Search

Currently, PSI delivers the most intense continuous muon beam in the world with up to a few 108 µ+/s. The High-Intensity Muon Beams (HIMB) project is developing a new target station and muon beamlines able to deliver 1010 µ+/s, with a huge impact for low-energy, high-precision muon experiments. While the next generation of proton drivers with beam powers in excess of the currently achieved 1.4 MW still require significant research and development, the focus of HIMB is to improve the surface muon yield with a new target geometry and to increase capture and transmission with a solenoid-based beamline in order to reach a total efficiency of approximately 10 %. We present the current status of the HIMB project., EPJ Web of Conferences, 282, ISSN:2100-014X, ISSN:2101-6275

With a nominal beam power of nearly 1.4 MW, the PSI High Intensity Proton Accelerator (HIPA) is currently at the forefront of the high intensity frontier of particle accelerators. Key issues of this facility are minimization of beam losses as well as safe operation of the SINQ spallation source. Particular attention is being recently paid towards an improved understanding of the properties of the SINQ beam line by both enhancing the beam transport simulations and developing new diagnostic elements which can also, in some cases, preserve the target integrity by preventing too large beam current density, inaccurate beam steering or improper beam delivery. Moreover, part of the SINQ beam diagnostic concept is being rethought in order to include important missing devices like BPMs. On the simulation side, newly developed composite calculations involving general purpose particle transport programs like MCNPX and BDSIM will deliver insights about beam losses and transmission through collimators. All recent and planned developments of the SINQ beam line will be discussed in this contribution.

The Paul Scherrer Institut operates two meson graphite targets, Target M and Target E, for creating the world’s most intense pion and muon beams by using 590 MeV protons and c.w. beam currents of up to 2.4 mA (=1.4 MW). The energy deposit on Target E is 20 kW mA−1. The proton beam feeds also the spallation neutron source SINQ, which operates in DC mode and produces thermal and cold neutrons. The SINQ target consists of a bundle of lead filled Zircaloy tubes. In this report the continuous developments of both target facilities and their operation are presented.

Two target stations in the 590 MeV proton beamline of the High Intensity Proton Accelerator (HIPA) at the Paul Scherrer Institut (PSI) produce pions and muons for seven secondary beamlines, leading to several experimental stations. The two target stations are 18 m apart. Target M is a graphite target with an effective thickness of 5 mm, Target E is a graphite wheel with a thickness of 40 mm or 60 mm. Due to the spreading of the beam in the thick target, a high power collimator system is needed to shape the beam for further transport. The beam is then transported to either the SINQ target, a neutron spallation source, or stopped in the beam dump, where about 450 kW beam power is dissipated. Targets, collimators and beam dumps are described.

A brilliance measurement was conducted on July 21, 2014 at the ICON beamline at SINQ as a benchmark before any potential changes are made to the liquid deuterium cold neutron source in a future extended shutdown period. The peak brilliance of the deuterium cold source at SINQ has been measured to be 3 . 3 ± 0 . 15 × 1 0 11 n cm−2 s−1 mA−1 A −1 sterad−1 at 1.8 A, and the total brilliance (energy-integrated) has been measured to be 9 . 1 ± 0 . 77 × 1 0 11 n cm−2 s−1 mA−1 sterad−1 for wavelengths above 0.7 A via a time-of-flight measurement at the ICON beamline. Using a detailed MCNP model, the peak brilliance has been calculated to be 3 . 1 ± 0 . 14 × 1 0 11 n cm−2 s−1 mA−1 A −1 sterad−1 at 1.65 A, and the total brilliance (energy-integrated) has been calculated to be 9 . 2 ± 1 . 2 × 1 0 11 n cm−2 s−1 mA−1 sterad−1 for wavelengths above 0.7 A. The peak brilliance value and wavelength position disagree only slightly between the measurement and model (7% difference in value, 8% difference in wavelength position), and the total brilliance agrees within the uncertainty bounds. The close agreement validates the models and benchmarks the state of the cold source.

We report on gold foil activation measurements performed along a vertical channel along the tank of the ultracold neutron source at the Paul Scherrer Institute. The activities obtained at various distances from the spallation target are in very good agreement with MCNPX simulations which take into account the detailed description of the source as built.

Solid deuterium (sD_2) is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD_2 must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD_2 material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN yield with time of operation after initial preparation or later treatment (`conditioning') of the sD_2. We show that, in addition to the quality of the bulk sD_2, the quality of its surface is essential. Our observations and simulations support the view that the surface is deteriorating due to a build-up of D_2 frost-layers under pulsed operation which leads to strong albedo reflections of UCN and subsequent loss. We report results of UCN yield measurements, temperature and pressure behavior of deuterium during source operation and conditioning, and UCN transport simulations. This, together with optical observations of sD_2 frost formation on initially transparent sD_2 in offline studies with pulsed heat input at the North Carolina State University UCN source results in a consistent description of the UCN yield decrease., Comment: 15 pages, 22 figures, accepted by EPJ-A

The Paul Scherrer Institut (PSI) operates the Meson production target stations E and M with 590 MeV protons at currents of up to 2.4 mA. Both targets consist of polycrystalline graphite and rotate with 1 Hz due to the high power deposition (40 kW at 2 mA) in Target E. The graphite wheel is regularly exchanged and disposed as radioactive waste after a maximum of 3 to 4 years in operation, which corresponds to about 30 to 40 Ah of proton fluence. For disposal, the nuclide inventory of the long-lived isotopes (T(1/2) > 60 d) has to be calculated and reported to the authorities. Measurements of gamma emitters, as well as 3H, 10Be and 14C, were carried out using different techniques. The measured specific activities are compared to Monte Carlo particle transport simulations performed with MCNPX2.7.0 using the BERTINI-DRESNER-RAL (default model in MCNPX2.7.0) and INCL4.6/ABLA07 as nuclear reaction models., 16 pages, 7 figures, presented at the 4th International Workshop on Accelerator Radiation Induced Activation - ARIA'17, May 22-24, 2017 Lund, Sweden

In a cyclotron-based proton therapy facility, the energy changes are performed by means of a degrader of variable thickness. The interaction of the proton beam with the degrader creates energy tails and increases the beam emittance. A precise model of the degraded beam properties is important not only to better understand the performance of a facility already in operation, but also to support the development of new proton therapy concepts. The exact knowledge of the degraded beam properties, in terms of energy spectrum and transverse phase space, depends on the model used to describe the proton interaction with the degrader material. In this work the model of a graphite degrader has been developed with four Monte Carlo codes: three conventional Monte Carlo codes (FLUKA, GEANT4 and MCNPX) and the multi-purpose particle tracking code OPAL equipped with a simplified Monte Carlo routine. From the comparison between the different codes, we can deduce how the accuracy of the degrader model influences the precision of the beam dynamics model of a possible transport line downstream of the degrader.

At a spallation neutron source, significant increase in the performance of neutron scattering instruments can be achieved if the target-moderator-reflector (TMR) and the following neutron guides are specifically tailored to the needs of different instrument classes. In order to define optimal quantities (e.g. positions of peak neutron flux, used wavelength band) for the Figure of Merit (FoM), a survey has been conducted at PSI covering the experience of the local instrument scientists. Based on this survey we introduce several FoMs which show the potential of tailoring the neutron spectrum to specific instrument needs. The developed methodology is adopted to optimize the top moderator in the conceptual design of the TMR of the European Spallation Source (ESS) Project. A parametrized geometry model of the ESS TMR is built in MCNPX and used within an optimization framework to study and optimize the moderator performance in the thermal and cold regions of the neutron spectrum. The results obtained with the optimized setup are compared to the ESS 2003 Project. Furthermore, experience is gathered while performing these simulations, e.g. the examination of the pulse shapes obtained with time-dependent calculations shows that for long-pulse target stations the peak brightness can with sufficient precision be obtained from time-independent calculations by scaling with the proton pulse duty factor.

The Paul Scherrer Institute (PSI) is the largest national research center in Switzerland. Its multidisciplinary research is dedicated to a wide ↓eld in natural science and technology as well as particle physics. The High Intensity Proton Accelerator Facility (HIPA) has been in operation at PSI since 1974. It includes an 870 keV Cockroft-Walton pre-accelerator, a 72 MeV injector cyclotron as well as a 590 MeV ring cyclotron. The experimental facilities, the meson production graphite targets, Target E and Target M, and the spallation target stations (SINQ and UCN) are used for material research and particle physics. In order to ful↓ll the request of the regulatory authorities and to be reported to the regulators, the expected radioactive waste and nuclide inventory after an anticipated ↓nal shutdown in the far future has to be estimated. In this contribution, calculations for the 20 m long beamline between Target E and the 590 MeV beam dump of HIPA are presented. The ↓rst step in the calculations was determining spectra and spatial particle distributions around the beamlines using the Monte-Carlo particle transport code MCNPX2.7.0 [1]. To perform the analysis of the MCNPX output and to determine the radionuclide inventory as well as the speci↓c activity of the nuclides, an activation script [2] using the FISPACT10 code with the cross sections from the European Activation File (EAF2010) [3] was applied. The speci↓c activity values were compared to the currently existing Swiss exemption limits (LE) [4] as well as to the Swiss liberation limits (LL) [5], becoming e↑ective in the near future. The obtained results were used to estimate the total volume of the radioactive waste produced at HIPA and have to be reported to the Swiss regulatory authorities. The comparison of the performed calculations to measurements is discussed as well.

A novel design of a gantry for proton therapy is investigated in which a degrader and emittance limiting collimators are mounted on the gantry. Due to the interactions of protons in these components there will be an additional neutron dose at the location where a patient is positioned during a proton therapy. The results of numerical study of this additional dose are presented. Neutron prompt dose at the patient position is estimated through the Monte Carlo simulation using the MCNPX 2.7.0 particle transport code. Secondary neutron and photon fluxes from the distinct beam loss points are taken into consideration and the resulting dose is calculated using realistic estimates of beam losses. The dependence of the dose on the beam energy and individual impacts of each loss point on the total dose at the patient position as well as on critical beam line components are estimated and potential design constraints are discussed. It has been found that compared with a conventional gantry the expected additional dose is higher but the optimization of the beam line configuration and additional shielding shall help to reduce the dose to an acceptable value., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Numerical analyses of machine induced background at the LHC are needed to evaluate the complete running environment of an experiment. In order to have a comprehensive view of the machine background in an experiment all of its sources, ranging from collimators’ cleaning inefficiency to distant and local beam-gas interactions need to be estimated; particles showering from the losses are then to be transported all the way to the experimental setup and the response of the detector evaluated. In this paper we describe a novel methodology implemented for the LHCb experiment to achieve this. Each step in the chain is simulated with software specific to the task and provides input to the subsequent step through a well-defined and clear interface. Further, we will discuss in detail the various steps in the chain together with the advantages such a modular method allows in evaluating operational conditions where scaling of the initial sources can be applied. We will also give some examples of the results obtained.

We present a new, handheld system for in vivo detection of radiotracers. The detection is based on scintillators coupled to Silicon Photomultipliers (SiPMs) and aimed at direct positron detection. The battery-powered system is wire-lessly connected to a PC. A graphical user interface allows controlling the probe functions and monitoring count rates, battery voltage and temperature. The probe is fully compatible with standard sterilisation procedures and has been successfully used in pre-clinical trials with human cancer patients. The use of the probe requires that the patient be administered a dose of the radiopharmaceutical F-18-fluorodeoxyglucose (FDG), a beta(+) emitting glucose analogue used for detecting tumours in oncology, which can still be detected during the operation. (C) 2011 Published by Elsevier Ltd.

Changing the configuration of the cold neutron source during an extended shutdown of the Swiss Spallation Neutron Source (SINQ) at the Paul Scherrer Institut is being considered for improving performance of the instruments that use the cold source. Proposed plans include making the REH external (ensuring that it is not filled with liquid D2) and using a REH that has been optimized to provide maximum gains between 3 and 6 A. The optimization study was done using the MCNP Monte Carlo particle transport code, but was made tenable by developing a quick flux reconstruction technique that allows the neutron guide reflectivity to be approximated and accounted for in the optimization figure of merit. Ultimately, a wedgeshaped REH that penetrates the D2 volume to about 4 cm from its center was determined to be optimal, and should provide an average gain of 24% from 3 and 6 A and a peak gain of 29% at 5.5.

With a nominal beam power of nearly 1 MW on target, the Swiss Spallation Neutron Source (SINQ), ranks among the world's most powerful spallation neutron sources. The proton beam transport to the SINQ target is carried out exclusively by means of linear magnetic elements. In the transport line to SINQ the beam is scattered in two meson production targets and as a consequence, at the SINQ target entrance the beam shape can be described by Gaussian distributions in transverse $x$ and $y$ directions with tails cut short by collimators. This leads to a highly nonuniform power distribution inside the SINQ target, giving rise to thermal and mechanical stresses. In view of a future proton beam intensity upgrade, the possibility of homogenizing the beam distribution by means of a fast beam rotation system is currently under investigation. Important aspects which need to be studied are the impact of a rotating proton beam on the resulting neutron spectra, spatial flux distributions and additional---previously not present---proton losses causing unwanted activation of accelerator components. Hence a new source description method was developed for the radiation transport code MCNPX. This new feature makes direct use of the results from the proton beam optics code TURTLE. Its advantage to existing MCNPX source options is that all phase space information and correlations of each primary beam particle computed with TURTLE are preserved and transferred to MCNPX. Simulations of the different beam distributions together with their consequences in terms of neutron production are presented in this publication. Additionally, a detailed description of the coupling method between TURTLE and MCNPX is provided.

We present a new, handheld probe for radiotracer detection in vivo and inside operating theatres, where PET scanners cannot be used for radioguided surgery. The device is based on scintillation detectors optically coupled to Silicon Photomultipliers (SiPMs). It is wirelessly connected to a PC, which, among other functions, optimises operating voltages to compensate for changes of the detector temperature. The probe is primarily aimed at and optimised for direct detection of β+ radiation at short distances. Nevertheless, it is also sensitive to γ, thus enabling the surgeon to localise tumours roughly at larger distances. The use of the probe has been demonstrated in first pre-clinical pilot trials with oncologic patients at the CHUV university hospital.

A handheld probe for direct positron detection based on scintillators coupled to silicon photomultipliers (SiPMs) is presented in this paper. The battery-powered system is optimised for intra-operative use. It is fully sterilisable and wirelessly connected to a PC running a graphical user interface. Successful pilot clinical trials have shown the use in oncological surgery.