Test of a fine vacuum motor as movement system for the panels of the STRIKE calorimeter

The diagnostic calorimeter STRIKE will be used to characteriz e the SPIDER beam, by measuring beam uniformity, beam let divergence and stripping losses . The diagnostic part of STRIKE is given by 16 carbon - fibre - ca rbon composite (CFC) tiles (37 6 x 142 x 20 mm 3 each) . Each of these tiles corresponds to one of the beamlet groups composing the S PIDER beam and they are arranged in a 4x4 matrix [1] . One - directional CFC guarantees both high f usion and sublimation temperature and a high ratio of thermal conductivity in the direction parallel to the beam with respe ct to the perpendicular. This second feature is very important as it allow s the observation of the beamlet footprint from the rear si de of the tiles , which is necessary to avoid issues related to carbon debris . As it has to be observed from behind, STRIKE is not equipped with cooling channels and therefore it can cool down only by thermal radiation. Therefore the SPIDER pulse duration i s limited when STRIKE is exposed to the beam (10 s every 20 minutes). A copper calorimeter is placed downstream STRIKE to intercept the whole beam power for long pulses operation. For this reason, STRI KE is formed by two panels which may displace laterally reaching a parking position . The distance between STRIKE and the grounded grid of the accelerator may be varied between two reference positions (d 1 =0.5m, d 2 = 1.0m) so to measure the beam divergence . The position of STRIKE is the n determined by three elem ents [2] : a basement which define the position inside the vessel (X 0 ,Y 0 ,Z 0 ), a trolley to move along the beam direction with respect to the basement position and a panel support on which the panels may slide out to open/close t he calorimeter. More details on such system may be found in [2] . To perform such positioning of the panels two motors are required for every direction, which means a total of four motors suitable for vacuum have to be purchase d. A precision in the positioning in the order of 0.1 mm is considered to be sufficient. As the vacuum level required in the SPIDER vessel is in the order of 10 - 5 mbar, the use of fine vacuum motors instead of high vacuum ones has been considered. To veri fy their outgassing rate and therefore their compatibility with the SPIDER environment, some tests were performed in a small vacuum chamber at Consorzio RFX. The result of such tests is hereby reported ; due to the aims of the measurements, it is not deemed necessary to employ c arefully calibrated instrumentation.