PSI, Villigen
ORNL, Oak Ridge, Tennessee
Operation and upgrade of very intense proton beam accelerators like the PSI facility and the SNS spallation source at ORNL is typically constrained by potentially large machine activation. Besides the standard beam diagnostics, beam tomography techniques provide a reconstruction of the beam transverse phase space distribution, giving insights to potential loss sources like irregular tails or halos. Unlike more conventional measurement approaches (pepper pot, slits) beam tomography is a non destructive method that can be performed at high energies and, virtually, at any beam location. Results from the application of the Maximum Entropy Tomography (MENT) algorithm to different beam sections at PSI and SNS will be shown. In these reconstructions the effect of nonlinear forces is made visible in a way not otherwise available through wire scanners alone. These measurements represent a first step towards the design of a beam tomography implementation that can be smoothly employed as a reliable diagnostic tool.
PSI, Villigen
At the PSI a high intensity proton accelerator complex is routinely operated with a final energy of 590 MeV and with a beam current of 2.2 mA. In the future the beam current will be increased to 3 mA, then carrying a beam power of 1.8 MW. Operating a facility at such a high beam power needs not only a performing and fast protection mechanism against failures but also protection against activation of the facility. This presents a challenge for the beam diagnostics since a high dynamic range of currents is handled. Furthermore several tools, control loops and procedures which are of utmost importance for minimizing the ever present losses in the facility will be presented together with the machine protection system. A new challenge for our facility is the new ultra cold neutron (UCN) facility, coming into operation this year and requiring the switch over from one beam line to another for a duration of 8 sec with the full beam power. Using a short pilot pulse of a few ms the beam position is measured and the beam centered in preparation of the long pulse. We will show the diagnostics that are involved and how we overcome the constraints given by the machine protection system.
Tsinghua University, Beijing
PSI, Villigen
TUB, Beijing
CIAE, Beijing
The 1.3 MW of beam power delivered by the PSI 590 MeV Ring Cyclotron together with stringent requirements regarding the controlled and uncontrolled beam losses poses great challenges with respect to predictive simulations. A new particle matter interaction model in OPAL is taking into account energy loss, multiple Coulomb scattering and large angle Rutherford scattering. This model together with the 3D space charge will significantly increase the predictive capabilities of OPAL. We describe a large scale simulation effort, which leads to a better quantitative understanding of the existing PSI high power proton cyclotron facility. The initial condition for the PSI Ring simulations is obtained from a new time structure measurements and the many profile monitors available in the 72 MeV injection line. A large turn separation and narrow beam size at the extraction turn is obtained. We show that OPAL can precise predict the radial beam pattern at extraction with large dynamic range (3-4 orders of magnitude). The described capabilities are mandatory in the design and operation of the next generation high power proton drivers.
PSI, Villigen
PSI is gradually upgrading the 590 MeV proton beam intensity from the present 2.2 mA towards 3 mA, which poses a significant challenge to the reliable operation of the accelerator facility. Of particular concern is the collimator system which is exposed to the dispersed beam from a muon production target. It shapes an optimal beam profile for low-loss beam transport to the neutron spallation source SINQ. The collimator system absorbs slightly more than 10 % of the proton beam power and the maximum temperature of the collimator system exceeds 350 C at 2.2 mA, which is close to the failure point. In this paper, we present a new collimator system design which could withstand the proton beam intensity of 3 mA, while fulfilling the intended functionalities. Advanced multi-physics simulation technology is used for the geometric and material optimizations, to achieve the lowest possible actual to yield stress ratio at 3 mA. A sensitivity study is performed on the correlation between the beam misalignments and the reliability of the key accelerator components in the proton downstream region. Also reported are the possible proton irradiation effects on the mechanical failure criteria.