• A.V. Aleksandrov
  ORNL, Oak Ridge, Tennessee

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H^- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The accelerator systems are equipped with variety of beam diagnostics. The beam diagnostics played important role during beam commissioning, they are used for accelerator tuning and monitoring beam status during production runs. The requirements to the various diagnostics systems are changing in the process of beam power ramp up. This talk will give an overview of the evolution of the major SNS beam diagnostics systems: commissioning, operation, power ramp up, and power upgrade.

• J.M. Carmona, B. Brañas, A. Ibarra, I. Podadera Aliseda
  CIEMAT, Madrid

The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA (CW) deuteron LINAC with the purpose of validating the technology that will be used in the future IFMIF accelerator. In such low energy and high current prototype accelerator, any device intercepting the beam could be destroyed. Thus, non interceptive profile monitors will be installed inside of a Diagnostics-Plate and along the High Energy Transport Line. CIEMAT group investigates a profile monitor based on the fluorescence of the residual gas. A high neutron and gamma flux environment (due to high deuteron beam current) stands for a hostile environment for most of electronic devices and fibers. The design must guarantee not only good spatial resolution but a reliable operation in such environment. Hence, different options for detectors, optical windows, fibers and shielding concepts have been considered to overcome these aspects. Transverse profilers will be used as well as a tool to perform emittance measurements through quad-scans. In this contribution, the design of a transverse profiler prototype for EVEDA, together with a brief discussion about mechanisms that can play a role in profile falsification will be presented.

• F. Senée, G. Adroit, R. Gobin, B. Pottin, O. Tuske
  CEA, Gif-sur-Yvette

Optical diagnostics based on the excitation of residual gas molecules are routinely used for high intensity beam characterization. Beam intensity, beam position and profile are measured by means of a CCD sensor. In addition species fraction and profile of each beam are measured using a Doppler shift method. As part of IFMIF-EVEDA* project, CEA is in charge of the design and realization of the 140mA-100keV cw deuteron source and low energy beam transport line. In the beam line, (D,d) reaction will occur and high neutron flux will be emitted when deuteron beam interacts with surfaces. Moreover gamma ray and activation will also occur. In order to protect diagnostics, coherent optic fibers could be used to transport the beam image outside the irradiated zone. A comparative study of two coherent fibers will be presented (FUJIKURA & SCHOTT), along with the characterization in magnification and attenuation of a 610 mm long fiber and its associated optics. To estimate the capability of such fibers to transport beam image, a dedicated experiment has been performed with proton beam produced by the SILHI source. The beam transverse profile has been compared with and without the optic fiber.

* International Fusion Materials Irradiation Facility - Engineering Validation and Engineering Design Activities

• K. Thomsen
  PSI, Villigen

For the neutron spallation source SINQ at PSI a novel visual monitor (VIMOS) has been devised to guarantee correct beam conditions, triggered at the occasion of irradiating the delicate liquid metal target during the MEGAPIE project. VIMOS is looking directly for the most relevant parameter: it checks whether any point on the target is hotter than allowed. For this purpose the incandescence of a glowing mesh right in front of the beam entrance window is observed by means of dedicated radiation hard optics and suitable cameras. Starting from the initial goal of reliably detecting beam anomalies in a timely manner the scope of the system has been extended to serve as a standard device for beam monitoring and fine tuning of the settings of the proton beam transport lines. Over the course of the five years of continuous reliable operation of this unique system valuable experience has accumulated, which is employed for steady improvements of the device with respect to endurance in the radiation environment, calibration, maintenance, and price. A summary of the operational experience of VIMOS will be reported as well as steps taken towards further upgrades.

• J. Marroncle, P. Abbon, F. Jeanneau, J.-Ph. Mols, J. Pancin
  CEA, Gif-sur-Yvette

Within the framework of IFMIF-EVEDA project, a high-intensity deuteron beam (125 mA - 9 MeV) prototype accelerator will be built and tested at Rokkasho (Japan) in order to validate the future IFMIF accelerator. One of the most challenging diagnostics is the Beam Transverse Profile Monitor (BTPM), which has to be a non-interceptive device. Two R&D programs have been initiated: one based on residual gas fluorescence developed by Ciemat Madrid (see J. Carmona et al. contribution) and another one based on residual gas ionization developed at CEA Saclay. The principle of the last one is to measure the current induced by the ionization electrons, which drift under an electric field influence, towards several strips to get a one-dimension projection of the transverse beam profile. Preliminary results of a first prototype tested on the IPHI Saclay accelerator will be shown, as well as a new prototype design. In the new design several improvements have been carried out which will be tested soon with continuous and pulsed beam at higher energy.