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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.

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

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.

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.

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.