. The viability of the magnetic design is checked with tracking simulations. The distribution of the large electromagnetic forces acting on the coil winding, evaluated using a 3D finite element analysis, is reported. The details of the superconducting coil, of the type of wires, and of the cable layout are presented. The conceptual design of the cryostat and the options for conductor protection against quench are proposed.

The Paul Scherrer Institute (PSI/Switzerland) is developing, within the PROSCAN project, a new method of proton radiotherapy for treating cancers using a gantry based spot scanning technique for irradiating deep-seated tumors. Among the innovative elements are the laminated magnets in the beam lines, including the newly conceived Gantry 2, that will enable rapid energy changes (<150 ms) to modulate the range of the scanning pencil beam in three dimensions over the tumor volume. The last and multifunctional 90° bending magnet in the Gantry 2 transport system is not only the largest, but also the most challenging element. The dynamic eddy current effects during ramping were reduced with a special arrangement of laminated parts in the central pole region of the magnet. The construction of the Gantry 2 is finished and the first proton beam reached the treatment area in May 2008. The start of the patient treatment program is planned for the near future. In this paper, the 90° bending magnet construction and the results of the magnetic measurements (both static and dynamic) are presented, together with the commissioning experiences of the Gantry 2 magnet system. The results of the magnetic measurements validated the design, showing a very successful reduction of the eddy current effects so that the fast switching between two treatment energy steps (1 to 2% of the total energy) can be realized in less than 80 ms.

The Paul Scherrer Institute (PSI/Switzerland) is planning an X-ray free electron laser facility (SwissFEL) using novel concepts for electron emission, high gradient acceleration and effective bunch compression. Based on a normal-conducting 5.8 GeV linear accelerator, SwissFEL will cover a spectral range of 0.1-7 nm wavelength. An ultra bright electron source was first developed and commissioned in 2008 followed by the construction of a 250 MeV accelerator facility in order to validate the concepts to generate and transport high brightness beams. This facility will be used in the future as the injector for the SwissFEL linac. An amount of typically 100 magnets of 4 different types (solenoids, quadrupoles, dipoles and correctors) is required in order to preserve the high brightness and the low emittance of the femto-second electron pulses. All the magnets are designed and magnetically measured at PSI in order to ensure that the required tolerances are fulfilled. The field gradient, the multipole contents and the magnetic center position are measured with two independent systems, an automated scanner and a uniaxial Hall Probe. We review the magnet design required for the injection phase and discuss the first results of the magnetic measurements.