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The copper coating has been proposed to stiffen the niobium superconducting cavity in order to reduce its deformations under Lorentz forces. The environment of thermal spray process is very important to get the wanted copper properties, as a consequence, the Inert Plasma Spray (IPS) process was used to realize the copper coating onto niobium. With the use,of X-ray diffraction method, the radiocrystallographic elastic constants (REC) of the IPS copper coating have been measured firstly, and then, in using the measured REC, the residual stress distribution has been determined secondly as a function of the depth in the copper coating and in the substrate.

Heat transfer from a plane surface to a saturated He II bath is studied up to and beyond the critical heat flux density q ∗ inducing film boiling. The experiments were performed with two similar test cells, denoted 1 and 2. Test cell 2 consists mainly of four OFHC copper rods heated at their top extremity and equipped each with three calibrated carbon resistors for in situ measurement of the thermal conductivity k Cu (T). Three of these test specimens are equipped with specially developed surface thermometers. The measured Kapitza conductance at high heat flux ( q ≤ 5 × 10 4 W m −2 ) as well as k Cu versus T data (temperature range 2–6 K) presents a good reproducibility between the four samples tested. The heat transfer characteristics were recorded at T bath = 1.8 K for different immersion depths H 0 of the heat transfer surface and the results are discussed. We also report on the experimental q ∗ versus H 0 data. These data measured on both test specimens either equipped or not equipped with surface thermometers, show a strong dependence of q ∗ on the sample surface cooling conditions.

Stiffening of bulk niobium SRF cavities is mandatory for reducing the frequency shift induced by Lorentz forces at high accelerating gradients. Experimental and computational data previously reported show that with the actual scheme (i.e. EB welded stiffening rings) the frequency shift of TESLA 9 cells SRF cavities is higher than the cavity bandwidth above Eacc=28 MV/m. We propose a new stiffening method, using a Plasma Sprayed Copper Layer (PSCL) onto bulk niobium cavities. As compared to the actual technique, this method offers several advantages (simplicity, reliability...). The first experimental data obtained with monocell cavities produced by this method demonstrate the efficiency of cavities stiffening with plasma spraying. Thermal and mechanical properties measured on niobium samples with a PSCL are also presented. These data will allow us choose the plasma spraying process suitable for achieving the best cavities performances.

MACSE, a pilot accelerator, has been built at Saclay in order to fully develop the technology of superconducting electron linacs. It consists of five niobium cavities powered by five klystrons. The 1.5-GHz, 5-cell cavities are equipped with coaxial couplers. The first cavity has a reduced phase velocity to capture the 100-kV electrons coming from the injector. It is followed by a four-cavity cryomodule. The present status and the first beam test are reported, along with some results of superconductivity R&D. >

In this work, the influence of the thermal spraying processes, atmospheric plasma spraying (APS), high velocity oxygen fuel (HVOF), and vacuum plasma spraying (VPS), on the microstructure and properties of copper coatings is discussed. The differences in microstructure, microhardness, and residual stress for each type of coating are shown. The X-ray diffraction (XRD) method is used to evaluate the mechanical anisotropical characteristics of the materials and the residual stress distribution. The particularity of this study is that the thickness of the coating is of the millimetre scale; the massive coating specimens without a substrate were obtained for XRD microelastic modulus measurements and for macrotensile measurement. Microhardness distributions have been obtained in coatings and in substrates that pass through the interface zones. It was observed that dense coatings could be obtained by industrial processes such as APS and HVOF, but they induce oxidation in the copper coating. The copper ox...

We describe the peripherical elements of CRYEBIS such as the electronics and the high voltage terminal. The results of the three main experimental series are given and discussed. Ions such as Ne 10+ , A 18+ , Kr 34+ and Xe 44+ are available with such a device which needs a long time for adjustment before being used on a machine.