117574118
Operation of the CERN 5-cell superconducting acceleration cavity in PETRA
116256770
Coupled microwave cavities for the detection of small harmonic displacements
122070366
EXPERIMENTS WITH THE CERN SUPERCONDUCTING 500 MHz CAVITY
Abstract We report on a series of experiments with a superconducting 500 MHz single cell cavity of “spherical” shape fabricated from niobium sheet material. Design, fabrication and different room temperature surface treatments of cavity including ion bombardment cleaning are discussed. An experimental test set up was used which includes diagnostic systems such as: temperature mapping of the outside cavity wall in subcooled helium, scanning solid state X-ray detector close to the cavity wall, light detection from the cavities inside, probes to measure internal free electron currents and a spectrum analyser to detect the electron induced excitations of higher order cavity modes. The following general characteristics of the cavity were observed: At 4.2 K an accelerating field of 3 MV/m can be achieved safely with low losses ( Q =2 × 10 9 ; P diss =8.4 W/m). The residual rf losses are concentrated in the high electric field region the cavity surface and cannot be attributed to normal conducting metallic impurities but show dielectric loss proporties. Resonant electron loading (multipacting) was never observed. At field levels exceeding 3 MV/m non-resonant electron currents start to load the cavity Q and give rise to the excitation of higher order cavity modes. The electron sources are point like and located in the high electric field region of the cavity. The field emission nature and the location of the electron sources are determined by temperature mapping and X-ray diagnostic measurements and analyzed by computer simulation of electron trajectories. In the region between 4 and 5 MV/m the cavity field is limited by thermal instabilities (quenching) originating from point like loss regions predominantly found at the bottom part of the cavity. Some of these defects were observed to be created during high field operations of the cavity in several instances.
113147976
The high energy separated beam and the rf-separator for IHEP (Serpukhov)
FOR IHEP (Serpukhov) N. GALJAEV, V. KOTOV, A. SAMOILOV and V. VAGHIN IHEP, Serpukhov, P. BERNARD, D. LAZARD, P. LAZEYRAS and H. LENGELER CERN, Geneva, Switzerland Presented by H. Lengeler In the framework of the scientific collaboration between IHEP (Serpukhov) and CERN (Geneva) the design of an RF-separated beam and the construction of an RF-separator is under way. They will provide high energy particles for bubble chamber experiments. Due to the short pulse duration of the RF-separator the separated beam can only work in conjunction with a fast ejection for the primary protons [1]. 1. Beam-layout The beam is designed to transport kaons and antiprotons up to 40 GeV/c, pions up to 60 GeV/c and protons up to 70 GeV/c. The layout is similar to the RF-separator beams already in use at CERN[2-3] and at BNL [4] which work in the energy range of 10—20 GeV/c It can be divided in three sections (cf. Fig. 1 and Table 1). 1. 1. Targetting and momentum analysis. The beam collects particles from the target under 0° and a first set of 4 quadrupoles (Q1—Q4) arranged in a triplet focuses the beam in the horizontal plane. The triplet (together with the collimators C1, C2) provides a horizontal acceptance αh = ± 5 mrad and a vertical acceptance αv= ±3,8 mrad. Normally αv has to be reduced in order to fulfill the requirements for a good separation (cf. chapter 2.3). The triplet is followed by 2 bending magnets BM1, BM2 of 6m length each. By using'a target with 2 mm horizontal width the minimum relative momentum bite obtained at the collimator C4 is Δp/p=±0,25%.
108725016
Superconducting RF Systems and Cryogenics
The subgroup on Supercondcuting RF Systems and Cryogenics was assigned the following tasks: (1) provide acceptable design recommendations for the accelerating structures and related RF and Cryogenics systems based on the parameters established by High Energy and Nuclear Physics needs (namely a final energy of 2.5 and 8 GeV at the end of the first and second stage, respectively, and the ability of accelerating simultaneously the 200{micro}A Nuclear Physics beam and the three bunches for High Energy Physics). (2) estimate the cost of such systems based on realistic, present day technology, with some assessment of future costs as technology and cavity manufacturing processes will improve. These tasks were carried out for the case of the original design which includes two racetracks of similar structure and with different energies, as well as for the more recent design of Amaldi and Coignet which is capable of reaching a center of mass energy of 15 GeV (alternate design). Design and cost estimates were done for a few cases of possible achievable gradients.
117386634
RF superconductivity at CERN : a status report
117909130
Microwave apparatus for gravitational waves observation
In this report the theoretical and experimental activities for the development of superconducting microwave cavities for the detection of gravitational waves are presented.